Prop overspeed at high altitude
Can anyone confirm that we are to not practice single engine work at flight levels (i.e. 25K, etc.) because I was told that when you retard the prop to right at feather and then bring the prop lever back up to cruise setting (1700 RPM) that the governor can not engage quickly in the thin air and a prop overspeed situation can develop.
And, are we to not pull throttles back to idle at altitude during this maneuver?
(PW PT6-52 turbo props with only 450 hours on a King Air)
Pilot was practicing single engine work. Pulled throttle and prop levers back to idle. When everything was stabilized he pushed prop lever back forward and all heck broke loose in that blown engine. It had to be shut down and metal and 'stuff' was thrown all over the Gulf.
Also read that 'zero thrust' imitation was to only pull prop back to 1600 RPM, not back to the idle detent.
Any thoughts on what happened?
Thanks