Magazine Articles

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

“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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]

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 […]