TBO and On Condition

[Romydog]

In the latest Go Flying magazine there is an article stating that Lycoming and Continental engines now need overhaul at TBO or 12 years. Mine is a Continental on a private cat aircraft and only 700hrs but older than 12 years - its been run on condition GR 24. Has EASA rules forced a 12 year overhaul life on low hour engines on private category?

[Pilot DAR]

Lycoming and Continental engines now need overhaul at TBO or 12 years

"Need" is relative. Most commomly, manufacturers express such "needs" in the form of service bulletins. The requirements to comply with a service bulletin vary with type of aircraft operation, and local aviation authority. If the aviation authority has chosen to absolutly require the compliance with the service bulletin by all owners, the service bulletin will be made mandatory by Airworthiness Directive, which most other authorities generally adopt.

So before you rush out for the overhaul at 11 years and 364 days, check if it is actually mandatory for your particular operation and aircraft. If it is not, make an informed decision. A very regularly run, well cared for engine can run on condition very safely much longer that 12 years and TBO. Mine (O-200) was 16 years and 3750 hrs when I decided to overhaul it, with the reason being a bit of metal in the oil. The source of the metal was a completely non-essential alternator coupling cover, and the rest of the engine was in excellent condition. It would have run much longer with no problem. That said, expect to repair/overhaul/replace cylinders and other such "consumable" components along the way.

Pilot DAR

[ben177]

We are in a similar situation, our O-320 is 12 years old next week. However, it seems that in the UK at least, it can be run on condition, provided it's not used for Public Transport. If I understood our engineer correctly, all that is needed is a compression test every 100 hours. db

[IO540]

The regs on this are supposedly changing under EASA but who knows what will happen.

Currently a privately used G-reg can run 'on condition' but AIUI you cannot place a plane onto the G register with an engine > 12 yrs since new or overhaul.

However there are countless things which you can run with but which are a no-no if going onto the G register....

[Romydog]

Thanks - my engine is fine and with 700hrs on it I dont want to do an uneccessary overhaul due to EASA changing to a 12 year rule on Continentals. I fly an Arrow on private cat with a TSIO 360 and have been operating on condition happily for the last 2 years but the Go Flying article threw me as it implies that even on private cat that overhaul is TBO or 12 years. I hope I can carry on as things stand - hopefully teh rules dont change

[smarthawke]

Becareful with the terms used here.

In the UK we (and not many other countries throughout the world) only used to abide by the hours and not calendar life for what was non-commercial 'Public Transport (Passenger)' CofA aircraft - those often used for flying training and hire. Provided the compressions were okay (every 100hrs), oil consumption within limits and no major leaks the engine could run for a further 20% of its TBO hours. This is called running 'on extension'.

Beyond TBO hours + extension the aircraft would be restricted to 'Private' use only - no club type hire or training. This is called 'on condition'. CAA Airworthiness Notice 35 covered this.

Now we are in EASA-land this is all covered by CAA CAP747 Generic Requirement 24 and we have to take in account the manufacturer's calendar based life as well as TBO hours.

The calendar time is also subject to a 20% extension just like the TBO hours. When 'on extension' the aircraft can still be used for flying training and hire as before.

Beyond the calendar life and/or TBO hours life + 20% extension, the aircraft can carry on as infinitum iaw GR24 but for Private use only.

I'll read the article when I see it and see how it's written.

[A and C]

Rather than get half the picture check out CAA CAP 747 GR24.

It is all you need to read on this subject.

Very quick off the draw Gerry

[Romydog]

Thanks I'll check out the details but bottom line - if its for private flying only, which mine is I can go on condition. My engine is 700 hours and 16 yrs old, manufacturer recommmends 1400 hrs or 12 yrs.

[smarthawke]

Just had a quick look at the article and I think the bit that may have caused confusion is:

"Your engine will now need to be overhauled at TBO or 12 years, whichever comes sooner. The same extension period and ‘on condition’ rules apply to calendar time as they do the TBO hours period."

I think it means that the 'on extension/on condition' rules apply to both TBO hours and calendar time and affect the allowed useage of the aircraft as mentioned in the previous paragraph:

"If your aircraft is flown under what used to be termed ‘public transport’ (i.e. for operation by a flying club for training or private hire) the engine can be run for a further 20% of the time beyond TBO subject to certain conditions. For ‘private use’ you can run the engine
further ‘on condition’ subject to requirements detailed in the CAA’s CAP747 Generic Requirements Number 24."

Hope that makes sense!

[Romydog]

Thanks it does -I was starting to get down thinking here we go again EASA doing its best to kill GA off! Now I will get back to thinking about flying

[mm_flynn]

Romydog,

Do you do oil analysis? Unless the engine lived in a desert 'preserved' for a number of years it falls into the category of 'not well used and likely to suffer corrosion'. You don't want to discover this problem as you are not quite clearing a hedge or gliding into a field!

For the older engine establishing a pattern with oil analysis every oil change can help detect when you have pushed on condition to the limit. It is only about $20 or so (and a competent mechanic to take the sample). When you read the accident reports of engine failure incidents, there are quite a few that wouldn't have happened if oil analysis was being undertaken.

[IO540]

Couldn't agree more re oil analysis.

It is done simply when changing the oil. Wait about 30 secs and then divert a bit into a little bottle. Run the engine first, to make sure it is well mixed up.

I bought a large # of prepaid kits for £6.50 each a few years ago, which get mailed to the USA for analysys, and I think there are some deals around, though not quite as cheap.

Unfortunately some of the really really obvious cases of fatal accidents and knackered engines, I don't think anybody was cutting open the oil filter either, and that is a whole lot more serious. Almost nobody (except IFR tourer owners possibly) does oil analysis but cutting open the oil filter should be 100% standard.

[Romydog]

Good idea - I will ask for one at the next oil change

[Pilot DAR]

I certainly agree with cutting open, and examining the oil filter. That's a major source of information about the wear occurring in your engine. I can't get quite so excited about oil analysis though. There's nothing wrong with it, but the information it can provide is somewhat limited, as most of the alloys used in the construction of the engine are one of just a few types. Thus the report could come back with a spike of a certain alloy, which could be any one of many parts. As the engine could also contain after market parts, which could be of a different alloy, some of the information reported could be a little decpetive.

I certainly agree with oil analysis for engines which were designed to benefit from this examination technique, as they often contain many different alloys, and the indications in the oil are more descriptive of wear in specific locations.

Certain common defects in these engines are not picked up by oil analysis (sticking valves, sticking piston rings, cracked cylinders, and pulled studs for example).

That said, for a few dollars, oil analysis can't hurt, just don't take it as the final indication of your engine's condition...

Pilot DAR

[scooter boy]

"cutting open the oil filter should be 100% standard" - especially for single engine IFR types like us IO540.

SB