There is no short answer to whether to move to N-reg.
I did it in 2005, mainly as a part of the process to get the FAA IR. My writeup, which is mostly still valid, is here.
You need to weigh it all up carefully.
The only possible way to control foreign reg aircraft (airframes) is via long term parking controls. These were proposed, and abandoned, by France and UK, in 2004/05. Italy did this more recently, kicking them out after 6 months. But all these measures are difficult because provisions need to be made for aircraft which cannot fly, due to technical reasons, so avoidance is easy.
EASA has not proposed any long term parking controls; instead they brought in a rather vague reg requiring FAA licensed pilots to obtain EASA licenses, ratings, and medicals, as well. That will probably substantially reduce the growth of the low-end N-reg community in Europe, and will ground anybody who did it for the FAA Class 3 medical.
The advantage of N-reg, which remains, is more flexible scheduled maintenance. The extent to which this is an advantage depends on the aircraft.
On the traditional Lyco- and Conti-engined aluminium types (and that includes the relatively modern TB20) there is very little which should be straight life limited. In fact on the TB20 I can't think of any item for which there is a genuine engineering justification for a life limit regardless of inspectable condition. This is the regulatory climate under which GA evolved in the USA, where the manufacturer can churn out SBs and MSBs but these can be ignored if the part is inspected, can be otherwise tested, or is simply not safety critical.
But on a DA42? I don't know. I do know people who maintain them and they are generally scathing on the quality of a lot of the parts. The view I hear is that it's a great plane if you are renting it but you wouldn't want to own it. What it comes down to is whether there are parts whose condition cannot be inspected and which must thus be replaced on some other criteria. If there are, N-reg isn't going to help you, because you will either still have to change them (they will be listed under Airworthiness Limitations or some such) or you will be flying a plane which is legal but not very safe. Does a DA42 have a lot of lifed parts, which don't need to be lifed for any technical reason, and which cost a lot of money? If so, what are they?
A US trust is about €500/year. A small detail. A move to N will be €5k, minimum.
A big chunk of the N-reg advantage is modifications, but this depends on what you are doing. If it is a Minor Alteration, it's a lot easier than EASA. If it is a Major, much depends on details.
N-reg is great for owners who are very fussy about doing the best possible maintenance, which they cannot get done by any EASA CAMO. Especially customer-assisted maintenance. For me, it's great!
Hi my name is Steve I fly an arrow at Liverpool, the engine is approaching 2000 hours its over 12 years since last overhaul, we train in the aircraft & have a DOT license which is renewed annually. I am under the impression that for CAA instructors to receive reward for their services we should follow manufacturers instructions (Lycoming) ie as for any commercial transaction the 2000 hour or 12 years if sooner rule should be adhered to & the engine zero houred. Can any body advise me the aircraft is on the N reg.
Steve B.
The point is: A manufacturer specified TBO is not an instruction, it is, per se, only a recommendation.
What counts is what the certifying aviation authority makes of these recommendations.
Now, the aircraft being an N-reg. but under a (British) DOT license is interesting. Im am afraid that in this constellation, the CAA has the last word. Sorry, can’t help much, other than to say: it’s a
The only scenarios which I vaguely recall might apply are
In this case I would ask the Dept for Transport. I have applied for their permission many times and looking at the last form, it didn’t list any such requirement. However the CAA is now taking over from the DfT and is reportedly selling the permissions from a website for about 70 quid, so maybe they are the better place to ask. I would ask in general terms what aircraft requirements they impose, to avoid drawing attention.
If nothing is imposed by the UK authorities then it is down to the State of Registry (the USA) and that doesn’t have any such requirements.
Manufacturer life limits are not mandatory under FAA Part 91 unless the limitation is listed in the MM under Airworthiness Requirements (or whatever it is called).
Why is there a 12 year life on engines?
A simple question!
The only engineering reason is the life of seals and other “rubber” parts. But if that was so, the on-condition concession should never be allowed.
I also hear that there is or may be a 12 year life limit on Thielerts, which is even more bizzare because that is a very different engine. It would be an amazing coincidence if some engineer calculated the same 12 years for that.
What is the history behind this?
Probably because back when the rule was drafted, engines getting more than five-six years in service without something major going bust were quite rare…
I discovered this time limit a few weeks ago. Apparently there is an annual visit for the engine after the initial 12 years, but I’m not sure if this can be dond forever or just for a limited period of time. Hopefully, I’ll fly enough to use the full time left on the engine before expiration !
What is the history behind this?
It only applies to engines where this is a requirement stated by the manufacturer. It is not a regulator imposed rule, it is simply the regulator ensuring that you comply with the manufacturer’s recomendation. So for the reason, ask the manufacturer.
I think government deciding whether a citizen should or shouldn’t comply with a self-serving third party recommendation concerning his property is inappropriate, and in this case it was never the intent of anybody except the governments who do it. The issue is not legally relevant for privately operated engines in the US, where US manufacturer recommendations for 12 year overhaul originated. Never has been, never will be.
When were the service bulletins recommending 12 year intervals between overhaul (not ‘life’ or ‘between rebuild’ BTW) first issued? They don’t directly affect me so I’m not going to look it up but I’d guess it was during the era of US manufacturer product liability lawsuit concerns. It’s certainly a great manufacturer defense against potential lawsuits from the owners of a major fraction of units in service. Regulatory requirements were never intended to be affected by it, otherwise they would have gone for an A.D. I don’t think the manufacturers considered they could get such a thing in place; there’s no way FAA would’ve gone along with it.
The technical justification for the overhaul, or more precisely the strip down for inspection which is the minimum requirement for an overhaul under the FARs, would be corrosion. All the rubber seals can be replaced without major disassembly, no? The silk thread or equivalent at the crankcase split line is easily inspectable and not prone to sudden or substantial leaks. Re Thielerts, their market seems relatively unconcerned with ‘other’ costs of ownership as long as they can can burn jet fuel. Thielert probably imposed the shortest calendar time interval it thought it could get away with, and with 12 years being an ‘industry standard’…
Forty-four years and counting on one, 18 years and counting on the other. They’ve both been stored pretty carefully so I’m actually more concerned about the condition of the latter because it’s flown less.
So, why 12 years? Why not 10?
Did they mean 10 but thought if they make it 12 it will look like they worked it out properly rather than just guessed (I do that in my business all the time; I would have gone for 11.5)?
Re Thielerts, their market seems relatively unconcerned with ‘other’ costs of ownership as long as they can can burn jet fuel
IMHO, Thielert “own” their service business to the same degree Cirrus “owns” its service business i.e. most owners go back to an official dealer (for a collection of reasons, probably). But nobody in their right mind would take a 30 year old Cessna to a Cessna dealer. Or even a brand new Cessna, after the warranty has run out 
The European fuel saving with a Thielert is so massive that there could be a PT6 hidden inside and you would still have a positive cash flow 
