Real stats on engine failures?

(Captain Wubba) wrote
Indeed. Interesting. But I'd still like to see some hard data.

Me too.

Since a big part of flying is risk
management, it would be very helpful to *really* know the risks
involved. If the odds of losing an engine are 1 in 50,000 hours, then
night/hard-IFR single-engine flying becomes a great deal more
appealing than if it is 1 in 10,000 hours.

And what if it's 1 in 1000 hours? Then night/hard-IFR single-engine
flying becomes foolhardy.

I'll try to go over the NTSB data more thoroughly, I think a
reasonable extrapolation would be that at least 1 in 4 in-flight
engine failures (probably more) would end up in the NTSB database.

That doesn't seem at all consistent with my experience. Of all my
acquaintances who have had engine failures, only one wound up in the
NTSB database because he died and took his passengers with him. One
severely damaged the airplane but walked away and contrary to
regulation never reported it. The plane was eventually rebuilt. The
others made safe landings.

Based on my experience, the it's more like 1 in 10 to 1 in 100.

Michael

Sorry I can't point you to the "harder" data you're looking for, but
here's perhaps a little perspective on the issue:

According to one NTSB Study, pilots with fewer than either 500 hours
total time, or 100 hours in type, are more likely to encounter an
inadvertent stall/spin than to have a genuine engine failure (i.e.: a
random-event engine failure, not one attributed to such pilot errors
as fuel mismanagement).


In my case, over 6,400 hours with 5,600+ hours of instruction given
(mostly doing spin, emergency maneuver, aerobatic, and tailwheel
training -- the type of flying that might be considered harder on an
engine than more routine types of flying), I've had several
non-critical engine anomalies that were successfully dealt with,
including:

Prop stoppages during spins due to a couple of students hanging on so
tight to the throttle that it choked off the engine -- we call that
"fright idle";

Clogged fuel injectors during take-off that only revealed themselves
at full throttle;

Primer controls that were not truly "in and locked" which has lead to
prop stoppages during idle power landings.


In addition, two legitimate engine failures as follows:

The first, a fuel injector failure as we entered the traffic pattern
(after practicing off field landings, no less!) -- landed without
further incident;

The second, carb ice in a Champ during a flight review choked off the
engine during a touch and go -- touched down on the taxiway abeam the
departure end of the runway, hit a parked Porshe, bent the airplane,
walked away without so much as a scratch.

Rich
http://www.richstowell.com



(Captain Wubba) wrote in message . com...
Indeed. Interesting. But I'd still like to see some hard data. This is
the kind of problem I run into...most of your pilot friends report
that they have had a failure, but the majority of mine report none.
And none of the 2000+ hour CFI types I asked (I asked 4 of them) have
ever experienced an engine failure. My dad was a pilot with well over
12,000 hours and never had one. Another relative had fewer than 500
hours total in his flying carrer and lost one on his first solo XC.

I asked another A&P I ran into at the airport tonight, and he said he
thought it should be at least 40,000 hours per in-flight engine
failure, but really wasn't sure. Since a big part of flying is risk
management, it would be very helpful to *really* know the risks
involved. If the odds of losing an engine are 1 in 50,000 hours, then
night/hard-IFR single-engine flying becomes a great deal more
appealing than if it is 1 in 10,000 hours.

I'll try to go over the NTSB data more thoroughly, I think a
reasonable extrapolation would be that at least 1 in 4 in-flight
engine failures (probably more) would end up in the NTSB database.
But the cursory review I made earlier made me think the numbers were
much less negative than I had considered before. And the opinions of
these A&Ps are very interesting, because while failure might not
require a total overhaul, it will require *something* to be done by a
mechanic...and if these guys are seeing 30-40 engines make it to TBO
for every one needing repair due to an in-flight failure, that might
well support the 40,000 to 50,000 hour hypothesis.

Cheers,

Cap


(Michael) wrote in message om...
(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

(Rich Stowell) wrote
Sorry I can't point you to the "harder" data you're looking for, but
here's perhaps a little perspective on the issue:

According to one NTSB Study, pilots with fewer than either 500 hours
total time, or 100 hours in type, are more likely to encounter an
inadvertent stall/spin than to have a genuine engine failure (i.e.: a
random-event engine failure, not one attributed to such pilot errors
as fuel mismanagement).

