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The Probability of an Engine Failure in a Certified GA SEP

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The Probability of an Engine Failure in a Certified GA SEP

Old 15th Mar 2015, 21:16
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The Probability of an Engine Failure in a Certified GA SEP

This comment on the EFATO thread got me thinking.

That's why we should expect it - on every take off. Be surprised if it keeps running!
Personally I think flight training spends an outsized amount of time and effort on bad occurrences that are quite rare and not nearly enough time on bad occurrences that are quite common.

If you are sitting at the edge of your seat waiting for the engine to fail on every takeoff and then are "surprised" when it doesn't than I think you are ascribing a much higher probability to the event than it warrants.

This does not mean you ignore the possibility of it happening. I think every pilot should review the EFATO vital actions prior to every takeoff and pay attention to the terrain surrounding the airport but an EFATO is just one of the many negative eventualities that could occur during the flight, many which are much more probable ( eg Carb icing).

The risk of most of these eventualities can be mitigated by a disciplined approach to flying, including good pre flight planning (Wx, NOTAMS, Fuel Calculations etc), effective checklist use and a good look out both in and out of the cockpit.

If those precautions are applied than an EFATO is very unlikely. If you look at the accident statistics the Least Common scenario is for an EFATO in for an aircraft that has

1) no outstanding maintenance issues,
2) Has sufficient fuel, no contamination, and from a correctly selected tank
3) Shows no anomalies during a complete and comprehensive runup
4) Was checked for Carb ice before lining up for takeoff, and
5) The engine gauges where in the green and the engine was developing full static RPM at the start of the takeoff role.

The accident statistics show that up to 80 % of SEP engine failures were caused by the actions or inactions of the pilot with fuel exhaustion/contamination/mis-selction and carb icing accounting for the majority of the engine failures.

I think it is important that my list of 5 actions are wholly in the control of the pilot and will dramatically lower the risk of an engine failure at every stage of the flight.

If you are slap dash about your walk around, rush through the runup and don't use a disciplined check list methodology, and then go out and do a bunch of PFL's; yes you will be safer than doing no training but you will be acquiring skills to deal with the engine failure you very likely have caused.

Engine failures do occur but I would strongly suggest that if you are serious in preparing yourself for this eventuality your training should start with reviewing actions that will reduce the possibility of the engine failure and then progress to practicing the actions that could restore power in the event of a failure and only then work on actually flying the forced approach manooever.

Well I am done for now but I expect this should engender a lively discussion.
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Old 15th Mar 2015, 21:56
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Big Pistons, I marvel at your faith in the collection of stressed rotating and reciprocating parts, held apart by a microscopic film of oil without which it will destroy itself within seconds, that comprises an aircraft engine. And we are talking not modern highly-developed, superbly engineered, highly computer-controlled very well developed modern automobile engines, but an old technology air cooled 1930s engine similar to what used to power classic Brit motorbikes, only larger.

You say:

the Least Common scenario is for an EFATO in for an aircraft that has

1) no outstanding maintenance issues,
2) Has sufficient fuel, no contamination, and from a correctly selected tank
3) Shows no anomalies during a complete and comprehensive runup
4) Was checked for Carb ice before lining up for takeoff, and
5) The engine gauges where in the green and the engine was developing full static RPM at the start of the takeoff role.
The engine that part-failed on me ticked all those boxes. So did the Lycoming in the PA38 in which the guy I knew died when it stopped at 300 feet.
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Old 15th Mar 2015, 22:10
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There are so many design faults in a Lycoming it is a surprise it runs for any length of time. So always be prepared for it to quit or run at reduced power.

Lycoming say they need to be run 40 hours a month to meet TBO and any failures are down to pilot handling ya!!.

So take care.
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Old 15th Mar 2015, 22:18
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And of course aircraft engines run at far higher power settings for much longer than a car engine does. At take off it runs at full power from near-cold for quite a long time. So even if it was as well engineered as a car engine (it's not - it's crude old technology) it would be less reliable.
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Old 15th Mar 2015, 22:47
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Engine failures do occur but I would strongly suggest that if you are serious in preparing yourself for this eventuality your training should start with reviewing actions that will reduce the possibility of the engine failure and then progress to practicing the actions that could restore power in the event of a failure and only then work on actually flying the forced approach manooever.
BPF

Aviate Navigate communicate ? Surely an engine failure at low level means you should be putting your full attentions into flying the aeroplane and selecting a suitable landing area not head down fiddling with mixture controls, fuel selectors etc ? that surely is the way to loose control and crash?
Too many fatal accidents are caused by pilots not aviating and putting their attention elsewhere trying to restart an engine at 200 feet is a big mistake

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Old 15th Mar 2015, 23:17
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Originally Posted by Shaggy Sheep Driver View Post




The engine that part-failed on me ticked all those boxes. So did the Lycoming in the PA38 in which the guy I knew died when it stopped at 300 feet.
From what I recall the engine partial failure left you with enough power to maintain level flight and re-position for a landing. I do not mean to make light of the fact that you successfully dealt with a very significant emergency but the engine did not "fail" in the way people are talking about in the other thread.

