Articles List
Supervised Maintenance
Who is allowed to perform maintenance on a certificated aircraft? The FAA rule that answers that question is 14 CFR 43.3—Persons authorized to perform maintenance, preventive maintenance, rebuilding, and alterations. This rule authorizes repair stations, A&P mechanics, repairmen working for a repair station, air carriers, Part 135 operators, and aircraft manufacturers to perform maintenance. The rule also allows pilot-rated aircraft owners to perform preventive maintenance on an aircraft that they own. What if someone who is not an A&P—say, a maintenance-involved aircraft owner—wants to do something that goes beyond preventive maintenance—say a repair or alteration or component overhaul or replacement? Or what if an aspiring aircraft mechanic wants to go to work as an apprentice at a aircraft maintenance facility in order to gain the 30 months of practical experience required to qualify to take the knowledge and practical tests to become an A&P? Well, 14 CFR 43.3 addresses that, too. Specifically, paragraph (d) of 43.3 says: 43.3(d) – A person working under the supervision of a holder of a mechanic or repairman certificate may perform the maintenance, preventive maintenance, and alterations that his supervisor is authorized to perform, if the supervisor personally observes the work being done to the […]
Concierge Maintenance
Rethinking the business model for maintenance of GA aircraft. For more than a decade, my primary care physician was Dr. F. She was a wonderful doctor with a deep understanding of internal medicine and superb people skills who cared deeply for her patients. I felt fortunate to have her as my doc. But over the years, her reputation spread, and her practice grew larger. The lead time for scheduling an appointment to see her became uncomfortably long. Visits to her office became an ordeal involving lengthy delays in her always-packed waiting room, after which I would get to see the doctor for 5-10 minutes if I was lucky. Then in October 2010, Dr. F died in the crash of a Beechcraft A36 Bonanza while on a humanitarian mission in Mexico. She was a member of The Flying Samaritans, a public benefit flying organization that operated free medical clinics at 17 locations in remote areas of Baja California. My doc regularly volunteered to participate in these clinics. (Decades earlier when I lived in Southern California, I was an active pilot for The Flying Sams.) That morning, the Bonanza took off from Ensenada headed for San Quintin. Aboard were Dr. F, another […]
Distrust and Verify
The Perils of Trying to Fix a Problem You Haven’t Seen For Yourself The phrase “trust but verify” was made famous by U.S. President Ronald Reagan in December 1987 after the signing of the Intermediate-Range Nuclear Forces (INF) Treaty with Mikhail Gorbachev. The phrase comes from a rhyming Russian proverb, “доверяй, но проверяй” (romanized as “doveryay, no proveryay”). More than three decades later, U.S. Secretary of State Mike Pompeo paraphrased the proverb when speaking about U.S.-China relations as “distrust and verify”—likely closer to the Russian proverb’s true meaning. This proverb—particularly the Pompeo version—is just as applicable to aircraft maintenance as it is to arms control. Far too often in my experience, A&P mechanics attack an aircraft with tools in an attempt to fix an issue based solely on a squawk by a pilot or aircraft owner without actually verifying for themselves that the description is accurate. The result is often a lot of wasted effort, unnecessary expense and downtime, and frustration for all involved parties. Let me illustrate what I mean with a couple of real-world examples… Cessna 310 Volt-Amp Meter Years ago when I served as the twin Cessna tech rep for the Cessna Pilots Association, I received a […]
Why Annual Inspections?
The big boys don’t do them—why must we? Given today’s acute shortage of GA mechanics and the difficulty owners are having getting their airplanes on shop schedules, I’ve been receiving an increasing number of inquiries about the need for annual inspections from frustrated aircraft owners. “Why is it necessary to have my airplane completely torn apart every 12 months?” one owner asked. “I’ve only flown about 40 hours since the last annual inspection.” “Wouldn’t it help solve the mechanic shortage if the FAA would let non-commercial operators like me do inspections every 18 or 24 months?” another owner asked. Those are great questions. I’ve long thought that the rule requiring small GA airplanes to receive a complete inspection every 12 calendar months didn’t make a lot of sense. Larger airplanes aren’t required to do it that way, so why are we? There are certainly parts of our small GA airplanes that need to be inspected frequently. For piston aircraft, that includes pretty much everything forward of the firewall. I’m talking about all that stuff that’s constantly trying to cook and vibrate itself to death. Inspecting that stuff once a year might not be often enough. I would probably also include […]
Can’t Sign It Off?
Can a mechanic who works on your plane refuse to sign it off or put it back together? Boston-based Cirrus owner Mark (not his real name) was flying his turbonormalized SR22 home to Norwood Memorial Airport on what was probably going to be his last flight prior to putting the plane in the shop for its 2024 annual inspection. While cruising over northern New England, the engine started running rough and the engine page on the MFD showed that the CHT of cylinder #2 had risen above 400°F and was continuing to rise. Mark went full rich and throttled back to stop the thermal runaway, then declared an emergency with ATC and made a precautionary landing. After an uneventful landing, Mark taxied the Cirrus to the sole FBO on the field, which included a big Part 145 Repair Station that just happened to be a Cirrus Authorized Service Center. He told the director of maintenance (DOM) about the rough-running engine and the rising CHT #2, and asked that the shop troubleshoot the issue. Mark then rented a car and drove home to Boston. The Shop’s Diagnosis A few days later, Mark phoned the shop to learn what they had found. […]
Unaffordable/Unavailable
Recently, a client with an older Cessna 182 Skylane reported that his nose landing gear strut was leaking fluid and repeatedly going flat. Inspection revealed that the original chrome strut piston had become badly pitted and was tearing up the nose strut seals. The owner’s shop checked the Textron Aviation parts system and found that they had one replacement strut piston in stock, and clearly, they were extremely proud of it. The price: $9,200. That’s nearly 10% of the fair market value of the whole airplane. Yikes! Salvage yards like BAS Parts Sales, Dawson Aircraft Parts and Salvage, Texas Air Salvage, Air Salvage of Dallas and Preferred Air Parts sometimes offer these strut pistons in as-removed condition for $2,500 to $3,500, but we couldn’t find one in stock at any of them. We even checked on eBay, but no joy. So, we concluded the best bet might be to find a shop capable and approved to re-chrome the pitted strut. As I’m writing this, we’re checking with Delta Strut in Stockton, California who specializes in Beechcraft landing gear repair but sometimes will work on Cessna and Piper struts. Fingers crossed. Although the cost of a new replacement nose strut piston […]
The Tale of Two Prebuys
My company manages a lot of prebuys. At any given point in time, we typically have a dozen of them in progress. We’ve managed thousands of them over the years, and seen the good, the bad, and the ugly. Most of the time, the aircraft turn out to be in decent shape and the outcome is a successful purchase by our client, often after some last-minute price negotiations based on prebuy findings of airworthiness discrepancies that we think the seller should pay to correct. Once in a while, however, the prebuy uncovers problems serious enough that we advise our client to walk away and find another purchase candidate. We always try to arrange for the prebuy examination to be done by a shop or mechanic highly experienced with the particular make and model involved, and who is truly independent. By independent I mean that the selected shop or mechanic has no prior exposure to the aircraft being examined, and no prior relationship with the seller or (if applicable) the seller’s broker. This is the only way we can have confidence that the prebuy findings will be thorough, honest and unbiased. Let me tell you about two of these prebuys. One […]
Minimally Invasive
What we can learn from medicine about fixing things without taking them apart. A longtime friend who was suffering from extreme fatigue and shortness of breath. She was diagnosed with congestive heart failure caused by aortic valve stenosis, and she required an aortic valve replacement. This was a very big deal that required open-heart surgery. It involved cracking her chest, placing her on a heart-lung machine, stopping her heart, cutting into her aorta, surgically removing the defective valve, suturing a replacement valve (harvested from a pig) in its place, suturing her aorta, restarting her heart, and closing up her chest. Afterward, she spent a week in the hospital and more than two months recovering at home. That occurred about 15 years ago. Now, the replacement valve is starting to give out, and she needs another valve replacement. This time, remarkably, the valve will be replaced without opening her chest or stopping her heart. Nowadays, most aortic valve replacements are done using a technique called transcatheter aortic valve replacement or TAVR. A small incision will be made in her groin, and a guide wire will be passed up through the femoral artery into the aorta, and through the aortic valve using […]
Savvy’s Borescope Initiative
Teaching owners (and mechanics) how to do borescope inspections right In my last column (“Ending the War on Jugs,” AOPA Pilot March 2024 issue), I talked at length about why we should use the borescope—not the compression tester—as the gold standard for assessing cylinder condition. Borescopes are now inexpensive (under $300) and capable of breathtaking image quality. These new borescopes let us diagnose cylinder issues accurately and often early enough that the problem can be remediated using modern minimally invasive techniques—lapping leaking valves in place, and freeing stuck rings with a simple solvent flush—thereby eliminating the need to incur the cost and risk of cylinder removal. But there’s a problem: Very, very few A&Ps know how to do a proper borescope inspection of cylinders. There’s little or no training on this subject in A&P school, and no relevant questions on the A&P knowledge tests. There’s nothing in any maintenance manual or service bulletin from aircraft or engine manufacturers that provides any guidance on this subject. Interestingly, Continental has “required” that a borescope inspection be done any time a compression test is performed, but they offer not a syllable of guidance on how to do one! What’s wrong with this picture? […]
Monitor-Specific FAQs
Concerning E.I. UBG-16, MGL and GRT monitors How do I upload data from a UBG-16? Files that come from a UBG-16 do not contain “heading names” for each of the columns in the file (each column represents a data series, such as EGT1). As such, if you were to upload such a file to SavvyAviation, we would not be able to tell which column was EGT1, which was CHT1, and so on. To work around this, you have to configure your aircraft’s profile with these mappings. This will tell us, for example, that Column 1 is EGT1, column 2 is CHT2, etc. You should be able to find these mappings in your aircraft logs at the time your UBG-16 was installed. If you do not have such entries, you may need to open the file and do some detective work. If you open the file with an editor, be very careful not to accidentally save over the original. This will almost certainly make it unusable. It is best to make a copy and open the copy. Here are the steps to provide us with the UBG-16 configuration: Note: The mappings apply to file uploaded after the mappings have been set. In […]
Choosing and Upgrading Your Engine Monitor
Aircraft owners often ask us for advice about what kind of engine monitor equipment we recommend installing in their airplanes. Owners who already have engine monitors installed often seek advice about upgrading them with additional capabilities or replacing them with newer, more advanced equipment. Engine monitor technology has been a fast moving target. More and more avionics manufacturers are now offering engine monitor equipment, both as stand-alone monitors and as monitoring capability integrated into multi-function displays (MFDs). New makes, models and features are being introduced all the time. In addition to the traditional firms that manufacture avionics for certificated aircraft, there are now many companies specializing in uncertified avionics for the experimental amateur-build (E-AB) market. Consequently, we’re not going to recommend any specific makes and models here. (If we did, this document would probably be obsolete before it was posted to the Internet.) Instead, we will talk about what features and capabilities we believe are most important in digital engine data monitor equipment, and what you should be looking for when choosing an engine monitor for your airplane. There are two major dimensions to consider: what kinds of data does the equipment capture, and what features does it offer? What […]
In-Flight Diagnostics
The best way to diagnose an engine problem is usually in the air. Note to reader: The procedures discussed in this article for gathering flight test data are described more fully in the “Flight Test Profiles” document found under the “Learn More” or “Help” menu items. Pease refer to that document when performing the flight tests. “My engine started running rough about halfway home yesterday,” my client reported, “so I dropped it off at the service center. Could you please work with my mechanic to troubleshoot this problem?” Arggghhh!!! So many aircraft owners have a knee-jerk reaction to put their airplane in the shop whenever problems arise. Apparently they assume that diagnosing the problem is the job of a mechanic. That’s like having a bellyache and making an appointment to see a surgeon. Like surgeons, aircraft mechanics are primarily in the business of fixing things that aren’t working properly. But before you go to a surgeon or a mechanic, you need to figure out what’s wrong. You need a diagnosis. Every diagnosis starts with data. If you’re feeling unwell, the initial data would probably come from a Q and A session with your primary-care physician resulting in a detailed account […]
Controlling the Combustion Event
Each time you change mixture, RPM or MP, it affects combustion timing. Understanding how is your best defense against harming your engine by doing something dumb. My last few columns focused on the physics of the combustion event in Otto-cycle engines. I’m sure this was fascinating to the two or three of you who are interested in combustion theory, but of what possible relevance is it to a pilot whose main concerns are measured in knots and dollars rather than milliseconds and PSI? Actually, it’s extremely relevant. That’s because you modify the speed, intensity and timing of the combustion process every time you move the throttle, mixture and prop controls. If you don’t have a clear mental picture of how changing MP, RPM and mixture affects the combustion event, you’ll never truly understand optimum power settings or leaning, and you’ll simply have to operate your engine by rote – which is exactly what most pilots do. Little was known about this stuff back when Beech wrote the POH for your airplane. Much of what we now know comes from recent research done by my old friend George Braly at GAMI’s Carl Goulet Memorial Engine Test Facility in Ada, Oklahoma, arguably […]
Detonation and Pre-Ignition
Often confused and misunderstood, these two abnormal combustion phenomena are as different as night and day. Although we often hear people describe what goes on inside the cylinders of an Otto-cycle engine as being an explosion – i.e., a violent, nearly-instantaneous event – it’s not. The air-fuel charge does not explode when ignited by the spark plugs, but rather burns in an orderly fashion, starting at the spark plugs and progressing across the combustion chamber until it is quenched upon reaching the cylinder walls and piston crown when air-fuel charge has been completely consumed and there’s nothing more to burn. The combustion event takes a significant period of time – roughly 6 milliseconds or 90° of crankshaft rotation, give or take. It’s crucial that peak pressure occur well past TDC, because the geometry of the crankshaft and connecting rod near TDC does not permit combustion pressure to be converted into useful work (i.e., crankshaft rotation), but simply generates excessive stress on the cylinder, piston, connecting rod and crankshaft. Figure 2 attempts to dramatize this point. Detonation But if the combustion process moves too fast and the pressure peak occurs too early, the result can be excessive pressure, excessive temperatures, and […]
Understanding CHT and EGT
These two key measurements can tell us a lot about what’s going on inside our cylinders. My column last month talked about the fact that our piston aircraft engines convert only about one-third of the energy contained in avgas into useful energy to the propeller. About half the fuel’s energy goes out the exhaust pipe, while the remaining one-sixth is transferred to the cooling air that passes over the cylinder fins and through the oil cooler. The wasted energy is measured and displayed on a triad of cockpit gauges: oil tempera-ture, cylinder head temperature, and exhaust gas temperature. The one-third that actually makes it to the propeller is reflected on another cockpit instrument: the airspeed indicator. CHT vs. EGT From a powerplant management perspective, it’s crucial to understand that CHT and EGT tell us quite different things about what’s going on inside the engine. CHT mainly reflects what’s going on in the cylinder during the Otto cycle power stroke before the exhaust valve opens, while EGT mainly reflects what’s going on during the exhaust stroke after the exhaust valve opens: High CHTs generally indicate that the engine is under excessive stress for its own good. That’s why it’s so important […]
Interpreting Your Engine Monitor
The modern probe-per-cylinder digital engine monitor is a marvelous tool for keeping tabs on your engine’s health and troubleshooting its maladies. Here are some tips for figuring out what those bars and digits mean. This is embarrassing, but I might as well come clean: Up until 2003, I was still flying my Cessna T310R with only the primitive engine instrumentation installed by the factory in 1979. I’d long since upgraded my avionics stack with conspicuous quantities of glass, including a Garmin GNS-530 navigator and a Sandel SN3308 electronic HSI. I’d installed an XM Satellite Radio receiver to pipe stereo music to my ANR headsets. I’d added VGs to the wings and vertical tail. I’d even reupholstered my seats with the latest visco-elastic memory foam padding. But I was still relying on 30-year-old steam-gauge engine instrumentation. A modern digital engine monitor had been at or near the top of my wish list for years. Yet somehow the $5,000 I had set aside for this upgrade always seemed to get preempted by something else (usually nonaviation-related) every March when my annual comes due. In addition, I secretly dreaded what I expected to be a difficult, time-consuming and tedious task of installing such […]
Ending the War on Jugs
Weak compression doesn’t always mean that the cylinder has to come off. For most of my nearly six decades as an aircraft owner and three decades as an A&P, the rule about cylinders was simple: If the compression reading was less than 60/80, the cylinder had to come off for repair or replacement, period. The mechanics who worked on my airplanes, then later mentored me about maintenance, and then still later became my professional colleagues seemed quite happy with this straightforward rule. (Mechanics are always happiest when they have clear guidance to follow.) In 1984, Continental muddied the water when they issued Service Bulletin M84-15 that substituted a “master orifice tool” in place of the traditional 60/80 go/no-go criterion. This allowed Continental cylinders to remain in service with compression readings down to the mid-40s so long as the leakage was past the rings. This guidance was based on dynamometer test cell research by Continental engineering demonstrating that an engine with all cylinders at 40/80 made exactly the same horsepower as one with all cylinders at 75/80. (Most A&Ps weren’t comfortable with this, and would still yank jugs if they measured anywhere in the 50s.) However, M84-15 also said that no […]
Unleaded Avgas—Cure or Curse?
Does unleaded fuel really cause exhaust valve seat recession? The October 27 announcement by the University of North Dakota (UND) flight school that it was terminating its year-long test of Swift UL94 unleaded avgas and returning to 100LL came as a shock and disappointment to many in the industry, me included. The school’s Director of Maintenance, Dan Kasowski, cited evidence of “significant” exhaust valve/seat recession in some of the Lycoming-powered Piper Archers in its training fleet. Kasowski was not more specific about the amount of recession or the percentage of cylinders or aircraft affected, saying only that the data is still being collected and is being forwarded to Lycoming for analysis. The UND announcement was shocking because virtually all previous tests of FAA-approved unleaded avgas—both Swift UL94 and GAMI G100UL—seemed to indicate that the effects of operating piston aircraft engines on these fuels was all positive with no negatives. In addition, decades of experience using 91-octane premium unleaded automotive gasoline in a wide range of low-compression aircraft engines ranging from Lycoming O-320s to Continental O-470s uncovered no problems whatsoever. So the UND findings were quite unexpected, to say the least. Is this a major setback for the long-awaited transition to […]
Time & Materials
Why is GA maintenance done on a T&M basis, which places all the risk on the aircraft owner and none on the shop? A successful surgeon put his Beechcraft Baron 58 in an Arkansas shop for a makeover. He wanted both engines overhauled, new paint and interior, and the steam gauges replaced with a modern glass panel. The shop estimated they could get all this done in about six months at a cost of about $200,000. Much to the doctor’s dismay, the work actually took two years the final bill was about $500,000.. I learned about this when a mutual friend called me to ask if there was anything I could do for the Baron owner, who was extremely upset and understandably feeling seriously ripped off. I told my friend that while I certainly felt the owner’s pain, there was really nothing I or anyone else could do to help. Like the vast majority of GA maintenance, the work was done on a time-and-materials (T&M) basis. This meant that the owner agreed to pay for all the labor expended by the shop and its subcontractors (e.g., the paint shop) on an hourly basis, and for any required parts (typically at […]
Deadly Switches
That ubiquitous key-operated ignition switch is fraught with peril On July 26, 2018, private pilot Lanny Steven Kramer of Sarasota, Florida, and his wife Fran flew to the Cleveland Regional Jetport (RZR) in Cleveland, Tennessee to run some errands, after which they returned to the airport to depart. Shortly before 5 p.m., Lanny was preflighting the Cessna 182 Skylane while Fran had opened the righthand cabin door and was preparing to climb into the right seat. Then Fran heard a noise that sounded like the plane’s engine was trying to start. She found Lanny lying on the ramp in front of the airplane. He had sustained severe head injuries and was non-responsive. The Skylane’s ignition key was in his pocket.Fran called for help, which quickly arrived. Lanny was transported to the hospital by medevac helicopter, but succumbed to his head trauma. NTSB Findings Accident investigators found that the righthand magneto of the plane’s Continental O-470 engine was “hot”—the mag’s P-lead was not grounded out by the cockpit ignition switch. They found that the switch was not in the OFF position, but rather was in an intermediate position between the OFF and RIGHT detents. In that position, the switch did not […]
Miracle in Sioux Falls
My hapless blunder en route to Oshkosh triggered a series of incredibly fortuitous events. It was mid-July and my annual pilgrimage to AirVenture Oshkosh was rapidly approaching. I’d finished preparing PowerPoint for the 11 different presentations I would be making. Now I started thinking about the upcoming flight. Flying from California to Wisconsin solo can get lonely, so I called my colleague Colleen Sterling and asked if she was interested in flying with me. After conferring with her husband Dave, they both accepted my invitation. Colleen and Dave are two of my favorite people. Both are very accomplished pilots—Dave’s a recently retired 787 captain—and both are A&P/IAs. They own five airplanes between them, all based at San Diego’s Gillespie Field (KSEE), and race three of them at Reno. Serious aviators!. On Friday, I flew my Cessna 310 to KSEE and stayed overnight with Colleen and Dave. We planned to launch early Saturday morning and fly at least two-thirds of the way to Oshkosh, remain overnight (RON), then depart Sunday morning to arrive at Wittman Field by noon. Northern Route Colorado looked awful on NEXRAD, so a northerly route via Salt Lake City looked prudent. Using Foreflight, I found a promising […]
Fortunate Catch
A maintenance-aware owner is the last line of defense against maintenance errors Corey owns a 1978 Bonanza A36 and is quite involved in its maintenance. He does his own oil changes and other preventive maintenance. He even bought his own borescope and uses it to keep tabs on the health of his cylinders. He’s my kind of aircraft owner! His most recent borescope inspection revealed what looked to him like burned exhaust valves in the #3 and #4 cylinders. He reported this finding to his local shop, and after verifying his diagnosis a decision was made to send the better cylinder out for overhaul by an engine shop in Tulsa and to replace the worse one with a new Superior Millennium. (I’m not sure whether any consideration was given to lapping the exhaust valves in place—maybe they were too far gone for that.) The work seemed to be proceeding smoothly. Before long, the shop installed the new and overhauled cylinders and had the plane almost buttoned back up when Corey stopped by to check on their progress. Informed that the airplane was almost ready for the break-in flight, Corey went over to eyeball his newly installed jugs—and he saw red. […]
Legal interpretations
If you ask FAA lawyers what a regulation means, the answer might surprise you We’ve all studied the regs. If you’re a pilot, you’ve spent hours poring over Part 61 (pilot certification, ratings, currency) and Part 91 (operating rulese, owner responsibilities), both of which are voluminous. If you’re a mechanic, you’ve hopefully memorized Part 65 (mechanic eligibility, privileges and limitation) and Part 43 (maintenance) which are comparatively shorter but quite pithy. These regulations are written and maintained by a large team of FAA lawyers who work for the Regulations Division of the FAA Office of the Chief Counsel. If you have a question about the meaning of a rule, you can write to the Assistant Chief Counsel for Regulations (AGC-200) requesting a legal interpretation. (It’s sort of like asking the IRS for a revenue ruling.) Your request will be assigned to one of the rulemaking attorneys responsible for that particular section of the FARs, who hopefully will prepare a detailed written legal interpretation to be signed by the Assistant Chief Counsel and sent to you. Hopefully you’re not in a hurry, because the wheels of government turn slowly. Response time is generally at least several months, sometimes a lot longer. […]
Unbelievable Compression
How reliable and valid is the almighty compression test? Each annual inspection begins with a moment of terror when the IA removes the top spark plugs and takes a compression reading of each cylinder. We hold our breath awaiting the verdict. If the numbers are good, we exhale and relax. If not, we anticipate the sticker shock of cylinder removal and repair or replacement—and we pray that opening Pandora’s box won’t result in an even costlier verdict requiring an engine teardown or replacement. Sound familiar? Been there and done that? I certainly have.This agonizing compression testing ritual takes place hundreds of thousands of times each year. The requirement for performing a compression test at each annual and 100-hour inspection is written right into the FARs—specifically Part 43 Appendix D—so your IA has no choice about doing it. I’ve seen serious buyers walk away from an excellent airplane because they didn’t like the looks of the compression readings during the pre-buy. Yet this obsession with compression readings is so very wrong on multiple levels. Why wrong? I will explain… For one thing, the differential compression test is spectacularly unreliable. This means that you can test a cylinder multiple times and get […]
Here to Help?
