You’ve probably said it to a nervous passenger: “Don’t worry, airplane engines almost never quit.” It’s only in World War II movies that engines cough and pilots have to save the day, right? This is mostly true for turbine engines, which have a stunningly good reliability record. Unfortunately, it’s far less true for piston engines.
The bad news
While the general aviation industry doesn’t exactly advertise engine failures, the numbers aren’t hard to find. According to the NTSB and FAA, there are somewhere between 150 and 200 accidents per year that are caused by power loss. Roughly a quarter of these are fatal, which makes this the second leading cause of fatal accidents, behind the much-maligned “loss of control-inflight.” For twins and experimental aircraft, the accident rate is even higher. Perhaps worst of all, such events seem to be holding steady, even though overall accidents have declined somewhat in recent years. Here are the statistics for 2014, the most recent year for which data is available and right in line with the five-year trend:
Data from AOPA paint a similar picture. Here is a chart from the most recent Nall Report, showing the cause of mechanical accidents. This excludes pilot error, but note that powerplant failures easily beat out other system malfunctions:
An interesting study from the Australian Transportation Safety Board (which does some first-rate safety research), offers more supporting evidence: there were 322 engine failures or malfunctions between 2009 and 2014. That’s over a dozen per year, in a country with fewer than 10,000 “sport and recreational” aircraft. While the poor reliability of Jabiru engines jumps out (with over 40% of the engine failures), the study still found 86 failures of Lycoming and Continental engines.
It’s worth pointing out that all these statistics almost certainly undercount the actual number of engine failures, since they only appear in these reports the result is an accident. An engine failure that leads to a safe landing at an airport will never show up in the statistics, and may not even make it to an insurance company’s figures.
The good news
Those numbers may be surprising to many pilots who have thousands of hours flying behind the latest engines from Lycoming and Continental, which seem to be smooth and trouble-free. Those numbers might even shake your confidence just a bit.
The good news is that “System Malfunction (Powerplant)” hides an awful lot of important details. That NTSB phrase merely defines the event, not the root cause. And by far the most common reason piston engines quit is because they don’t receive fuel, either due to fuel starvation (the airplane has fuel but it doesn’t make it to the engine) or fuel exhaustion (the airplane truly ran out of it). These two causes account for over one-third of engine failure accidents, but they are completely under the control of the pilot.
Pilots will probably always find ways to run out of fuel, but it bears repeating that a few good habits can dramatically reduce your chances of such an engine failure. Having a hard one-hour minimum is a great place to start – under no circumstances can you still be flying with less than one hour of fuel in the tanks. Next, spend some time understanding the fuel system so you can always get that fuel to the engine, especially in twins and older airplanes with complicated fuel systems. Take a little time away from practicing a rare emergency and instead discuss different fuel scenarios that might pop up. Finally, always know how much fuel was in the tanks at engine start and know your real-world fuel burn rate. Depending on those, and not as much on the gauges, will lead to more realistic decision-making.
Behind those mental mistakes on the list of engine failure causes is a surprise (at least for me): fuel contamination. While I’ve been fortunate to never find bad fuel in 20+ years of flying, even in some quiet parts of the Caribbean, it does happen and it can have serious consequences. Again, though, this is almost totally preventable, in this case by performing a thorough preflight every time and staying with the airplane whenever it’s fueled to verify you get the right type.
Next comes caburetor icing, which is either impossible (fuel injected engines) or preventable (by using the carb heat). The penalty for pulling that knob is fairly small in most airplanes, so when in doubt you should use it – even if the conditions seem inhospitable for icing. A carburetor temperature gauge is a good idea too, especially for some Continental models.
By the time you get to real mechanical failures such as a failed magneto or a broken connecting rod, the numbers are fairly small – less than 20% of all powerplant problems. Some of these are simply bad luck, with the pilot dealt a bad hand by a sudden part failure, but it’s not all up to fate. A decent number of these mechanical failures were due to faulty maintenance, typically soon after major repair work or overhaul. This argues for high quality maintenance, but it also supports Mike Busch’s theory of Reliability Centered Maintenance, where overhauls are completed on-condition, not based on an arbitrary time limit.
The right habits
What’s the takeaway for pilots and aircraft owners? First, the easy stuff. Develop good habits regarding fuel management and maintain the discipline to follow them every time. Sample fuel before every flight, buy from reputable FBOs, and make sure your fuel caps seal tightly. Use carb heat (if applicable) on every flight to prevent icing, not just when the engine starts to run rough.
Beyond those everyday basics, a wise owner will seek out high quality maintenance, but perhaps only when it’s really needed. The right balance will keep the engine under close supervision, with regular oil analysis and borescopes, but avoid added risk by doing invasive part replacement too often. When maintenance is performed, pilots should be skeptical on the first flight after overhaul or parts replacement. In other words, don’t make that first trip a hard IFR trip over the mountains.
Of course some traditional advice also helps a lot: fly the airplane regularly, avoid cold starts, and operate the engine conservatively (especially with respect to CHT). The biggest payoff from these habits is in longevity, especially when it comes to preventing corrosion, but there is certainly some improvement in reliability to be had as well.
Following these rules can reduce your chances of an engine failure by over 75%, which should make you feel a lot more comfortable on your next flight over remote terrain. But that still means the fan out front can stop turning. In that situation, all you have to fall back on is good training and realistic planning. Based on the numbers above, practicing engine failure scenarios as a part of your regular training is time well spent, and continuously thinking about forced landing sites in flight doesn’t hurt either.
Engines can and do fail, but a little preparation and a little paranoia should keep you from adding to those statistics.