Whiplash first fligh report
The q40 guys launch at 22,000 to 23,000, so 29,040 in the air is believable, maybe? An 8" diameter prop has a tip speed of 689 mph at 29040 rpm. As tip speed approaches the speed of sound (758?) prop efficiency drops off drastically. The q40 planes average about 180 mph around a race course, I wonder what they do in a straight line?
I thought I read a few years ago they radared one of the lancairs at the 1/4 scale race at 240 mph.