When it comes to maintenance problems, the FAA might be able help you but only in very limited ways. My April column, titled “Booted Out of Annual,” related a true story of a Bonanza owner who put his plane in the shop for its annual inspection, got into a disagreement with the shop’s manager, and wound up having his plane thrown out of the shop in pieces. The beleaguered owner ultimately contacted the local FSDO (against my advice) for the purpose of filing a complaint against the shop. An Airworthiness Safety Inspector (ASI) there appeared to take pity on him and helped him out of this predicament. Shortly after this column appeared in print, I received a long, thoughtful email from a gentleman I’ll call “Fred” who was retired from the FAA after two decades working at both a FSDO and an FAA Regional Office. (I thought “Fred the Fed” had a nice ring to it.) Fred was very concerned that my April column might give AOPA PILOT readers a wrong impression about when it is and isn’t appropriate for an owner to ask the FSDO for help, and what FAA personnel are and aren’t allowed to do. Fred and […]
Mechanic Crisis
THERE ARE NO LONGER ENOUGH A&PS TO MAINTAIN OUR GA AIRPLANES “The annual I scheduled more than a year ago got cancelled on a five-week notice,” read a recent post to the Beechcraft Bonanza Owners Facebook group. The unhappy owner went on to say that it was going to be impossible for him to find another IA to do the annual inspection of his Bonanza, which was coming due in just five weeks. The Bonanza owner posted the cancellation notice he received from his shop’s director of maintenance. In it, the director of maintenance said he was just not able to hire, train, and retain enough A&Ps to keep up with the shop’s scheduled workload. He also cited supply chain issues that delayed completion, and not enough hangar space to accommodate aircraft that were “in limbo” awaiting needed parts or outside work. “Sometimes I just look at the shop schedule and sigh,” the director of maintenance wrote. “I have a hard time saying no, and that has led to working seven days a week for far too long. I cannot do that anymore. I need to cancel some upcoming annual appointments.” Critical A&P shortage This post by the Bonanza owner […]
Booted Out of an Annual
This unfortunate aircraft owner was placed in an untenable position by an unreasonable maintenance manager Sometimes truth is stranger than fiction. I’m going to change the names—I’ll call the aircraft owner “Oliver” and the A&P/IA “Isaac” and the shop manager “Maurice—and avoid geographical references. But I swear this really happened. The story started some months ago when Oliver put his recently acquired 1960 Beech Debonair in the shop on his home airport for its 2022 annual inspection. This is his first airplane and was the first annual on his watch. He delivered the plane to the shop on a Friday. Monday morning, the shop’s young A&P/IA, Isaac, ran up the engine to heat up the oil and cylinders, then started draining the oil and performing a hot compression check. All compressions tested okay except for cylinder #6 which measured 40/80. Cylinder #6 was borescoped, and the images did not reveal any obvious issues. Isaac cut open the oil filter and inspected it. A small amount of metal was found in the pleats, so Isaac placed the filter media in a plastic bag and overnighted it to Aviation Laboratories along with an oil sample. Meantime, the maintenance manager Maurice—who is not […]
Ethics of Misdiagnosis
Should you have to pay for work or parts that don’t fix the problem? “Mike, I have an ethical question for you: How should an aircraft owner determine fair compensation to a mechanic for parts and labor that were unnecessary?” The email was from a 1947 Piper PA-12 Super Cruiser owner—I’ll call him Don—who had just received an invoice from his shop and was wondering whether or not to pay it. Don explained that his Lycoming O-235-C1 engine had always started easily. That changed after the last annual inspection when his A&P told him that he should be starting the engine with the mag switch set to LEFT since only the left magneto was equipped with an impulse coupling for starting. Don had been starting the engine on BOTH for the past 20 years, and he found the engine almost impossible to start using the procedure his mechanic had prescribed. Don reported this to his A&P, who proceeded to replace the primer. There was no improvement in starting, so the A&P replaced the left magneto. Still no improvement. The A&P asked Don to check the idle mixture by performing an idle RPM rise test. Don performed the test and reported […]
A Matter of Trust
How far does your IA have to go to verify that your aircraft is airworthy? The subject line of the email got my attention: “Annual gone wrong…please help!” The author—let’s call him Morrie—identified himself as a first-time airplane owner. “I have my Citabria in for annual now,” Morrie said, “and I feel like one of your Savvy Maintenance columns is unfolding in front of me and my wallet. I had no issues with my first annual inspection last year, but I took it to a different IA this year and things seem to be unravelling.” Morrie explained that the original 115 hp Lycoming O-235 engine on his 1975 Citabria 7ECA has been replaced in 1996 with a 150 hp Lycoming O-320. That engine was overhauled in 1999, and the logbook entry made by the A&P who overhauled it stated “all ADs were complied with.” “My current IA is saying that is not good enough, and that he cannot verify the part number and serial number of the camshaft that was installed and therefore says he needs to tear down my engine!” The AD that had Morrie’s IA so concerned was a very old one—AD 63-23-02 published in 1963—that affected Lycoming […]
Obsessed with EGT
Don’t use exhaust gas temperature as a leaning reference I respond to at least 100 queries from aircraft owners and pilots each week. At least a dozen of those are questions or requests for advice about leaning, and most of them relate to EGT. A few common ones: Q: My POH recommends leaning to 50˚F rich of peak EGT, but your articles/webinars/books seem to say I shouldn’t do this. What’s with that? A: Back in the 1960s or 1970s when your airplane’s POH was written, engineers believed this was a good way to lean the engine. Since then, we’ve learned a lot more about the effect of mixture on the combustion event—in large part through the research efforts of George Braly at the world’s most advanced piston aircraft engine test facility he created at General Aviation Modifications, Inc. (GAMI) in Ada, Oklahoma—and we now know that 50˚F rich of peak (ROP) is very nearly the WORST possible mixture for engine longevity. I recommend against leaning to 50˚F ROP because I want your engine to live long and prosper. Q: When leaning my engine to XX˚F ROP/YY˚F LOP, should I use the first cylinder to peak, the last cylinder to peak, […]
System Awareness
Situational awareness requires being aware of your aircraft’s systems, too. On Saturday, August 26, 2022, a young CFI took off from Monterey, California in a Cessna 172 on a “Discovery Flight.” His passengers were a young couple, with the man occupying the left front seat and the woman seated in the back. The CFI occupied the right front seat. The airplane leveled off at 3,500 feet, at which point the CFI turned the controls over to the male passenger and started giving him basic instruction. The flight proceeded first north, then west following the coastline to Santa Cruz, did some maneuvers and airwork, then turned southeast to return to Monterey. Not long afterwards, the CFI sensed that the engine was losing power, and the tachometer confirmed this. He quickly ran through the memory items on his loss-of-power checklist: pitch to best-glide speed, mixture full rich, primer locked, carb heat on, fuel selector set to BOTH, etc. None of this helped, and the engine continued to lose power and RPM. At this point, the CFI looked at the oil pressure and temperature gauges. The oil pressure gauge read zero! The CFI advised NORCAL Approach that he had an engine emergency. Approach […]
When Data Doesn’t Look Right
Using AI and deep learning to detect anomalous engine monitor data Nowadays more than half of the piston GA fleet is equipped with some sort of recording digital engine monitor. Older ones tend to be fairly primitive and record just EGTs and CHTs and not much else. Modern ones have myriad sensors and capture numerous temperatures, pressures, voltages, currents, air data, attitude, acceleration, and GPS position data. A modern engine monitor with a few dozen sensors and a one-second sampling rate records more than 100,000 measurements per hour of flight. This data can have immense diagnostic value. In a perfect world, our engine monitors would analyze all this data in real time and alert us whenever something doesn’t look right. But even state-of-the-art avionics have an extremely limited ability to do this. Some engine monitors will alarm when various data values—CHTs, TIT, oil temperature and pressure, etc.—fall outside user-configurable minimum or maximum values. Others alarm only when values hit the manufacturer-specified redline (which is often way too late to save the day). Yet others offer no alarms at all. No engine monitor does what our human data analysts at Savvy Aviation are trained to do: to look for patterns in […]
Real-Life Breakdowns
Dealing with mechanicals away from home base. Every aircraft owner dreads a mechanical breakdown while away from home on a trip. In the five and a half decades that I have owned an aircraft—I bought my first plane in 1968 and have always flown lots of long trips—I’ve been the victim of such mechanicals more times than I have fingers. From firsthand experience, I can tell you that these events are emotionally charged. You’re typically stuck somewhere you don’t want to be and at the mercy of strangers you don’t know whether or not to trust. It’s usually frustrating, frightening and exasperating. It always puzzled me that there was no nationwide or worldwide breakdown assistance program for GA owners and pilots, something analogous to what AAA provides for motorists. So, in 2016 my company launched one—SavvyBreakdown—and today we have thousands of GA airplanes enrolled in the program. We operate a toll-free hotline that connects pilots-in-distress with one of our seasoned A&P/IA account managers on a 24/7/365 basis, and we deal with every possible sort of away-from-home problem you can imagine—hundreds of them every year. Let me tell you about a half-dozen real-life breakdown incidents and how we dealt with them… […]
What Price Speed?
Optimal flying in a world of expensive avgas. With fuel prices at all-time highs, it’s more important than ever for pilots of GA airplanes to fly in a fuel-efficient fashion. I am especially sensitive to this issue because I fly a piston twin that guzzles 30 GPH and suffer post-traumatic stress each time I refuel. So, how can we get the best bang for our avgas buck? Well, it turns out that there are a bunch of things that contribute to fuel-efficient flying. A good place to start is our choice of airspeed. There are a number of contenders for the title of “most fuel-efficient airspeed.” The most obvious candidate is the airspeed at which drag is minimized, often referred to as “best L/D” and often found in the POH as “best glide speed.” For my Cessna 310, best L/D is 111 KIAS at max gross and lower at lighter weights. For a Cirrus SR22, it’s 92 KIAS, and for a Cessna 172 it’s 65 KIAS. This is the airspeed that will get you from point A to point B using the least amount of fuel, and the airspeed that will provide the greatest possible range starting with a given […]
On a Short Leash
The best maintenance shops often warrant the closest owner oversight. I’m frequently asked by aircraft owners to recommend good maintenance shops in a particular area, and my company maintains a large database of maintenance resources to facilitate such referrals. Our team of more than 20 A&P/IA account managers keep close track of their experiences working with hundreds of shops, and we do our best to steer our clients to the ones with which we’ve had the best outcomes and—perhaps more importantly—away from those that were not so good. Often I find myself telling a client, “this is an outstanding shop that does thorough inspections and excellent work, but be prepared for a big bill unless you keep them on a short leash.” I do not mean this as a criticism of the shop. It simply reflects the reality that the best shops tend to do very thorough inspections and uncompromisingly meticulous repairs, and generally tend to have a perfectionist approach to maintenance. These are exactly the attributes we want the shop to have, but the result can be serious sticker shock unless the owner actively throttles the shop back by explicitly directing them to perform only the work desired nothing […]
Disastrous Annual
Out-of-control annual inspections are painful—and avoidable. I received a heart-wrenching email from the owner of a Southern California flight school—I’ll call him Chuck—who operates 10 airplanes, mostly Cessna 172s and Piper Archers and Arrows, with a Seneca twin and a Cessna 140 taildragger thrown in for good measure. With a fleet like that, Chuck has a lot of experience with airplane maintenance and annual inspections, so he’s not the sort of person you’d expect to get into deep maintenance kimchee, but sadly that’s exactly what happened. Chuck wanted to expand his business to provide air tours, so he purchased a 1957 Twin Beech E18S with for $160,000 with the help of a bank loan and spent another $40,000 to upgrade the avionics. Then it came time for the first annual inspection on Chuck’s watch. His regular mechanics didn’t have any Beech 18 experience, so Chuck decided to fly the airplane some 350 nm to a specialty shop in Northern California that was well-known and apparently well-respected in the Beech 18 community. Chuck told the shop’s owner that he would be using the Twin Beech for an air tour operation, and wanted to make sure it was safe and airworthy. Chuck’s […]
TBO 5000!
This Skyhawk’s Lycoming had a 2,000-hour TBO, but it lasted a bit longer—3,000 hours longer to be exact. What follows is true, though the names have been changed… It was 2011 and Unruly Flyers had a problem. This 14-member Midwest flying dlub’s only aircraft—a 1997 Cessna 172R—had a Lycoming IO-360 engine that was rapidly approaching its 2,000-hour TBO, forcing the club to decide. Overhaul would put Unruly Flyers on the ground for at least three months. Replacment with a Lycoming rebuilt might shorten the downtime but increase the cost. Unruly’s board was struggling with this decision, and decided to coax the club’s former maintenance officer Zachary “Whit” Wittington to come out of retirement. Whit wasn’t an A&P, but he’d been flying GA for more than two decades and had proven himself to be exceptionally maintenance-savvy. Whit agreed to reassume his former role, and at the next Unruly board meeting (pun intended) asked all the right questions: Q: Are we having problems with the engine? A: No. Q: Why are we thinking about overhauling or replacing it? A: It’s at TBO. Q: Are we required to do anything at TBO? A: Guess not. Q: Why not continue it in service? A: […]
What we have here is a Failure to Rotate
Is the conventional wisdom wrong about why exhaust valves burn? Piston aircraft engines have an awful lot of moving parts. Way too many, if you ask me. The thought of thousands of separate metal parts reciprocating, rotating, wiggling, wobbling, and rubbing against one another thousands of times a minute ought to make you nervous—it sure does me. It’s something I try hard not to think about while airborne, maintly because I fly a lot better when not distracted. Of those thousands of moving parts, two kinds are the most worrisome: the ones most likely to blindside you with a costly, premature, unbudgeted-for engine overhaul or replacement, and the ones most likely to make you fall out of the sky (or at least soil your undies). The biggest offender in the safety-of-wallet category is the camshaft—and for Lycomings, the cam followers a.k.a. tappets—which prepresents by far the leading cause of premature engine teardowns. (Especially if you don’t count prop strikes, which you really shouldn’t since the prop isn’t part of the engine.) In the safety-of-flight category, hands-down the most-wanted villains are exhaust valves. Exhaust valves can ruin you day in at least two different ways: they can stick or they can […]
Tulip Fever?
“You snooze, you lose” or “caveat emptor”? The market for used GA airplanes is crazy right now. In the five decades I’ve been paying attention to such things, I’ve never seen anything like it. Other GA industry veterans I’ve spoken with all tell me the same thing. There’s an airplane buying spree going on, apparently driven by pent-up demand and historically low interest rates, and prices have been going through the roof. How crazy? Well, I’m looking at a listing for a very low-time 2021 Cirrus SR22-G6-GTS with an asking price of $1.25 million. Seriously? Cirrus’s 2021 factory price list shows a price of $886,800 for this airplane brand new, which strikes me as awfully pricey for a four-seat single-engine piston airplane. Why would anyone pay a $363,200 premium for a slightly used SR22? Perhaps because the slightly used one is available today and a new 2022 model from the factory has an 8-month wait time. Buyers have itchy trigger fingers at present, and just don’t want to wait. All this somehow reminds me of the Dutch “tulip fever” of the 1630s (admittedly slightly before my time). It was a textbook bubble then and strikes me as unsustainable now. You […]
Grading on the Curve
You can learn a lot from your airplane’s report card Jack owns a 2016 Cirrus SR22 with a Garmin Perspective glass cockpit—basically a G1000 on steroids. His MFD records tons of data on an SD card—CHTs, EGTs, oil pressure and temperature, MAP, RPM, fuel flow, altitude, TAS, electrical bus voltages and current, even GPS coordinates—and Jack regularly uploads this data to my company’s SavvyAnalysis platform. Once uploaded, Jack’s data is automatically scanned by a sophisticated machine-learning algorithm for evidence of failing exhaust valves. Whenever Jack requests it, selected flights are scrutinized by Savvy’s team of professional data analysts who prepare a comprehensive report on the health of Jack’s engine and the appropriateness of his powerplant management procedures. In addition, Jack receives regular “report cards” that graphically shows how his SR22 stacks up when compared to a “cohort” of more than 1,500 other normally aspirated Cirrus SR22s that followed by SavvyAnalysis. Jack’s report cards display numerous parameters related to performance, efficiency, longevity and health of his aircraft and its engine, and essentially “grades them on the curve” to show Jack how his aircraft is stacking up when compared to the other aircraft in his cohort. How Am I Doing? In late […]
Spring-Loaded to Teardown
Does your engine REALLY need to be euthanized? “I’m in trouble. Can you help?” The owner of the vintage Mooney was obviously stressed. He identified himself as a highly experienced military pilot but a first-time aircraft owner who’d recently flown his airplane to Florida on business. When it came time to return home, the Mooney’s Lycoming IO-360 wouldn’t start. He took it into the local shop on the field, who discovered that the left magneto’s case had cracked. Since the left magneto is the one used to start the engine in this airplane, that seemed to be the smoking gun that would explain why it wouldn’t start. The shop proposed to order a replacement magneto, and the owner approved. “Now they’re telling me the engine needs to be torn down!” he told me in a panic-laced voice. “It’s nowhere close to TBO, and I really can’t afford an overhaul right now.” “Why does the mechanic think the engine needs a teardown?” I queried, finding it hard to imagine how a bad magneto could justify something so drastic. The owner explained to me that when the A&P removed the damaged left magneto, he observed that two of the steel balls from […]
Cylinder Rescue
Low compression doesn’t always require cylinder removal Sam’s 1979 Piper PA-34-200T Seneca II was in the shop, and Sam was not happy. The shop had just done a compression test on the plane’s two Continental TSIO-360-EB3B engines and had given Sam some unwelcome news… “Compression on left #4 is 35/80 and right #3 is 31/80,” Sam reported. “These engines are factory rebuilds installed in 2014, and they’ve been flying about 150-200 hours per year. The left engine had cylinder #4 replaced less than 1,100 hours ago and now needs to be replaced again. The right engine had cylinder #3 replaced only 500 hours ago and now needs to be replaced again. Apparently, I am doing something drastically wrong with these engines. It cannot be normal to have to replace NINE cylinders in 1,750 hours—two of them TWICE! What am I doing wrong?” Repetitive cylinder removals like the ones Sam experienced often trigger such guilt feelings, but the truth is that usually it’s not the fault of the owner or pilot. More likely they’re the fault of trigger-happy mechanics who were trained that low compression automatically requires removing the cylinder. It doesn’t. What it does require is a good borescope inspection […]
Balky Alternator
Chasing down an elusive charging system gremlin Intermittent problems are the worst! They always seem to happen at the worst possible time, like when you’re in the middle of nowhere away from home base. They never seem to happen when you want them to happen, like when you’re trying to show them to your A&P so he can troubleshoot and fix them. Case in point: Nearly 30 years ago, not long after I bought my Cessna 310. I was in the middle of a 4,000-mile cross-country that took me from California to Illinois, Kansas, Oklahoma, and back home to California. I was not an A&P at the time, simply a maintenance-involved airplane owner. (The A&P would come a decade later.) The first sign of trouble occurred as I was starting engines at Champaign, Illinois headed for Wichita. With both engines running, I noted that the amber warning light marked “ALT FAILURE: R ALT” did not go out the way it should have. I didn’t know whether this was a genuine alternator failure or just a malfunctioning idiot light, but figured I’d better try to find out. I shut off the known good alternator (the left one) to see what would […]
Propwash
How often does your propeller REALLY need to get overhauled? “Your prop is due for overhaul,” says your IA who you hired to do your annual inspection. “It’s been six years.” If your airplane has a constant-speed prop, overhauling it is going to set you back about $3,000 including removal and installation labor. If it has deice boots, figure another $1,000. If you fly a twin like mine with two full-feathering constant-speed deiced props, well…ouch! Nowadays most props have a TBO of 2000 or 2400 hours and 60 or 72 months, whichever comes first. Doing the math, you’d have to average more than 400 hours per year for the 2000 or 2400 hours to come first. For most of us, it’s the calendar time component of the TBO that always comes up first. The average owner-flown GA airplane flies roughly 100 hours a year, which means that the prop will come “due” for overhaul after just 500 or 600 hours. If you fly less than 100 hours a year, it’s even worse. Do we really have to overhaul our props every five or six years regardless of how few hours are on them? Does it even make sense to do […]
Hot Heads
What to do about uncomfortably high CHT For decades now, I’ve been preaching that the two keys to piston aircraft engine longevity are avoiding extended periods of disuse and managing CHT. If you allow your engine to sit unflown for weeks at a time, you risk internal corrosion—and corrosion is the number one reason that engines fail to make TBO. If you allow your CHTs to get too hot, you increase the stress on the engine’s reciprocating components (especially connecting rod bearings and bushings, piston pins, and valves), and increase the risk of catastrophic failure from destructive detonation, preignition, and head-to-barrel separation. In a perfect word, we would have sensors in each of our cylinders measuring peak combustion chamber pressure and instrumentation that would let us see this in the cockpit. This is exactly the way engines are instrumented when they run on GAMI’s engine test stand in Ada, Oklahoma—the most sophisticated piston aircraft engine test facility in the world. But it’s not practical to install this sort of instrumentation in our aircraft, so CHT is the best proxy for internal cylinder pressure (ICP) that we have. If we want to protect our engines against excessive ICP, we need to […]
Machine Learning
This cutting-edge technology could revolutionize GA maintenance. The exhaust valve is the most likely component of a piston aircraft engine to fail catastrophically. When one fails, combustion ceases in the cylinder, the engine loses power and starts running rough. This usually results in a precautionary landing—on-airport if you’re lucky, off-airport if you’re not. It’s particularly serious with a four-cylinder engine, because a four runs a lot worse on three than a six does on five. Occasionally, the liberated valve fragment gets wedged into the piston crown, which can shatter the piston and cause a total power loss, sometimes with fatal results. That’s why it’s so important to detect incipient exhaust valve failures early before they can cause serious problems. The traditional way is the annual compression test, but that isn’t a very reliable method because loss-of-compression typically doesn’t occur until the valve is very sick and close to failing. A borescope inspection is vastly better and can detect failing valves a lot earlier. AOPA publishes a great poster to help mechanics understand what to look for—Google “Anatomy of an Exhaust Valve Failure.” Unfortunately, most shops don’t do regular borescope inspections, and the ones that do typically do them only at […]
A Mechanic’s Liability
If your A&P seems over-cautious and self-protective, there’s good reason. By Mike Busch Mechanics have always been subject to FAA sanctions: certificate suspension or revocation, fines, warning notices, letters of correction, and remedial training. But enforcement actions against GA mechanics were exceedingly rare. The most common way for a mechanic to run afoul of the FAA is to “pencil whip” a logbook entry—for example, stating that some Airworthiness Directive (AD) was complied with or some other inspection or repair was performed—and then the FAA finds that the work wasn’t actually done as documented. If a mechanic is caught “autographing a lie” by the FAA, his certificates are probably toast. That said, it’s pretty easy for mechanics to avoid getting crossways with the FAA. The regulations that govern mechanics (Part 43) are far more concise and understandable than those that govern pilots and aircraft owners (Parts 91). Part 43 contains just 13 rules and they’re remarkably straightforward. Reduced to its essentials, Part 43 simply requires that a mechanic: Pretty commonsense stuff. A mechanic who makes a good-faith effort to follow these simple rules is unlikely to get hassled by the Friendlies. Civil Liability But an A&P who complies with these regs […]
Misfueled!
