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Extending aircraft life beyond what is published by manufacturer

Folks,
image the following /hypothetical of course/ situation. Your aircraft has service life limited by manufacturer – by number of flight hours. You are reaching the limit. Initial idea was to move the aircraft into “experimental category” and kept if flying – but this is not accepted by CAA “the wing will fail as the wing has no knowledge if it is in experimental or normal category and we will not let you do it”.
Do you guys agree with this interpretation of Experimental category, is this common accross Europe ? Isn´t someone here aware of some EASA guidance material on this? Or am I just simply too optimistic and the 5 minutes I logged this afternoon are really the final ?

LKKU, LKTB

The experiment is flying the wing in excess of the calculated life. Calculations are typically approximate and conservative, so from an engineering POV its a legitimate activity.

This is an actual “problem” on some aircraft. Often thirth parties design either a modification, or design additional more frequent and detailed inspections, often using NDO methodes to determine the actual status.

A structural DOA would be the place to be, as you are not allowed to get in this “major changes” yourself.

JP-Avionics
EHMZ

Initial idea was to move the aircraft into “experimental category” and kept if flying – but this is not accepted by CAA “the wing will fail as the wing has no knowledge if it is in experimental or normal category and we will not let you do it”.

Some non-EASA registries will accept such aircraft, and some less-than-diligent owners have been known to push this workaround to the point of actual fatigue failure…

Often thirth parties design either a modification, or design additional more frequent and detailed inspections, often using NDO methodes to determine the actual status.
A structural DOA would be the place to be, as you are not allowed to get in this “major changes” yourself.

Yes, this comes under Part 21, and there are organisations whose Part 21 approval is specifically limited to the design of alternative repair procedures. I’m based at one that does it for piston engines.

LKBU near Prague, Czech Republic

Which European CAA allows a certified aircraft to be moved to the non-certified route?

The general rule is “if it can have a CofA it must have a CofA”. This protects CAA and maintenance industry revenues.

I think the UK has a few types which can exist on either Cert or Annex 2 but I don’t know if you can freely move them.

You can put an N-reg onto “Experimental” but then it has severely limited movement rights in Europe. In practice these cannot be enforced (unless you draw attention) but…

Administrator
Shoreham EGKA, United Kingdom

Obviously the purpose of Experimental Category is to avoid the need for approved organizations to design an approved life extension modification.

Its truly ridiculous that the bureaucrats mentioned in the OP’s post are unable to understand that the Experimental Category exists to facilitate doing things outside of a conservative, government approved ‘box’ that exists for the safety of the uninvolved public.Their authority is properly limited to regulation of operations within that regulatory box, not the entire range of human activity within the geographic area they claim as their own.

Last Edited by Silvaire at 11 Oct 20:00

Which European CAA allows a certified aircraft to be moved to the non-certified route?

European in purely geographic sense – Russia, for example. There are plenty of private “experimentals” there that are none other than superannuated CofA aircraft from the First World countries – including even such machines as C421.

LKBU near Prague, Czech Republic

Which European CAA allows a certified aircraft to be moved to the non-certified route?

Eg. Sweden. I know a guy there wo moved his ST-10 to experimental status and installed a 4-blade-prop, among other things.

LOAN Wiener Neustadt Ost, Austria

Your aircraft has service life limited by manufacturer – by number of flight hours. You are reaching the limit. Initial idea was to move the aircraft into “experimental category” and kept if flying – but this is not accepted by CAA “the wing will fail as the wing has no knowledge if it is in experimental or normal category and we will not let you do it”.

Well. All (I think, or at least most) RVs by Vans have service life limitations on the main wing spars. I don’t remember exactly what it is, but 10-15 thousand hours or something. You can also purchase anodized spars. Anodizing is good for corrosion protection, but bad for fatigue. RV’s with anodized spars have a couple of thousand hours less service life. This of course makes the point of anodizing pretty much obsolete, but must people somehow wants anodized spars no matter what. People do crazy things Being experimental, the builder/owner is the “factory”, so all such things are considered recommendations, they are not mandatory in a legal sense. The local CAA can make it mandatory however, and in Norway such recommendations from the kit manufacturer are all mandatory. It’s the CAA that decides if the aircraft is airworthy or not.

In Norway there would be no problem moving that aircraft into the experimental category, since as I understand it, it is no longer airworthy. It will then become an experimental restoration project. You would still have to make it airworthy though, and that would mean at least stripping the structure and look for cracks, but most probably it would mean building new wings or at least fixing the structure in some way that extends the life. For a Cub, building a new wing takes a couple of weeks (It’s a whole industry out there making Cub parts), but for more complex aircraft, such repairs may not even be worth considering, unless you can find a low time wreck with the parts you need.

The general rule is “if it can have a CofA it must have a CofA”. This protects CAA and maintenance industry revenues.

This is not correct, although not entirely wrong. Experimentals in most parts of the world does indeed get a C of A from the authorities. It is certification or not certification that is the issue. When an aircraft leaves the “certified world”, it can never go back. For the CAA, a certified aircraft is much less work than an experimental. Experimentals are per def one offs. Each experimental aircraft receives a C of A based on inspection of each individual, while a certified aircraft receives the C of A based on the certification (pure paper work for the CAA). So, if an aircraft can remain in the certified world, it must remain certified world. Each country has slightly different rules, but for an aircraft to be moved to the experimental category, it generally has to have lost the airworthiness as a certified aircraft (crash, old age and similar). It could also be that certification is not possible, like many Russian aircraft, then the experimental category will be the only way to keep them airworthy.

ENVA ENOP ENMO, Norway

The general rule is “if it can have a CofA it must have a CofA”

This is not correct, although not entirely wrong

If I had time I could dig up the UK CAA publication which basically said exactly what I said!

If you could just move a certified aircraft (say a PA28 or a TB20) to what is for all practical purposes a “homebuilt” category, with the only cost being

  • can’t fly abroad without obtaining permissions (well… in theory )
  • can’t do any paid work in it

then somewhere between 90% and 99% of the European GA fleet would do it immediately.

If you can’t use a spanner, you can still use a company to maintain your “homebuilt” and I have actually come across 2 people who do.

So I think there must be some massive wires crossed in this discussion.

Administrator
Shoreham EGKA, United Kingdom
16 Posts
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