wrote in message
ups.com...
If I buy a used homebuilt, is it possible for me to make big
modifications, such as installing a larger engine, adding long range
fuel tanks, floats, etc., assuming there was an A/P to sign-off on
it? Any FAA approvals required? Is it likely an A/P would be willing
to make major changes like this or is the liability too great?

This issue comes around from time to time, and I am sorry to admit that I
don't recall the citations.

However, IIFR, there is a considerable risk in this, iven when you are a
certificated mechanic. Basically, the amateur build experimental (in the
US) does not have a type certificate, but does have an approved set of
operating limitations which have a similar function. The beginning of a
possible problem is that a significant change, which could even be change in
the propeller pitch, could trigger an additional test period--and a larger
or smaller engine almost certainly would do so. The problem that could
start is that, once the test period is reopened, you may or may not be
permitted to return to the earlier configuration in the event that the
modification proves less than satisfactory. Again, as the story was related
to me, all of the above are possible problems even when you are an A&P
and/or the original builder.

Some people also sell/purchase used amateur built aircraft as "parts"
because of the liability issues. That could also have the beneficial effect
of causing you to accomplish a much more thorough inspection of your "new"
aircraft before taking flight. Presuming that you make sufficient repairs,
modifications, and/or new construction; that could reasonably make you the
new "original" builder of the aircraft as most recently constructed.

Again, I don't recall the citations and cannot swear to their accuracy. I
would suggest that you start by talking to your local EAA tech
counselor/inspector, and then possibly the EAA home office. Ultimately, if
you procede with a project of this magnetude, you will end up talking to
someone in an FAA engineering office your local FSDO will have a phone
number and department name if you can't find it anywhere else.

Peter