Aircraft Motion
Physics of Aircraft
Weight and Thrust
Secondary Controls
Straight and Level
Aircraft Design Features
The Stall
Practice Exam

Controlling Lift

A pilot controls the lift that the aerofoil creates by adjusting speed, angle of attack or both.

Changing Angle of Attack

Increasing the angle of attack (at a constant speed) will increase the total reaction force – increasing both lift and drag.

This only applies up to a certain angle of attack, known as the critical angle of attack, which is at roughly 16°. At the critical angle of attack the aerofoil is creating the maximum possible lift. Beyond the critical angle of attack the airflow over the aerofoil is no longer able to smoothly follow the surface and abruptly breaks away, creating a turbulent flow of air at the back of the aerofoil. Beyond the critical angle of attack, lift is significantly reduced and drag rapidly increases.

Changing Speed

At higher aircraft speeds, and thus higher relative airflow speeds, the total reaction will increase – which increases both lift and drag.

For an aircraft in flight, the lift created depends on both the angle of attack and speed. In level flight at slower speeds a greater angle of attack is needed, and at higher speeds a smaller angle of attack is needed.