The Stability Of Helicopter Under The Influence Of Atmospheric Gravity Waves

With increasing space activities of human, the importance of the effects on aircraft by spaceenvironment is becoming more extrusive. Atomospheric gravity waves are the most important andcommon dynamic processes in the middle atmosphere. Gravity waves play an important role in thebalance of global energy when they propagation in the upper atomosphere. On the other hand,helicopters are slso widely used to execut various tasks due to its charactistics. The study of thehelicopter at home and abroad is still continue. The main research gravity waves in this paper arecaused by mountain terrain and airflow, because the helicopter will be affected when it’s fiying in themountain.This paper firstly did a comprehensive study on generation principle, form factor, propagationprocess, research methods, and discussed the relationship between atmospheric gravity waves and thebackground wind.Then discussed the causes of mountain gravity waves and the conditions affected the propagationvelocity. So we can conclude that the strength of disturbance is concerned with mountain terrain,speed of airflow,direction of airflow and angle of the slope when the mountain gravity wavesgenerted by air flow through the mountain.And then we analysised the dynamic equations of helicopter. thus through using smallperturbation principle, we can get a simplifying assumption and establish a small perturbation model.Based on the characteristic equation,we will get the eigenvalues. By the eigenvalues, we judge thehorizontal and vertical stability of helicopter which caused by the disturbance of gravity waves in thehovering and fly, to promote stability of helicopter flight research.Finnally we can conclude that the more steep of mountain slope, the greater velocity of flow,thegreater angle between airflow direction and slope, the amplitude of mountain gravity wave velocitywill be greater and the wave will more easily broken which will generate turbulence,so the impact onthe stability of helicopter will be greater through the numerical computation and the brief analysis.When the helicopter hovering,the longitudinal stability caused by disturbance changed a little,whilethe disturbance played a promoting to the lateral stability. When the helicopter fiying, the longitudinalstability turned into unstable, while the lateral stability changed a little.