As for the Pa 38 crash the accident report stated the cause of the crash was


The most likely cause of the engine stoppage was stiffness of the fuel selector valve causing it to be in an intermediate position, reducing fuel flow to a level too low to sustain continuous engine operation.
I would suggest that there was at least some indication that the fuel valve was not working properly and thus the potential to have prevented the engine failure was present. I also find it hard to believe that an engine starved of fuel did not give some indication that there was something wrong on the takeoff run.

I think it is also very unfortunate the accident report stated that there appeared to be no attempt to lower the nose after the failure. The climb attitude was held until the aircraft stalled, although tragically the pilots only reaction appeared to do the least important thing of all, make a radio call.

I realize that 2 people died in this accident and my remarks may seem insensitive but I believe this accident has lessons that should not be glossed over.

Engines with properly selected fuel selectors don't stop. If there is any doubt about how the selector feels or whether it is properly positioned than you should not takeoff.

As has been already mentioned in many other threads the first action by the pilot when confronted by an EFATO must be to lower the nose. If you do nothing else but keep the wings level you will probably survive, but letting the aircraft stall at low altitude is a death sentence.

Last edited by Big Pistons Forever; 15th Mar 2015 at 23:39.
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Old 15th Mar 2015, 23:34
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Just interested to know which PA38 accident we are talking about here?

Slightly off thread I find a lot of pilots do not turn the fuel selector to OFF at the termination of a flight and many are not aware of the safety catch to do so. This action confirms that is physically possible to select OFF, reminds the pilot how to do so (both actions required for fire in flight or for crash/committal checks in event of engine failure) and procedurally is a checklist item.

The most likely cause of the engine stoppage was stiffness of the fuel selector valve causing it to be in an intermediate position, reducing fuel flow to a level too low to sustain continuous engine operation.
1) no outstanding maintenance issues,
Debatably this was an "outstanding maintenance issue"? Or maybe this issue should have been rectified before flight.

Last edited by fireflybob; 16th Mar 2015 at 00:12.
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Old 16th Mar 2015, 07:21
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The last two SEPs which apparently reputable UK flying schools presented to me for flight had long-running engine maintenance 'issues' which the schools concerned knew about and had chosen not to resolve. One of them had two problems each of which was unacceptable.

I don't remember that sort of thing being a feature of my (halcyon?) days as an FI. I do wonder if it is perhaps quite common nowadays...
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Old 16th Mar 2015, 08:18
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First of all I would like to draw attention to widen scope. Risk mitigation of EFATO is probability and severity, so high degree of attention is to be spent mostly for the second.

Yes, the 5 list does cover a great number of fatalities reasons and I often find myself shaking head when reading accident reports, but, being a pilot means also to do mistakes, frequently. The beauty is to do only the once not killing you.

In our current world of full-insurance-coverage thinking it may appear archaic to be aware of death, but this also make part of the soul of a pilot (in contrast to a flying bus driver). So what is all that excitement about? I do a fatal mistake, I die, so what? The only thing to take care of is to not hurt somebody else upon doing so.
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Old 16th Mar 2015, 10:02
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Big Pistons, you may read elsewhere in one of these EFATO threads that partial engine failures lead to more deaths that complete failures. Having had one, I concur.

The PA38 I referred to did indeed have a faulty fuel selector, but there is nothing in the AAIB report that says that should have been noticed by the pilot. My understanding is that he moved the selector handle to the correct position, but wear in the mechanism meant the tank was not correctly selected.

One guy died in hospital after the crash - the pilot. His passenger received terrible burns but survived.

Where I would question that pilot's actions prior to T/O is that he changed tanks then took off, so any problem with that tank - fuel, selector, or whatever, wouldn't manifest itself until he was in the air. I used to fly that very aeroplane, and I used to change tanks before the power checks, so plenty of time for subsequent problems to happen while we were still on the ground (they never did, but that was when that aeroplane was much newer).

