(Captain Wubba) wrote
Howdy. I was discussing with a friend of mine my concerns about flying
single-engine planes at night or in hard IFR, due to the possibility
of engine failure. My buddy is a CFI/CFII/ATP as well as an A&P, about
3500 hours, and been around airplanes for a long time, so I tend to
give credence to his experiences. He asked me how often I thought a
piston engine had an in-flight engine failure. I guestimated once
every 10,000 hours or so. He said that was *dramatically*
over-estimating the failure rate. He said that in his experience it is
at least 40,000 to 50,000 hours per in-flight engine failure.

The only vaguely official number that I've ever seen came from a UK
accident report for a US-built twin. The UK investigators queried the
FAA on engine failure rates for the relevant engine, and the only
answer they got was that piston engines have failure rates on the
order of 1 in 1000 to 1 in 10000 hours. This is consistent with my
experience. I've had one non-fuel-related engine failure (partial,
but engine could only produce 20-30% power) in 1600+ hrs. Most people
I know with over 1500 GA hours have had an engine failure.

50,000 hours is not realistic. Excluding a few airline pilots (who
have ALL had engine failures) all my pilot friends together don't have
50,000 hours, and quite a few of them have had engine failures.

I've heard the maintenance shop thing before, but you need to realize
that most engine failures do not result in a major overhaul. Stuck
valves and cracked jugs mean that only a single jug is replaced;
failure of the carb or fuel injection system (my problem) affects only
that component. And oil loss will often seize an engine and make it
not worth overhauling.

There are no real stats on engine failures because engine
manufacturers and the FAA don't want those stats to exist. The FAA
could create those stats simply by requiring pilots to report engine
failures for other than fuel exhaustion/contamination reasons, but
will not.

The truth is, FAA certification requirements have frozen aircraft
piston engines in the past, and now they're less reliable than
automotive engines (not to mention ridiculously expensive).

Michael