摘要
飞机在空气中运动或者空气流过飞机时，就会产生作用于飞机的空气动力，飞机各部分所受到的空气动力的总和，叫总空气动力，通常用R表示。一般情况，这个力是向上并向后倾斜的，根据它所起的作用，可将它分解为垂直于相对气流方向和平等于相对气流方向的两个分力。垂直方向的力叫升力，用Y表示。升力通常是起支托飞机的作用。平等方向阻碍飞机前进的力叫阻力，用X表示。
When a plane fly in the air or the air wash the plane, the plane will encounter some degree of air resistance. The summation of air dynamics of the each part of the plane can be called overall air dynamics, which is instead of R usually. Commonly, the dynamics is upwards and decline backwards. According to the function, we can separate it into two dynamics. One is upright to the direction of the airflow, which can be called lift. Another is equality to the direction of the airflow, which can be called resistance. The lift can support the plane in the air, the other hand resistance can block the airplane.
