Cross Section of a Wing
翼剖面
Mean Camber Line
Slice the wing exactly in half, the mean camber line is the precise center of the wing thickness.
Any point on the mean camber line, the top slice equals to the button slice.
Leading Edge
The point on the front-end of the mean camber line of the wing.
Trailing edge
The point on the rear-end of the mean camber line of the wing.
Chord Line
When you join the trailing edge and leading edge. You will get the chord line.
Relative Airflow
The direction of the air movement relative to the wing.
AoA(Angle of Attack)
The angle between the chord line and the relative airflow.
Airspeed（TAS）
The aircraft speed relative to the airflow.
因为实际的大气密度难以测量，所以难以使用TAS计算升力。忽略位置误差（Position Error），低速飞机使用IAS计算升力时所采用的密度也应是所在飞行高度于国际标准大气表中的密度。
Wing Surface Area
Air density
More molecules equal higher density.
Lift formula
Lift equals to half of the coefficient of lift multiplying air density, square of airspeed and wing surface area.
密度取决于当前飞行高度/温度/压强（计算多用ISA），机翼面积取决于飞机类型。因此，飞行员控制飞机升力本质上是在控制飞机的空速（Airspeed）和迎角（AoA）。
飞机平飞时（升力恒定），若要低速飞行（Slow Flight）就需要增加飞机的迎角，补偿速度对升力的减少量。
· END ·
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