倾转旋翼机外吊挂飞行平衡性研究

TRIM ANALYSIS OF TILT-ROTOR AIRCRAFT WITH SLUNG LOAD

通过考虑旋翼滑流对机翼、平尾和垂尾的气动干扰,结合叶素理论及动量理论,建立带外吊挂载荷的倾转旋翼机飞行动力学模型。在此基础上,以倾转旋翼机XV-15为例,在MATLAB平台上采用Levenberg-Marquardt算法对模型进行定常直飞状态配平计算,并将结果与NASA数据对比,验证了模型的正确性,分析了在不同飞行速度及飞行模式下外吊挂物对其飞行操纵量和姿态角的影响。计算结果显示:在直升机模式下,外吊挂对总距影响较大,对俯仰角的影响随着速度的增加而逐渐减小,这与传统直升机相比有所不同;在过渡阶段,外吊挂可有效减缓俯仰角的减小,并且减小纵向操纵量;在固定翼模式下,不建议使用外吊挂模式飞行。

By considering the influence of rotor wake on wings and horizontal as well vertical stabilizers, and by combining the blade-element theory and momentum theory, a model for a tilt-rotor aircraft with slung load is developed. Based on the model, taking an XV-15 tilt-rotor aircraft as an instance, the trim results of straight forward flight under different airspeed and flight modes are obtained with the Levenberg-Marquardt method on MATLAB platform. And compared them with NASA＇s reference data, the model is proved to be valid. The influence of slung loads on the control strategy and Euler angle is also analyzed. The results show that： under a helicopter mode, the slung load influences deeply the collective pitch, and its influence on pitch angle attenuates as the increase of velocity, which displays a difference with traditional helicopter; under a conversion mode, the slung load can effectively slow down the decrease of the pitch angle as well as longitudinal stick; under an airplane mode, the flight with slung loads is not suggested.