To solve a problem with prop gearing, I'm planning to use an Ivoprop, in-flight, electrically adjustable prop. But I remember back in the 1980s, constant speed props needed advanced training if nothing else because of the engine oil powered, mechanical coupling to the engine. Additionally, too much pitch and throttle could lead to detonation and certainly at high prop pitch there would be rpm limited power and thrust if a go-around is needed.
So I understand in 1997 the FAA required complex airplane endorsement for "an airplane that has a retractable landing gear, flaps, and a controllable pitch propeller, . . . " (para 61.31.) I understand this is the "AND" of all three elements are required. So a controllable pitch propeller alone is not enough to require a 'complex airplane endorsement,' right?
On the practical side, the risks of a variable pitch prop are real. Too much pitch, low altitude and adding full throttle could put a high compression engine into detonation. I've seen this in manual transmission cars when in a high gear and flooring the accelerator triggered the 'ping.' Certainly, I'll want to address this during ground testing but I haven't read much about such testing. Have you come across articles that address prop pitch, altitude and detonation?
I know 100LL gives us a built-in, detonation advantage but that is more true for the relatively low, 8-to-1, compression engines. However, I'm planning to run a 9-to-1 compression engine which reduces the detonation margins.