Real stats on engine failures?

"Peter Duniho" writes:

[...] I have seen and heard of too many oil leaks, fuel
leaks, rubbing tubes and various parts coming loose or falling off...all
caused by "maitenance".

Well, granted, the engines on your plane require a much more specialized
maintenance crew than the one Lycoming on mine. But in spite of the very
real possibility of human error during maintenance, as far as I know more
engine failures are prevented by maintenance than are caused by it. I would
be very surprised if you could find statistics to the contrary.

I'm a Lycoming-running statistic (n=1). I "lost" an engine because the
throttle cable came off months after the engine was replaced at annual.
Fortunately I noticed it on the runup. But it happened the night before
when I was dodging lightning on the approach to Durango. (I didn't notice
it then because I rolled in just ahead of the hail and was more interested
in getting under cover than parking perfectly.)

I have way too many examples of mechanics screwing up my plane.

--kyler

"Kyler Laird" wrote in message
...
(Captain Wubba) writes:

So what is it? If the engine-failure rate is one failure for every
50,000 flight hours, I'll feel much less reticent about night/IFR
single-engine flying than if it is one in 10,000 hours. Anybody have
any facts or hard data, or have any idea where I might be able to
track some down?

Don't forget that you're safest with a single-cylinder engine. If
you have a six-cylinder, you're *six* times as likely to have a
failure.

...or at least that's what I've learned from some of the geniuses
who talk about twins vs. singles.

Not so, smart ass. You don't have six oil pumps, six crank seals, six fuel
pumps, six alternators, six crankshafts, 12 magnetos, 6 carbs, ect, ect, on
that six cylinder engine, do you?
--
Jim in NC

"Kyler Laird" wrote in message
...
I'm a Lycoming-running statistic (n=1). I "lost" an engine because the
throttle cable came off months after the engine was replaced at annual.
Fortunately I noticed it on the runup.

An engine failure on the ground isn't an engine failure.

Seriously though, that's the whole point of preflight inspections and
runups. The only question here is what's more likely to cause an
*in-flight* engine failure. Is it maintenance? Or lack of maintenance?

I too have had a variety of "failures" (engine-related and otherwise), some
of which were a direct result of work done on the airplane. Fortunately,
none happened in flight. But the fact that a mechanic is falliable does not
mean that the engine is better off without the mechanic.

If any of you "mechanics are bad for my airplane!" folks actually have some
hard numbers to show that airplanes not given any maintenance are more
reliable than airplanes that have received maintenance, by all means, show
it (I don't believe you can). Otherwise, you are taking a cute joke WAY too
far.

Pete

David Megginson wrote
I'm curious where the statistics are that show that most pilots cannot
handle an AI failure in IMC. This FAA report

http://www1.faa.gov/fsdo/orl/files/advcir/P874052.TXT

states that vacuum failures are a factor in an average of 2 accidents per
year, and that there is an average of one vacuum-related accident for every
40,000 to 50,000 GA IFR flight plans filed. That doesn't tell us much,
though, since we don't know how many non-fatal vacuum failures occurred
during those flights.

I have about 700 hours flying behind a dry pump, and one catastrophic
failure. I also have about 1400 hours flying planes with gyros (some
of my time is in gliders and no-gyro taildraggers) and at least three
gyro failures. I have to believe that vacuum or gyro failure occurs
AT LEAST once every 1000 hours.

Assuming that the average GA IFR flight plan leads to 30 minutes of
IMC (I know a lot of them are filed procedurally so I'm being
pessimistic) that still sounds like 1 accident in 20,000 hours. So it
sounds to me like 95%+ of the pilots who experience vacuum or gyro
failure are handling it without an accident.

From what I've seen of GA IFR pilots, at most 10% are getting
recurrent training in partial panel operations to PTS standards.

