Danny
They all had this sonorous undertone, but the AT6A/Harvard had the aboriginal 600 hp "Wasp" - well, you can hear it on the clip. It was reckoned that the two-blade prop tips were supersonic.
As someone who something to do with Harvards at 5 FTS (RAF Thornhill, S. Rhodesia) in the early 1950's ISTR that this turned out to be an urban myth. The diameter of the prop (8ft?) x the 2,600 rpm round the circumference wouldn't have led to the prop tips travelling faster than sound (760 mph). However, mathematics have improved since them and I'm willing to be corrected!
...and fond memories of 21 Wasps all going at once as here!
