Engine reliability

[pmccarthy]

In choosing between a well- used GA aircraft and a new factory- built RAA machine, I considered that engine reliability would be equal. I thought about range, useful load, cost and so on, but not that he risk of forced landings might be different.

 

What is the evidence for reliability on a 912ULS, for example, if properly maintained? I ask this because there are many other posts where RAA pilots seem to spend half their lives landing dead stick in paddocks. GA pilots are trained to keep a safe landing field in mind but I have never obsessed about it. Of course any engine can stop during cruise but what are the odds? I recently completed a Bass Strait crossing at relatively low level (3000 ft)because of cloud, is that considered irresponsible?

 

I'm not saying don't practice forced landings, I just want to know whether my aircraft is inherently less reliable than the trusty old Cherokee.

 

 

[turboplanner]

Well the statistics are out there to be researched, and then you'd have an excellent idea without all the whistling past the graveyard that goes on.

 

 

[cscotthendry]

I suspect that one of the factors that would affect the reliability figures of recreational aircraft engines is the number that are maintained by the owner and the variability of their mechanicing skills and knowledge.

 

That said, you might get some comparable statistics if you restricted your statistics gathering to professionally maintained engines in recreational aircraft such as those from flying schools.

 

Edit:the fact that Rotax now specify 2000 hour TBO, (even for non-certified engines) says a lot to me about their reliability. When you think about it, if you manage to clock up 100 hours per year, the engine should be capable of 20 years of flying!

 

 

[facthunter]

No engine used commercially is allowed to run for 20 years without a stripdown.

 

TBO is a term more flexible than it used to be so I wouldn't regard it as anything more than a CLAIM in most cases. ( The reduction gear has to be serviced at 400 hours in the case of the rotax). ALL engines have a requirement for servicing. They are never entirely fit and forget.

 

Anytime you fly over tiger country or an expanse of water in a single engine aircraft you MUST accept that IF the engine fails, you have a problem.

 

ALL engines can fail, at any time.

 

One of the advantages of the Rotax 4 stroke is that you don't have to fiddle with the main part of the engine and it doesn't have a problem with cylinder wall corrosion when the engine is left idle, for considerable time.

 

There is no doubt that some servicing although well intentioned is not done well by qualified personnel and owner servicing. There are advantages in both, which could be commented on at length requiring a separate thread topic. Nev

 

 

[turboplanner]

I suspect that one of the factors that would affect the reliability figures of recreational aircraft engines is the number that are maintained by the owner and the variability of their mechanicing skills and knowledge.

I assume from his comments he is talking about buying one - Owner maintenance statistics and operator statistics might be hard to split.

 

My own decision on where to go was made by a study of forced landings over three or four years between RA owner/L2/LAME maintained as a group, and GA LAME maintained, and it was a no contest - pointed one way.

 

 

[old man emu]

There is one word to sum up engine reliability: "Quality"

 

Quality of raw materials the engine is made from; Quality of forging/milling/shaping practices in the manufacture of components; Quality of assembly procedures for the engine by the manufacturer; Quality of procedures employed when the engine is operating AND between operations; Quality of the maintenance regime. For the majority of aero-engines, the first three on the list rarely occur. However, I believe evidence exists that one manufacturer fails on the third point.

 

So that lets us point the finger at the way that the engine is used as being the initiator of engine failures.

 

Give an engine a hard life (lots of circuit work, or frequent cycles between full and low power generation (aerobatics, glider towing, parachutist dropping) and you can expect more rapid travel down the path the component failure. On the other hand, fly only two or three hours per year and you can expect failures caused by chemical reactions between the atmosphere and components.

 

Failure to follow the manufacturer's maintenance procedures; doing what an 'expert' told you even though it contradicts the manufacturer's procedures; failure to keep up to date with service advice from the manufacturer. An aero-engine is the product years of study of metallurgy, thermodynamics, and various fields of mechanical and production engineering. If you are an expert in all these areas, then, sure, modify your engine. If not - if it ain't broke - don't fix it.

 

Lavishing Quality on any engine (even a Sino-copy) will keep it operating for the term of its engineered life expectancy. Spare the Quality and spoil the engine.

 

OME

 

 

[pmccarthy]

That makes a lot of sense to me. If you fly around 100 hours per year, some trips and some circuits, follow the manufacturer's regime, use a good engineer for maintenance and don't muck about with the machine then it is reasonable to expect it will not let you down.

 

 

[facthunter]

It only takes one small part not installed correctly or manufactured wrong to stop an aircraft engine. A recent incident with a later series Continental broke an exhaust rocker because there was a casting flaw in it. I don't believe that in the past a rocker would have been made using the casting process and they would have all been forged.

 

I don't believe we train as well as we used to. Costs are continually under downwards pressure and the tender process generally leads to accepting the lowest bidder, who may not even be able to fulfil the contract because the undercut price was nor sustainable or it relied on corners being cut, so quality suffers. Nev

 

 

[turboplanner]

That makes a lot of sense to me. If you fly around 100 hours per year, some trips and some circuits, follow the manufacturer's regime, use a good engineer for maintenance and don't muck about with the machine then it is reasonable to expect it will not let you down.

More research required - there are engines failing which have been professionally maintained.

 

 

[damkia]

QA/QC/HACCP principles at play in the overall reliability.

 

Failure in anything from the basic metallurgy, through to selection of appropriate materials, then the engineering and manufacture, and then to the end user' treatment and maintenance of the engine will all have an effect on reliability long term.

