I am a FAA ppl flying G registered a/c in the UK. I have the opportunity to conduct difference trg onto an a/c with a controllable pitch prop. Under FAA rules (FAR sect 61) complex is defined as flaps, retractable gear AND cpp from what I can see.
Can any one advise if just a cpp requires a complex endorsement by an FAA approved instructor?
A you don't need a Complex endorsement to fly the aeroplane, you are good to go under the FARs. Get the UK FI to write in your logbook anyway that you have been cleared to fly the aeroplane and then you cover all eventualities (i.e. if you ever decide to get an EASA PPL).