Magazine Articles

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 […]

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 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 […]

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 […]

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, […]

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. […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 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 […]

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 […]

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 […]