Abstract
The tilt-rotor aircraft has often been proposed as a means to increase the maximum speed of the conventional helicopter. The tilt-rotor aircraft consists of three primary flight modes that are the helicopter flight mode in low forward speed flight, airplane flight mode in high forward speed flight, and conversion flight mode. The aim of this paper is to develop a nonlinear flight dynamics mathematical modeling method of tilt-rotor aircraft and investigate the dynamic stability characteristics of tilt-rotor aircraft. First, a nonlinear tilt-rotor aircraft flight dynamics model is developed. The trim and linearized results are present to verify the model. Then, using a numerical differentiation technique, the dynamic stability of the tilt-rotor aircraft is assessed. The results show that the flight speed and nacelle angle would affect the magnitude and the trend of the aerodynamic derivatives. The damping of the pitch short period mode and the Dutch roll mode is insensitive to flight speed while they could be affected by nacelle angle. In all flight modes, as flight speed increases, the natural modes become more stable.
Highlights
The maximum speed of a conventional helicopter is restricted due to aerodynamic limitations, installed engine power, and airframe drag [1]
We focus on the variation trend of the stability derivatives in three flight modes, and natural modes are presented
The main conclusions from the current work are as follows: (1) The XV-15 tilt-rotor flight dynamics model developed in this paper is proved to be valid
Summary
The maximum speed of a conventional helicopter is restricted due to aerodynamic limitations, installed engine power, and airframe drag [1]. Reference [5] provides comparisons between the models developed for the XV-15 and flight data. It is clear that there are some literature regarding the tilt-rotor aircraft; the majority of these studies focus on flight dynamics modeling and handling quality evaluation. The dynamic stability of the tilt-rotor aircraft is less investigated, in particular, the variation trend of the stability derivatives in three flight modes. To this end, the aim of this paper is to examine the stability derivatives of tilt-rotor aircraft in three flight modes.
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