Abstract: A model is described in this paper, which is used to discuss the changes of the flight height and velocity during the transient flight from hover to forward flight of a helicopter. First, the calculation method is given, the results of which are validated against the flight data of an example SA365N. Finally, for general helicopters, some useful results are provided in various control inputs and states of engine breakdown. The conclusions can be used as references to the pilot in flight.

Key words: flight char act erist ics, tr ansient flight, ho ver, low speed fo rw ar d flig ht