 

There is one particular engine that may have a materials and design weakness causing issues.

 

 

[Powerin]

From what I have researched Rotax and Lycoming are the most reliable piston engines. There has been a claim made on another thread that Rotax are good at hiding warranty problems. I'm not sure, a good search around the web is hard pressed to find many complaints about Rotax.

 

As an aside, a friend flies a fairly new GA aircraft with a Continental engine. Apparently there have been a few problems with the quality of the engines. The friend had a problem with the engine which was repaired under warranty. Wanting to know a bit more about the problem, and if it could be avoided in the future, he sent an email off to Continental asking a few questions. The reply email came from the LEGAL department of the company.....

 

 

[turboplanner]

The claim on the other thread was never backed up with any evidence and I'd take as just mischief making.

 

On the Continental reaction, that's normal. When someone's question starts to cross over into looking for a commitment, it's normally checked by Legal. I've done that many times just to be sure. Someone's just being lazy getting legal to write the letter, or there's an ego in legal. Either way not significant.

 

 

[Powerin]

On the Continental reaction, that's normal. When someone's question starts to cross over into looking for a commitment, it's normally checked by Legal. I've done that many times just to be sure. Someone's just being lazy getting legal to write the letter, or there's an ego in legal. Either way not significant.

That's probably the case. However the problems are real such as out-of-round components with tolerances way out of specs, like valve guides. But it is a bit perturbing when an owner doing due diligence and innocently asking advice from a manufacturer receives a threatening reply from legal.

 

 

[turboplanner]

Well where you've actually found specific faults and advised the factory, everything is elevated and they don't have a leg to stand on, so in that case I also would be making sure that any letter was reviewed and written by legal, because they know there's a good chance it could be used as evidence against them, so given that situation it's not to threaten or intimidate you.

 

 

[Guest Maj Millard]

Facto, Where did get the 400 hr gearbox check figure from ?...At 800 hours (8 years at normal usage) it's recommended you check the gearbox, which is twice what you have suggested... OR if the engine /gearbox has suffered a propstrike or sudden stoppage, which is normal common sense. They do include checking of the friction overload clutch (if fitted), which is mentioned as part of a 100 hrly maintenance event. It's only a five minute check at best with the right gear, and I haven't found one yet that is below recommended tolerance....B Floods normal 800 hr gearbozx check generally runs about $8-900 bucks if all is well, which would work out at about $100 a year if done every eight years.......................................................Maj...

 

 

[pmccarthy]

I understood the gearbox check was only if you run on Avgas. But I haven't looked it up as I have about 600 hours left to do so.

 

 

[Guest Maj Millard]

No I believe it's regardless of wether you run avgas or not....I'll do more checking and get the full story............................................Maj...

 

 

[facthunter]

I think it's only the clutch damping that needs to be checked. and as you say it is not fitted to some models. My point is that ALL engines require some inspection. The main thing I have found with rotax 4 strokes is the balance of the carbs, the carb mount rubbers and the exhaust system cracks. Nothing major.... Nev

 

 

[nomadpete]

Engine Reliability:

 

I am interested to know if there are any statistics about aircraft engine failures - that are related in terms of MTBF for each brand/ model? It is no good just saying that 'X' number of brand 'Y' engines failed this year. We need to know in relation to hours flown, just as accident statistics should be related to hours flown, and numbers of landings, not just to the calender year.

 

As it is now, we get to hear individual cases (some folk delight in bagging out a particular brand) which cannot be extrapolated to give a realistic picture of reliability.

 

Since all failures should have been reported to RAAus, it would only take a modest data filter to provide a list of engine reported failures related to brand/model/hours in service.

 

 

[damkia]

Engine Reliability:I am interested to know if there are any statistics about aircraft engine failures - that are related in terms of MTBF for each brand/ model? It is no good just saying that 'X' number of brand 'Y' engines failed this year. We need to know in relation to hours flown, just as accident statistics should be related to hours flown, and numbers of landings, not just to the calender year.

As it is now, we get to hear individual cases (some folk delight in bagging out a particular brand) which cannot be extrapolated to give a realistic picture of reliability.

 

Since all failures should have been reported to RAAus, it would only take a modest data filter to provide a list of engine reported failures related to brand/model/hours in service.

Start with a polite request to the new Tech Manager for the information to be published, then graduate to aFOI application to RA-Aus if that is blocked/fails. This will be a good test of the supposed new "transparency" and goodwill with the members

 

This should not be "private" information, as it is the members that are contributing data to the RA-Aus, and as such you should have access to this information as much as you have access to a financial statement published every year, for the members perusal and for regulatory reasons.

 

 

[Guest Maj Millard]

I don't expect FOI would be applicable with the RAAus as it is not a government department, and basically more of a private corporation even though we contract to carry out work on behalf of CASA..........A polite request to the new tech manager may be a good start...it is information we should have available to us as members and pilots.................................Maj...

 

 

[pmccarthy]

I suspect from hearsay that only half of the reportable incidents are reported. I guess that the statistics of various causes for the reported incidents would still be valid, but the absolute number of incidents would be higher than the reports suggest.

 

 

[frank marriott]

I would suggest that it might be a good idea to give the new manager and his team some space to get the current situation sorted before any requests for stats and the like.

 

 

[turboplanner]

OK, well I'll go back to the original question and the answer is yes.