When piston airplanes are fueled with Jet A, bad things can happen. On March 2, 2008, a turbonormalized Cirrus SR22 was destroyed when it crashed shortly after takeoff in Rio de Janiero, Brazil, killing all four people aboard. Shortly after the aircraft departed from runway 20, the airplane’s engine lost power, and the aircraft hit a building and exploded. Further investigation revealed that the aircraft had been refueled with Jet A instead of 100LL. On April 17, 2015, a Cessna 421B crash-landed on a highway shortly after takeoff from Lufkin, Texas, resulting in one serious and two minor injuries. According to the pilot, the aircraft seemed to perform normally during the runup, takeoff and initial climb. Passing 2,100 feet AGL, the left engine sputtered and lost all power. Within 30 seconds, the right engine also lost all power and the big cabin-class twin descended for a forced landing. The airplane landed hard, damaging the wings and fuselage and rupturing the right fuel tank, finally coming to rest in the grassy median of a highway. The smell of jer fuel was prominent at the accident scene. Investigators found that the FBO’s Jet A truck had recently had its wide duckbill-style nozzle […]
The Great Beyond (TBO)
Lessons learned from geriatric engines. Time Between Overhaul (TBO) is a strange concept. The FAA, in its infinite wisdom, requires aircraft engine manufacturers to publish TBOs for their engines, but doesn’t require aircraft owners to abide by them. You are free to continue flying behind your engine as it remains airworthy. Yet many owners and mechanics start getting nervous as they see tach time approach published TBO. Countless numbers of healthy engines are needlessly euthanized when their time-in-service approaches that consecrated number. For Part 91 operators, doing so is not an FAA requirement—it’s more like a religious belief. My Teachable Moment teach·a·ble mo·mentnoun(U.S.) an event or experience which presents a good opportunity for learning something about a particular aspect of life. [Oxford English Dictionary] My teachable moment that convinced me to stop believing in overhauling at TBO came about 30 years ago. In 1987, I purchased a Cessna 310 twin whose two TSIO-520 engines were just 100 hours shy of Continental’s published TBO of 1,400 hours. It didn’t take long for me to get there. When I did, I asked for advice from several friends who were veteran A&P/IAs. (This was long before I was an A&P myself.) Their unanimous […]
What Plane Should I Buy?
Thoughts on finding a good purchase candidate An extraordinary number of GA airplanes were bought and sold in 2020. I imagine this was somehow related to the pandemic, although I’m not sure exactly how. What I do know is that my company had been averaging about 10 prebuys per month in 2019, but by the summer of 2020 we were doing 50 prebuys per month. As I write this part way into 2021, the rate has gradually dropped back to about 30 per month, which is still much higher than it used to be. A significant number of these are first-time airplane buyers. They go online to sites like Aircraft Shopper Online, Controller, and Trade-A-Plane Online and are confronted with an overwhelming number of possible purchase candidates. Many come to me asking for help in how to narrow the field down to a few. Single or twin? Retractable or fixed gear? High wing or low wing? High-time or low-time engine or airframe? What’s Your Mission? When I’m approached for advice by a prospective buyer, my first question is generally, “How do you plan to use this airplane? What’s your typical mission?” Is the aircraft going to be used primarily for […]
Annual Deadlock
What happens when an owner and an IA can’t agree? By Mike Busch Sam is a pilot, engineer and serial entrepreneur who lives near Washington DC. About 10 years ago, he bought a 1966 Cessna 182J Skylane that is based and maintained in nearby Maryland. It’s been a pretty economical airplane to operate and maintain. Sam’s IA charges a flat-rate of $1,200 for the annual inspection, and Sam told me that “I’ve never paid more than $3,300 for an annual inspection plus repairs.” About a year ago, Sam flew his airplane to the West Coast on business. While there, the Skylane’s annual inspection came due. Sam decided to take his plane to a well-known California shop—let’s call it “Alpha Aviation”—for the inspection. Because of the airplane’s benign maintenance history, Sam didn’t anticipate any big surprises. Imagine his shock when Alpha Aviation sent him an 11-page preliminary discrepancy list itemizing 63 discrepancies, 40 of which were identified as “affecting airworthiness status.” Inspection Findings Ten of the 40 airworthiness discrepancies involved compliance with Airworthiness Directives. Some of these were routine recurrent inspections—seat tracks, ignition switch, oil filter adapter, fuel filler caps, flap actuator jackscrew—that would be expected in any Cessna 182 annual […]
How Risky is Maintenance?
An FAA review of 10 years of NTSB data tries to quantify the risk. I’ve been known preach about the virtues of maintenance minimalism—a.k.a. “if it ain’t broke, don’t fix it”—and the risk of maintenance-induced failures—a.k.a. “MIFs.” But just how risky is maintenance? How often to MIFs occur? How serious are the consequences when they do? When asked these questions, I usually lick my finger, hold it up in the breeze, and say that roughly three-quarters of GA accidents are pilot-caused and one-quarter are machine-caused. Licking again, I say that of the machine-caused ones, roughly half are mechanic-caused (i.e., MIFs). That would put the fraction of GA accidents caused by MIFs at around one-eighth give or take a few spitballs. While cleaning out my office recently and rummaging through stacks of old papers (most of which I threw in the trash), I ran into an old FAA study that might shed a little more light on this subject, and help quantify the risk of maintenance more accurately than my aforementioned spit balling. Published in December 2002, the FAA study titled General Aviation Maintenance-Related Accidents: A Review of Ten Years of NTSB Data analyzed NTSB accident investigation reports involving GA accidents […]
How Mags Fail
Preventing and dealing with magneto-ignition system failure. Both the FARs and their predecessor CARs require that certificated spark-ignition recip-rocating aircraft engines—the kind most of us fly behind—have fully redundant dual ignition systems: PART 33—AIRWORTHINESS STANDARDS: AIRCRAFT ENGINESSubpart C—Design and Construction; Reciprocating Aircraft Engines§ 33.37 Ignition system. Each spark ignition engine must have a dual ignition system with at least two spark plugs for each cylinder and two separate electric circuits with separate sources of electrical energy, or have an ignition system of equivalent in-flight reliability. There’s a good reason for this: Ignition system failures are relatively commonplace. Without a properly functioning ignition system, the engine could quit, the airplane could fall out of the sky, and people could get hurt. How often do ignition systems fail? Well, spark plug failures happen a lot, but the consequences aren’t usually serious—usually they’re not even noticeable—precisely because we have two spark plugs in each cylinder, and one is enough to keep the cylinder producing power. Usually, the only sign that a spark plug has failed in-flight is that the EGT on the affected cylinder rises by 50°F or so. Unless you have an engine monitor installed and keep it in “normalize mode” […]
How Mags Work
The spark plugs in most piston aircraft engines are still powered by 120-year-old technology. My airplane’s piston engines utilize a magneto ignition system. If you’re flying a certificated airplane, chances are good that yours does, too. The fact that we’re still stuck with these superannuated mechanical black boxes is a testament to just how hard it is to get modern technology FAA-certified. Magneto ignition first appeared on the 1899 Daimler automobiles, and high-voltage magnetos were introduced by Bosch in 1903. Mags were largely abandoned in autos in the 1920s in favor of battery-powered ignition. Electronic ignition systems (EIS) are almost universally used on experimental amateur-built aircraft but are still quite rare on certificated airplanes thanks to FAR Part 33 (“Airworthiness Standards: Aircraft Engines”) which remains firmly routed in the Dark Ages. The S-1200 magnetos on my airplane are essentially indistinguishable from the ones that Bendix built in the 1940s. Since so many of us are still flying behind these archaic “tractor mags” it’s probably a good idea for us to understand how they work. A high-voltage magneto is a self-contained ignition system that converts mechanical rotation into high-voltage pulses that are used to fire the spark plugs and does so […]
It’s Baffling
Rigid baffles and flexible baffle seals are critical in keeping your engine cool. The Cessna T210 owner was clearly frustrated with his new engine installation: “I recently had my engine rebuilt and had a new baffle kit installed. The CHTs for cylinders #5 and #6 are always 20ºF to 30ºF hotter than the rest. During climb the difference gets even bigger. Cylinder #5 and #6 CHTs are very difficult to keep below 400ºF during a climb, even with the cowl flaps open and full-rich mixture. Should I consider giving them some air? On cylinder #6, why not cut one or more holes in the white aluminum baffle in front of the cylinder? On cylinder #5, why not drill one or more holes in the horizontal aluminum plate located behind the oil cooler?” After looking at the marked-up photo from the T210 owner, I replied that cutting holes in the baffles was definitely NOT a good idea, and that doing so would undoubtedly make the cooling problems worse, not better. It was apparent that this owner didn’t understand how the powerplant cooling system in his aircraft works, or what the function of the baffles is. He’s not alone—some A&P mechanics don’t […]
Good Eyes! Great Catch!
Maintenance-induced problems are common, and it often an experienced pair of eyes to diagnose them. Elko Regional Airport (KEKO) is located in northeast Nevada at an elevation of 5,000 feet above sea level, and is known for its competitive avgas prices. It’s pretty much in the middle of nowhere…but if you happen to be flying from the Pacific Northwest to Arizona, KEKO is a convenient midway fuel stop. That’s exactly what Jack was doing one fine Thursday afternoon in his Cirrus SR22 Turbo. The airplane had been performing flawlessly, so after landing at Elko Jack was floored to find engine oil dripping out of the left exhaust stack and streaked along the left underside of the fuselage. This is not the sort of thing that you want to see when you’re in the middle of nowhere. Jack checked with the FBO but their A&P had gone home for the day. He phoned Savvy Aviation’s 24/7 hotline number and quickly got a callback from Tony Barrell A&P/IA, one of Savvy’s most experienced account managers and former director of maintenance at a large Cirrus Service Center. Remote Diagnosis Jack sent Tony several smartphone photos of his oil-covered airplane. “No mechanic is available […]
Your Engine’s Lifeblood
There’s a lot more to piston aircraft engine oil than you might think When it comes to piston aircraft engines, the role of engine oil is complicated. It lubricates moving parts to reduce friction and wear, but that’s only one of six key functions it performs, and perhaps not even the most important one. The lubrication requirements of slow-turning direct-drive Continentals and Lycomings that most of us fly behind are really quite modest compared to the high-revving engines in our automobiles. Lubrication demands tend to vary with the square of RPM, so a car engine with a 7000 RPM redline has vastly more demanding lubrication requirements than an aircraft engine with a 2700 RPM redline does. Lubrication vs. Friction & Wear Friction occurs because even the smoothest metal surfaces have microscopic peaks and valleys known as asperities. Whenever surfaces come in contact, these asperities adhere to one another via tiny micro-welds. If those surfaces are in relative motion, the micro-welds constantly fracture and re-form, resulting in friction and wear. Friction is the resistance to relative motion and wear is the loss of material. Both are due to the fracture of the micro-welds. The purpose of lubrication is to reduce friction […]
The Looming Mechanic Shortage
What if your airplane breaks and there’s no one to fix it? Being a dyed-in-the-wool technology freak, I drive a Tesla Model 3. It has been a superbly reliable vehicle that doesn’t require maintenance very often. But when it does, I take my Tesla to the nearest Tesla dealership, where it is worked on by factory-trained mechanics who work on nothing but Teslas all day long and know them like the backs of their hands. The situation was very similar in 1968 when I bought my first airplane, a brand new 1968 Cessna 182 Skylane. I based it at what is now called “John Wayne Airport” in Santa Ana, California. In those days, there were three big aircraft dealerships on the field: a Cessna dealer, a Piper dealer, and a Beechcraft dealer. When my Skylane needed maintenance ,I took it to the Cessna dealership on the field who employed a half-dozen factory-trained A&Ps who worked on nothing but single-engine Cessnas all day long and knew them like the backs of their hands. The Cessna dealership also had a parts room to die for, so when my airplane needed some component to be replaced it was likely to be in stock. […]
Fresh Annual
Why it’s no substitute for a proper independent prebuy. Every month I receive hundreds of emails from aircraft owners seeking advice or assistance. For the most part, I genuinely enjoy these interactions and the opportunity to help fellow aircraft owners. Occasionally, however, I run into something that I find deeply disturbing. That was the case with a message I received recently from a 60-hour student pilot—let’s call him Dan—who had just purchased his first airplane in Texas and flown it back home to California accompanied by his flight instructor. The aircraft in question was a 1974 Piper Warrior PA-28-151. “Part of my deal with the previous owner was that he would have a complete annual inspection performed and any airworthy discrepancies corrected before I took delivery,” Dan said in his email. “The annual was completed with no squawks in mid-February and I flew it back from Texas in early March.” “The airplane seemed okay on the ferry flight to California,” Dan continued, “except for the rate-of-climb which was averaging only 300-500 feet per minute. I guess we didn’t really notice it since all the airports we used had long runways. But after getting it back to my home field in […]
Why Valves Stick…
…and how you can avoid engine damage and power loss if you know the answer. If you fly behind a Continental or Lycoming, each of your engine’s cylinders has two valves, intake and exhaust. The valves open and close by sliding in and out through close-tolerance tubes called valve guides that are press-fit into the cylinder heads. The valves are opened by a valve train consisting of a cam lobe, a lifter (tappet), a pushrod, and a rocker arm. They are closed by a pair of strong concentric valve springs. A sticking or stuck valve is one that no longer slides smoothly in and out through its valve guide. This can happen when there is a build-up of deposits on the valve stem and/or inside the valve guide. Of course, you knew all that. What you might not know is what these deposits are made of (it’s not carbon), what causes them to form (it’s not heat), what happens when they do (it’s not pleasant), and how you can prevent this from happening (it’s not hard). Morning Sickness and Worse If the valve guide isn’t excessively worn, there’s not much clearance between the guide and the valve stem. The clearance […]
Justice Denied?
When it comes to GA crashes, the NTSB doesn’t always get it right, nor does the jury In December of 2012, a father and his son arrived at the airport to pick up the father’s Cessna 421C cabin-class piston twin, which had been in the maintenance shop for months receiving a new paint job and an annual inspection. Both father and son were experienced multiengine pilots. The son had earlier flown the aircraft on an hour-long post-maintenance test flight with a mechanic in the right seat. The test flight revealed that the left engine’s RPM was 100 RPM over red-line and its fuel flow was a couple of gallons per hour low. After landing, the mechanic made adjustments to the left engine’s RPM and fuel flow and corrected a few minor cosmetic issues. The plan was for the son to fly the aircraft to a nearby airport that was its home base, and for his dad to drive to meet him there. The pilot ran up the engines on the ramp in front of the shop for several minutes before taxiing to the departure runway of the non-towered airport. According to the mechanic who watched the takeoff, the airplane lifted […]
Predictive Maintenance
Condition-based maintenance meets big data and artificial intelligence For the past 20 years, I’ve been preaching the gospel of Reliability-Centered Maintenance (RCM), the then-revolutionary philosophy of maintenance developed in the 1960s at United Airlines by aeronautical engineer Stanley Nowlan and mathermatician Howard Heap. RCM was almost universally adopted by the airlines in the 1970s, by military aviation in the 1980s, and by high-end business aviation in the 1990s. The only segment of aviation that hasn’t yet enthusiastically adopted RCM is owner-flown GA. I’ve made it my personal crusade to change this, and to help drag lightplane maintenance kicking and screaming into the 21st century. RCM arose from a rigorous analysis of historical data by Nowlan & Heap showing that the airlines’ maintenance programs called for more preventive maintenance than necessary, and that such excessive maintenance was actually making aircraft safety and dispatch reliability worse rather than better by increasing the incidence of maintenance-induced failures (MIFs). At the time, these findings were considered heresy by most folks in the airline maintenance organizations, who had been taught to believe that maintenance is a good thing and more maintenance is always better. In spite of these objections, the airlines adopted RCM anyway. Not […]
Hot Seat
Is it legal to install uncertified equipment in a certificated aircraft? I receive and answer hundreds of emails each week from aircraft owners, pilots and mechanics who have maintenance-related questions. One I received several weeks ago seems worth sharing: Mike, I need your help. I am a member of flying club, and during the recent annual of our club Skyhawk someone got the bright idea to install automotive seat heaters in the plane without an STC or Form 337. This seems like it might be a violation of the regulations. Is it? Why would our club’s A&P participate in the installation of uncertified equipment and then sign off the aircraft as airworthy? Should I question all the other work this A&P performed? Should I report him to the local FSDO? This pilot’s strong reaction was clearly predicated on his understanding that all equipment in a certificated aircraft must be FAA-approved. Lots of aircraft owners and mechanics believe the same thing. I’ve even heard FSDO inspectors say this. But this common misconception is simply wrong. Let’s examine why. A bit of Googling revealed that there are two kinds of aftermarket automotive seat heaters available: external heating pads that attach to the […]
Risky Business
Why it’s nearly impossible to install a cylinder properly when the engine is on the airplane. Cylinder replacement is a highly invasive and risky procedure with a long history of causing catastrophic in-flight engine failures that cause airplanes to fall out of the sky. I have been personally involved with at least a half-dozen of these maintenance-induced catastrophic engine failures—either as expert witness or investigator—where the engine either “threw a rod” through the crankcase or suffered the complete separation of a cylinder from the engine, resulting in a total loss of power. In some cases, the pilot made a successful forced landing; in others, the outcome was serious injury or death. Cylinder replacement—and especially replacement of multiple cylinders at once—is a procedure that needs to be executed perfectly. If it isn’t, there can be dire consequences. Yet it’s a procedure that most career general aviation A&Ps perform routinely without any apparent concern. Why aren’t these mechanics nervous? Undoubtedly because they are convinced that they always perform the cylinder transplant procedure properly, and that only careless or incompetent mechanics screw it up. That’s wrong, and here’s why. Is “properly” impossible? Roger D. Fuchs—veteran A&P/IA, aircraft engine overhauler, accident investigator, expert witness, […]
Shear Joints
When using fasteners loaded in shear, things can get interesting. Last month, I wrote about joints involving threaded fasteners loaded in tension—that is, along the bolt’s longitudinal axis. Such “tension joints” are used to fasten connecting rods to crankshafts, cylinders to crankcases, and even occasionally wings to fuselages (notably in Beechcraft airplanes). I emphasized the critical importance of fastener preload to the structural integrity of such joints and discussed why the most common method of tightening such fasteners (using a torque wrench) is not a particularly good way to establish the correct preload. But, there’s an entirely different kind of bolted joint: one where the fastener is loaded at right angles to the fastener’s axis. If the plane you fly isn’t a Beechcraft, chances are your wings and tail surfaces are attached to the fuselage by such “shear joints.” In fact, if you fly an aluminum spam can (like I do), it probably has thousands of shear joints—rivets are virtually always loaded in shear, not in tension. However, chances are that the shear joints that fasten your wings and tail feathers use bolts, not rivets, to facilitate them being de-mated from the fuselage. Shear Strength The strength of most shear […]
Tense Bolts
When using threaded fasteners in tension, it’s all about the preload. Threaded fasteners are ubiquitous in aviation. Look at any GA aircraft and you’ll find hundreds of them if not thousands. They attach wings to the fuselage, cylinders to the crankcase, connecting rods to the crankshaft, and instruments and avionics to the panel. They hold on cowlings, fairings, inspection plates, floorboards, and just about anything else that might need to be removed to gain maintenance access. They’re so numerous and so familiar that we tend to take them for granted. But, when used in safety-critical high-stress applications—like holding on wings, cylinders and connecting rods—there’s complexity to threaded fasteners that is often not well understood or fully appreciated by the maintenance personnel who are responsible for ensuring that they’re safe and secure. Mechanics often don’t treat these critical fasteners with the respect they deserve. The result can be scary. Threaded fasteners go by a variety of names. As a general rule, they are called “bolts” if they are designed to mate with one or two threaded nuts, “screws” if they are designed to mate with a threaded hole in one of the items to be joined, and “studs” if they are […]
Hostage Situation
Don’t fall victim to an overzealous mechanic. Mark is the owner of a beautiful Cessna 185 Skywagon based in the San Francisco Bay area. Awhile back, Mark and his wife travelled to Minden, Nevada in this airplane to visit with Mark’s mother-in-law who was ill. A few days later, they returned to the airport intending to fly home. But when Mark started the Skywagon’s engine—a Continental IO-520—he saw just about the last thing a pilot wants to see: The oil pressure gauge never budged from the zero mark. [Expletive deleted.] After a brief period of “this can’t be happening!”, mark shut down the engine and started thinking about what to do next. It was a Sunday, of course. (These things always happen on weekends when all the maintenance shops on the field are closed.) The only sign of life at this non-towered airport was the presence of a couple of linemen at the airport’s sole FBO. Mark approached one of the linemen and asked if he knew of any A&P mechanics in the area that might be able to help with his predicament. The lineman rummaged around in the office and emerged with the phone number of a local A&P […]
Evicted
Thoughts about being temporarily booted out of my hangar. From the time I first acquired my Cessna 310 in 1987, it has been hangered at Santa Maria Public Airport. Initially, I kept it in a large community hangar. Then in 2003, after a long wait on the airport hangar list, I was able to secure a hangar of my own rom the airport. My hangar is 40 feet wide and 30 feet deep. It easily accommodates my Cessna 310 with lots of room to spare. There’s space for my workbench, my toolbox, a large couch, refrigerator, microwave, and two large shelving units where I keep spare parts, hardware, chemicals and such. It’s not quite as comfortable as some of my neighbor’s hangars—no carpeting, Wi-Fi, or large-screen TV—but it has been a great place to store and work on my airplane over the past 16 years. At first my rent for this nice big hangar was $461 per month. Over the 16 years I’ve occupied it, the rent has gradually increased to its present $692 per month. Still, as hangar rents go, I consider it to be a great deal. If I was based near Los Angeles or San Francisco or […]
What is Preventive Maintenance?
What may you do to your aircraft without A&P involvement? More than you might think. The FAA defines who may perform maintenance on certificated aircraft in FAR 43.3. This rule lists all the usual certificated suspects: mechanics, repair stations, air carriers, repairmen employed by a repair station or air carrier, and (under certain conditions) aircraft, engine, propeller and appliance manufacturers. The rule also permits maintenance to be done by ordinary non-certificated folks provided it’s done under the supervision of and approved by a certificated mechanic. Beyond that, FAR 43.3 permits a pilot to perform preventive maintenance on an aircraft owned or operated by that pilot, provided the aircraft is used strictly for non-commercial operations under Part 91. Pilots may do this all by themselves without any A&P involvement. How cool is that? What exactly is this preventive maintenance stuff that pilots are permitted to do on their own recognizance? Ah, there lies the rub! The phrase “preventive maintenance” is defined in FAR 1.1 (Definitions) as follows: “Preventive maintenance means simple or minor preservation operations and the replacement of small standard parts not involving complex assembly operations.” That’s about as clear as mud. What exactly are preservation operations? Which ones are […]
FAA’s Safety Continuum
The Friendlies are remarkably friendly to Part 91 folks Aircraft owners and pilots love to bash the FAA. We grumble and whine about all the labyrinthine regulations and requirements the Agency burdens us with, and how much it increases our complexity and cost of flying. I’m occasionally guilty of this myself—witness my “Double Standard?” column in last month’s AOPA PILOT in which I kvetched about the FAA’s failure to require A&Ps to undergo recurrent training and re-evaluation. In truth, we Part 91 operators have it pretty darn good compared with our brethren in almost every other nation on the planet. We also have it exceptionally good compared with charter operators (Part 135) or air carriers (Part 121) or large aircraft in non-commercial operations (Part 125). This isn’t by accident. It’s in accordance with one of the FAA’s most fundamental guiding principles—something the Agency polysyllabically calls the “Safety Continuum.” “Safety Continuum: The level of safety established by regulation, guidance and oversight that change based on risk and societal expectations of safety. The safety continuum applies an appropriate level of safety from small UAS to large transport category aircraft. The differing level of safety balances the needs of the flying public, applicants and […]
Double Standard?