Michael

jim rosinski wrote:

Well, for those of us less studly than this, I'd still take an engine
failure over gyro failure in IMC under most conditions. Maybe given
the time/money to train "properly" gyro failure isn't such a major
emergency. But I don't have either the time or the money, so this
instrument-rated pilot isn't flying IFR till he gets a plane with
backup gyros or electric AI.

Yow! I hope that you mean an engine failure in fairly high IMC (i.e. the
ceiling well above terrain and obstacles). Compared to a forced landing
with, say, a 300 ft ceiling in an area with lots of hills and towers, flying
in IMC with the TC and mag compass sounds like a walk in the park.

The FAA report I quoted earlier in this thread stated an interesting fact --
all of the GA fatalities during their study period due to vacuum failure
were in high-performance planes with retractable gear. Nobody was spiraling
in a 182 or Cherokee Six after a vacuum failure in IMC, much less a Skyhawk
or Cherokee. I'm sure that they do happen, but they must not be so common.

That suggests to me that in the unlikely event I ever can afford a
high-performance retractable, the first action in event of lost gyros should
be to lower the gear, airspeed be damned.


All the best,


David

Michael wrote:

http://www1.faa.gov/fsdo/orl/files/advcir/P874052.TXT

Assuming that the average GA IFR flight plan leads to 30 minutes of
IMC (I know a lot of them are filed procedurally so I'm being
pessimistic) that still sounds like 1 accident in 20,000 hours. So it
sounds to me like 95%+ of the pilots who experience vacuum or gyro
failure are handling it without an accident.

That sounds pretty reasonable. As I just mentioned in another posting, the
report also mentions that all of the fatal GA accidents from vacuum failures
in their study period happened in high-performance aircraft with retractable
gear.

From what I've seen of GA IFR pilots, at most 10% are getting
recurrent training in partial panel operations to PTS standards.

In Canada, partial panel is not even part of the IFR flight test (though we
do learn it during training). On the other hand, we have to retake our
entire flight test every two years, and the examiner can always fail
something (including the AI) if he/she wants to. The other benefit is that
without the partial panel and unusual-attitude recovery, we can take our
flight tests in actual IMC, as I did.


All the best,


David

(Rich Stowell) wrote
Really? If that were true, then there would be hard data.
Yes, really

No, not really. No hard numbers on actual engine failures (or
stall-spins for that matter) - only the ones that led to an NTSB
reported accident.

True, but that's stating the obvious since NTSB only gets involved in,
and thus only reports on, those encounters that have led to actual
accidents.

But this hideously skews the picture. The only way the events are
comparable is if the probability of an engine failure leading to an
accident is approximately equivalent to the probability of a
stall-spin leading to an accident. This is exactly what I am
disputing.

Define "rarely." From an industrial accident prevention standpoint,
the theoretical ratio 1:30:300 is often applied wherein for every 331
hazardous encounters of a similar type, only one will progress as far
as an actual accident (significant damage and/or injury). The rest
fall under "incidents" and "hazards."

That ratio is nothing more than an expression of ignorance. In
reality, depnding on the hazard the numbers can be very different.

Industrial safety types love to quote statistics like this to scare
people, but in reality there is usually a reason why some hazardous
encounters lead to accidents or incidents while most do not. It's not
random. These reasons generally have to do with individual skill,
knowledge, and experience as well as factors the industrial safety
people are never told because they involve routine violations of
safety rules. Often the same dynamic plays out in NTSB
investigations.

In other words, typically 1 out of 331 encounters of a similar type
results in an accident, whether it's precipitated by an engine failure
or an inadvertent stall/spin.

No, this is total nonsense because stall-spins and engine failures are
not similar. First of all, a mechanical failure generally occurs in a
manner that is beyond the pilot's control. When the main seal blows
out, or the engine swallows a valve, or a rod goes through a cylinder,
or the fuel injectors clog with rust - that's almost always completely
independent of pilot skill, knowledge, and judgment. On the other
hand, an inadvertent stall-spin is caused by the pilot. Therefore,
we're not even looking at the same population.

