Irrespective of what rules may apply, the decision to leave the helicopter with the rotors under power (idle or otherwise) is an act of making a choice. All choices come with one or more tradeoffs. Some of the tradeoffs associated with this choice include saving time, saving engine cycles, etc, but other tradeoffs include some increase in risk, even when done "properly." How much risk is open to debate. Accident reports show that it is not always done properly and that the risk can be more than is understood. And, this type of event, even though preventable in many cases, seems to keep on happening even though rules, flight manuals, etc call some degree of attention to the risk involved.
My flight operations manual generally requires a qualified pilot in the PIC seat with hands on cyclic and collective when rotors are turning. Works for me, but perhaps not for all.
Last edited by EN48; 31st May 2014 at 18:59.