Why aren’t A&Ps trained as well as pilots are? I never really wanted to become an A&P. All I really wanted was to be able to maintain my own airplane without adult supervision. Heck, I’d been doing virtually all the maintenance of my 1979 Cessna Turbo 310 myself for about 10 years. The various A&Ps who had agreed to supervise me all agreed that I now knew more about the maintenance aspects of my than any of them did. It seemed like high time for me to take full responsibility for my work and be able to sign it off. All I really wanted was something like the Limited Repairman Certificate that the FAA grants to the builder of an Experimental Amateur-Built (E-AB) aircraft that permits them to maintain their own machine. I had absolutely no desire to swing wrenches on any aircraft other than my own. Sadly, the FAA offers nothing comparable for the owner of a certificated aircraft who wants to do his own maintenance (although I certainly wish they did). My only option was to earn an A&P mechanic certificate. It was an all-or-nothing proposition. The FAA sure doesn’t make it easy to earn an A&P certificate. […]
I Wanna Sue!
When things go awry in the sky, litigation isn’t necessarily the best remedy. My email inbox contained a message with the subject “Legal Question – Advice Needed.” That didn’t surprise me because although I’m not a lawyer, I do regularly participate in aviation litigation—mostly arising from air crashes—as an expert witness and consultant, mainly in cases that involve mechanical or maintenance issues. The email was from a private pilot who owned a Liberty XL2 that he purchased used nine months earlier. After he flew the aircraft for about 80 hours, the aircraft’s Continental IOF-240-B engine developed a serious engine problem that revealed itself by a low oil pressure indication. The owner’s mechanic ultimately traced the problem to the cluster gear on the rear of the engine’s crankshaft, which was found to be damaged where the starter pinion engaged the cluster gear at each engine start. “The metal from the damaged gear contaminated the engine and ultimately caused catastrophic damage to the engine,” the owner explained. “I was very lucky that I was not in flight as I was holding short and just seconds from takeoff clearance when I noticed the low oil pressure alarm. The engine still ran and I […]
A Matter of Policy
Understanding aircraft insurance If you own an aircraft, you probably have aircraft insurance. Whether it’s the right amount of the right coverages is worth exploring. Here’s what I’ve learned in my 50+ years of aircraft ownership plus extensive discussions with veteran industry insiders who have forgotten more than I’ll ever know on the subject. Anatomy of a policy All insurance policies are contracts in which the insurer promises to pay benefits to the insured if certain defined events occur, provided that the insured has paid the agreed-to premium and met certain other conditions. Policies are contracts of adhesion, meaning that the insurer drafts the contract and offers it on pretty much a take-it-or-leave-it basis. This can pose a trap: Insureds rarely receive a copy of the policy until after they’ve already agreed to it, and even then they rarely read it. The good news is that courts tend to interpret any policy ambiguities in favor of the insured. Insurance policies can appear intimidating, but they’re not that complicated. They consist of two sections: a declaration (which identifies the insured, the insurer, the policy period, the premium amount, the kinds and maximum limits of coverage, and any applicable deductibles), and the […]
Rush to Judgment
Before doing something expensive or invasive, slow down “My Cirrus SR22’s oil pressure has been slowly decreasing,” reported Oliver, one of my company’s managed maintenance clients. “At full power the pressure used to be 41-43 PSI, but over the past three months it has dropped to 36-39, and half the time I get a low oil pressure warning at idle. Should I get this checked now, or wait until the annual?” Oliver’s account manager Eric—a very experienced A&P/IA and one of the savviest engine guys in our company—advised that this should be checked sooner rather than later. “Oil pressure in the 30s is too low,” Eric told Oliver. “I would actually prefer to see it around 50 PSI. It’s easy to adjust oil pressure. Let’s have that done no later than the next oil change.” Oliver normally has his airplane maintained at the small shop on his home field, but the shop was booked solid and told Oliver that they couldn’t put his plane on the shop schedule for at least three or four weeks. Oliver checked with several other small shops, who all told him the same story. Now quite concerned about his decreasing oil pressure and wanting to […]
Preheating: Whys and Hows
Not preheating a cold engine is a effective way to damage it Preheating is important. A single cold start without proper preheating can produce more wear on your engine in less than a minute than 500 hours of normal cruise operation I’m often asked how cold it has to be before preheating is necessary. There’s no hard and fast answer, because the damage done by an unpreheated cold start depends on a variety of things, including the type of engine, its age and condition, and what kind of oil is being used. A brand new or freshly rebuilt or overhauled engine is more vulnerable to cold start damage than a tired old engine at TBO. Generally, I consider any start in which the engine is cold-soaked to a temperature below freezing (32°F or 0°C) to be a misdemeanor and any start below about 20°F (–7°C) to be a felony. The colder the temperature, the worse the crime (and the ensuing punishment). A common misconception is that the main reason cold starts are bad for engines is that the engine oil is thick and viscous and doesn’t flow well. Since it takes longer for oil pressure to come up when the […]
Powerplant Resurrection
Reviving an engine that has been inactive for months or years Piston aircraft engines hate to sit unflown. During lengthy periods of disuse, the protective oil film strips off critical surfaces like cylinder walls, cam lobes and tappet faces, exposing them to risk of corrosion pitting. Then afterwards, when the engine is finally “dry started” with the oil film depleted, these critical surfaces can be subject to abnormal friction and wear until oil flow is restored and these splash-lubricated surfaces get coated with oil once again. The engine suffers as a result. Unfortunately, this sort of thing happens a lot. My own Cessna 310 was grounded on November 1st when its annual expired. My planning was to complete the annual in December, but I wound up catching a nasty virus that had me confined to quarters for a couple of weeks. Now it’s looking like the plane won’t be ready to fly again until late January. My engines are not happy about this. Recently I was contacted by a pilot who acquired a 1968 Shrike Commander that had been sitting unflown in a hangar in Oregon for the past 14 years. The new owner asked me for suggestions on how […]
Errors of Distraction
When mechanics get interrupted, bad things can happen I was recently contacted by the owner of a Cessna Hawk XP (R172K)—I’ll call him “Sam”—who seemed rather shaken by a recent series of events. He told me he was a student pilot with solo flight privileges and ready to make his first solo cross-country flight in pursuit of a private pilot certificate. Sam and his CFI had flown the Hawk from its home base to a small well-regarded maintenance shop at a nearby airport for some adjustments to the fuel system of the airplane’s Continental IO-360 engine. At the shop, the A&P/IA—I’ll call him “Rick”—found leaks in the system and recommended that the fuel system be removed sent out for overhaul. Sam agreed to this, and since this would ground the plane for several weeks and its annual inspection was coming due not long afterwards, Sam asked Rick to perform an annual inspection on the airplane while the fuel system was being overhauled. About six weeks later, Rick called Sam to advise that the aircraft was ready for pickup. Sam and his CFI went to the shop to fly the plane back to its home base. They pre-flighted the aircraft and […]
Breaking Good
Taking the complexity out of cylinder break-in From time to time, every piston aircraft owner faces the question of how best to break-in new cylinders. Sometimes this involves just one or two newly-replaced cylinders, other times all cylinders have been replaced simultaneously (“top overhaul”), and yet other times the entire engine has been major overhauled or exchanged for a new or rebuilt. Regardless, the cylinders must be properly broken in. It’s not hard to do this, but it’s also not hard to screw it up and that can be a costly and frustrating mistake. If you Google the phrase “aircraft cylinder break-in” you’ll be amazed at how much has been written on this subject. Each engine manufacturer has a service bulletin to provide guidance on how to do this (e.g., Continental M89-7R1, Lycoming SI 1427B), as do manufacturers of PMA cylinders (e.g., ECi, Superior). Many well-known engine overhaul shops provide their own break-in instructions (e.g., RAM, Penn Yan, Victor), and various type clubs have also weighed in on the subject. Even Shell Oil has written its own break-in recommendations. If you digest this myriad guidance, you’ll probably find yourself seriously confused. Although there are some common threads that everyone seems […]
Just Inspect It, Please
Mechanics should never make repairs without owner approval The co-owner of a Beechcraft Bonanza emailed me that his airplane had been inspected and maintained by a trusted mechanic at his home field in California until this year, when the mechanic retired. Forced to use another shop for this year’s annual inspection, the owner and his airplane partner carefully chose one that his type club recommended as “a center of excellence” for Beech airplanes. “We were shocked by all the items requiring repair or replacement, and by the cost of doing that work. We may just have had the benefit of affordable work done all these years, or we may have been overcharged and taken advantage of by this new-to-us shop.” The owner attached the shop’s invoice, which contained 24 line-items describing what was done. The invoice total was something north of $15,000, more than three times what the owners had been accustomed to spending at annual inspection time. Dissecting the invoice The top item on the invoice was $2,660 for the annual inspection itself. It covered 28 hours of labor at $95 per hour, a figure that I considered fair and reasonable for a flat-rate annual inspection of a Bonanza. […]
Post-Maintenance Checklist
What to do when you pick up your aircraft from the shop My company employs 14 A&P mechanics, 11 of whom are very seasoned IAs with decades of GA maintenance experience. The other day, one of them was asked by a client what he should look for during the preflight immediately following an annual inspection. The IA decided it might be useful to create a post-maintenance checklist for owners, so he posed the client’s question to our whole group. A vigorous discussion ensued. Many owners incorrectly assume that when an aircraft completes its annual inspection, it has been thoroughly scrutinized by well-trained eyes and can be depended upon to be in condition for safe flight. Mechanics know better. The first flight after maintenance is by far the most likely time for something to go wrong with the machine. After all, it has just been partially disassembled, inspected, and then reassembled. While the inspection process is intended to uncover discrepancies, the reassembly process is vulnerable to human error which can result in maintenance-induced failures (MIFs). Obvious stuff Our group started tossing out ideas about what owners should look for after maintenance in addition to their usual preflight items. Initially, the discussion […]
Operating Oversquare
The myriad benefits of high manifold pressure and low RPM I bought my first airplane at age 24 shortly after I relocated from New York to California. It was a brand new 1968 Cessna 182 Skylane that I picked up at the Cessna delivery center in Wichita, and flew home to California. In preparation for that momentous event—and to make my insurance underwriter happy—I got a very thorough checkout in a flight school Skylane with a very senior CFI. This was my very first “complex” airplane. All my time up to that point had been in Cessna 150s and 172s and Cherokee 140s—all airplanes with fixed-pitch props and primitive engine instrumentation. Knowing this, my instructor placed a lot of emphasis on teaching me how to use the Skylane’s constant-speed propeller, and how to manage the powerplant using manifold pressure (MAP) and RPM and EGT. One thing the CFI stressed repeatedly was the importance of never operating the engine “oversquare”—that is, with MAP greater than RPM/100. Under his persuasive tutelage, I was taught that a “square” power setting of 25 inches and 2500 RPM was acceptable, an “undersquare” one of 23 inches and 2500 RPM was even kinder to the engine, […]
Turbo Failures
They can be deadly if the pilot hasn’t been taught what to do The release of my book Mike Busch on Engines prompted lots of reader correspondence. One particularly interesting email came from the owner of a 2007 Cessna Turbo Stationair (T210H)—I’ll call him Chuck—based in Aspen, Colorado: I am terrified of the turbocharger. There have been several fatal accidents in Cessna T206s and T210s caused by turbocharger failures. Worse, there does not seem to be any way to determine the condition of the turbocharger or wastegate other than visual inspection during an annual. Even then, it doesn’t seem as if we can tell much about turbocharger condition by simple visual inspection. I replied to Chuck that I’d been flying behind turbocharged engines for more than 30 years and that a turbocharging system was nothing to be frightened of, provided that it’s inspected and maintained conscientiously. I added that I had personally experienced an in-flight turbosystem failure in my own airplane several years ago and that it was no big deal: The engine simply reverts to being normally-aspirated. Chuck offered his opinion that at least two fatal Lycoming-powered T206 accidents involving turbocharger failure may have been caused by engine stoppage […]
Piston Powerplant Progress
It has been a lot like watching paint dry I recently completed work on my second book, a 500-page monster titled Mike Busch on Engines (available on Amazon). It was a yearlong effort that involved reviewing hundreds of my past articles about piston aircraft engines, deciding which were still relevant, organizing them into a coherent series of sections and chapters, and bringing it all up-to-date. In the process, I couldn’t help but reflect on what has changed in the 50 years since I bought my first airplane…and what has stayed the same. For the most part, the engines themselves haven’t changed much. The Continental TSIO-550-K that powers the new-production Cirrus SR22T is not much different from the Continental TSIO-520-BBs that power my 1979 Cessna Turbo 310, and those are both close second cousins to the Continental O-470-R that powered my first airplane, a 1968 Cessna 182 Skylane. The Lycoming IO-360-M1A that powers the new-production Diamond DA40 XLS is nearly indistinguishable from the Lycoming IO-360-A1B6 in the 1971 Cessna 177RG Cardinal owned by my editor Colleen Keller. The Continental O-470, TSIO-520 and TSIO-550 type certificates were issued in 1952, 1956, and 1980 respectively. The Lycoming IO-360 was certified in 1960 as […]
Fire in the Hole
Spark plugs start the fire going, and need some TLC We all know what aircraft spark plugs do: They accept high-voltage pulses from a magneto or electronic ignition unit and produce an electric spark inside the cylinder’s combustion chamber to ignite the air/fuel mixture and initiate a flame front. They do this about 20 times per second under hostile conditions of extreme temperature and pressure. A spark plug has three coaxial components: a center electrode, a ceramic insulator, and steel barrel. The barrel is threaded on both ends; one end screws into the cylinder head and the other end mates with the ignition lead. The insulator is made from aluminum oxide ceramic to provide good strength, thermal conductivity and dielectric properties. The center electrode comes in two flavors: massive and fine-wire. Magic decoder ring My twin Cessna has a dozen URHB32E spark plugs installed in the left engine and a dozen RHB32Es installed in the right engine. These cryptic-looking part numbers tell a lot about the characteristics of my spark plugs, so let’s take a moment to decode them. The “U” prefix on my left-engine plugs simply means that they come from Tempest Plus, one of the two U.S. firms […]
An IA’s Dilemma
“Autographing a lie” is the worst FAR violation a mechanic can commit By Mike Busch | A&P/IA An IA is an experienced A&P mechanic who—by virtue of having earned an Inspection Authorization—is empowered by the FAA to make aircraft airworthiness determinations in connection with annual inspections and major repairs and alterations. This is a weighty responsibility that IAs take very seriously. The late, legendary Bill O’Brien—who for many years served as the most senior mechanic in the FAA—once described the role of an IA as “a one-man FAA-Approved Repair Station.” From time to time, IAs find themselves facing tricky situations. That was certainly the case with one IA from Utah—let’s call him Rick—who recently contacted me for advice. Rick was halfway through a routine annual inspection on a 1982 Cessna 172 when he learned something that created a dilemma for him. As Rick related it to me, he was having a chat with a friend—let’s call him Fred—who is also an IA and whose shop is right next door to Rick’s. When Rick mentioned to Fred that he was doing an annual on this particular 172, Fred said that he was familiar with the airplane. Some months earlier, the Skyhawk’s […]
The Bottom End
What’s inside your engine’s crankcase? Reciprocating aircraft engines come in a variety of different cylinder arrangements—radial, inline, V, and opposed—but most engines used in piston general aviation are horizontally opposed four- and six-cylinder engines. These engines have two banks of cylinders—left and right—directly opposite each other, with a single crankshaft between them. The crankshaft is enclosed in a crankcase, which also contains the camshaft, connecting rods, bearings, gears, and various other components that are collectively referred to as “the bottom end” of the engine. It’s bad news if something goes wrong with any of these bottom-end components, because it’s necessary to remove the engine from the aircraft and “split the case” to gain access, and that gets expensive. Crankcase Think of the crankcase as the engine’s ribcage. Besides supporting itself, the crankcase supports all the other components of the engine—internal ones like the crankshaft and camshaft, and external ones like the cylinders and engine-driven accessories. It must provide a liquid-tight enclosure for the lubricating oil that bathes the bottom-end components when the engine is running. It also incorporates provisions for attaching the powerplant to the airframe. Crankcases are typically made of cast aluminum alloy that is both lightweight and strong. […]
Where Fuel and Air Meet
Basics of piston aircraft engine fuel metering systems If you fly a piston aircraft, chances are it has a spark-ignition (SI) engines that burns gasoline. There also exist compression-ignition (CI) engines—also called diesels—that burn kerosene, but in today’s GA fleet they’re still few and far between. While CI engines spray liquid fuel at high pressure directly into the combustion chambers, SI engines combine air and gasoline together to form a combustible air-fuel charge that is ingested into the combustion chambers and then ignited electrically by spark plugs. To be combustible, the charge must have an air-fuel ratio between 8-to-1 and 18-to-1 by weight. Anything less than 8-to-1 is too rich to burn, and anything more than 18-to-1 is too lean to burn. The chemically perfect mixture—what a chemist would call “stoichiometric”—has an air-fuel ratio of about 15-to-1 by weight, and the mixtures we actually use when flying tend to be fairly close to that ratio. The process of creating a combustible charge with the desired air-fuel ratio is called “metering” and it’s not as easy as it sounds. The hard part is to keep the air-fuel ratio constant at all power settings and altitudes, and to do so in a […]
Planes and Cars
Some thought-provoking comparisons I received a thought-provoking email from AOPA PILOT reader Nate Bissonette of St. Paul, Minnesota that started me thinking about differences between automobiles and GA airplanes. According to data from the U.S. Department of Transportation, the average American driver puts in 13,474 miles behind the wheel each year. Males drive more than females: 16,550 versus 10,142 miles per year; I’m not sure why. The same study indicates that the average vehicle speed is a maddeningly slow 32 miles per hour, which probably says something about how much time we spend in traffic and waiting at stop signs and red lights. Nate suggested a thought experiment in which our cars were equipped with Hobbs meters. Divide 32 mph into 13,474 miles to calculate that the average automobile would put roughly 421 hours on its imaginary Hobbs every year. These days, most piston aircraft engines have 2,000-hour TBOs. What if cars did, too? At 421 hours per year, your car engine would reach TBO in about 4 ¾ years and the odometer would read about 64,000 miles. “When’s the last time you heard of somebody driving a Toyota Corolla that needed major engine work at 64,000 miles?” Nate asked […]
Making Metal Behave
How we coax metal aircraft parts into doing what must be done Metal is neat stuff. It’s strong, hard, and tough. It’s easy to form, work, shape and machine. It’s fireproof and can stand up to high temperatures. But these properties aren’t unique to metal. Ordinary cotton fiber actually has higher tensile strength than the aluminum alloys we use to build airplanes, and Kevlar is stronger than even high-tensile strength steel. Diamond and carbides (artificial diamonds) are harder than the hardest metals. Ceramics can withstand heat that would cause metal to melt. Wood is easy to shape and machine, and aviation-grade Sitka spruce is nearly as strong as aluminum alloy, at least if the stress is applied with the grain What makes metal so useful is that it exhibits all of these properties. You might say that metal is the Cessna Skylane or Piper Dakota of aircraft construction materials—it may not be the best at any particular thing, but it sure does a lot of things well. Stress/strain, elastic/plastic What primarily sets metal apart from other materials is how it deforms when a force is applied to it. Metallurgists call the applied force “stress” and the deformation it causes “strain.” […]
Where’s the Smoking Gun?
When aircraft problems occur, we always want an explanation but don’t always get one I receive thousands of emails from aircraft owners each year, but this one was unusual. It was nearly 3,000 words long—twice the length of this article. The 7,500-hour CFI who wrote it clearly needed to “vent” about something that scared the bejeezus out of him three months earlier and that he’d clearly still not gotten over. The writer was a member of a glider club and, on the day in question, was instructing a student in a two-place sailplane that departed under tow behind a Cherokee 235 towplane. Shortly after takeoff, as both aircraft were about 100 feet AGL, the Lycoming O-540 engine in the towplane suffered a partial power loss and the aircraft quit climbing. The CFI radioed to the towplane pilot, who suggested that the glider might want to consider releasing the towline. However, the CFI determined that he was too low for the glider to execute a successful 180 back to the airport, and elected to remain on tow. The tow pilot also had the ability to release the towline, but opted not to do so, either. The towplane flew a very low […]
GA Engine Summit 2017
Industry and the FAA meet to discuss GA piston engine issues In mid-September 2017, I was invited to participate in a two-day “GA Engine Summit” meeting in Burlington, Massachusetts—about 30 minutes’ drive northwest of Boston. This meeting was a long-awaited sequel to the first GA Engine Summit that took place in December 2015, which I also attended. This year’s summit was attended by a veritable Who’s Who of piston GA. It was hosted by the FAA’s Aircraft Certification Service, and attended by representatives from across the piston GA industry. Attendees included numerous representatives of the FAA’s Engine and Propeller Standards Branch—formerly known as the Engine and Propeller Directorate—and other FAA branches involved with piston GA. Aircraft owners and pilots were represented at the meeting by AOPA’s David Oord, EAA’s Doug Macnair, HAI’s Zac Noble, COPA’s Roger Whittier, and CPA’s Paul New. Also attending were representatives from Continental Motors, Lycoming, Pratt & Whitney, Hartzell, Superior Air Parts, RAM Aircraft, DeltaHawk, Electroair, and the NTSB. FAA Realignment There was much discussion of the FAA’s sweeping reorganization—they called it “realignment”—that took effect last July. Both the Aircraft Certification Service (AIR) and the Flight Standards Service (AFS) had their org charts massively redesigned. This […]
Grand Theft Propeller?
Can a mechanic hold an aircraft hostage? Or just part of it? The mechanic who phoned me sounded agitated. He explained that he’d been an A&P for quite a while, but had earned his IA recently and was relatively new to the business of doing annual inspections. An owner had brought a 1950s-vintage Piper PA-22 Tri-Pacer to him for an annual. During the inspection, the IA discovered that the aircraft’s Sensenich metal two-blade fixed-pitch propeller was in a severely corroded state. The prop was so badly corroded that not only did the IA consider it unairworthy, but seriously doubted that it was repairable. Consequently, he advised the owner of the Tri-Pacer that the airplane needed a new prop. The owner was not happy about the IA’s verdict and initially resisted his recommendation, but finally reluctantly agreed to pay for a new propeller. He made of telling the IA that he wanted the old propeller back. When the IA inquired why, the owner indicated that he was planning to list the old prop on eBay in hopes of getting some money for it to help defray the cost of the new propeller. The IA was horrified. “You can’t do that,” he […]
The Disaster That Didn’t Happen
Thanks to teamwork, tens of thousands of aircraft owners dodged a devastating bullet As I write this, the aviation blogosphere and Twitterverse are abuzz over the near-disaster at San Francisco International Airport, when an arriving Air Canada A320 on a night visual approach to runway 28R came scant seconds—and less than 100 feet—from touching down on a parallel taxiway on which four other airliners were queued up for takeoff. It was teamwork—a radio call by an alarmed airline pilot prompting the tower controller’s instruction to “go around”—that averted what might have been one of the worst accidents in aviation history. Fortunately, that catastrophe didn’t happen. I’m focused on another near-disaster that was averted at the last possible moment, one that hit closer to home. I’m talking about the threatened Airworthiness Directive against camshaft gears on Continental 520-, and 550-series engines that might have cost the owners of Bonanzas, Cessnas, Cirruses, Columbias, Mooneys, and other Continental-powered GA airplanes tens of millions of dollars a year. My own Cessna 310 has two of the affected engines, so this would have hit me right where it hurts. This disastrous AD didn’t happen—although it came perilously close. As with Air Canada, last-minute teamwork saved […]
By The Book?
