Explain that to a Mechanic that was killed in Orlando
He was ground running a 300 to warm up the engine oil (yes they did it with the rotors engaged, at flying RPM (don't ask me why, I guess they wanted to reduce the risk of shaft overspeed [when rotors are not engaged], or maybe just wanted it to warm up quicker) The practice has since been stopped.
He applied collective to slow the rotors, just after engine shut down. The helicopter got into ground resonance (I will not go into the details of what happened next) He was killed, may he rest in peace. There were a bunch of un-willing witnesses, as it was right in front of the hangar.
As you can imagine the rotors would of been at a high RPM for this to have happen. Just be careful.
My question, what's is the rush??? OK in windy conditions I can understand some assistance in stopping the rotors. But otherwise, you can not wait the extra couple of minutes??
DT