How reliable are engines?

[pmccarthy]

In another thread, engine reliability has been raised. Some people don’t trust single engined aircraft. So let’s have a quick survey. 
 

What is your experience of engine failure in normally-aspirated aero engines? Express it as engine failure per thousand hours of your flying experience. Limit it to Lycoming, Continental and four-stroke Rotax engines. Perhaps only answer if you have at least 500 hours of flying experience. Of course we are talking about mechanical failure, not fuel a management issues.

 

Auto conversions, older or minor makes, turbo and injected engines not included.

 

My experience, for what that is worth, is zero failures per thousand hours.

[old man emu]

Before the hoary old chestnut of Jabiru engines comes into this - and I think you should not have excluded them - have all those problems in the early engines been resolved in the newer engines? 

[turboplanner]

You need to make your mind up whether you are talking about GA operations maintained by LAMES or RA operations maintained by owners/Clubs - big difference. and big data input given GA operators are not normally going to be looking at a Revreational Aviation site.

[old man emu]

One of my professors once told me that a little bit of data, no matter how doubtful, is better than no data at all.

[turboplanner]

In frame rebuild at 14,400 hours.

[facthunter]

Very carefully framed question .WHY? If you limit input, you're not getting a current picture. What engine are you referencing turbo?  Nev

[turboplanner]

an internal combustion engine with a conventional block and pistons.

[spenaroo]

id like to make a point that Ive made before when talking about re-purposing existing engines.
we use hours not distance travelled. but its fairly similar.
 

lets say a harley-davidson averages 50km/h. it needs a new crank at 100,000kms
so 100,000, divided by 50 = 2000
therefore the engine life in time is about 2000 hours. which to my understanding is similar to an air cooled aero engine.

I know the flight school I learned in worked of the budget of 1 Jabiru engine failure per 1000 hours. and later swapped to Rotax.

which brings up another point, how many cars do you see by the side of the road with mechanical issues...
but you would expect a car from the 70's to be more likely to break down then a car built in that last 10 years.
wouldn't the same case exist with aircraft... only id argue we have an older average engine age then that of cars on the road currently

[facthunter]

Car engines LOAF most of the time.  You also don't run them flat out for the first 5 minutes of every trip. A lot of the problems with aero engines is they don't get used enough and/or do short runs. It takes about 40 minutes of flight to warm the motor right through.. The worst thing you can do is leave it in front of the clubhouse all day and then taxi it to the hangar late in the day and then not fly it for many weeks. .  Nev

[spenaroo]

6 minutes ago, facthunter said:

Car engines LOAF most of the time.  You also don't run them flat out for the first 5 minutes of every trip. A lot of the problems with aero engines is they don't get used enough and/or do short runs. It takes about 40 minutes of flight to warm the motor right through.. The worst thing you can do is leave it in front of the clubhouse all day and then taxi it to the hangar late in the day and then not fly it for many weeks. .  Nev

Speak for yourself, where's the fun if the the wheels aren't spinning as you exit the driveway.

but yes, there is differences with the constant RPM and varied load

[facthunter]

Reliability doesn't mean fit and forget. For OLD motors an appropriate inspect and rectify process assures reliability. Some of these older motors are also modified lately  in a way the makers would not approve of. ie Harsh oil rings that  weren't used in the day and fitting car type pistons. You inspect your airframe why not the motor? . Hand propping meant compressions are felt when priming.  Nev

[old man emu]

Do you pay as much attention to your car's engine as you do to your aircraft's engine?  Because pilots know that when the engine stops Life gets testing. 

 

Provided the manufacturer is strict with quality control of everything from the raw materials, through casting and machining, to component assembly a modern ICE with regular attention is hardly likely to have a failure over a long service life. I'll add the rider to that statement by saying anything is possible, but modern metallurgy and manufacturing standards have reduced to probability of a failure to almost insignificant levels, despite how hard the engine is pushed.

 

Do you really think that manufacturers are telling you the absolute truth when they tell you that their engine produces maximum horsepower at a certain RPM? Just look at WW2 military aero engines, especially for fighters. Pilots were told that maximum power that could be used for takeoff was such and such RPM. But if the need came to get the F out of danger, just crash the gate to get combat power for a maximum of 5 minutes for most engines. Then when you get home, tell your crew chief that he needs to do an engine swap.

 

Like car engines, aero engines are built for reliability. The aviation workhorse, the Lycoming IO-360, only has a compression ratio of 8.5:1, which is low enough to enable it to use 91/95 avgas. Power is quoted at 180 HP at 2700 RPM.  But the  POH says . Normal cruise is 65-75% power, 2200-2700 RPM (no more than 75%)with 65% as the conservative setting. Operating the engine like that wouldn't raise a sweat in a sauna.

