Running an Engine 'On Condition'

[In Altissimus]

More questions...

What exactly are the implications of running an engine in a Private C of A aircraft 'on condition'.

I know that a 50 hour check is required - but what does that entail/cost?

[Timothy]

Does Pt mean PT or Pvt? Makes a big difference :p

Timothy

[In Altissimus]

Oops - Private.

I'll edit.

[LowNSlow]

In Alt on a Private C of A you can run an engine until it falls to bits. As you say, this is subject to a 50 hour check which will involve an oil change (as it should now and I think a compression test has to/should be(?) carried out. This will ensure that all the cylinders are contributing their proper share of the work (within specified limits). So as long as your compressions are greater than 65/80 and there are no shiny bits in the oil or oil filter then you can keep running the engine. If you tell A & C which engine you have, I'm sure that the details of the specific tasks will be forthcoming. My 50 hour checks usually coincide with the Annual so I don't know how much they cost.
It will eventually wear out of course but regular oil changes and regular flying should keep it sweet. I had a 2,500 hour Continental O-200 in an Aerobat and, after a top overhaul, it was sweet as a nut. On the other side of the coin, I know of an Arrow that was flying around with a 3,500 hour engine. It sounded like a bag of bolts and I wouldn't have used it as a boat anchor but it did work and it was legal......

[A and C]

As reported above on a private C of A in theory the engine can run on for ever ( 20% past normal OH on public transport).

The engine is subject to the normal 50 hour / 6 month check but the compresion check is only required at the 150 hour check or the annual ( but it is wise to do it at the 50/6m check ).

Running "on condition " is in by opinion a bit of a doulble edged sword on the one hand extra engine life is always an atractive idea but once the engine getts much past normal OH time things start to wear a lot faster for example the big end and main bearing shells ( that are cheap to replace ) start to wear and this tends to wear the crank shaft oval.

If the crank goes out of limits on ovality and has to be replaced then it will cost you a lot more that the value of the extra hours that the extention this is why I personaly wont take an engine past OH+20% because in the long run it just wont make financal sence.

The amount of flying that you do also has a big effect on the engine life , if you are doing more than say 150 hours a year then run to the full OH +20% but if you are only doing 50 hours a year then I would not go past 10% as internal corrosion will be taking effect ( this is one of the reasons that under LAMS the CAA introduced the 6 month check including an oil change what ever the hours the aircraft has flown.

This having been said I know full well that some one will make a post telling us about his Tiger Moth that has run on the same engine since its de-mob in 1947 and with oil changes on the decade but I get to see a lot of engines and this above is a guide drawn from knowlage across a wide fleet of aircraft were some engines dont get as far as normal OH time.

[In Altissimus]

Interesting guys - thanks.

The engine in question is a Hewland AE75., and I'm currently doing c.100hrs/yr - although I would expect that to rise slightly if I buy the 'plane in question.

Trouble is, it seems the expert engineer for these beasts has a bit of a vested interest (I'm not implying anything dodgy here) as he has a virtual monopoly on the maintenance front. Hard to get a truly independent view.

[LowNSlow]

In Alt still after the ARV then :ok: glad to see that FaPoGai didn't put you off!

You could do worse than go to G-INFO and write to the registered ARV owners and see what their experiences with the Hewland have been. It is a bit of a one-off engine and I doubt that there's a broad experience base out there.

[jmdoug]

I have a feeling that I've half read something somewhere that the "on-condition" option is going to disappear at some point.

Something to do with EASA possibly and an absolute time limt for piston engines?

Jim

[IO540]

A and C

Have you noticed any correlation between engine life and whether the aircraft has been hangared?

[smarthawke]

Just a minor correction......

The 'on condition' inspection (including the compression check) has to be carried every 100 hrs or annually, whichever occurs first.

It is all detailed in CAA Airworthiness Notice 35.

One point to note, the cylinder compression check is done with the piston at top dead centre so it will only tell you how the valves and rings are seating, not whether the cylinder itself has a crack in it.

In my experience, total achieved life has more to do with regular, careful useage than living indoors.

As for the Hewland engine, by far the best option would be to contact other operators and see what their experiences are.

[A and C]

Nothing in AN 35 states that a compression check has to be done at 100 hours AN35 para 3.1.1 only calls for an "inspection" however it refers to a chapter of CAAIP's that recomends that this is done or the prop pulled over to check the compression.

I think that I will continue to do a comp check at each 50 hour check but it is not a requirement it is all down to the engineers discretion.

IO540

It is my feeling that engine life is down to regular use and oil changes more than hangarage ,if your engine is usage then the Shell oils with the corrosion inhibiter seem to help.

Hangarage however is a big factor for the airframe and avionics , it is my opinion that the money that you save with outside parkng is more that ofset with the extra maintenance costs.

[stiknruda]

Sorry a bit off-topic.

A and C, am I correct in understanding that there are only 5 D licence holders in the UK?

If so, where do I get a list of them from? I can probably hazard a guess that two are Messrs Mills and Newby, but who are the rest?

Thanks


Stik

[S-Works]

I believe Martin Jones at Airspeed Aviation is another.

[smarthawke]

A&C,

What AWN35 says is carry out the 'on condition' inspections every 100 hrs (50 hrs for crop dusters) iaw CAAIPs (Inspection Procedures).

In CAAIPs it says to do a compression check if only by pulling the prop through by hand and feeling the compression 'manually' - it goes on to say that an alternative method is to use a differential compression tester.

sticknruda

Another well known and respected D licensed man is Rob Ronaldson near Oxford.