The issues are complex as the definition of 'flight time' relates to a number important issues - which are not necessarily aligned. The recent proposal for amendment of ICAO Annex 6 Part III (which has now been accepted and will be applicable from later in the year) contains this amendment to the definition of flight time.
Flight time helicopters. The total time from the moment a helicopter’s rotor blades start turning until the moment the helicopter finally comes to rest at the end of the flight, and the rotor blades are stopped.
Note 1. The State should provide guidance in those cases where the definition of flight time does not describe or permit normal practices. Examples are: crew change without stopping the rotors and rotors running engine wash procedure following a flight. In any case the time when rotors are running between sectors of a flight should be included within the calculation of flight time.
Note 2. This definition is only intended for the purpose of flight and duty time regulations.
Jim