Last time I heard a curious mechanical noise was one of the last times my dad flew us to Quincy to see family pre-pandemic in his Bonanza.
Right after takeoff I could swear I was hearing a fairly high pitched mechanical whine where the pitch would rise and fall in kind to changes in engine RPM. Dad couldn't really hear it and everything looked nominal so I tried to forget it. Overall the flight was uneventful.
After takeoff on the return leg, upon raising the gear a voltage warning popped up on the panel and we circled back to land. Turns out the alternator failed and my wife and I had an unexpected 4 hour drive back home
