For conversion mode of tiltrotor aircraft from helicopter mode to fixed wing airplane mode

an analysis method based on the transition flight's characteristics of morphing

and speed change was established to investigate the nacelle conversion envelope.The method includes the lower speed and higher speed envelopes.A detailed analysis of the matching relationship between the rotors aerodynamic forces and wing aerodynamic forces in the conversion mode was conducted.The lower conversion boundary was restricted by wing stall and the upper conversion boundary restricted by available power limited by engines.The XV-15 tiltrotor aircraft was taken as an example to analyze the conversion envelope.The results fairly agree with the XV-15 data

showing that the calculation methodology for the nacelle conversion envelope of tiltrotor aircraft is reasonable and effective.