Really? If that were true, then there would be hard data.

What the NTSB study REALLY says is that these low time pilots are more
likely to encounter an inadvertent stall/spin LEADING TO AN ACCIDENT
than to have a genuine engine failure LEADING TO AN ACCIDENT. This is
because an engine failure rarely leads to an accident (at least if the
ones known to me are any indication) but an inadvertent stall/spin
usually leads to an accident.

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.

In my case, over 6,400 hours ...
... two legitimate engine failures as follows:

2 in 6400 hours is very much consistent with my experience. It's also
very much consistent with the 1 in 1000 to 1 in 10000 number the FAA
provides.

Michael

(Michael) wrote in message . com...
(Rich Stowell) wrote
Sorry I can't point you to the "harder" data you're looking for, but
here's perhaps a little perspective on the issue:

According to one NTSB Study, pilots with fewer than either 500 hours
total time, or 100 hours in type, are more likely to encounter an
inadvertent stall/spin than to have a genuine engine failure (i.e.: a
random-event engine failure, not one attributed to such pilot errors
as fuel mismanagement).

Really? If that were true, then there would be hard data.


Yes, really -- see "A Study of Light Plane Stall Avoidance and
Suppression." By D.R. Ellis, Report No. FAA-RD-77-25, 1977, p. 6. As
for the "hard data" behind this finding, that's for you to follow up
on since this is your research project


What the NTSB study REALLY says is that these low time pilots are more
likely to encounter an inadvertent stall/spin LEADING TO AN ACCIDENT
than to have a genuine engine failure LEADING TO AN 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.


This is
because an engine failure rarely leads to an accident (at least if the
ones known to me are any indication) but an inadvertent stall/spin
usually leads to an accident.


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."

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. 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.

While it is true that one accident classification may be more
prevalent than another (e.g.: more stall/spin fatalities than ground
loop fatalities), the ratio of accidents-to-total encounters may very
well be equal. In that case, 1 out of 331 would be the same for engine
failures leading to accidents as for stall/spins leading to accidents,
or any other accident type. I guess one could argue that 1 accident
out of every 331 hazardous encounters is "rare" regardless of the
cause. In that context, one could then argue that compared to the
total number of stall/spin encounters, stall/spin accidents are
equally as "rare" as engine failure accidents.


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." See "General Aviation Pilot Stall
Awareness Training Study," by William C. Hoffman and Walter M.
Hollister, Report No. FAA-RD-77-26, 1976, p. 6.

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.

For example, stall while at 1-g and Vso and give it some yaw = spin;
stall at 1.95 times Vso with +3.8-g's (that's the same as saying "Va
and the design limit in the Normal Category") and give it some yaw =
spin; give any airplane the right amount of g's at a given airspeed
and give it some yaw = spin.

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.

Rich
http://www.richstowell.com

Rich

Some other data to put in the pot.

The Air Force paid some one (Rand Corporation or some other think
tank) to do a study on accidents vs flying time.

It basically came out that there were two spikes, one around 500 hours
and the other around 1000 hours. The 500 hour accidents were
attributed to cocky over confidence. Not sure right now what the 1000
spike was but it was caused by something we could train around or
change procedures, etc. to reduce as I recall.

Big John



On 25 Nov 2003 07:57:26 -0800, (Rich Stowell)
wrote:

Sorry I can't point you to the "harder" data you're looking for, but
here's perhaps a little perspective on the issue:

According to one NTSB Study, pilots with fewer than either 500 hours
total time, or 100 hours in type, are more likely to encounter an
inadvertent stall/spin than to have a genuine engine failure (i.e.: a
random-event engine failure, not one attributed to such pilot errors
as fuel mismanagement).


In my case, over 6,400 hours with 5,600+ hours of instruction given
(mostly doing spin, emergency maneuver, aerobatic, and tailwheel
training -- the type of flying that might be considered harder on an
engine than more routine types of flying), I've had several
non-critical engine anomalies that were successfully dealt with,
including:

Prop stoppages during spins due to a couple of students hanging on so
tight to the throttle that it choked off the engine -- we call that
"fright idle";

Clogged fuel injectors during take-off that only revealed themselves
at full throttle;

Primer controls that were not truly "in and locked" which has lead to
prop stoppages during idle power landings.


