ok on the plane i fly, SW4, and i'm sure others as well, the barber poll automatically decreaces the Vne/Mmo above approx 17,800ft. on the Sw3, the calculation is done manually ie in your head 2kts/1000ft. my question is why does the Vne/Mmo need to be decreased at all, is it a limiting speed in relation to the propeller and the speed of sound (my personal theory) or does it have something to do with structrual integrity of the a/c. I have already discounted the idea that it is some sort of limiting critical mach # on the wing as the Mmo of the Sw4 is .52 which is still very much within subsonic flight for everything except the propellor, mayby. ok hope this makes sense, i look forward to hearing some responses, thanks