Must manufacturer’s maintenance guidance be followed? Have you ever had your mechanic tell you something like this: “It has been six years since your propeller was last overhauled, so we’re going to have to overhaul it this year as required by Hartzell.” “Your magnetos are past due; Continental requires that they be overhauled every four years.” “The trim tab actuators need to be disassembled, cleaned and lubricated—the Cessna maintenance manual says this must be done every 200 hours.” “The Instructions for Continued Airworthiness for your Garmin autopilot requires that the servo clutches be checked for proper breakaway torque at every annual inspection.” “We need to pull the wing bolts on your Bonanza and send them out for non-destructive testing—Beech requires this every five years.” “The regulator on your STC’d oxygen system needs to be sent out for overhaul every five years according to the manufacturer’s Instructions for Continued Airworthiness.” A&Ps tell aircraft owners stuff like this all the time, and most owners consent to having the work done in the belief that it’s required. In most cases, the A&P is acting in good faith. Aircraft mechanics are always trained to do things “by the book,” and most truly believes that […]
Back In The Game
The first flight after maintenance is special. My client wanted to buy a Bonanza A36, and narrowed his search to two promising candidates. One had recently suffered a “forgot to remove the tow bar” prop strike, necessitating an engine teardown inspection and prop overhaul, but the seller was very upbeat, suggesting that his misfortune actually represented a windfall for my client: While this tow bar event has been a royal pain, we have ultimately ended up with a greatly upgraded plane and one that the buyer can have a extremely high level of understanding and confidence of the condition of the engine at 1,237 hours. This plane won’t need a pre-buy, because more information than one could ever dream of getting in a pre-buy is already available. Less than a week later, my client received this downbeat follow-up from the seller: I wanted to let you know the Bonanza is off the market—permanently. On the test flight after the new prop, tear down, etc., the prop had an overspeed situation and the engine blew up while my partner was on the way to San Juan. No one was injured in the accident. It is kind of sad, she was such a […]
Traveling Toolkit
What “stuff” do you carry in your airplane? It’s a well-known fact: Most mechanical problems occur between Friday night and Sunday afternoon when you’re hundreds of miles from home base. The difference between a minor annoyance and a major travel disruption can hinge on whether you brought along the “stuff” necessary to get back in the air quickly. I’m talking about several kinds of “stuff”—service information, a survival toolkit, and spare parts and supplies. I fly lots of long-range missions in my airplane, and I always carry quite a bit of such “stuff” with me. It has bailed me out of trouble more times than I care to count. Service Information Service information is perhaps the most important thing to carry. If you have a mechanical problem on a weekend and are lucky enough to find an A&P to help you out, he cannot legally work on your airplane without the maintenance manual (MM) for your make and model. If it turns out that he needs to order a part to get you back in the air, he’ll also need access to the illustrated parts catalog (IPC) for your make and model to figure out what part number to order. […]
Outside the Box
Compared to Lycocontisauruses, the Rotax 912 is delightfully different. The past 20 years may well have yielded more outside-the-box ideas than any other comparable period in history. The iPod redefined the music industry in 2001. Facebook, YouTube and Twitter (2004–2006) redefined how we interact. The iPhone (2007) not only redefined “cell phone” but changed our lives in too many ways to count. Airbnb (2008) redefined “lodging,” Uber (2009) redefined “ground transportation,” and the iPad (2010) and Foreflight (2011) redefined our GA cockpits. (Remember when we schlepped around 15 pounds of Jepp binders, and spent mind-numbing hours keeping them updated?) Wow! While all this amazing innovation was happening, few U.S. aviators noticed that an obscure Austrian subsidiary of a Canadian company mostly known for its two-stroke snowmobile, motorbike and ATV engines was quietly redefining the small (under 150hp) four-stroke piston aircraft engine. Few noticed, that is, until 2004 when the FAA approved the LSA rule, and sexy factory-built Special Light Sport Aircraft started entering the U.S. aircraft registry and showing up at Oshkosh, Lakeland and Sebring. Nearly all those S-LSAs turned out to have same engine: the Rotax 912. (Huh? Ro-who? Isn’t that the engine used on ultralights? The one that […]
Borescope Ascendancy
Time to topple the venerable compression test? The differential compression check has been a mainstay of piston aircraft engine maintenance for the last 80 years. Like anything else in aviation that’s been around for a long time, various Old Wives’ Tales (OWTs) have evolved about the procedure, passed on from journeyman mechanic to apprentice, and later taught in A&P schools and documented in various textbooks and advisory circulars. Ask your mechanic why he performs a compression check a certain way or interprets the test results as he does, and if he’s honest he’ll probably answer, “That’s the way I was taught to do it and that’s the way I’ve always done it.” One pervasive OWT has it that compression readings in the high 70s are excellent, in the low 70s are good, in the high 60s are marginal, in the low 60s are poor, and anything below 60/80 is unairworthy. Another widely accepted OWT is that an engine with compressions in the low 60s is a “tired engine” that will not put out full rated horsepower. Both are dead wrong. More than three decades ago, Continental Motors issued a service bulletin (M84-15) debunking the first of these OWTs by establishing […]
Field Approvals
Do you really need the FAA’s blessing to modify your aircraft? A Bonanza owner wanted to power his portable GPS and his iPad simultaneously in flight, so he asked his avionics shop to install an extra cigar lighter socket on the panel. He was told that doing so would require preparing an FAA Form 337 and obtaining a Field Approval from the local FSDO, and he was warned that this might be time-consuming and costly. Later, the owner made the same request of his A&P mechanic, who said “no problem,” installed the socket and signed it off with a simple logbook entry. Who was right, the avionics shop or the A&P? A Cessna 210 owner had his A&P install a gear mirror on the underside of the left wing so he could visually check that his landing gear was down and locked. Several years later, during an annual inspection, an IA told the owner that there was no Form 337 for the mirror and that it would have to be removed before the IA could sign off the inspection as airworthy. The IA indicated that the only alternative would be to ask the local FSDO to send out an airworthiness […]
Buy…or Walk Away?
Thoughts about when to purchase and when to pass. Who among us hasn’t spent hours looking at Trade-A-Plane or Aircraft Shopper Online looking for that perfect low time airplane with a fresh engine overhaul, new paint and interior, great avionics, and a bargain price? Dream on! Common sense says if you find one, there’s probably a good reason that it’s underpriced … like maybe lost logbooks, major damage history, wing spar corrosion, an expensive AD that hasn’t been complied with, or some other big-time skeleton in the closet. My aircraft appraiser friend Brian Jacobson tells the colorful story of a fellow who bought a gorgeous-looking piston twin back in the mid-1970s. It was just two years old and had less than 100 hours on the Hobbs meter, and the new owner bragged about what a “steal” he’d gotten on it. Then he tried to get the airplane added to the Part 135 certificate of his local FBO, and the aircraft’s true story came to light. It seems that at just 38 hours since new, the original owner of the twin ran it off the end of a short runway and into a water-filled drainage ditch. The aircraft sat partially submerged […]
Actionable Intelligence From Big Data
Comparing individual aircraft to others of their ilk. Last month, I described some interesting studies my colleagues and I have been doing with “big data” collected from digital engine monitors aboard more than 7,000 airplanes over more than a million flights. We demonstrated empirically that significantly more flights are flown with headwinds than with tailwinds, that Lycoming CHTs run 20°F hotter than Continental CHTs, and that recently designed airplanes provide better engine cooling that legacy ones (among other things). Now let’s look at how big data analysis is providing aircraft owners with specific actionable intelligence about their individual airplanes, helping them uncover problems with both hardware and operating technique. Report cards Last year, we started generating regular “report cards” to subscribers who have been uploading enough engine monitor data to the SavvyAnalysis platform to support statistically significant findings. These are emailed to the owner, and analyze a dozen or so critical flight parameters related to performance, efficiency, and engine longevity. Most importantly, it compares those parameters with all the other aircraft we follow of the same type. Here’s what such a report card looks like: This one is for a normally-aspirated Cirrus SR22. It covers 27 flights that were uploaded […]
General Aviation and Big Data – Part 1
Analyzing data from a million GA flights can yield interesting results. Pilots have long suspected that when it comes to headwinds and tailwinds, the deck is stacked against them. I think the late Bob Blodget, Senior Editor of FLYING Magazine, captured how most pilots feel about this when he wrote that “we all come to the conclusion that there are always more headwinds than tailwinds; and that the headwinds are always stronger than reported or forecast, and the tailwinds weaker.” Blodget wrote those words in 1968 and died in 1973. In his time, we could only speculate about such things. But in today’s era of computerized avionics and big data, we can prove them. My colleague Chris Wrather is a longtime friend, pilot, Bonanza owner, and A&P mechanic with a Ph.D. in operations research. Among other things, he oversees the SavvyAnalysis division of my company. Over the past four years, we’ve built a database of digital engine monitor data comprising more than a million flights flown by about 7,000 piston-powered general aviation airplanes. Digital engine monitors typically capture data from myriad sensors between 10 and 60 times a minute. This means that for each of those million-plus flights, we’ve captured […]
Buyer Beware
If a plane is listed for sale cheap, there’s always a reason. “Hey Mike, this is Danny in Louisiana,” read the email. Danny is one of my clients who used to own a Cirrus SR22 and now flies a Cessna 182 Katmai STOL conversion. “Would you look at this 1965 Cessna 310I on eBay and let me know if you think a $35K price without a pre-buy would be wise. I have three buddies (plus myself) that are interested in working on twin rating, so we would be sharing the risk. Thanks in advance for your opinion.” The email ended with a link to the eBay listing. With a sigh, I braced myself and clicked the link. “This is one of the nicest twin Cessna 310I’s out there,” the eBay ad proclaimed. Let’s think about this: It’s a 50-year-old all-metal airplane, and Cessna built these aircraft with absolutely no internal corrosion proofing. This one is based in Baton Rouge, one of the highest corrosion-risk areas of the United States. It had suffered a gear-up landing awhile back, but somehow managed to avoid being declared a constructive total loss by the owner’s insurance carrier. Oh, and it had 7,639 hours on […]
Stuck in Reykjavik
When the pilot of a round-the-world flight found himself AOG in Iceland with electrical issues, remote diagnosis saved the day. Ademilola “Lola” Odujinrin has a passion for aviation. He’s 37 years old, resides in Nigeria with his wife and two school-age children, and was first bitten by the flying bug at age 7 when his airline-pilot uncle invited him onto an airliner flight deck (back in the days when such visits weren’t prohibited). Lola earned his private pilot certificate at age 20. A decade later, he followed in his uncle’s footsteps to become a commercial pilot flying Boeing 737s. Lola is also an overachieving athlete and adventurer, who in 2010 cycled 2,000 miles from Morocco to London in 17 days. So it was no big surprise when he announced his intention to become the first African to fly solo around the world. The aircraft Lola chose for this mission was N313CD, a 2004 Cirrus SR22 that would be “tanked” to hold enough fuel to provide endurance of 17+ hours, and equipped with survival gear, HF and sitcom radios, and a bunch of GoPro cameras. Organizing and obtaining funds for this mission (dubbed “Project Transcend”) took ten years and was fraught […]
Whoa! This Isn’t an Inspection!
A&Ps are trained to find things wrong with your aircraft. But there’s a time and place for that, and it comes once a year. It was the week before AirVenture 2016. Normally, I would never perform any maintenance on my trusty Cessna 310 immediately before departing on an important trip, for fear I might break something. But this time I had no choice. The FAA had issued AD 2016-7-24 on April 26, 2016, requiring replacement of the attach hardware at both ends of the elevator trim tab push-pull rod within 90 days. As soon as the AD hit the streets, I’d ordered the required hardware, but it took a while before I received it. Once it arrived I drove to my hangar with the intention of replacing the hardware in compliance with the AD. But I was surprised to discover that there was not adequate maintenance access to the nut and bolt at the forward end of the pushrod. I couldn’t figure out how the hardware could be changed without removing the whole elevator. I checked with Paul and Phil, two A&P colleagues who I knew did a lot of Cessna maintenance, but neither had ever had occasion to perform […]
Differential Diagnosis
Fixing is usually the easiest part of aircraft maintenance. Figuring out what’s wrong is usually the hardest part. By Mike Busch | A&P/IA A funny thing happened on my way to Milwaukee… It was 2013 and I was flying my trusty 1979 Cessna T310R to speak at the annual national convention of the Flying Physicians Association. My talk to the flying docs was on the subject of troubleshooting. Little did I know that my troubleshooting skills were about to be put to the test. I went wheels-up from my home base in Santa Maria, California, about 8 AM, headed for Denver’s Front Range Airport. The forecast called for thunderstorms after 1 PM, and my plan was to arrive early enough to miss them. The plan worked…although less than an hour after my arrival, a tornado touched down about 5 miles north and shut down Denver International Airport for a while. The next morning, all was calm at Front Range as I taxied out for takeoff, destined for Milwaukee’s Timmerman Airport. I was cleared for takeoff, released the brakes, smoothly advanced the throttles to the stop and started my takeoff roll on runway 17. Uh oh! Something felt wrong. It was […]
Whom Should You Trust?
Before following expert advice, choose your expert with care. We aviators are of necessity a trusting lot. We constantly trust other people with our lives, our safety, and our financial wellbeing. We trust nameless and faceless air traffic controllers to keep us from hitting anything. We trust our A&P to keep our aircraft safe to fly for ourselves and our passengers. We trust our engine manufacturer and overhaul shop to build an engine that won’t quit at night or in IMC over hostile terrain. We trust our AME to keep us out of trouble with the Friendlies in Oke City (at least until the Class 3 medical goes away, knock on wood), our broker to help us find an aircraft to buy that isn’t a lemon, our aircraft insurance agent to keep us out of hot water if something goes wrong, and the list goes on. But how can we tell if these experts upon whose expertise we depend are genuinely trustworthy? How do we know they’re giving us good advice? Should we rely on what they tell us? Should we seek a second opinion? Maybe a third? We don’t usually get to choose which air traffic controllers we depend […]
What Does “Airworthy” Mean?
The definition of this ubiquitous term depends on the context. A bit over two years ago, a fellow I’ll call “Bob” bought a 10-year-old Cirrus SR22 from another fellow I’ll call “Sam.” Prior to the purchase, Bob had a very thorough pre-buy performed by an independent A&P/IA, who gave the airplane a clean bill of health. This pre-buy was so comprehensive that would have qualified as an annual inspection, but for some strange reason the IA signed it off as a 100-hour inspection instead. As a result, Bob would up having the airplane annualed just a few months later when the prior annual inspection expired. The annual was performed at a large, well-known Cirrus Authorized Service Center—the very same service center that had performed the previous annual inspection on the airplane for Sam prior to the sale. So Bob was floored when the shop reported that all six cylinders had head cracks in the vicinity of the top spark plug holes. The shop assured Bob that Continental Motors would replace the cracked cylinders at no cost, although Bob would be on the hook for the several thousand dollars of labor involved in doing the top overhaul. Once the six cylinders […]
Is Repair a Lost Art?
Aircraft parts are expensive, so we really should be repairing rather than replacing them whenever possible. When the co-owner of a 1976 Cessna 172M emailed me, she had just come from talking to her mechanic and was clearly in a state of sticker shock: “Where can I locate a used battery box for my Skyhawk without having to rob a bank? Our Gill battery (that has constantly leaked from shortly after we bought it) has caused corrosion that cannot be repaired, so we are told. Our plane is down for its annual, and apparently will remain unairworthy until this issue is resolved to the FAA’s standards. “In the past, we’ve used acid-proof paint to protect the aluminum box, and pads to soak up any leakage, but the problem has now become severe enough that the A&P says we have to replace the whole box. I thought our current one could be repaired, but according to the mechanic the bottom of the box has the stamp on it that makes it legal, and that area is damaged and needs to be replaced. “New boxes from Cessna are nearly $1,000, which we find totally ridiculous and unacceptable. What can we do? Are […]
A Mechanic’s Signature
What do you do if a mechanic working on your airplane tells you, “I can’t sign it off”? Dick is the maintenance officer of an 80-member flying club in northern New Jersey. The club operates several aircraft including a 2011 Cessna Skyhawk SP powered by a Lycoming IO-360-L2A engine. The engine has now reached 2,400 hours—400 hours beyond Lycoming’s published TBO of 2,000 hours. In a phone call, Dick explained to me that at the Skyhawk’s recent annual inspection, the four-cylinder Lycoming had compressions in the high 60s and low 70s. It wasn’t using much oil. The oil filter was clean, and the oil analysis report had no red flags. Most experienced A&Ps would agree that the parallel-valve four-cylinder Lycomings are the most bulletproof piston engines in general aviation, and that the Lycoming IO-360-L2A is the best of breed. If flown frequently and regularly, they often make it to 4,000 hours or more between overhauls. The flying club’s shop in New Jersey didn’t see it that way. Although the shop signed off the Skyhawk’s recent annual inspection as airworthy, they made it clear to Dick that they were profoundly uncomfortable with the club continuing to operate the engine beyond TBO. […]
LSAs: Who’s Guarding the Henhouse?
The new crop of factory-built LSAs are impressive and exciting, but the maintenance regulations for them are…ah…different I recently returned from the U.S. Sport Aviation Expo in Sebring, Florida, the foremost aviation event devoted to light sport, homebuilt, and ultralight aircraft. I was a first-timer at this event, having been invited by the show organizers to give a keynote address and a couple of technical forums. I accepted this invitation not because I had any expertise in this lightweight corner of the general aviation envelope—all of my prior knowledge and experience having been with standard category certificated aircraft—but because I sensed this was an exciting and rapidly growing segment of general aviation and this would be a great opportunity for me to learn about it. And learn I did. I had the opportunity to spend quality time with such legendary experts as Prof. H. Paul Shuch (LSA maintenance guru), Phil Lockwood and Dean Vogel (Rotax engine gurus), Wally Anderson (who operates Synergy Air, the nation’s largest Van’s RV build-assist center and also the manufacturer of the RV-12), and Mike Schofield (Dynon Avionics marketing manager), among others. It was like drinking from a firehose. How far we’ve come In July 2004—just […]
Inaugural GA Engine Summit
FAA’s Engine & Propeller Directorate meets with GA to improve how ADs are dealt with. Early last December, I had the privilege of attending a two-day meeting at the offices of the FAA’s Engine & Propeller Directorate (EPD) in Burlington, Mass., about 30 minutes’ drive northwest of Boston. The meeting was billed as the first “GA Engine Summit.” It was the brainchild of AOPA’s Rob Hackman and EPD’s Wayne Maguire. The purpose was to try to improve the relationship between the FAA and the GA community, a relationship that has been strained nearly to the breaking point in recent years by a series of draconian Airworthiness Directives (ADs) against Superior and ECi cylinders that I’ve referred to as the FAA’s “war on jugs.” The meeting was attended by a litany of FAA executives and subject matter experts from EPD, the Small Airplane Directorate (SAD), and FAA Headquarters. Industry was represented by delegations from AOPA, EAA, the Aeronautical Repair Station Association (ARSA), Continental Motors, Lycoming, Superior Air Parts, Danbury Aerospace (former owners of ECi), and a number of others. When Rob Hackman left AOPA last June, his successor Dave Oord (AOPA VP of regulatory affairs) picked up the ball, and it […]
Fear and Balderdash
Maintenance decisions need to be fact- and evidence-based. The current owner of the vintage J-model Bonanza emailed me for advice. He’d purchased the airplane just four months earlier with a fresh annual inspection, and was already stressing out about what to do about his engine at the next annual eight months hence. According to the owner, the airplane’s Continental IO-470 engine was the original one that had been in the airplane when it rolled out of the factory in 1958. It had been overhauled seven years later in 1965 at its published TBO of 1400 hours, and then overhauled again nine years later in 1974 when it hit TBO again. Now the engine was once again at 1400 hours SMOH, but this time it had taken more than 40 years to get there. The owner explained that the engine was using about a quart of oil every three hours, but was otherwise running strong and smooth with decent compression readings and not making metal. He wanted my opinion as to whether he should be considering a major overhaul at the forthcoming annual, a top overhaul, or no overhaul. “Considering this engine is 57 years old and more than 40 years […]
Watch Your Language!
When requesting maintenance, the words you use can be very important. The voice on the phone identified himself as a Cessna 182 owner—let’s call him Jim—who said he was considering overhauling his O-470-R engine and could use some advice. I asked Jim why he was considering overhauling his engine, thinking maybe it was approaching TBO and hoping to convince him this wasn’t a valid reason to tear down a perfectly healthy engine. As it turned out, this engine wasn’t yet close to TBO. Jim said his A&P recently pulled a cylinder because it had a leaking exhaust valve. With the jug removed, the mechanic discovered a badly worn cam lobe and showed it to Jim, explaining that the engine would need to be removed from the airplane and have its crankcase split in order to replace the damaged cam. The mechanic offered to do the work himself in-house (rather than send the engine out), and estimated the engine repair would come to roughly $10,000, including parts and labor. Jim agreed and authorized the mechanic to proceed. In a follow-up conversation, Jim asked his A&P whether it might make sense to overhaul the engine, given that it was already going to […]
Insurance Woes
When repairs are covered by insurance, it’s the owner’s job to keep things under control. By the time he contacted me, the aircraft owner—let’s call him Fred—was boiling mad. Fred had bought an airplane last year, and the pre-buy and subsequent annual inspection gave his new-to-him bird a clean bill of health. Yet even before Fred ferried the airplane to his home base, mechanical gremlins started to appear. The alternator failed. Some serious exhaust issues required repair. These and various other discrepancies started Fred thinking that perhaps the clean pre-buy and annual were a bit overoptimistic. Then ATC reported the transponder wasn’t working. Fred sent it to an avionics shop, who told him it was an old tube-type unit that was uneconomical to repair, and that he’d be money ahead installing a new transponder. Just prior to ferrying the airplane to the avionics shop, Fred discovered that the autopilot was malfunctioning. He had to pull a circuit breaker stop it from alarming. Then as he entered the pattern to land, the whole avionics stack went dark and Fred wound up landing no-radio. Fred taxied the plane to his home-field shop, but his A&P was unable to duplicate the failures, nor […]
Blame the Hardware
When pilots screw up, plaintiff lawyers always seem to sue equipment manufacturers. In June 2014, I posted an item to the AOPA Opinion Leaders Blog titled “The Dark Side of Maintenance.” It talked about what I refer to as “maintenance-induced failures” (or “MIFs” for short). In my blog post, I gave a bunch of examples of such MIFs—aircraft malfunctions that were the unintended result of errors during maintenance. One of the examples I gave involved an early model Cirrus SR22 that was equipped with a Sandel SN3308 electronic horizontal situation indicator (EHSI). The Cirrus owner emailed me that he’d been plagued by intermittent heading errors on the EHSI. When I questioned the owner, I learned that he’d been suffering these problems for about three years, and that they started right after his shop performed the scheduled 200-hour replacement of the Sandel’s projector lamp. Coincidence? I’d seen this exact same problem in my own Sandel-equipped Cessna 310. It’s invariably due to inadequate engagement between the connectors on the back of the instrument and the mating connectors in the mounting tray. It’s essential to slide the instrument into the tray just as far as possible before tightening the clamp. It’s a bit […]
Tectonic Shifts
Changing competitive landscape in piston GA aircraft and engines. By Mike Busch I just returned from EAA AirVenture 2015 in Oshkosh, where aviation firms traditionally make major announcements. This year was no exception. One of the most significant announcements to me (as an aircraft owner and maintenance professional) was the one by Continental Motors that they had acquired the assets of Danbury AeroSpace of San Antonio, Texas. “Danbury who?” you might ask. Actually, Danbury is a major supplier of piston aircraft engine components and experimental engines sold under the Engine Components International (ECi) and Titan brand names. ECi and Titan Engines Inc. are wholly-owned subsidiaries of Danbury. I found the Continental/Danbury announcement significant because it will result in major changes to the competitive landscape in the piston aircraft engine market. In my view, these changes will be excellent news for some aircraft owners and rather bad news for others. Some background To put this in perspective, we need to go back four decades to a time when two Texas-based companies—Superior Air Parts (SAP) and Engine Components Inc. (ECi)—first obtained FAA Parts Manufacturer Approvals (PMAs) to produce replacement parts for Continental and Lycoming engines. Prior to that time, Continental and Lycoming […]
Don’t Go Overboard
Suppressing the urge to overreact to and overkill problems. The Bonanza owner encountered an engine problem 11 hours after his aircraft came out of annual. He had crossed the Sierra Nevada Mountains VFR at 12,500 feet westbound enroute to the Bay Area, and was descending through 11,000 feet when he felt a bit of engine roughness. After doing an in-flight mag check and studying his JPI engine analyzer, his initial guess was that he had a bad spark plug in the #3 cylinder. But the problem got worse, and so after landing the pilot took the plane to a local mechanic and asked him to perform a compression check. Sure enough, the #3 cylinder measured 20/80 with air whistling past the exhaust valve. Clearly the cylinder was going to have to come off and the exhaust valve and seat replaced. So far, nothing unusual here. Happens all the time. What I found interesting about this story was how the owner reacted to this burned valve episode. Here’s a brief excerpt of the email he sent to his A&P: “I think the valve may have been burning itself (or the valve seat) to a worse condition as I continued to fly. […]
Backdoor Rulemaking?
