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ELA1 / ELA2 maintenance (merged)

So according to part ML we can choose to do say prop overhaul on condition and not need to justify it?

You have to justify it but there is no pre-approval of your justification (= maintenance program). Only when you are subject to an inspection like ACAM they could say that your maintenance program is in violation. Let’s say you write in your maintenance program that like for 2 stroke ship diesels, the engine oil is not replaced during the engine lifetime.

I didn’t want to go that far :-) but how would one phrase a deviation from prop overhaul time from scheduled to on-condition?

Obviously the main hurdle will be the ARC. Whatever you do needs the support of your Part 145 (CAMO no longer required) or Part 66 freelance. For the prop you could just copy the wording from the German maintenance programs, that would hardly be something a mechanic would object to. It’s very simple, just mentions to check it for dents, oil leakage, etc.

Cool. I just hope the Swiss CAA will not have the typical Swiss German reaction to Part ML.

Shorrick_Mk2 wrote:

Swiss CAA will not have the typical Swiss German reaction to Part ML.

They probably will, but who cares, it is still law even in Switzerland.

LSZK, Switzerland
Southend, United Kingdom

I have not been able to find anything related to possible relaxation of TBRs rather than TBOs, and this is relevant to all private operators of Thielert-powered aircraft. Would they be able to operate this engine on-condition after expiry of the TBR, as is possible in the US under Part 91?

I suppose one could justify it as follows:

-all TBR components of the engine will still be replaced as per the recommendations of the manufacturer (see note below)
-the engine core, cylinders, crankshaft do not seem to have a bad reputation of failures.
-engine oil analysis, cylinder pressure checks, boroscope inspections would be put in place
-in sofar applicable: the engines have been operated conservatively, as witnessed by data read-outs.
-in case of an engine reaching calendar TBR before reaching flight-hour TBR: automatic calendar time extension makes sense.
-for DA42 flyers: engine failure is less critical (please, I don’t want to spark another discussion on this )

  • note: one could even argue that some components need not be replaced. I am still a little p*ssed about having had to spend thousands on hoses and pipes which appeared to be perfectly fine. And, as to TBR intervals, I could argue that the gearbox on my CD-135 is good to go for 600 hrs instead of 300 (same gearbox as for the CD-155, but Continental says that only for new (-135 or -155) engines one qualifies for 600 hrs, a genuine piece of shafting that I’d rather avoid

Of course one needs to make an analysis as to whether one would be penny-wise and pound-foolish, because additional inspections may turn out to be more expensive than (some) extended engine life-time savings.

I suppose it does opens up issues like where to put limits of on-conditions parameters (notably cylinder pressures) etc.


Last Edited by aart at 05 Aug 18:39
Private field, Mallorca, Spain

My opinion – and my personal plan as and when Part ML comes in is to refer often to Part-91. It is a much bigger dataset and info on failures is obtainable via a type club.

Interestingly, somewhere in the Part ML NPA document, there is a table for calculating risk, and a twin is viewed as being lower risk.

EASA “soft law” (AMC and GM) regarding ELA1 maintenance is now available.

Last Edited by Guillaume at 22 Oct 16:34
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