Just by virtue of the fact that the pilot allowed the inadvertent
stall-spin situation to develop, we can expect that he is less likely
to handle it properly. The same is not true of engine failure.

In the case of NTSB data, one could
extrapolate to get a feel for the order of magnitude of problems
pilots deal with in a particular category by multiplying the number of
accidents by 331.

This is absolutely ridiculous. In addition to the issue of hazard
exposure (mechanical engine failures don't discriminate but
stall-spins do) there is also the issue of hazard magnitude. Off
field landings in gliders, for example, are VERY rarely fatal. The
ratio there is 5000:1. On the other hand, I would be amazed if the
fatality ratio for midairs was much better than 3:1. 331 may be a
good all-around average in aviation (or it may not - data are not
available) but to apply it indiscriminately to all types of hazards
makes no sense at all.

For that matter, most engine failure fatalities in light singles are
not the result of collision with terrain (which is usually survivable)
but of failure to maintain flying speed (which usually isn't). That's
basically a stall/spin anyway.

Two things: First, approximately 19 percent of stall/spin accidents
are preceded by an engine failure. But the primary accident cause is
still listed as "stall/spin."

There is one school of thought that considers this proper. Just
because engine power is lost is no excuse to stall and spin. Gliders
don't even have engines. However, that doesn't change the fact that
had the engine kept running, the stall-spin would likely not have
happened.

Second, the contention that "failure to maintain flying speed" is
"basically a stall/spin anyway" is pure myth. Spins are the result of
two ingredients that must coexist: yaw and stall. And neither yaw nor
stall is a function of airspeed. Up to the point where the wings
decide to bend or break, stalls and spins can and do occur at any
airspeed, and in any attitude.

That's all great, but the reality is that in normal flight (not
involving aerobatics or other abrupt maneuvering) stall avoidance is
all about keeping your airspeed up. Those 19% of stall-spins caused
by engine failure are the result of trying to stretch the glide or
maneuvering to make a landing area, and likely both.

In my experience, and based on the research I've read, I'd postulate
that the majority of stall/spin accidents occur with the airplane
operating somewhere between 1.07 to 1.20 times Vso and 1.15 to 1.41-g.
In other words, with pilots pulling into an uncoordinated, accelerated
stall while turning at bank angles between 30 and 45 degrees.

That's great, but had those pilots maintained at least 1.3 Vso for
these maneuvers, they would not have stalled. Thus saying airspeed is
irrelevant is technically correct but not particularly useful.

Yes, you can stall at any airspeed in any attitude. I've stalled at
100+ kts (in a plane which normally stalled at 60 kts), full power,
and the nose 80 degrees below the horizon - as an aerobatic instructor
I'm sure you know exactly what I did wrong to make that happen. That
doesn't change the reality - in an engine-out situation, the
stall-spin is caused by a failure to maintain flying speed.

Michael

"Morgans" writes:

Don't forget that you're safest with a single-cylinder engine. If
you have a six-cylinder, you're *six* times as likely to have a
failure.

...or at least that's what I've learned from some of the geniuses
who talk about twins vs. singles.

Not so, smart ass. You don't have six oil pumps, six crank seals, six fuel
pumps, six alternators, six crankshafts, 12 magnetos, 6 carbs, ect, ect, on
that six cylinder engine, do you?

Correct, genius. Similarly, there are engine problems that are quite
independent of the number of engines on a plane.

--kyler

"Peter Duniho" writes:

"Kyler Laird" wrote in message
...
I'm a Lycoming-running statistic (n=1). I "lost" an engine because the
throttle cable came off months after the engine was replaced at annual.
Fortunately I noticed it on the runup.

An engine failure on the ground isn't an engine failure.

Like I said, I lost it in flight. I noticed it on the ground.

--kyler

"Kyler Laird" wrote in message
...
Like I said, I lost it in flight. I noticed it on the ground.

I think you're missing the point (even ignoring the apparent inconsistencies
in the event you're trying to describe).

Pete