Cessna gets caught with its hand in the FAA’s cookie jar. On February 10, 2014, the Cessna Aircraft Company did something quite unprecedented in the history of piston GA: It published a revision to the service manual for cantilever-wing Cessna 210-series airplanes that added three new pages to the manual. Those three pages constituted a new section 2B to the manual, titled “Airworthiness Limitations”: This new section purports to impose “mandatory replacement times and inspection intervals for components and aircraft structures.” It states that the new section is “FAA-Approved” and that compliance is required by regulation. Indeed, FARs 91.403(c) and 43.16 both state that if a manufacturer’s maintenance manual contains an Airworthiness Limitations section (ALS), any inspection intervals and replacement times prescribed in that ALS are compulsory. FAR 91.403(c) speaks to aircraft owners: §91.403(c) No person may operate an aircraft for which a manufacturer’s maintenance manual or instructions for continued airworthiness has been issued that contains an Airworthiness Limitations section unless the mandatory replacement times, inspection intervals, and related procedures specified in that section … have been complied with. and FAR 43.16 speaks to mechanics: §43.16 Each person performing an inspection or other maintenance specified in an Airworthiness Limitations section of a manufacturer’s maintenance manual or Instructions for Continued Airworthiness shall perform […]
Discrepancy Discretion
Who decides whether or not your aircraft is airworthy? By Mike Busch My column in the May 2015 issue of EAA Sport Aviation, titled “Fix It Now…Or Fix It Later,” discussed how to deal with mechanical problems on the road. It offered some specific advice about how pilots and aircraft owners can decide whether a particular aircraft issue needs to be addressed before further flight or whether it can safely wait until the aircraft gets back home. I considered the advice I offered in this article to be non-controversial and commonsensical, so I was quite surprised when I received an angry 700-word email from a very experienced A&P/IA condemning my article and accusing me of advising owners to act irresponsibly and violate various FARs. The author of this strongly-worded censure—I’ll call him “Damian” (not his real name)—is someone I’ve known for some years. Damian is a regional field service manager for a leading GA aircraft manufacturer, but he made it clear that the views he expressed in denouncing my article were his own and not those of his employer. It has long been clear to me that Damian doesn’t think much of my opinions about GA maintenance, and that I […]
Why I Hate Pulling Jugs
It’s riskier business than most owners or A&Ps realize. Regular readers of this column know how I feel about changing cylinders in the field. I hate it. Especially when several cylinders are changed at one time; this is risky business. Changing them all (the so-called “top overhaul”) is even riskier. In my column in the June 2014 issue (“Cylinder Work: Be Afraid”), I explained the nature of the risk: Changing cylinders involves messing with the ultra-critical clamping force (“preload”) of critical threaded fasteners. And it’s extremely difficult to ensure that the correct preload is achieved when tightening those fasteners with a torque wrench, even if the manufacturer’s procedures are followed to the letter. A couple of recent NTSB Probable Cause reports illustrate this issue rather vividly. Both of these reports were literally hot off the press as I’m writing this column. I offer them here without comment, because they speak for themselves. Spun bearing, broken crankshaft NTSB Identification: ERA14LA193Accident occurred: Friday, April 11, 2014 in Louisa, VAProbable Cause Approval Date: 04/27/2015Aircraft: CESSNA U206G, registration: N156SAInjuries: 1 Serious, 1 Minor. Narrative: The pilot reported that, during the flight before the accident flight, he noted that the oil pressure was slowly fluctuating, so he chose to change the […]
Alterations
Clearing up confusion about aircraft mods. You want to modify your certificated aircraft. Let’s say it’s something simple like adding an extra cigarette lighter socket to power your portable GPS or cellphone charger. Or installing an external mirror so you can verify your landing gear is down. Or tweaking your engine cooling baffles to get more cooling air to the #5 cylinder. Or replacing your original 100-watt incandescent landing light lamp (that’s always burning out) with a modern LED lamp that draws less current, puts out more light, and has a 10,000-hour useful life. No big deal, right? Well, apparently that depends on whom you ask. One aircraft owner told me that when he asked his avionics shop to install an extra cigarette lighter socket, he was told that doing so would require preparing an FAA Form 337 and obtaining a Field Approval from the local FSDO; he was warned that this might be difficult and costly. The owner later made the same request of his A&P mechanic, who said “no problem” and installed the socket and signed it off with a simple logbook entry. Who was right, the avionics shop or the A&P? Another owner reported that he had […]
Fix It Now…Or Fix It Later?
You’re on a trip when a mechanical arises. First you mutter the obligatory expletives, and then you must decide: Should you get the problem fixed now, or live with it until you get home? Nothing is more frustrating than dealing with mechanical problems on the road. It’s always uncomfortable when you’re far away from your usual support system—your trusted mechanic, your hangar, your toolbox. To add insult to injury, mechanicals invariably seem occur at the most inconvenient possible time and place—like Sunday at Sheepdip County Airport when you’ve just gotta be back at work Monday morning. It’ll be a miracle if you can find a local A&P at Sheepdip on a Sunday…and if you do, he’ll probably be named “Bubba” and you might just get the uneasy feeling that Bubba knows he’s got you by the short ones. It’s natural to ask yourself whether it’s really necessary to fix the problem before further flight, or whether it’s okay to press on and get it resolved after you return home. There’s a strong temptation to defer the maintenance until a more convenient time, and often that’s a perfectly reasonable thing to do. But sometimes it isn’t—witness numerous NTSB accident reports in […]
Oleos
Oleopneumatic shock struts use hydraulic fluid, compressed gas, and darn clever engineering to improve our landings. If every one of our landings were a “greaser” and if runways never had bumps or potholes, then the landing gear on our airplanes could be dead simple. Wheel assemblies rigidly attached to the airframe would work fine, just as they did on the toy wagon and roller-skates I had when I was a kid. In the real world, some landings (“arrivals”?) involve embarrassingly firm touchdowns. Some of the runways and taxiways we use are not exactly pool-table smooth, either. That’s why nearly every airplane ever built has been equipped with a shock-absorbing landing gear designed to survive considerable abuse. Lightweight aircraft can often get away with a simple spring-loaded gear. Many older designs (like the venerable Piper Cub) use a simple hinged gear leg with stranded rubber cords used to absorb the shock of landing. Mooneys use a stack of shock-absorbing rubber doughnuts for the same purpose. Many aircraft, notably Cessna singles, use shock-absorbing spring steel gear legs, an elegantly simple design pioneered and patented in the 1930s by air racer Steve Wittman. Cessna licensed the design from Wittman in the 1940s, introduced […]
150 Year-Old Technology
Most of us are still flying (and driving) behind powerplant technology that dates from the 19th century. The original four-stroke Otto-cycle internal-combustion engine was patented in 1862 by a Frenchman named Alphonse Beau de Rochas. More scientist than engineer, de Rochas never actually built an operational engine. The first working prototype was built by a German engineer named Nikolaus A. Otto, who was ultimately rewarded for his efforts by winning a gold medal at the Paris Exposition in 1867 and having the four-stroke cycle named after him. The first practical Otto-cycle engines were built by another, better known German engineer named Gottlieb Daimler, who together with his lifelong business partner Wilhelm Maybach built a one-cylinder automobile engine in 1885 and a two-cylinder engine in the now-classic “V” configuration in 1889. Daimler died in 1900, and in 1926 his company Daimler Motors Corporation merged with Benz & Co.—founded by two-stroke engine pioneer Karl Benz—to create Daimler-Benz AG. The basic power-generating component of an internal-combustion engine is the cylinder assembly, whose major components are a cylinder, a piston, and a pair of valves or ports (intake and exhaust). Each up or down movement of the piston within the cylinder is termed a […]
The Perfect Mechanic
What to look for when choosing an A&P to work on your aircraft. Over the past 45 years, I’ve had the opportunity—and often the privilege—of working with hundreds of aircraft mechanics. At first it was as a naïve aircraft owner having them perform inspections and repairs on my airplane. Later it was as a student and apprentice swinging wrenches under their supervision as I struggled to learn their craft. More recently, having become an A&P/IA myself, it has been mostly as a colleague consulting about thorny mechanical problems with hundreds of my clients’ airplanes (and occasionally my own). I’m greatly indebted to these mechanics—some more than others—for they taught me everything I know about aircraft maintenance, and also a good deal about human nature. I never cease to be struck by the remarkable variety of talented people involved in aviation in general, and in aircraft maintenance in particular. Some of the finest aircraft mechanics I’ve ever known come across loquacious and cock-sure, while others are taciturn and exude quiet confidence. Some seem to have heads bursting with knowledge and expertise, while the wisdom of others seems to be focused in their steady, calloused hands. Some approach aircraft problems thoughtfully and […]
Silent Killer
If you think CO-related accidents are rare, think again… On January 17, 1997, a Piper Dakota departed Farmingdale, New York, on a planned two-hour VFR flight to Saranac Lake, New York. The pilot was experienced and instrument-rated; his 71-year-old mother, a low-time private pilot, occupied the right seat. Just over a half-hour into the flight, Boston Center got an emergency radio call from the mother, saying that the pilot (her son) had passed out. The controller attempted a flight assist, and an Air National Guardhelicopter joined up with the aircraft and participated in the talk-downattempt. Ultimately, however, the pilot’s mother also passed out. The aircraft climbed into the clouds, apparently on autopilot, and continued to be tracked by ATC. About two hours into the flight, the airplane descended rapidly out of the clouds and crashed into the woods near Lake Winnipesaukee, New Hampshire. Both occupants died. Toxicological tests revealed that the pilot’s blood had a CO saturation of 43% — sufficient to produce convulsions and coma—and his mother’s was 69%. On December 6 that same year, a physician was piloting his Piper Comanche 400 from his hometown of Hoisington, Kansas, to Topeka when he fell asleep at the controls. The […]
Prebuy Do’s and Don’ts
If you’re buying an aircraft, here’s how to structure the prebuy. Over the past six months, my company’s prebuy activity has gone right through the roof. We’ve been responding to 30 to 50 prebuy requests a month, perhaps four times as many as we were seeing a year ago. I’m not quite sure what this means for the health of general aviation. On one hand I’m seeing a lot of owners selling their airplanes, but on the other hand I’m seeing a lot of other folks buying them. And on one hand I’m seeing owners selling their airplanes because they can’t afford to keep them and aren’t using them enough, but on the other hand I’m seeing owners selling their airplanes because they’re upgrading from singles to twins or from pistons to turbines. Occasionally, the sellers turn out to be banks trying to get rid of repossessed planes. It’s a confusing picture, but overall my impression is optimistic. As manager of prebuys, my company always represents prospective buyers in these transactions. (Often the sellers are represented by brokers, although sometimes they’re do-it-yourselfers.) Having managed more than 500 prebuys in the past few years we’ve pretty much got it down to […]
Energy and Efficiency
Why are our piston aircraft engines so @#$%*! inefficient? Our piston aircraft engines convert chemical energy into mechanical work, but they don’t do it very efficiently. It turns out that only about one-third of the energy contained in the 100LL we burn winds up getting to the propeller and doing useful work to propel us through the air. The remaining two-thirds winds up getting lost between the fuel truck and the prop hub. At today’s stratospheric avgas prices, that’s pretty depressing. Let’s do the math Consider a Continental IO-550 engine rated at 300 hp. If the fuel system is set up properly per Continental Service Bulletin SID97-3F, fuel flow at maximum takeoff power is about 26.6 gallons/hour or 156 pounds/hour. How much chemical energy does that fuel provide? We can calculate that. 100LL is rated at a “minimum lower heat value” of 18,700 BTUs per pound. Let’s convert that figure into something more meaningful to pilots like you and me: (1) divide 156 pounds per hour by 3,600 seconds per hour to get .0433 pounds per second. (2) multiply by 18,700 (the thermal content of 100LL in BTUs per pound) to get 810 BTUs per second. (3) multiply by 1.414 […]
Human Error
“To err is human…” but when humans make mistakes working on aircraft, bad things can happen. During the century since the Wright Brothers first flew, the predominant perpetrator in aircraft accidents has shifted dramatically from machine to human. Today, human error is responsible for about 90% of aircraft accidents and incidents. It’s not that people have become more careless, forgetful, inattentive or reckless. It’s that aircraft and aircraft components have become much more reliable. As component failures become fewer and fewer, human failures represent an ever-increasing percentage. Most of the efforts of the aviation research community have focused on errors committed by pilots. This is appropriate, since 75 to 80 percent of serious aviation accidents are due to pilot error. Yet roughly one-eighth of accidents are still caused by maintenance errors, and many of those are serious ones, sometimes fatal. In the wake of the 1988 explosive decompression of Aloha Flight 243 and the 2000 fatal stab-trim-jackscrew crash of Alaska Flight 261—there has been an increased focus on maintenance errors by the airlines. But in my view, not nearly enough attention has been given to maintenance errors in general aviation, where the incidence of maintenance-induced failures is more prevalent. Kinds […]
A Mechanic’s Liability
If your mechanic seems over-cautious and self-protective in his approach to maintaining your airplane, he has good reason. Mechanics have always been subject to FAA sanctions: certificate suspension or revocation, fines, warning notices, letters of correction, and remedial training. But during the 1960s and 1970s—the heyday of piston general aviation—such enforcement actions against GA mechanics were exceedingly rare. That’s no longer the case. In 1978, the FAA added a new rule (FAR 43.12) making it a violation for any mechanic to “make, or cause to be made, any fraudulent or intentionally false entry in any record or report that is required to be made, kept, or used to show compliance with any requirement under this part [of the FARs].” In plain English, 43.12 makes it a violation for a mechanic to “autograph a lie”—to “pencil whip” a logbook entry, maintenance release, yellow tag, etc. If a mechanic signs a logbook entry stating that some airworthiness directive (AD) was complied with or some other inspection or repair was performed and the FAA discovers that the work wasn’t actually done as documented, the mechanic is toast. The penalties for violating 43.12 are extraordinarily severe. An individual mechanic accused of violating it almost […]
A Highly Modified Skyhawk
How does an IA deal with a situation like this? The maintenance officer of a small flying club asked if my company would be willing to manage the maintenance of the club’s 1976 Cessna 172M. The airplane had been flying about 200 hours a year, and had faced a number of maintenance challenges. After trying a number of different maintenance shops, the maintenance officer decided he could use some professional help. My firm usually doesn’t take on flying club aircraft for a number of reasons. But the club’s maintenance officer was persuasive and convinced me to make an exception for this particular Skyhawk. We enrolled the airplane in our managed maintenance program, and assigned one of our most senior IAs—the Director of Maintenance of a Cessna Authorized Service Center—to serve as its “account manager.” The account manager contacted the club’s maintenance officer and started gathering information about the airplane and its maintenance history, while I turned my attention to other matters, knowing that the Skyhawk’s maintenance was now in capable hands. Within hours, the account manager pinged me and suggested that I might want to take a closer look at the club’s “highly modified 172.” That got my attention. I […]
Cylinder Work: Be Afraid
It is nearly impossible to install a cylinder properly when the engine is on the airplane. Here’s why. I suppose it comes as no surprise to readers of this column that I’m not exactly a fan of top overhauls. I never like to see any cylinder removed from any piston aircraft engine unless there’s absolutely no alternative. I truly hate to see multiple cylinders removed simultaneously. Removing all cylinders at once—the so-called “top overhaul”—is something I try to avoid at all costs, except it truly extraordinary circumstances. One of those truly extraordinary circumstances has had my phone ringing off the hook in recent weeks. The calls have been from frantic owners of Continental 520- and 550-series engines whose Superior Millennium-brand investment-cast cylinders are being euthanized by Airworthiness Directive 2014-05-29 and its predecessor 2009-16-03 that is legislating thousands of these magnificent cylinders out of existence the moment they reach the calendar age of 12 years. Sadly, I’m forced to tell these aircraft owners that it’s too late to fight this AD and that there’s really nothing they can do but comply. I can only imagine what my phone will doing this summer if the FAA issues its long anticipated AD against […]
Scuzzy Skyhawk
Why a thorough, independent prebuy examination is so essential, even for a simple 172. The prospective buyer was looking for a Lycoming-powered Cessna 172 Skyhawk, and had a budget of $35,000. He searched online and found one being offered with an asking price in the high 20s, a price that left some room in his budget to fix and upgrade a few things. A Google search revealed that the subject aircraft had served in the Texas Civil Air Patrol, and then somehow made its way to another owner in the Midwest, several hundred miles from the prospective buyer’s home base. Recognizing that he needed help in arranging for an impartial prebuy in a distant location, the prospective buyer decided to use my company to manage a prebuy on his behalf. My company works with hundreds of service centers all across the nation. We consulted our database, quickly recommended a trustworthy shop near the seller’s location, and set up the prebuy examination on the shop’s schedule. As is our practice with all managed prebuys, we provided the prebuy shop with a two-phase checklist customized to the aircraft being examined. Two-phase approach Our two-phase approach to prebuy examinations is deliberate. Phase One […]
Ferry Permits
If your aircraft isn’t airworthy but you need to fly it anyway, here’s how. As every pilot knows, it’s strictly against the rules to fly an unairworthy aircraft: §91.7 Civil aircraft airworthiness. (a) No person may operate a civil aircraft unless it is in an airworthy condition. (b) The pilot in command of a civil aircraft is responsible for determining whether that aircraft is in condition for safe flight. The pilot in command shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur. Now that sounds fine in theory, but sometimes it doesn’t work out so well in practice. Recently, for example, one of my clients managed to decapitate a runway light with his propeller at an airport in Florida that didn’t have any maintenance services on the field. We were able to get an A&P to drive to the decapitation site in a pickup truck and hang a loaner prop on the airplane, but we then needed to fly back to the shop to have the engine removed for a proper post-prop-strike teardown inspection. Another client inadvertently let his airplane “go out of annual” while the airplane was tied down at an airport in southern New Jersey. There […]
Not-So-Plain Bearings
There’s a lot more to engine bearings than meets the eye. According to Miriam-Webster, a bearing is “a machine part in which another part turns.” Most aircraft have lots of them. Wheels spin on their axles with the help of tapered roller bearings. Magnetos, alternators, generators and starter motors incorporate ball bearings to support their rotors. The landing gear trunions on my Cessna 310 pivot on needle bearings. Variable-pitch propeller blades are supported by large-diameter ball bearings. Turbine engine rotor shafts spin in ball and roller bearings. All these bearings consist of inner and outer “races” with spherical or cylindrical rolling elements between them. Such “rolling-element bearings” do a superb job of supporting a shaft in precise position while permitting it to rotate with very little friction. But tear down a Continental or Lycoming engine and you won’t bearings like those. The bearings in which the crankshaft, crankpins, camshaft, rocker shafts and piston pins run have no races, balls, rollers, needles or other moving parts. They’re just curved pieces of metal—known variously as “plain bearings” or “sleeve bearings” or “bushings”—that rely on sliding elements rather than rolling ones. Plain bearings are usually constructed of two semicircular halves called “shells”; one-piece […]
High Oil Consumption
Don’t do anything rash until you’re sure where the oil is going. A fellow named Ted phoned me to say that his 1984 Cessna T210 was in the shop for its annual inspection, and his mechanic was suggesting a $14,000 top overhaul. “Mike, I’ve read a lot of your articles and I know you’re not a big fan of top overhauls,” Ted told me, “so I thought I’d ask your opinion before I tell my mechanic to proceed.” “What’s the problem with your engine?” I asked. Ted told me his oil consumption had suddenly increased dramatically to a quart every 3 or 4 hours, and that the compressions on his 1200-hour engine were mediocre (mostly 60s, a couple of high 50s). The mechanic said his cylinders were “tired,” that this was typical for a mid-time Continental TSIO-520-R, and that turbocharged Continentals seldom make TBO without cylinder replacement. I counseled Ted to slow down and take a thoughtful approach. While his increased oil consumption was certainly a matter of concern, it wasn’t yet an airworthiness or safety-of-flight issue. Continental says maximum permissible oil consumption for this 310 hp engine is about one quart per hour (and Ted’s oil consumption wasn’t anywhere […]
Mechanic, Heal Thyself
All airplanes occasionally get sick. Even mine. Every year, I take my airplane on a big summer trip around the U.S., speaking at various aviation events and culminating with a week at EAA AirVenture. This year’s trip was 50 days long—June 17th to August 5th—and covered 6,500 nautical miles, put 40 hours on the Hobbs, and consumed $7,500 of 100LL. I’ve owned my 1979 Cessna T310R for 25 years, and it’s been an amazingly reliable machine. However, this year’s trip involved an unprecedented number of airplane problems, almost as if the airplane had saved up five years’ worth of glitches and decided to dump them on me all at once. This made the trip more…ah…interesting. My first destination was Champaign, Illinois for three days of simulator training. The forecast called for thunderstorms over the Front Range starting at about 2 pm Mountain Time, so I figured if I launched from California by 8 am Pacific, I’d be able to make it over the high terrain and land at Denver’s Front Range Airport by 1 pm, beating the bad weather by an hour. I’d RON in Denver and launch for Illinois first thing the next morning. The plan worked perfectly, although […]
Damage History
The term “damage history” is not well-defined. Here are some thoughts on the subject. One of my clients just had a fancy digital engine monitor installed in his airplane. During the installation, the shop hired to do the work drilled a half-inch hole in a non-structural area of the cabin sidewall to accommodate the OAT probe, then realized that the hole was in the wrong place—the OAT probe wouldn’t fit due to interference—and and had to drill another hole in a more suitable location. The shop fessed up to its mistake, and assured my client that the first hole would be patched and painted so that it would be completely undetectable, and that this would be done at no cost to the client. “Oh my god,” the client said to me in obvious panic, “does this mean that my airplane now has ‘damage history’? What will this do to its resale value?” I get this a lot. In the past two years, for example, there have been a half-dozen prop strikes among my managed maintenance clientele. All occurred either with the gear down-and-locked or down-and-welded, and in all cases but one there was no airframe damage whatsoever. A few of […]
FAA’s War on Jugs: An Update
Yikes! It’s far worse than I expected, and it must be stopped. By Mike Busch I must be losing my touch. When I last wrote about this subject 9 months ago—in the February 2013 issue of EAA Sport Aviation—I reported that in 2009 the FAA effectively legislated out of existence Superior Millennium-brand investment-cast cylinders (that many considered to be the best-built cylinders for Continental engines available at the time), and that the FAA was working busily to do the same thing to ECi TITAN-brand cylinders (that many consider to be the best-built cylinders for Continental engines available today). In that article, I said that the Superior AD 2009-16-03 mandated the life-limiting of 8,000 investment-cast Millenniums at an FAA-estimated cost to owners of $12.4 million, and I estimated that the forthcoming AD against ECi TITANs would life-limit 20,000 cylinders at a cost of $30 million. Wow, did I ever blow those estimates! The FAA issued its Notice of Proposed Rulemaking (NPRM) for the ECi TITAN AD on August 12, 2013, and when I read it I was absolutely floored. It turns out that the proposed AD would actually euthanize 36,000 cylinders on 6,000 Continental 520- and 550-series engines at an FAA-estimated […]
Rough Engine
Understanding the underlying causes of engine roughness is the key to eliminating it. One of the most common squawks reported by pilots and aircraft owners is a rough-running engine. If the roughness can be duplicated during a ground runup, then the mechanic might have a chance to troubleshoot it systematically. Most of the time, however, the roughness is apparent only in-flight. Since the mechanic can’t reproduce the problem on the ground, he’s usually reduced to using guesswork—throwing parts, labor and money at the problem and hoping to get lucky. We call this process “shotgunning” and it’s something aircraft owners should try to avoid at all costs. The way to avoid it, of course, is never to put your mechanic in a position where he has to guess what’s wrong. I can’t count the number of times I’ve seen expensive components—especially magnetos and fuel pumps—overhauled or replaced in an attempt to cure engine roughness. Those are usually desperation moves on the part of a mechanic who has run out of ideas. It’s unfortunate, because there’s almost no way a fuel pump problem can cause an engine to run rough, and it’s extremely rare for a magneto issue to cause an engine […]
Thinking Slow
