ATSB report on engine failures 2009-2014

[Garfly]

https://www.atsb.gov.au/publications/investigation_reports/2013/aair/ar-2013-107/

[Oscar]

Lots to digest there.

 

When reading it, people might like to consider a few incidental facts to put what has been reported in perspective.

 

The reported rate of failure for Jabiru engines is 3.1 /10,000 hours. That is a probability of 0.31 in 1000 per flying hour. For the average private owner doing around 50 hours/year, that means 20 years of operation. Or, multiplied out: an engine failure is likely to happen once in 60 years of their flying.

 

FTF's, I think, average around 7-10 times that usage: so an engine failure once in every five-six years of operation, should be expected. Some FTFs appear to get that sort of life: 1000 hours trouble free, then a full Top Overhaul, and back into service.. Some FTF's shred their engines on average about every 350 hours ( and my own aircraft has a documented history of the latter as usual in its life before I came to own it). One has to ask: is this above-average failure rate the fault of the engine or the operation?

 

Now here's another interesting little fact: the 'safe fatigue life' for components in light General Aviation, is set at 1/1000 flying hours as a 'safe' life.

 

So: which would you, as a conscientious, conservative private owner/operator rather bet on: the noise going out once in the next 3,000 hours of operation, or something in the airframe breaking in the next 1,000 hours of operation?

 

Just asking....

 

 

[kasper]

Separate thread already running on this

 

http://www.recreationalflying.com/threads/atsb-report-into-light-aircraft-engine-failures.147230/

 

 

[djpacro]

Now here's another interesting little fact: the 'safe fatigue life' for components in light General Aviation, is set at 1/1000 flying hours as a 'safe' life...

Nope, not a fact at all. For parts which require a safe life then it is whatever it turns out to be. If for a part it is, say 1000 hours, for discussion then it will not break (unless operated contrary to that expected for fatigue life determination) at that safe life which is a small fraction of the life determined for it. Simply buy another one and take comfort in the safe life concept.

[Nobody]

Lots to digest there.When reading it, people might like to consider a few incidental facts to put what has been reported in perspective.

 

The reported rate of failure for Jabiru engines is 3.1 /10,000 hours. That is a probability of 0.31 in 1000 per flying hour. For the average private owner doing around 50 hours/year, that means 20 years of operation. Or, multiplied out: an engine failure is likely to happen once in 60 years of their flying.

 

FTF's, I think, average around 7-10 times that usage: so an engine failure once in every five-six years of operation, should be expected. Some FTFs appear to get that sort of life: 1000 hours trouble free, then a full Top Overhaul, and back into service.. Some FTF's shred their engines on average about every 350 hours ( and my own aircraft has a documented history of the latter as usual in its life before I came to own it). One has to ask: is this above-average failure rate the fault of the engine or the operation?

 

Now here's another interesting little fact: the 'safe fatigue life' for components in light General Aviation, is set at 1/1000 flying hours as a 'safe' life.

 

So: which would you, as a conscientious, conservative private owner/operator rather bet on: the noise going out once in the next 3,000 hours of operation, or something in the airframe breaking in the next 1,000 hours of operation?

 

Just asking....

'Oscar,

 

I am not sure where you get the 1/1000 hours for safe fatigue life. AC 23-13 is a useful discussion of what the FAA requires of manufacturers for fatigue approval and testing. The safe fatigue life is whatever the manufacturer determines from calculations, analysis and test and is the life at which a component should be replaced. When a structure gets to the end of its "safe life" using the factors in AC23-13 there is a 99.97777% chance that the part will not have a detectable fatigue crack.

 

http://www.faa.gov/documentLibrary/media/Advisory_Circular/ac23-13A.pdf

 

 

[Oscar]

Only going on the advice of a CAR 35 engineer with about 45+ years of experience in the industry. I'm not a statistician, but my source of information has credentials going back 25 years plus, that his knowledge of fatigue life issues is internationally recognised ( and accepted by ICAO-signatory authorities, including CASA.)

 

But, I may be quite wrong.

 

 

[Oscar]

Nope, not a fact at all. For parts which require a safe life then it is whatever it turns out to be. If for a part it is, say 1000 hours, for discussion then it will not break (unless operated contrary to that expected for fatigue life determination) at that safe life which is a small fraction of the life determined for it. Simply buy another one and take comfort in the safe life concept.

Yep, good comment: the 1/1000 hours is taken by the FAA as the figure at which a manufacturer needs to act. Reputable manufacturers will react to the first instance of a failure they can pin down to unforeseen fatigue consequences of a component. In a world where having nude piccies of you splashed over the Internet gets a US$50M+ judgement - no Textron is going to just sit idly by and say: ' hey, let's just let this one slide, shall we?'

 

 

[facthunter]

Just about every metal aircraft will have cracks in its airframe once it has been a few years in service. Operators keep an eye on them and plate or otherwise repair them all the time to an approved method.

 

Most "Normal" flat four crankcases will have some crack in the first engine life. I don't recall any mention of a Jabiru engine case cracking. The through bolts are the main issue. Realistically 3 per 10,000 hours of operation isn't something to get too worked up about. . The life of a Red Bull racer engine might only be 20 hours You probably have an equal chance of a fatal bird strike, Running into bad weather. out of fuel. having a nosewheel break off etc You make your own luck in many ways. Choice of engine is one. Not one incident resulted in a fire which is much more serious than a failure. A gypsy Major today would be unlikely to be more reliable and needs head work at 3-400 hours. The pattern of stud/bolt breakages is too scattered/random to draw a conclusion of much meaning . There may be an RPM setting to avoid . Most motors have at least one. The hydraulic lifters seem to have caused an additional problem. There are quite a few reasons I would not use them, myself, and I know there are others who feel the same way.

 

There are some figures to ponder on in that report. What real conclusions one can derive is another matter. The Lycoming performance figures are skewed by ONE engine with repeated magneto failures. That should not have been included as it's not anything of value by it's unique nature. Nev