Engine life span?

[QantasEagle]

ty

[Flyin'Dutch']

Plenty of engines are running happily 'on condition' well beyond their official TBO and on the other hand it is not unheard off to have a nearly new/recently overhauled engine fail.

If you are not happy with the way the syndicate runs the aeroplane/spends its money then that may be a reason to change boats but that is maybe a different matter than running the engine past TBO.

[QantasEagle]

FlyingDutch, thanks and I understand that any engine can fail - but do you have the stats on the likelihood of this happening?

[Flyin'Dutch']

Nope, and neither has anyone else.

The numbers are too small and the operating characteristics too diverse to produce any meaningful figures.

[Lowtimer]

"Hours run" is a highly arbitrary way of assessing the likley wear and tear on an angine in any case. With cars we do it by miles rather than hours. You could just as easily make out a case for doing it by "total number of revolutions" run. Some jets, e.g. I believe the Allison in the Bell Jet Ranger engine, are lifed by the number of starts. For most of the piston engines we fly, cold starts are the time when most engine wear takes place, so an aeroplane that is flying most of the day would usually have a far longer time to actual failure (in hours run) than one that gets flown twice a week. And the limiting factor for a lot of light aeroplane engines is internal corrosion that takes place when they are not running at all. So running "on condition" actually makes a lot more sense than running to an arbitrary hours limit, providing it is being properly inspected. If your group looks after the aeroplane, changes the oil often, pre-heats it in the winter and flies it regularly it might go on for a very long time

[skydriller]

If your group looks after the aeroplane, changes the oil often, pre-heats it in the winter and flies it regularly it might go on for a very long time

Could someone explain what is involved in 'pre-heating', and when you would need to do it to an aeroplane?

I have worked in North-West Canada for a few winters and when possible we would plug in our trucks overnight to stop them freezing up (there was a special plug in the grill) but we were talking temperatures of -20 to -40 deg C ... and colder!!

Regards, SD..

[Lowtimer]

The very finest way of doing it is to pump hot oil at working temperature through the engine for half an hour before you start it, every time. That's what some of the more advanced warbird operators do, though it really is a very high standard of mollycoddling. Bristol Mercury engines are not thick on the ground though, so you can see their point. If you can get the oil and indeed the whole engine up to temperature before it starts turning, start-up wear will be negligible. The main issues are the viscosity of the oil when it start pumping, and the clearances on the engine.

The colder the weather, the greater the benefits. If it is a 30 degree summer day in the UK, your oil is nice and thin and runny - even the straight-weight W100 that our Yak uses will get straight to the task of lubricating the engine. The oil pressure comes up quickly, and it does not go too high. (Oil pressure relief valves have been known to stick causing excessive oil pressure to break something - usually the pipe downstream of the pump.)
If it is winter, even the winter-weight W80 is pretty reluctant to move round the engine at 0 degrees celcius, and the oil pressure takes longer to arrive. It also takes a lot more ground running time to get the mass of the engine up to a proper working temperature, and all that time it is not only burning fuel but also more stressed than when it is thoroughly warmed though. It also takes less prime to start, so there is less risk of hydraulic locking and less petrol washing the oild film off the bores. So heating the oil before you start is a Good Thing, and heating the whole engine is also helpful. Unless you have a massive pre-heater unit of the type they used to use in airline service, it is actually far easier to use a very modest heat source to prevent the engine getting cold in the first place. So in the winter we put the aeroplane away in the hangar, close up the gaps and holes in the cowling, you can wrap an old duvet round the cowling if you want, and wire up small low-powered electric heaters to keep things from getting cold. Tactics include fish-tank heaters in the oil tank, or (better) electric heating pads that go right around strategic areas. The oil tank or sump (depending on the oil system) is the most important part to keep warm, but if you have insulated the engine compartment keeping the oil warm keeps everything reasonably warm. The cost of the electricity is pennies, it more than pays for itself with just the saving in fuel for the warm-up. And it keeps the engine in better nick! (By the way, it helps car engines live a long time, too!).
For us this is really a priority in sub-zero (celcius) temperatures, and personally I think it's worth while in any ambient temperature below about 10 degrees C.