Whatever, in my book one should be EXPECTING an engine fault at any time in flight, but especially at T/O. This doesn't mean 'sitting on the edge of the seat', merely not being surprised (OK, not being overwhelmingly surprised) when the power dies away at 300 feet.
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Old 16th Mar 2015, 10:07
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I think there is an issue here, comparing apples with pears. There are distinct markets, the club rental market, the owner/operator market. Both hinge on knowing the aeroplane. The owner has a distinct advantage. He, to a certain degree, knows what he has done to his aeroplane, (or should do), therefore in the frame of EFATO, he should and could do all he can to mitigate the occurrences. Proper/correct maintenance regimes, proper and diligent walk rounds, adherence to owner SOP.

The renter relies on someone else having done all of the above, and places faith on the rental organisation to have a duty of care. I have seen, and been in, some right buckets, but I had the go/no go decision. I have seen some poor decisions made by owners, and again have invoked my go/no go decision.

Life is chance, therefore, if we could predict when the engine may fail, we would all be very rich. I do not think stats exist of failures in the two categories mentioned above, but I would maintain that pilot error is still the main cause of death, even when the engine quits. We generally do not hear about successful engine failure landings, but we tend to here all about them when they go wrong.
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Old 16th Mar 2015, 10:14
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"Slightly off thread I find a lot of pilots do not turn the fuel selector to OFF at the termination of a flight "

Personally - I never do this as I think it is safer to keep it on.

If I walk up to the aircraft and it is sat in a pool of fuel I am not going to fly it! If I switch the fuel off I may not find out about the issue till later...

The fuel selector often has no maintenance schedule. I know of a number of aircraft that have suffered fuel selector failure at the point of max fuel pressure - normally just after takeoff and the pilots have been killed or burned - and one when the pilot was sprayed with fuel but got the cub down and it did not go bang.

I check my selector every 3 months. This confirms it is working.

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Old 16th Mar 2015, 10:25
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Slightly off thread I find a lot of pilots do not turn the fuel selector to OFF at the termination of a flight.
I never do. As Part of Pre-flight I do check it is movable and turn it one time left-right-both-off, so at latest upon engine start I have a fair chance to see trouble on the ground. If I would turn it off, fuel may evaporate during parking and the lines may not be fully filled (had this once a couple of years ago), plus with open valve any small leakage in the fuel feeder will be smellable.
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Old 16th Mar 2015, 10:32
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Ditto, I always leave my selector on a tank, never put it to OFF.
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Old 16th Mar 2015, 12:38
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So even if it was as well engineered as a car engine
I've had several car engines fail on me and 0 aero engines.
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Old 16th Mar 2015, 12:52
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I have had three in certified Pistons, 1 in permit Rotax and 2 in turbines.......
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Old 16th Mar 2015, 13:09
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I've had several car engines fail on me and 0 aero engines.
How often do you PFC your car?
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Old 16th Mar 2015, 13:26
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Big Pistons, I marvel at your faith in the collection of stressed rotating and reciprocating parts, held apart by a microscopic film of oil without which it will destroy itself within seconds, that comprises an aircraft engine. And we are talking not modern highly-developed, superbly engineered, highly computer-controlled very well developed modern automobile engines, but an old technology air cooled 1930s engine similar to what used to power classic Brit motorbikes, only larger.
I had a BSA 650 in the early 60s that never let me down once, from one end of the country to the other in some pretty filthy weather at times.
I now have it's bigger brother in the form of a Continental C90 up front and it too has never missed a beat in the 7 yrs it's been pulling me around. 3100 hrs in the book.
I've just fitted an electric fuel pump which the a/c didn't have before. If there is a time when I might expect an EFATO it will be the next time I leave the ground. There will be a considerable amount of taxi time & full power run ups before that happens.
I wonder how many failures occur just after maintenance, and how many are maintained by the owner, (permit types) versus maintained by commercial ops?
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Old 16th Mar 2015, 13:54
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How often do you PFC your car?
Well yes, that would have caught one of them, I don't fly off in a plane with an oil pressure indication reading zero.

(Actually it was the tachometer reading zero, but that was, if I'd known the car's system well enough, an indication of an oil problem.)
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Old 16th Mar 2015, 14:51
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Ditto, I always leave my selector on a tank, never put it to OFF.
Then how do you know you can turn it OFF if you need to?

Last edited by fireflybob; 16th Mar 2015 at 15:08.
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