In addition, two legitimate engine failures as follows:

The first, a fuel injector failure as we entered the traffic pattern
(after practicing off field landings, no less!) -- landed without
further incident;

The second, carb ice in a Champ during a flight review choked off the
engine during a touch and go -- touched down on the taxiway abeam the
departure end of the runway, hit a parked Porshe, bent the airplane,
walked away without so much as a scratch.

Rich
http://www.richstowell.com



(Captain Wubba) wrote in message . com...
Indeed. Interesting. But I'd still like to see some hard data. This is
the kind of problem I run into...most of your pilot friends report
that they have had a failure, but the majority of mine report none.
And none of the 2000+ hour CFI types I asked (I asked 4 of them) have
ever experienced an engine failure. My dad was a pilot with well over
12,000 hours and never had one. Another relative had fewer than 500
hours total in his flying carrer and lost one on his first solo XC.

I asked another A&P I ran into at the airport tonight, and he said he
thought it should be at least 40,000 hours per in-flight engine
failure, but really wasn't sure. Since a big part of flying is risk
management, it would be very helpful to *really* know the risks
involved. If the odds of losing an engine are 1 in 50,000 hours, then
night/hard-IFR single-engine flying becomes a great deal more
appealing than if it is 1 in 10,000 hours.

I'll try to go over the NTSB data more thoroughly, I think a
reasonable extrapolation would be that at least 1 in 4 in-flight
engine failures (probably more) would end up in the NTSB database.
But the cursory review I made earlier made me think the numbers were
much less negative than I had considered before. And the opinions of
these A&Ps are very interesting, because while failure might not
require a total overhaul, it will require *something* to be done by a
mechanic...and if these guys are seeing 30-40 engines make it to TBO
for every one needing repair due to an in-flight failure, that might
well support the 40,000 to 50,000 hour hypothesis.

Cheers,

Cap


(Michael) wrote in message om...
(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

Thanks for that, Big John,

I recall seeing similar stats -- I'll have to dig around in my files
to find the context and the reason for that second spike at 1,000
hours ... so much to do!

I posted a follow-up to Michaels response to my post as well.

Rich
http://www.richstowell.com



Big John wrote in message . ..
Rich

Some other data to put in the pot.

The Air Force paid some one (Rand Corporation or some other think
tank) to do a study on accidents vs flying time.

It basically came out that there were two spikes, one around 500 hours
and the other around 1000 hours. The 500 hour accidents were
attributed to cocky over confidence. Not sure right now what the 1000
spike was but it was caused by something we could train around or
change procedures, etc. to reduce as I recall.

Big John



On 25 Nov 2003 07:57:26 -0800, (Rich Stowell)
wrote:

Sorry I can't point you to the "harder" data you're looking for, but
here's perhaps a little perspective on the issue:

According to one NTSB Study, pilots with fewer than either 500 hours
total time, or 100 hours in type, are more likely to encounter an
inadvertent stall/spin than to have a genuine engine failure (i.e.: a
random-event engine failure, not one attributed to such pilot errors
as fuel mismanagement).


In my case, over 6,400 hours with 5,600+ hours of instruction given
(mostly doing spin, emergency maneuver, aerobatic, and tailwheel
training -- the type of flying that might be considered harder on an
engine than more routine types of flying), I've had several
non-critical engine anomalies that were successfully dealt with,
including:

Prop stoppages during spins due to a couple of students hanging on so
tight to the throttle that it choked off the engine -- we call that
"fright idle";

Clogged fuel injectors during take-off that only revealed themselves
at full throttle;

Primer controls that were not truly "in and locked" which has lead to
prop stoppages during idle power landings.


In addition, two legitimate engine failures as follows:

The first, a fuel injector failure as we entered the traffic pattern
(after practicing off field landings, no less!) -- landed without
further incident;

The second, carb ice in a Champ during a flight review choked off the
engine during a touch and go -- touched down on the taxiway abeam the
departure end of the runway, hit a parked Porshe, bent the airplane,
walked away without so much as a scratch.

Rich
http://www.richstowell.com



(Captain Wubba) wrote in message . com...
Indeed. Interesting. But I'd still like to see some hard data. This is
the kind of problem I run into...most of your pilot friends report
that they have had a failure, but the majority of mine report none.
And none of the 2000+ hour CFI types I asked (I asked 4 of them) have
ever experienced an engine failure. My dad was a pilot with well over
12,000 hours and never had one. Another relative had fewer than 500
hours total in his flying carrer and lost one on his first solo XC.