[QantasEagle]

Thanks for the replies chaps.
Unfortunately the aircraft is in the middle of a cold airfield with no possibility of hangarage (nor has had ever) and no special measures like those described- guess also given the flying time of about 300 hours per year then the wear and tear had been substantial

[Lowtimer]

Actually 300 hrs a year is a lot more than many privately owned aircraft clock up. If it has been flown on a few days a week rather than on a few days each month, it will be much less prone to internal corrosion.
You don't say what type of engine it is, but if it can be run on a suitable multigrade oil that goes a long way to addressing the cold-start oil viscosity issues.

[Flyin'Dutch']

Multigrades are a lot better at protecting engines in these conditions and are easier on the battery and starter as well.

SD, you can buy preheaters that do not require electricity. Have a look at www.sportys.com.

http://www.sportys.com/acb/webpage.cfm?&DID=19&WebPage_ID=68 for the heaters and associated gubbins.

FD

[MLS-12D]

I agree with Flyin'Dutch's comments.

TBO-busting is not a sin (see generally here (http://www.avweb.com/news/columns/187037-1.html)), and there is a lot to be said for the saying "if it ain't broke, don't fix it". Of course, regular compression checks, oil analysis, etc. would be prudent. And a lot depends upon the particular engine type, and aircraft use (e.g., a O-360 is much more likely to exceed TBO than an AIO-360, especially if the latter is regularlay used for aerobatics).

To the best of my knowledge, Lowtimer is quite correct that an engine operated ~300 hours per years is significantly more likely to exceed TBO than one that is operated, say, ~25 hours annually.

If you are really interested, I strongly recommend obtaining a copy of Firewall Forward: Maintaining Power (volume 4 in the Light Plane Maintenance Library, ISBN 0-9613139-1-9). Part III of that book (pages 113-15149), entitled "Getting the Most Engine Life", contains two chapters ("Getting to TBO and Beyond" and "Major Overhaul") that are full of useful and reliable information. Additionally, Chapter 3 ("Cold-Weather Safeguards") has good stuff on pre-heating.

Speaking of pre-heaters: here (http://www.avweb.com/news/maint/182846-1.html) is a link to a decent little article on AvWeb (and see also the preheat section in "Yes, it's Winter" (http://www.avweb.com/news/columns/182657-1.html)). Aviation Consumer's article "Pad, Plug or Flamethrower?" (http://www.aviationconsumer.com/pub/31_3/misc/5044-1.html) is also worth reading. Personally, I prefer the flexibility of forced air (something like this (http://www.ultimategear.com/airpreh.html), although you could probably make your own for less money).

[ozplane]

Not that it helps here but I heard that a well-known ooperator of Trislanders has got to about 5000 hours on one of it's engines. They are run to a strict regime but I guess it's all short hops.

[IO540]

I reckon an engine that does 25hrs/year is going to be knackered (internal corrossion) before the year is out, however one spreads the hours out.

[S-Works]

On the flip side I have put just over 1000hrs on my engine in just over 2.5yrs and it has only just gone past TBO before needing overhaul. The last 3 50hr checks have all revealed increasing metal in the oil filter. The cost of finding out what is causing the problem on a life engine was a false economy so I bought a new Millenium engine which goes in at the end of this month.

With a few minor exceptions all the flying hours were done by me and I coddle and cossett the engine like a newborn as it is me who has to pick up the full tab for repairs. I keep it hangered and in the winter it has an engine heater so always starts with warm oil. I never taxi untill the engine is fully warm. It is not used for training so no abuse either.

The guy I bought it off did about 50hrs a year for the 5 years he had it.

So there is nothing saying a well flown engine will just keep on going either!

Sods law will have an engine fail when there is the least money around to pay for it!

[Rod1]

One other thing to watch out for. If you run too far past TBO you will not get the trade in discount which is based on the value of the old engine for use in a Zero time rebuild. This can add many 1000’s to the cost of replacement, just by going a little too far past TBO.

Rod1