Stefan wrote:
If a pilot sits into an approved airplane, reads the approved
instructions and acts as instructed, then I think I this pilots has all
the right to assume that the installation works as expected. That's why
such installations are so expensive.

And if you believe that, there's a bridge I'd like to sell you.

Seriously, what you say makes sense in theory. The difference between
theory and practice is often much greater in practice than it is in
theory. In theory, the installations are expensive because thorough
and competent engineering review (by the DER) assures that version 1.0
works properly. In practice, becoming a DER has little to do with
thoroughness and competence and everything to do with having
connections in the FAA.

Anyone who has worked on the maintenance side of GA for any length of
time has his own share of stories about totally incompetent
modifications that gained FAA approval. This one is small potatoes in
comparison with some of the ones I know.

Thus you have to accept that if you are flying version 1.0 of anything,
you are a test pilot and must behave accordingly. There is a very
expensive mandatory process in place to assure that this does not
happen, but the process doesn't work.

Michael