Why many career A&Ps are not great troubleshooters. I recently had a fascinating exchange with my friend and colleague Paul New. Paul is an A&P/IA and a truly extraordinary aircraft mechanic who was honored by the FAA as the National Aviation Maintenance Technician of the Year in 2007 (the year before I was so honored). But that’s where the historical similarity between me and Paul ends. While I came to aircraft maintenance rather late in life, Paul has been immersed in it since childhood, helping his A&P/IA dad with numerous aircraft restoration projects well before he was tall enough to see over the glareshield without sitting on a phone book. In 1981, Paul earned his degree in Avionics Technology from Southern Illinois University, and spent five years managing avionics shops for a commuter airline and an FBO. In 1986, he returned to Jackson, Tenn. to work with his dad in the aircraft restoration business once again, and in 1989 he purchased Tennessee Aircraft Services, Inc. from his dad and developed it into one of the premier Cessna Service Centers in the southeast US, performing both general maintenance and major structural repairs. Over the years, Paul and I have formed an […]
AOG Rescue
A mechanical problem away from home is every aircraft owner’s worst nightmare. Here’s how one owner dealt with such a nightmare…with a little help. On an otherwise-peaceful Saturday morning, I received a panicky text message from Mark, a Cessna 185 owner from the San Francisco Bay Area. Mark said that he and his wife had flown to Minden, Nevada in their beautiful Cessna 185 to take care of an ill relative. A couple of days later, when Mark started the aircraft to depart for home, the engine registered no oil pressure. The Cessna has the original factory-installed direct-reading oil pressure gauge — no electrons or connectors or data acquisition modules involved — so if the gauge reads zero, you can pretty well take it to the bank that there really is no oil pressure. And that’s not a great way to begin a Saturday morning. Mark took the aircraft to the local A&P on the field, who plumbed an external pressure gauge to the engine, started it briefly, and verified that indeed there was no oil pressure. The A&P then cut open the oil filter, and informed Mark that there was “significant bearing metal” in the filter, and that the […]
“But My Mechanic Says…”
Aircraft owners get lots of bad advice from their A&Ps. Ever wonder where the A&Ps get it from? “I know you’re a strong proponent of the in-flight mag check,” emailed the aircraft owner, “but I have been advised against doing this by my A&P due to concerns that I could get a serious backfire that could damage the engine. I read somewhere, maybe in one of your articles, that if the engine quits during the in-flight mag check to pull the mixture first, then switch back to both mags before coming back with the mixture to prevent a backfire. Please advise…” I told the owner that he had it exactly right, and his A&P had it wrong. For one thing, the A&P had his terminology mixed up: there’s zero risk of a “backfire” (which is combustion in the engine’s intake manifold); what the IA was really concerned about is an “afterfire” (which is combustion in the exhaust manifold). Afterfires cause a scary “pop” noise but generally don’t hurt anything. Obviously, this aircraft owner had done his homework and knew perfectly well how to avoid this situation: If you turn off one magneto and the engine quits, pull the mixture control to […]
Compression in Context
Few aviation maintenance tasks are so misunderstood—and so responsible for inappropriate work and expense—as the routine differential compression test. It happens every year: We put our aircraft in the shop for its annual inspection. The IA pulls out the compression test gauges and measures each cylinder while we hold our breath and pray silently until the verdict is rendered. If the readings are good, we can smile and relax; if not, we brace ourselves for the inevitable sticker shock. I learned an important lesson about compression tests in Spring of 2002, shortly after I became an A&P, when I did something dumb: I pulled a perfectly good cylinder off of my engine! Had I known what I know now, I wouldn’t have touched that cylinder. But at the time, I thought I was doing the right thing. (It does seem like most of the wisdom I’ve gained over the years came from first exhausting all other alternatives.) I had downed my airplane for its 2002 annual inspection, and the first items on my checklist were to drain the hot oil and perform a hot compression test. All cylinders measured in the 70s except one; that one measured 60/80 with air […]
The Blame Game
When “stuff happens” to your aircraft, it’s not always someone else’s fault. Regular readers of this column know that I grumble a lot about “stupid mechanic tricks” made by career A&Ps who should know better. Some have accused me of mechanic-bashing. That’s a bit harsh, but I’ll readily admit to being a hard marker when it comes to genuinely dumb mistakes made by folks who work on airplanes for a living and hold themselves out as being maintenance professionals. Last week, for example, one of my clients had a hole punched clean through the wing of his airplane during a routine tire change when a mechanic discovered he didn’t have the proper jack points and tried jacking the airplane by its tiedown rings—something explicitly forbidden by the maintenance manual. Last month, at one of the best-known service centers in the US, a young mechanic (“nugget”) installed a new battery in a high-performance single-engine airplane belonging to another of my clients, and managed to reverse the polarity and destroy $13,000 worth of electrical components and avionics. The month prior, it was an alternator drive hub that came loose because the installing mechanic neglected to torque it properly and install the cotter […]
The Redundancy Trap
The best way to protect against the in-flight failure of any aircraft component is to have two. Or is it? CIVIL AVIATION REGULATIONSPART 13—AIRCRAFT ENGINE AIRWORTHINESSSubpart B—Reciprocating Engines§ 13.111 Ignition system. All spark ignition engines shall be equipped with either a dual ignition system having at least two spark plugs per cylinder and two separate electrical circuits with separate sources of electrical energy, or with an ignition system which will function with equal reliability in flight. FEDERAL AVIATION REGULATIONS (14 CFR)PART 33—AIRWORTHINESS STANDARDS: AIRCRAFT ENGINESSubpart C—Design and Construction; Reciprocating Aircraft Engines§ 33.37 Ignition system. Each spark ignition engine must have a dual ignition system with at least two spark plugs for each cylinder and two separate electric circuits with separate sources of electrical energy, or have an ignition system of equivalent in-flight reliability. Both the FARs and their predecessor CARs require that certificated spark-ignition reciprocating aircraft engines—the kind most of us fly behind—have fully redundant dual ignition systems. There’s a good reason for this: Ignition system failures in these engines are relatively commonplace. Without a properly functioning ignition system, the engine could quit, the airplane could fall out of the sky, and people could get hurt. How often do ignition systems fail? Well, spark […]
A Little Dab’ll Do Ya…In
Even a seemingly trivial mistake by a well-intentioned mechanic can have dire consequences. On April 19, 2005, a 1966 Beechcraft Debonair was cruising at 8,500’ on a VFR flight from Van Nuys to San Jose, Calif., when the pilot heard a loud noise and the Continental IO-550 engine started running rough. The pilot checked the oil pressure and oil temperature gauges and found both had normal readings in the green. He throttled back, advised Oakland Center that he was diverting to Paso Robles, and began descending. Then there was another loud bang from the engine compartment, engine RPM dropped dramatically, and the cockpit started to fill with white smoke. The PIC—a 32-year-old 500-hour commercial pilot who had recently earned his CFI—throttled back to idle, made a mayday call to Oakland Center, and established an 80-knot glide. The smoke cleared from the cockpit and the pilot determined that he was within gliding distance of Paso Robles Airport. Just as it seemed like the story might have a happy ending, the Debonair’s lefthand engine cowling door popped open and stayed open. That increased drag and caused the rate of descent to increase to nearly 1,000’/minute. The pilot now realized he wasn’t going […]
Diagnostic Tales from the War Zone
Troubleshooting is best accomplished by first gathering data and then analyzing it logically. The owner of a 2005 Cessna T182 was in Key West Florida when he experienced unusual roughness immediately after engine start. The EGT and CHT on the #3 cylinder seemed unusually low at first, but the roughness seemed to clear up before he took off on a local sightseeing flight. The next morning as the owner attempted to depart Key West for home, the roughness reappeared but this time didn’t go away as the engine warmed up. Leaning seemed to help some, but he did not resolve the problem completely. Once again, cylinder #3 was cold. Why is the cylinder cold? The owner took the aircraft to a local mechanic, who ran the engine and concluded that the RSA fuel servo was at fault. He discussed the problem with another technician who agreed with his diagnosis. The mechanic proposed to remove the RSA fuel servo and overnight it out to Precision Airmotive for bench testing and repair. This would leave the aircraft grounded and the owner stranded in Key West for a week. The estimated cost for an overhauled fuel servo was about $2,000. As luck would have it, […]
Separation Anxiety
Can we prevent these catastrophic head-to-barrel separations? On February 24, 2012, the National Transportation Safety Board issued Safety Recommendation A-12-7 to FAA acting administrator Michael Huerta, expressing great concern over 29 cylinder head fatigue failures of Titan-brand cylinders manufactured by Engine Components, Inc. between 2003 and 2009 and installed on Continental IO-520, TSIO-520 and IO-550 engines. The NTSB recommended that the FAA issue an Airworthiness Directive (AD) requiring repetitive inspections of these cylinders every 50 or 100 hours, and mandatory retirement of the cylinders at Continental’s published TBO. If the FAA issues such an AD—and I hear rumors that the FAA is working on a Notice of Proposed Rulemaking (NPRM) as I write this article—it would affect more than 20,000 ECi Titan cylinders, and cost aircraft owners roughly $30,000,000. It wouldn’t be the first such AD, and most likely not the last. Déjà vu all over again In May 2007—years before I became a columnist for EAA Sport Aviation—I wrote an article titled “Double Trouble” recounting the misadventures of a Cessna 182 owner who was flying at 6,000’ through the desolate Dakota Badlands when his 1,600-hour Continental O-470-U engine suffered a catastrophic head-to-barrel separation of the #1 cylinder. (See Fig. […]
How Much is Too Much?
There’s metal in your oil filter. Now what? “I’ve been a happy aircraft owner until this morning,” Frank wrote me. “My aircraft is in the shop for its annual inspection, and the mechanic just called to say that they found magnetic chips in the oil filter, and the big-bore Continental engine would have to be taken out and completely disassembled. Do you have any advice how to proceed?” Ouch! I asked Frank to email me a photo of the filter contents, and he did. (See Figure 1.) I saw a few curved magnetic whiskers and a few small bronze-colored chips. Certainly enough to get my attention and pique my curiosity about their source, but hardly anywhere close to warranting a $20,000 engine teardown. I asked Frank a few follow-up questions and learned that his engine’s starter drive adapter had recently started slipping and had been replaced. The small quantity of metal in the filter struck me as being entirely consistent with what one would expect to see from a failing starter drive adapter. So I advised Frank to have his mechanic change the oil and oil filter, then go fly the airplane for 10 hours or so, and then have […]
Red Box, Red Fin
How NOT to lean your engine. At my July pilgrimage to EAA AirVenture in Oshkosh, I had the opportunity to speak to thousands of pilots and aircraft owners on a wide variety of subjects ranging from reliability-centered maintenance to TBO busting to corrosion, and to conduct a half-dozen informal hour-long Q&A sessions addressing whatever maintenance-related issues were on their minds. In those sessions, I received more questions about one topic than all others combined: leaning. Some of the questions focused on Old Wives’ Tales about lean-of-peak (LOP) operation: Q: Won’t operating LOP hurt my engine, burn my exhaust valves, etc.? A: It’s a lot easier to damage your engine ROP, much less likely LOP. Q: Can my carbureted engine be operated LOP? A: Most can. Using carb heat helps. Only way to know is to try it. You can’t hurt anything by experimenting with LOP operation. Q: Can my injected engine be operated LOP without GAMIjectors? A: Some can, some can’t. Only way to know is to try it. You can’t hurt anything by experimenting with LOP operation. Q: Can my engine be operated LOP without an engine monitor? A: Sure. I operated LOP for a decade before I installed […]
Mini or Maxi?
Is your mechanic a minimalist or a maximalist? I’m an unabashed maintenance minimalist. I believe in doing only maintenance necessary to make an aircraft safe, reliable, and compliant with regulations. I believe that doing more maintenance than that is not only a waste of time and money, but that it also makes the airplane less safe and reliable. I think about aircraft maintenance the way I think about surgery—not as a good thing, but as a necessary evil. Sometimes it has to be done, but we don’t get extra credit for doing more than necessary to make the airplane safe, reliable and legal. This “less is more” maintenance philosophy has served me well for decades, and has become an established science (“Reliability-Centered Maintenance” or “RCM”) widely adopted by airlines, military aviation, high-end bizjets, and industrial activities from nuclear power plants to water treatment plants to offshore oil platforms. But this philosophy is heresy to many GA mechanics who were taught in A&P school that maintenance is a good thing, and that more maintenance is better. I deal with such “maintenance maximalists” all the time in my managed-maintenance practice. We often wind up having some interesting discussions. Occasionally even an arm-wrestling […]
Flying Efficiently
In a world of $7 avgas, it’s more important than ever to get the best bang for the buck. How can we get the best fuel economy from our airplanes? Given the painful cost of avgas these days, this is a question on lots of airplane owner’s minds. That goes at least double for unfortunate folks like me and Mac McClellan who fly twins. So it’s a subject I’ve thought about—and researched—quite a bit. It turns out that there are lots of pieces to this puzzle. There are all sorts of things we can do to optimize efficiency. Some are simple; some are a bit more complex. It does take considerable attention to detail to fly as efficiently as possible. Throttle Let’s start with something simple: throttle position. Our piston aircraft engines are always most efficient at wide-open throttle (WOT). Retarding the throttle from its wide-open position closes the throttle butterfly valve in the carburetor or throttle body, and literally chokes off the engine’s air supply, intentionally reducing its volumetric efficiency. It doesn’t take rocket science to figure out that this is not something you want to do when striving for maximum engine efficiency. (Could you operate at maximum efficiency […]
Cam Distress
When your engine finally needs to be overhauled, the most likely cause will be corrosion-induced distress to the cam lobes. I recently received an email from a Skylane owner in Miami, Florida who was understandably upset after receiving bad news from his IA, and looking for a second opinion: “My 1980 Cessna 182Q went into annual, and I received a call from my IA a day later telling me that two cylinders had low compression (38/80). My IA pulled the cylinders, and just called me to say my engine is DEAD! I’m attaching some photos so you can see the reason for his pronouncement. “The engine was last overhauled in 1987 by Mid-State Aircraft Engines (no longer in business), and is at about 1,600 hours and 25 years SMOH. Published TBO for this engine is 1,500 hours. “Please let me know what you think I should do. If I do need an overhaul, could you recommend an overhaul shop, or would you recommend a factory reman?” The owner attached some photographs of his Continental O-470-U engine showing a cam lobe in questionable condition (see Figure 1) and a severely spalled lifter (see Figure 2). I added these photos to my […]
Teardown!
The decision whether or not to tear down an aircraft engine is among the most difficult and agonizing ones we make. My company manages the maintenance of many hundreds of piston-powered GA airplanes, so we frequently deal with all manner of engine problems. Our biggest challenge involves diagnosing the problems and then deciding what work needs to be done to get the problems resolved. In making these decisions, we work hard to resolve problems in the most minimally invasive way possible. For example, we never let a mechanic pull a cylinder unless we’re absolutely convinced through non-invasive techniques—borescope inspection, engine monitor data analysis, spectrographic oil analysis, scanning electron microscopy of oil filter contents, etc.—that cylinder removal is genuinely warranted. We very seldom approve a so-called “top overhaul” (replacing all cylinders at once) since it is almost never the case that more than one or two cylinders actually need to be replaced. By far the most agonizing decisions we have to make involve whether to remove an engine from the airplane and send it to an engine shop for a teardown. Tearing down an engine is the most invasive thing you can do to an engine. It’s expensive—typically $15,000 for a […]
Spark Plug Wars
We’re seeing an epidemic of Champion spark plug problems. Champion insists its plugs are fine and the problems are self-inflicted. The truth may be a bit more complicated. By Mike Busch Premature failures of Champion-brand aviation spark plugs first showed up on my radar screen several years ago. My company manages the maintenance of nearly 400 piston-powered airplanes, the lion’s share of them high-performance singles and twins powered by Continental 520- and 550-series engines. So there are roughly 5,000 spark plugs flying in our “fleet” at any given point in time. The overwhelming majority of those spark plugs were Champions. I’d been using Champion spark plugs in my own airplane for decades without any problems, but my personal experience had been exclusively with their conventional massive-electrode plugs (RHB32Es to be exact). In contrast, more than half the airplanes managed by my company were using Champion’s top-of-the-line fine-wire iridium RHB32S plugs. These exotic fine-wire plugs are very pricey—about $125 apiece (list price) compared with about $40 for massives. However, the fine-wire plugs should last about 1,500 hours (compared to 400-500 hours for massives), so their life-cycle cost should theoretically be comparable. What we were seeing, however, was premature failures of these […]
The Decision Point
During every annual inspection, there’s a particular point in time when you and your IA need to sit down and make decisions. Regular readers of this column know how strongly I feel about aircraft owners taking charge of their maintenance and managing the mechanics and shops they hire to work on their aircraft. An owner should never authorize any maintenance without first fully understanding the scope and detail of each proposed maintenance task to be done, and knows the answers to these questions: The annual inspection is generally the most difficult time for an owner to exercise such management and oversight. It’s difficult for two reasons. First, when you put your aircraft in the shop for an annual inspection, you have no idea what sort of discrepancies will be found during the inspection. So you have no way of anticipating the extent, time and cost of the work. Second, the aircraft is usually in the shop for quite a while at annual—typically a week or two, sometimes longer—and most owners don’t have the time or inclination to hang around the shop and oversee the work. Despite these difficulties, the annual inspection is the most important time for you to exercise […]
Trust But Verify
Before you approve any costly or invasive repair to your aircraft, make sure the discrepancy is real. Arguably the worst part of being an aircraft owner is the annual ordeal of putting your plane in the shop every 12 calendar months and then bracing yourself for bad news. Over the past 4 years, my company has managed more than 700 annual inspections and more than 6,000 lesser maintenance events, so it’s a safe guess that we’ve dealt with tens of thousands of mechanical discrepancies. Sometimes the bad news is painful and costly to the aircraft owner. But surprisingly often, it turns out to be nothing more than a false alarm. A couple of months ago, for example, a client’s single-engine airplane went into a big, well-known Florida service center for its annual ordeal. Within hours, the shop reported that cylinder #3 measured 38/80 on the compression test, with air audible at the exhaust tailpipe. (This was a Continental engine, and the master orifice no-go limit was 46/80.) The mechanic attempted to “stake” the #3 exhaust valve but was unable to improve the reading. The shop said the #3 cylinder needed to be removed and sent to a cylinder shop to […]
Breakdown!
A mechanical problem away from home is every aircraft owner’s worst nightmare. Here are some thoughts about how best to deal with one. As a tech rep for the three largest airplane type clubs in the world (ABS, CPA, COPA) and as the founder and CEO of the world’s largest professional maintenance management firm for owner-flown aircraft, I’ve helped guide thousands of aircraft owners through challenging troubleshooting scenarios, difficult annual inspections, major structural repairs, engine overhauls, and just about every other kind of maintenance event that can befall an airplane. But of all of these, the ones that invariably elicit the most gratitude have been those where I’ve been able to help an aircraft owners deal with a mechanical breakdown away from home. Here’s what one of my managed-maintenance clients emailed me recently: “I always appreciate it when you guys save me money on my annual inspection and other routine maintenance. But when you helped me out with that charging system failure during my recent fishing trip to Montana, that was truly priceless!” After having dealt with a goodly number of breakdown assistance situations over the years (including a few involving my own airplane) and having seen both good outcomes […]
The Most Unforgivable Sin
Running out of fuel only happens to the other guy, right? I usually don’t write about experimental aircraft because my 45 years of aviation experience has been almost exclusively with certificated normal-category airplanes. However, I’m making an exception this month. This column was prompted by the June 16, 2001 crash of an experimental Lancair IV-P (NTSB reference LAX01FA212) that claimed the life of veteran pilot Tony Durizzi. I didn’t know Tony personally, but I did research his accident carefully, and I believe there are some terribly important lessons to be learned from it—lessons that might just cause you to question some of the most basic things your CFI taught you, and perhaps to change some of your most basic flying habits. At least I hope so Tony who? Anthony J. Durizzi’s flying career started well before my time. Back in the mid-1960s, when I was just earning my private ticket, Tony was flying big radial-engine transports in Southeast Asia for Air America, the big airline operated covertly by the CIA. Colleagues who shared a cockpit with Tony agreed that he was an outstanding pilot with superb stick-and-rudder skills. You had to be to survive in Air America. In the early […]
How to Flunk an Annual Inspection
Under the FARs, an annual inspection is a pass-fail test. Sometimes failing is the best course of action. Of the nearly 200 rules in Part 91 of the Federal Aviation Regulations, far and away the most expensive for most aircraft owners is this one: § 91.409 Inspections. (a) …No person may operate an aircraft unless, within the preceding 12 calendar months, it has had—(1) an annual inspection in accordance with part 43 of this chapter and has been approved for return to service by a person authorized by §43.7 of this chapter… This means that once a year, we have to turn our aircraft over to an eagle-eyed A&P/IA or FAA-certified repair station and pay them to perform an annual inspection. We then have to pay the shop or mechanic to repair all the airworthiness discrepancies that they find and to comply with all applicable airworthiness directives, airworthiness limitations, and other regulatory airworthiness requirements. The ultimate object of this costly exercise is to obtain a logbook entry containing the cherished magic words that permit us to fly the airplane for another 12 calendar months: I certify that this aircraft has been inspected in accordance with an annual inspection and was determined to […]
When to Overhaul
How do you decide when it’s time to overhaul your engine? If not at TBO, then when? Regular readers of this column know that I’m not a big fan of the idea of overhauling engines at TBO. I consider engine TBO to be a thoroughly discredited concept that has cost aircraft owners hundreds of millions of dollars by causing perfectly healthy engines to be euthanized arbitrarily. The notion of overhauling aircraft engines at a particular number of hours was abandoned many decades ago by the airlines and the military. Piston GA is the last segment of aviation that still subscribes to this ridiculous idea. The TSIO-520-BB engines on my Cessna T310R have a published TBO of 1,400 hours. Both of my engines are now at 2,800 hours—200% of TBO—and still doing just fine, thank you very much. Many of my managed-maintenance clients are well past TBO. One whose engine has a 2,000-hour TBO is now at 3,200 hours and doing just great. There are several reasons that TBO is such a flawed concept. One is that engine life has very little to do with engine hours in service. Hours is not what limits the life of our engines. The biggest […]
Intervals
When are manufacturer-specified inspection, overhaul and replacement intervals mandatory for a Part 91 operator? “It has been six years since your propeller was last overhauled, so we’re going to have to overhaul it this year as required by Hartzell.” “Your magnetos are past due; TCM requires that they be overhauled every four years.” “We need to clean your fuel nozzles and adjust your fuel injection system annually as specified by the engine manufacturer.” “The trim tab actuators need to be disassembled, cleaned and lubricated—the Cessna maintenance manual says this must be done every 200 hours.” “The Instructions for Continued Airworthiness for your Garmin autopilot requires that the servo clutches be checked for proper breakaway torque at every annual inspection.” “We need to pull the wing bolts on your Bonanza and send them out for non-destructive testing—Beech requires this be done every five years.” “The regulator on your STC’d oxygen system needs to be sent out for overhaul every five years according to the manufacturer’s Instructions for Continued Airworthiness.” I see mechanics telling my clients these sorts of things every day. An important part of my job is to advise my clients to decline most of these things because (1) they’re […]
My $.02 On $6.00 AVGAS
My 1979 T310R is equipped with a Shadin fuel totalizer which—like my fuel gauges—is calibrated in pounds of fuel (rather than gallons). So when the price of 100LL reached $6.00 per gallon, I half-jokingly turned to a pilot friend who was flying with me in the right seat and explained that those fuel quantity and fuel flow indications were displayed in dollars and dollars per hour, respectively. (I say half-jokingly, because I was also half-crying.) When I bought the airplane in 1987, avgas cost around two bucks a gallon, and topping off my twin for a long trip typically cost me around $300 (which seemed bad enough at the time), but today that same top-off costs me $900, which is enough to make me seriously question how long I can continue to do this. 100LL prices in perspective In trying to wrestle with this issue, I spent some time researching fuel prices on the Internet, and what I found out was startling and somewhat counterintuitive. Take a close look at the 40-year history of 100LL prices that I put together in Figure 1. Pretty interesting: While nominal 100LL prices rose from around 75 cents a gallon in 1972 to the […]
Warranty Schmarranty!
