Stalls

To fully understand the components of lift and stalls, you need to know the terms associated with a wing:

• Leading edge = forward-most point of the wing

• Trailing edge = rearward-most point of the wing

• Chord line = an imaginary straight line drawn from the trailing edge to the leading edge

• Mean camber line = a line drawn from the trailing edge to the leading edge that stays exactly between the top and bottom edges of the wing

The angle of attack describes the angle between the relative wind and the chord line of the wing. You can almost think of this as how much wind is hitting the top of the wing vs. the bottom of the wing.

If you were to stick your hand out the window of a moving car, and your hand was perfectly parallel to the ground, your hand’s angle of attack would be 0°. If you suddenly angled the forward portion of your hand to the sky, your hand and arm would instantly be pulled upwards due to the high angle of attack. Remember – the angle between the wind and the chord line of the wing (aka the direction the wing – or your hand – is pointing).

A stall occurs when the wing exceeds its CRTICAL angle of attack. The critical angle of attack is the point at which the air can no longer flow smoothly over the wing, and eddies and buffets after going over the leading edge of the wing. This hampers the speed at which the air can flow over the wing, thus the LOW pressure above the wing disappears. No low pressure above the wing = no lift.

When a stall occurs, the nose of the airplane will typically fall (unless the controls hold the nose back, which further exacerbates the stall condition). When the nose falls, airspeed increases and the angle of attack decreases, thus remedying the stall condition and restoring normal flight.

The problems arise when stall occurs too close to the ground. The aircraft does not have enough available altitude to build up speed and recover before colliding with the ground or a ground structure.