I asked another A&P I ran into at the airport tonight, and he said he
thought it should be at least 40,000 hours per in-flight engine
failure, but really wasn't sure. Since a big part of flying is risk
management, it would be very helpful to *really* know the risks
involved. If the odds of losing an engine are 1 in 50,000 hours, then
night/hard-IFR single-engine flying becomes a great deal more
appealing than if it is 1 in 10,000 hours.

I'll try to go over the NTSB data more thoroughly, I think a
reasonable extrapolation would be that at least 1 in 4 in-flight
engine failures (probably more) would end up in the NTSB database.
But the cursory review I made earlier made me think the numbers were
much less negative than I had considered before. And the opinions of
these A&Ps are very interesting, because while failure might not
require a total overhaul, it will require *something* to be done by a
mechanic...and if these guys are seeing 30-40 engines make it to TBO
for every one needing repair due to an in-flight failure, that might
well support the 40,000 to 50,000 hour hypothesis.

Cheers,

Cap


(Michael) wrote in message om...
(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

Big John wrote:

It basically came out that there were two spikes, one around 500 hours
and the other around 1000 hours. The 500 hour accidents were
attributed to cocky over confidence.

I read the same thing about ten years ago. As I recall, the 1000 hour spike was
also tentatively attributed to overconfidence.

George Patterson
A man who carries a cat by the tail learns something that can be learned
no other way.

I don't have any personally but I have a friend that has had three in
3500hrs. One connecting rod failure in a 210. A crankshaft failure in an
Azetec and I forget the details of the third failure. It has been estimated
that 10% of Malibus have had inflight engine failures of some kind.

Mike
MU-2

"Captain Wubba" wrote in message
om...
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
place where he works sometimes as a mechanic has plenty of planes come
in for overhauls and annuals, and he estimates that for every plane
that has had an engine failure before TBO, at least 20-30 make it to
TBO without any failure (which would extrapolate to a similar figure).
The flight school he teaches at has 7 Cessnas used for primary
training and rental that have flown at least 40,000 hours total in the
six years he has been there, and they have not experienced a single
engine failure.

I emailed Lycoming, and (unsurprisingly) they told me they did not
keep records about engine failure rates.

So I'd like to find out if anyone has done any objective analysis of
certificated, piston-engine failure rates in light airplanes. I have
seen all kinds of 'guesses', but little in the way of objective facts.
After analyzing NTSB accident data and comparing to annual GA
flight-hours, I'm starting to think my friend is on the right track,
but that is a relatively small sample, and has some methodologial
flaws. It's funny. I know 20,000 hour CFIs who have never had an
engine failure, and I also know 300 hour PP-ASELs who have had engine
failures.

Just for giggles, I asked 8 pilot friends/relatives if they had ever
had an engine failure. The only 'yes' was a relative who lost an
engine after takeoff on his first solo cross-country in 1958. And I
know one other pilot who had an engine failure, who I wasn't able to
talk to.

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?

Thanks,

Cap

"Mike Rapoport" wrote in message
link.net...
I don't have any personally but I have a friend that has had three in
3500hrs. One connecting rod failure in a 210. A crankshaft failure in an
Azetec and I forget the details of the third failure. It has been
estimated
that 10% of Malibus have had inflight engine failures of some kind.


It'd be interesting to know the maintenance history of those birds that did
have failures (skimped maintenance, etc).

It's also be interesting to know the total operating hours of the Malibu
fleet, Lycoming vs. Continental...

Well there is no maitenance on connecting rods and crankshafts.

Mike
MU-2


"Tom S." wrote in message
...

"Mike Rapoport" wrote in message
link.net...
I don't have any personally but I have a friend that has had three in
3500hrs. One connecting rod failure in a 210. A crankshaft failure in
an
Azetec and I forget the details of the third failure. It has been
estimated
that 10% of Malibus have had inflight engine failures of some kind.


It'd be interesting to know the maintenance history of those birds that
did
have failures (skimped maintenance, etc).

It's also be interesting to know the total operating hours of the Malibu
fleet, Lycoming vs. Continental...