Magazine Articles

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 […]

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 […]

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 […]

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 […]

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 […]

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. […]

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 […]

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, […]

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 […]

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 […]

“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 […]

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. […]

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 […]

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 […]

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.” […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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. […]

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 […]