One of the challenges pilots face in powered flight is what to do when the flight becomes unpowered. Clyde Cessna noted nearly a century ago that, “If the engine stops for any reason, you are due to tumble, and that’s all there is to it!” There’s a lot more stuff to hit these days, and most failures don’t occur in the wide-open spaces of south-central Kansas where Clyde spent his days.
Although far less common today, engine failures can be catastrophic. Bad places include: Shortly after takeoff, over cities (and housing developments stupidly located off the ends of runways), mountainous terrain, tall trees, and large bodies of water. We confidently tell our passengers that if the engine stops, the aircraft turns into a glider and we’ll just find a field and settle gently to Earth. Way too often, the obstacles make the impact not survivable—or the pilot stalls the aircraft prior to touchdown.
A joint FAA/industry safety committee recently studied fatal piston powerplant failure accidents. The results suffered from a lack of data. Not surprisingly, human error in manufacturing, maintaining, and ignoring engine warning signs were a significant part of the problem. Some problems were predictable, and others—such as metallurgy or a manufacturing error—were unlikely to be spotted until after the fact.
There just isn’t a good tracking system to show when and how failures occur. The manufacturers have some data but it’s far from comprehensive, and generally not public. Likewise, the FAA’s service difficulty report system is not robust. Many times a part will fail or begin to fail, but it’s quietly replaced—and no record is kept on what, when, or why.
There’s a raging debate over when to overhaul engines, with manufacturers calling for TBOs at certain times, but many run well beyond the recommended period with careful operation. In too many cases an engine never makes it to the recommended overhaul period based on how it’s operated—or, perhaps, because a part was not properly manufactured or installed.
Incorrect engine assembly is a significant problem. The committee discovered improperly torqued bolts on engine cases and cylinders in at least six fatal accidents. The automotive industry uses direct tension indicating (DTI) technology that provides a visual check for proper torque. They are single-use mechanical load cells used to indicate when the required tension has been achieved in structural fastener assemblies. The FAA is developing a standard that would allow these telltale fasteners to be used on aircraft engines.
The better path, rather than hoping for divine intervention, is prevention. Pilots can’t do much about how the engines are built but we can be far more watchful. Use engine diagnostics and monitoring just as the airlines do. Otherwise, you’re relying on miracles.
When the oil is changed, get it analyzed. Oil filters should be cut open and carefully examined for metal parts. Borescoping should be done at annual and at 100-hour inspections. The scope is relatively inexpensive; every A&P should have one and become proficient in its use. By looking inside every cylinder one can see long-term overhaul predictors such as scuffing and corrosion. More critically, internal cracks and the telltale color changes of a failing exhaust valve caught early may save you from more than just a tiptoe through the tulips.
Today, with glass instruments, the ability to view the operation has never been better. But you don’t need a full-up panel retrofit—an engine analyzer will fit in a standard hole and will pay for itself in the first two or three years. The instrumentation on many older big-bore engine aircraft consists of a single cylinder head temperature and EGT probe, which just can’t do the job. Online chat rooms of every high-performance aircraft owner’s group have robust discussions on engine operation, and for good reason. The engines are much more delicate than basic trainers and excruciatingly expensive to fix/overhaul. Improper operation will drain your aviation bank account faster than almost anything else.
In primary training aircraft, instruction is often little more than “Don’t lean below 5,000.” The “heart stop method” may be the only option if there’s no exhaust gas temperature gauge. The mixture is pulled back until the engine runs rough and then enrichened to smoothness—primitive but OK for small engines flown regularly. It sure doesn’t teach much about how to take care of bigger equipment, and many transitioning pilots receive only the most basic engine management training.
The engine analyzer is one of the best investments an owner can make in getting maximum hours from engines and cylinders. It may give early warning when engine indigestion could lead to a tumble, as Clyde put it. In the immortal words of Mark Twain, “Put all your eggs in one basket and then watch that basket.”
Web: www.airsafetyinstitute.org
Bruce Landsberg is the former president of the AOPA Foundation and is a senior safety advisor to the AOPA Air Safety Institute.
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