[facthunter]

Most Aero engines have Upper RPM  (Overspeed) limits. IF exceeded for a given time the motor is junked.. Aero engines are made as light as they can be and still retain reliability. Weight of the engine in the car is not of great concern but prewar car race engines were built for a life of 1800 Kms. Nev

[IBob]

4 hours ago, old man emu said:

One of my professors once told me that a little bit of data, no matter how doubtful, is better than no data at all.

With due respect to your prof, I'm not at all sure that is universally applicable.
I did a lot of work on industrial regfrig, boiler, timber kiln, hot water systems etc. This involved monitoring, logging and displaying as required all sorts of temps, pressures etc.
We used to say that faulty data is worse than no data, in that it can lead you to faulty conclusions.
And for the same reasons, when presented with stats, I have always wanted to see the raw data, not the data as it has been interpreted by somebody else.....

[facthunter]

I've only had one partial failure of a VH light aircraft  engine  A Continental 0-300 with a failed hydraulic lifter. I've had at least 6 Big radials fail and one catch on fire on the ground due to a stuck primer solenoid..  Had 2 Rotax 9 series events due to the people who worked on them  not being clued, requiring outlandings.  Nev

[fallowdeer]

 

 

I don’t subscribe to the “never fly over something you can’t land on” school of thought. 
 

If we avoid stall/spin events at low altitude, running out of fuel, encounters with mountains and IMC, and loss of control events, overruns and failed go arounds we’ve  eliminated a massive percentage of mishaps. These are circumstances that are eminently avoidable.

 

One favourite destination I have involves a 50nm leg of water there and back.  The destination is a very unimproved strip 4m wide nestled in hills with very quirky approaches.  Whilst the emotional fear is ending up in the drink and feeding the sharks it’s way more likely that any mishap is going to occur on takeoff/landing.  Couple of very sketchy strips in the mountains provide similar overall circumstances.

 

Perhaps a more  interesting question would be to ask aviators to consider

”What percentage of your flying do you consider that, if you had a catastrophic engine failure, you’d be extremely unlikely to survive?”

 

My answer over the hours  I’ve flown would be well under 1%.  So considering the reliability of our well maintained engines the real risk is consigned to the far distant dire dark corner of the risk matrix.   Very, very, very unlikely to happen, but you’re screwed if it does.    Kind of the opposite of winning the lottery….

 

 

[RFguy]

4 hours ago, spenaroo said:

Speak for yourself, where's the fun if the the wheels aren't spinning as you exit the driveway.

but yes, there is differences with the constant RPM and varied load

it's funny a bit- true story here -  when I get in my car and do a U turn , and  then if the road ahead is dead straight.. I tend to out of aircraft habit,  floor it, until I realise I am not on a takeoff roll....

Edited June 30, 2023 by RFguy

[facthunter]

 Mr PLOD will enjoy your explanation. Wheeel spinning will classify you as a HOON.. I do it too just because you CAN and a long one without any axle tramp is worth admiration.    Nev..

[Garfly]

13 minutes ago, RFguy said:

when I get in my car and do a U turn , and  then if the road ahead is dead straight.. I tend to out of aircraft habit,  floor it, until I realise I am not on a takeoff roll....

But I guess the worst part is that you straddle the centre-line!    ;- )

[facthunter]

All planes these days have a hand throttle but it works opposite to a tractor. The PEDALS work opposite to a billy cart too. For a while I was all over the place in the Chipmunk... Nev

[Area-51]

When you have nerves of steel Carrillo rods and enough horsepower and really good brakes and tyres you can drive all over the place at WOT; what are you talking about? 🤷🏼‍♂️

[facthunter]

It's never grabbed ME much. I've more respect for the vehicle. I don't use Stillsons and cold chisels on motors either. Have I missed out on much?   Nev

[Area-51]

3 hours ago, facthunter said:

It's never grabbed ME much. I've more respect for the vehicle. I don't use Stillsons and cold chisels on motors either. Have I missed out on much?   Nev

A 10lb mallet 🤷🏼‍♂️

[facthunter]

You  use a hammer on a cold chisel   The machine barbarian's tool kit. Knock a few fins off so the shifter works on the spark plugs. I'd better cease now or some will pick up too many clues. Nev

[IBob]

I have the best set of cold chisels!
They're actually Sears Roebuck 'Craftsman' wood chisels. Made out of some super tough stainless material:  impossible to sharpen to anything like a wood shaving edge, but otherwise totally indestructible, I've been dealing to rock and concrete with them for 40mumble years....)