You bought a $40,000 engine, and it turns out to be a lemon. That’s okay, you’re covered under warranty, right? Hmmm… On a breathtakingly beautiful spring day in April 2011, one of my clients landed his 1980 Cessna T210 at its home base—a high-altitude airport (5,000 feet MSL) surrounded by 10,000-foot mountainous terrain in all quadrants—and taxied to his tee-hangar. While pushing the airplane into the hangar, the owner noticed some oil leaking from the bottom of the engine cowling, and brought it to the attention of a local A&P. The mechanic inspected the engine—a Continental TSIO-520-R—and said the oil seemed to be leaking from the rear cover of the engine’s starter adapter where the shaft for the alternator drive pulley emerges. The mechanic washed down the engine with solvent and had the owner do a thorough engine runup. Oil was now found to be leaking from the area around the starter adapter shaft in copious quantities. The shaft itself seemed to be off-center in the boss on the rear cover of the starter adapter, and exhibited excessive free play. An overhauled/exchange starter adapter was ordered from Niagara Air Parts with next-day-air shipping. Meantime, the mechanic pulled the engine’s oil […]
Is your airplane too broken to fly?
The rules about flying with inoperative equipment are complicated, and have changed a lot. Here’s the latest. Is your airplane squawk-free? I know mine isn’t. At any given point in time, you’ll find a yellow Post-it Note on the instrument panel of my 1979 Cessna T310R listing all known squawks. Any time I notice a discrepancy, I jot it down so I won’t forget to deal with it next time I’m wrenching on the airplane. At the moment, there are six items on my Post-it Note list: Six known discrepancies is a lot—perhaps an all-time record for me. It reflects that fact that I’ve been busy at work and haven’t had the time to work on my airplane for a while. I should be ashamed of myself. All these items need to be fixed, but none of them strike me as being particularly serious—certainly not ones that rise to the level of being “airworthiness items.” From time to time, however, my Post-it Note has contained more serious items such as “left vacuum pump inop” or “right alternator inop.” Those were obviously more urgent discrepancies and needed to be dealt with sooner rather than later. Too broken to fly? How serious […]
Owner-Produced Parts
If your certificated aircraft needs a replacement part that’s ridiculously expensive or downright unobtainable, the FAA will allow you to produce one yourself. The 1960s and 1970s were the biggest years for production of piston GA airplanes. By the peak production year of 1979, manufacturers like Beech, Cessna, Mooney, Piper, and others were pushing new airplanes out the door as fast as they could, and owners were snapping up all they could produce. All this came to a crashing halt in the early 80s, when the effects of a double-dip recession were magnified by passage of massive tax reforms that eliminated financial incentives to buy new airplanes. Piston GA manufacturing all but ceased altogether, and it has never really recovered. It’s no surprise, then, that most of the piston GA aircraft flying today are between 30 and 50 years old. Keeping these aircraft flying is becoming more challenging every year, particularly with respect to finding replacement parts. Some manufacturers—notably Cessna—continue to do a far better job of keeping replacement parts available for these decades-old, out-of-production aircraft than we have any right to expect. Some other manufacturers (who shall remain nameless) don’t support their legacy aircraft nearly as well. Many parts […]
Battery TLC
The care and feeding of aircraft batteries. Last month, in Part 1 of this article, we discussed the construction, chemistry, types and characteristics of lead-acid aircraft batteries. This month, we’ll talk about the care and feeding of those batteries, including charging and discharging, conditioning, capacity testing, and deciding when a battery should be retired and replaced. Charging Charging a lead-acid battery involves three phases: (1) a constant-current phase during which charging voltage gradually increases; (2) a constant-voltage phase during which charging current gradually tapers off to very low levels as the battery approaches its fully-charged state; and (3) a float (or trickle) charge phase that maintains the battery in its fully-charged condition and offsets the battery’s natural tendency to self-discharge. Although this is a fairly complicated procedure, we now have very reasonably priced microprocessor-controlled battery charges that can perform this automatically. Keep in mind, however, that your aircraft’s charging system is strictly a constant-voltage charger, which is why it’s a very bad idea to fly with a deeply discharged battery (e.g., after maintenance or a GPU start). The aircraft’s charging system will charge a deeply discharged battery at an excessive rate (because it is a “dumb” charger without current limiting), […]
About Batteries
Sensitive and fragile compared to their automotive brethren, aircraft batteries need TLC if you don’t want to be left stranded. Aircraft batteries are the Rodney Dangerfields of general aviation. They get no respect. We let them sit unflown for weeks at a time, sometimes months. We deep-discharge them by forgetting to turn off the master switch. Then we jump-start the airplane with a ground power unit and go fly as our alternator fries them with excessive charging current. We fail to check our bus voltage regularly, resulting in long periods of undercharge or overcharge. If we’re lucky, the electrolyte level gets checked once a year at annual inspection time. Then we cuss them out when the airplane won’t start on a cold Sunday winter morning in Sheepdip, Nebraska, and there’s no mechanic or battery cart on the field. Not Die-Hards We probably learned these bad habits from our experience with automobiles. Car batteries are big, heavy, robust brutes that can tolerate this sort of abuse. Aircraft batteries aren’t and can’t. They’re fragile and sensitive. They’re not Die-Hards. Aircraft batteries are built to be lightweight and compact. They have a small fraction of the capacity of our automotive batteries—typically 10-35 ampere-hours […]
Is it safe? Is it airworthy?
We often treat the words “safe” and “airworthy” as if they were synonyms. They’re not. On the landing roll, something didn’t feel right. The Cessna pulled strongly to the left. The pilot had to apply full right pedal and some right brake to keep it on the runway. As the pilot struggled to make the turnoff, it became clear what was wrong: The left main landing gear tire was flat. Naturally, this happened away from home base while the pilot was stopping for fuel and lunch in the middle of an important trip. (Doesn’t it always?) The pilot needed to get his airplane fixed and back in the air as quickly as possible. He contacted the local shop on the field—one he wasn’t familiar with—and asked them to recover his aircraft and fix the flat tire. The mechanic said that he had a new tire in stock for $200 and a tube for $50. Labor was estimated at two hours at a shop rate of $85/hour. It looked like this $100 hamburger would turn into a $500 hamburger. Having few options, the aircraft owner approved the work and asked the mechanic to use his best efforts to complete it quickly […]
Making Metal?
How to ensure that nothing is coming apart inside your crankcase. I’d been working with a Bonanza owner in Memphis for several weeks helping him chase down a problem with his Lycoming engine. Yes, Lycoming—the aircraft was an A36 with a Machen conversion to a fire-breathing 350 hp Lycoming TIO-540-J2BD engine. The owner of this hot-rod Bonanza initially reported that the engine had exhibited several episodes of rough running after startup, but that the engine seemed to run smoothly once it warmed up. The owner emailed me a data dump from his JPI engine monitor, which confirmed my suspicions that his “morning sickness” was caused by a couple of sticky exhaust valves in cylinders #4 and #5. Sticking exhaust valves is a fairly common malady in Lycomings, which is why Lycoming Service Bulletin 388C and Service Instruction 1481A call for doing a “valve wobble test” every 400 or 1000 hours (depending on what kind of exhaust valve guides are installed). The owner wound up taking his sick engine to an excellent engine shop near Memphis. The shop pulled the rocker covers and found the #4 exhaust valve springs black with carbon from a badly leaking exhaust valve guide. #5 had […]
The Waddington Effect
Contrary to popular belief, more maintenance isn’t necessarily better. Often it’s worse—a lesson that was learned during WWII. I’ve written at length in prior issues of EAA Sport Aviation on the subject of Reliability-Centered Maintenance (RCM), the scientific and engineering discipline of designing optimum maintenance programs to provide the highest levels of safety and reliability at the lowest cost. RCM originated in the late 1960s from the work of Stanley Nowlan and Howard Heap at United Airlines, and quickly became the “bible” for how maintenance was done throughout the air transport industry. RCM was adopted by the U.S. military beginning in the mid-1970s, by the U.S. commercial nuclear power industry in the 1980s, and by many other industries in the 1990s. Today, RCM is the way maintenance is done in all segments of aviation except one: general aviation. Actually, RCM is now being widely adopted in high-end GA—at the Citation X, Gulfstream, Challenger and Global Express level—but not yet at the low end of the aviation food chain where most of us hang out. (One of my missions is to change that.) RCM Principles Fifty years ago, in the 1960s (when I first became a pilot and aircraft owner), aviation […]
Slippery Stuff
More about what aircraft owners should know about piston aircraft engine oil. Last month, we began our discussion of piston aircraft engine oil by discussing the types and properties of the various kinds of engine oil available, and I offered some thoughts about which oils I prefer and why. This month, I’ll continue the discussion by addressing oil additives, oil consumption, oil level, oil-change intervals, oil filter inspection and oil analysis. Aftermarket additives For as long as I can remember, there have been pitchmen promoting “miracle in a can” oil additives that claim to eliminate friction and wear, increase fuel economy, improve your landings, raise your IQ, and rescue your marriage. The granddaddy of these is Marvel Mystery Oil. Folks have been pouring this red, sweet-smelling stuff into aircraft engines for more than 80 years. It was developed in 1923 by Burt Pierce, the inventor of the Marvel carburetor, and was intended as a fuel additive to clean carburetor jets. Why folks started using as an oil additive escapes me. The name “mystery oil” came from the fact that Burt Pierce refused to divulge its formula. So far as I can tell, MMO doesn’t do any harm if used in […]
All About Oil
What aircraft owners should know about piston aircraft engine oil. This is the first of a two-part article about the lubricating oil we use in our piston aircraft engines, and we’ll be covering a lot of territory. We’ll discuss the various types of engine oil—monograde versus multigrade, mineral oil versus synthetic—and the pros and cons of each. We’ll talk about aftermarket oil additives and whether they’re beneficial or just hype. We’ll touch upon oil consumption, optimum oil level, and how often to change the oil. We’ll also address oil filter inspection and spectrographic oil analysis, and how we use them to assess engine health. Six Key Functions If I asked you to explain the purpose of engine oil, I imagine you’d probably say something like “to lubricate moving parts and reduce friction and wear.” Now that’s certainly correct as far as it goes, but lubrication is only one of six key functions that oil must perform in your piston aircraft engine. In fact, the lubrication needs of our big displacement, slow-turning piston aircraft engines are really quite modest, compared for example to the high-revving engines in our automobiles. Lubrication demands tend to vary with the square of RPM, so a […]
The Mag Check
You’ve been doing mag checks since your first flight lesson, but are you doing them right? From your first days as a student pilot, you were undoubtedly taught to perform a “mag check” as part of each pre-takeoff runup. But do you know how to do it correctly, what to look for, and how to interpret the results? Surprisingly, many pilots don’t. To begin with, most Pilot Operating Handbooks tell you to note the RPM drop when you switch from both mags to just one, and give some maximum acceptable RPM drop and sometimes some maximum acceptable RPM difference between the two mags. For example, the POH for my TCM-powered Cessna T310R specifies that an RPM drop more than 150 RPM on either mag or a difference more than 50 RPM between the two mags is unacceptable. Many Lycoming-powered aircraft specify a maximum drop of 175 RPM and a maximum difference of 50 RPM. Lycoming’s revised guidance on mag checks On June 18, 2010, Lycoming issued Service Instruction No. 1132B revising its guidance on how pre-flight mag checks should be performed. Some highlights of this new service bulletin: The entire revised Service Instruction 1132B may be found online at http://www.lycoming.textron.com/support/publications/service-instructions/pdfs/SI1132B.pdf EGT […]
Return to Service
Mechanics approve an aircraft for return to service after maintenance by signing a logbook entry, but pilots actually return the aircraft to service by flying it. Never forget that on the first flight after maintenance, you’re a test pilot…so please act accordingly. For months, a client of mine had been searching for a Bonanza A36 to buy. He’d narrowed his search to two very promising candidates. One of them had recently suffered a “forgot to remove the tow bar” prop strike. This necessitated an engine teardown inspection and prop overhaul, both paid for by insurance. The seller was appropriately upbeat in his communications with my client: The engine in the plane was torn down and no damage that was a result of the tow bar incident was present. I’ve included the log book entries for the tear down and the final entry for the annual. While this tow bar event has been a royal pain in the rear, we have ultimately ended up with a greatly upgraded plane and one that the buyer can have a extremely high level of understanding and confidence of the condition of the engine at 1,237 hours (like no other plane on the market). A […]
EGT Myths Debunked
Pilots still seem to have a lot of misconceptions about EGT. Let’s see if we can clear some of them up. These days, pilots of piston-powered aircraft seem to be fixated upon exhaust gas temperature (EGT). Scarcely a day goes by that I don’t receive a phone call or email or support ticket asking some EGT-related question. Pilots will send me a list of EGT readings for each of their cylinders and ask me if I think they look okay, whether I think their EGTs are too high, what maximum EGT limit I recommend, why their EGTs seem to be higher in the winter than in the summer, or why the EGTs on their 1972 Cessna 182 are so much higher than the ones on their friend’s 1977 model. They’ll voice concern that the individual cylinders on their engine have such diverse EGT readings, worry that the spread between the highest and lowest EGT is excessive, and ask for advice on how to bring them closer together. They’ll complain that they are unable to transition from rich-of-peak (ROP) to lean-of-peak (LOP) operation without producing EGTs that are unacceptably high. Each of these questions reveals a fundamental misunderstanding of what EGT […]
How To Destroy Your Engine
Destructive detonation and pre-ignition events can destroy your engine in two minutes flat. Know the symptoms, and act fast! At least once a year, I am contacted by an aircraft owner whose piston aircraft engine was destroyed or severely damaged by a destructive detonation or pre-ignition event. But lately, the pace seems to be quickening. In a recent 12-month period, I’ve encountered three of them. One recent incident involved Cirrus SR-20 powered by a 200 horsepower TCM IO-360-ES engine. The plane was equipped with a snazzy Avidyne Entegra MFD with an integrated engine monitoring system called “EMAX.” The CHT data downloaded from the EMAX system tells the short tale of this engine’s demise: Everything looked fine until about two minutes after the pilot applied takeoff power, at which point the #1 cylinder’s CHT began to climb rapidly compared to the other five cylinders. At the three-minute mark after brake release—with the aircraft at roughly 2,000’ AGL—CHT #1 rose above 400°F and set off a high-CHT alarm on the MFD. CHT #1 continued its rapid rise—nearly 1°F per second—that continued unabated until the piston and cylinder head were destroyed approximately five minutes after takeoff power was applied and two minutes after […]
Exhaust Valve Failures – Part 2
We have the technology to prevent these failures by detecting them in the incipient phase. Last month we discussed how exhaust valves fail and why they sometimes fail prematurely. This month, we’ll shift our focus to how we can monitor exhaust valve condition, detect incipient valve problems, and deal with them before in-flight failure occurs. I started last month’s column with a description and photos of an in-flight exhaust valve failure that occurred in my airplane nearly 20 years ago. That failure occurred “back in the bad old days” before we had the sophisticated engine monitoring tools that we have today—specifically spectrographic oil analysis, borescope inspections, and digital engine monitors. Nowadays, there’s no excuse for such an in-flight failure because we have the technology to detect these problems early. Anyone who experiences an in-flight exhaust valve failure today just wasn’t paying attention. Borescope Inspections In my opinion, regular borescope inspections should be our first line of defense against exhaust valve failure. The borescope is an optical probe (see Fig. 4) or a subminiature digital camera (depending on which model is used) that can be inserted through a spark plug boss (usually the top one). It is used to perform a […]
Exhaust Valve Failures – Part 1
Exhaust valves are the most heat-stressed components in your piston aircraft engine, and the most likely to fail prior to TBO. Here’s what you need to know about them. I experienced my first in-flight exhaust valve failure about twenty years ago. The engine started running very rough (as you might expect of a six-cylinder engine that was only running on five cylinders). After I landed, I noticed that the manifold pressure at idle was several inches higher than normal, confirming that something was definitely wrong with the engine. I put the airplane in the hangar, removed the top cowling and the top spark plugs, and performed a differential compression test. Five of the cylinders measured just fine, but one measured 0/80 with a hurricane of air blowing out the exhaust pipe. It was pretty obvious that this jug was going to have to come off. Once I wrestled the cylinder off the engine and looked at the exhaust valve, it was pretty obvious that something was missing (see Fig. 1). A fragment of the exhaust valve face had broken off and departed the premises for parts unknown. Luckily, it opted to depart through the wastegate and to spare the turbocharger […]
Work Orders and Invoices
Your maintenance shop’s paperwork can make all the difference between a good outcome and a nightmare. When he contacted me, the owner of a pristine turbonormalized A36 Bonanza seemed obviously frustrated: I manage to fly only 50 to 75 hours a year, but my annual inspections have been running between $8,000 and $12,000 every year despite my low flying time. I think my mechanic is very honest and thorough, but I think he spends about 100 hours doing the inspection. Perhaps he is overdoing it? I asked the owner to fax me his invoices from this shop for the past two years so I could review them. He did, and when I reviewed the invoices, I found them profoundly disturbing. It wasn’t just the totals that bothered me—about $7,000 for the 2008 annual and more than $12,500 for the 2009 annual—but the obscure, perhaps even intentionally cryptic nature of the invoices that made them almost impossible to evaluate. I’ve been looking at maintenance invoices for more than two decades, but these were perhaps the most inscrutable I’ve ever encountered. Let me show you what I mean: This invoice contains an astonishingly detailed description of the work performed that goes on […]
Who’s the boss?
Every pilot understands the notion of “pilot in command.” That’s because we all had some certificated flight instructor (CFI) who mercilessly pounded this essential concept into our heads throughout our pilot training. Hopefully, it stuck. As pilot-in-command (PIC), we are directly responsible for, and the final authority as to, the operation of our aircraft and the safety of our flight. Our command authority so absolute that in the event of an in-flight emergency, the FAA authorizes the PIC to deviate from any rule or regulation to the extent necessary to deal with that emergency. (14 CFR §91.3) In four and a half decades of flying, I’ve overheard quite a few pilots dealing with in-flight emergencies, and have dealt with a few myself. It makes me proud to hear a fellow pilot who takes command of the situation and deals with the emergency decisively. Such decisiveness is “the right stuff” of which PICs are made, and what sets us apart from non-pilots. Conversely, it invariably saddens me to hear a frightened pilot abdicate his PIC authority by throwing himself on the mercy of some faceless air traffic controller or flight service specialist to bail him out of trouble. How pathetic! The […]
Is this engine airworthy?
How do we assess whether a piston aircraft engine is airworthy? Compression tests and oil consumption are only part of the story—a smaller part than most owners and mechanics think. My friend Bob Moseley is far too humble to call himself a guru, but he knows as much about piston aircraft engines as anyone I’ve ever met. That’s not surprising, because the man has been rebuilding Continental and Lycoming engines for the four decades, so there’s not much about these engines that he hasn’t seen, done, and learned. From 1993 and 1998, “Mose” (as his friends call him) worked for TCM as a field technical representative covering Missouri, Kansas, Iowa, Nebraska, North and South Dakota, Minnesota, and the portion of Canada north of those states. “Then I made someone at the factory mad,” he says, “so they gave me Arkansas.” (Not really, but it always gets a laugh.) These days, Mose and his wife Rita operate a small shop called SkyTEK Inc. located at Fulton, Missouri, about 100 miles west of St. Louis. [http://www.skytekonline.com/] The company offers a wide variety of engine-related services including custom overhauls, prop strike inspections, cylinder work, accessory repairs, fuel injection system setup, and all manner […]
Reliability-Centered Maintenance (Part 3)
By Mike Busch To apply RCM principles properly to the maintenance of our piston aircraft engines, we need to analyze the failure modes and failure consequences of each major component part of those engines. Last month, we looked at the issue of catastrophic failures of piston aircraft engines, and saw that the predominant risk of such failures is greatest when the engine is young, not when it’s old. This month, we’ll examine the critical components of these engines, how they fail, what the consequences of those failures have on engine operation and safety of flight, and what sort of maintenance actions we can take to deal with those failures effectively and cost-efficiently. Crankshaft It’s hard to think of a more serious piston engine failure mode than a crankshaft failure. If it fails, the engine quits. Yet crankshafts are rarely replaced at overhaul. Lycoming says their crankshafts often remain in service for more than 14,000 hours and 50 years! TCM hasn’t published this sort of data, but TCM crankshafts probably have similar longevity. Crankshafts fail in three ways: (1) infant-mortality failures due to improper material or manufacture; (2) failures following unreported prop strikes; and (3) failures secondary to oil starvation and/or […]
Reliability-Centered Maintenance (Part 2)
Last month, we examined the principles of RCM used by the airlines and military to achieve cost-effective maintenance. Now, let’s explore how RCM can be applied to our small GA aircraft, and especially to our piston aircraft engines. For three decades, the airlines and military have been using Reliability-Centered Maintenance to slash maintenance cost and improve reliability. Most of these benefits have come from replacing fixed overhaul intervals with on-condition maintenance. Unfortunately, RCM has not trickled down to the low end of the aviation food chain. Maintenance of piston GA aircraft remains largely time-directed rather than condition-directed. Most GA owners dutifully overhaul their engine at TBO, overhaul their prop every 5 to 7 years, and replace their alternators and vacuum pumps every 500 hours, just as Lycoming, TCM, Hartzell, McCauley, Kelly Aerospace and Parker-Hannifin recommend. Bonanza owners have their wing bolts pulled every 5 years. Cirrus owners replace their batteries every 2 years. And the beat goes on… Does any of this make sense? After analyzing reams of operational data from a number of major air carriers, RCM researchers concluded that fixed-interval overhaul or replacement rarely improves safety or reliability, and often makes things worse. When does TBO make sense? […]
Reliability-Centered Maintenance (Part 1)
A strategy known as “Reliability-Centered Maintenance” has drastically reduced the cost of maintaining transport and military aircraft, while simultaneously improving dispatch reliability. Isn’t it time we applied this approach to piston GA? More than 30 years ago, in 1974, the U.S. Department of Defense commissioned United Airlines to prepare a report on the techniques used by the airline industry to develop cost-efficient maintenance programs for civil airliners. The resulting report, titled Reliability-Centered Maintenance [F. S. Nowlan & H. Heap, National Technical Information Service, 1978] described a radically different approach to aircraft maintenance, based on rigorous analysis of traditional maintenance practices and evaluation of their shortcomings. Traditionally, a major emphasis of aircraft maintenance programs had been defining specific overhaul and retirement intervals (TBOs) in order to achieve a satisfactory level of reliability. However, engineering analysis of reams of operational data from a number of major air carriers produced fascinating insights into the conditions that must exist for scheduled maintenance to be effective. Two discoveries were especially surprising: For example, RCM researchers determined back in the 1970s that scheduled overhauls on turbine engines do not produce any reliability or economic benefit, and that maintaining such powerplants strictly on-condition provides longer life, reduced […]