Wind Shear
Wind shear is the change in wind speed and/or direction, usually in the vertical. The characteristics of the wind shear profile are of critical importance in determining the impact for an aircraft on takeoff or landing.
Headwind-to-Tailwind Shear
When a headwind shears to a tailwind, there will be a sudden decrease in airspeed and pitch attitude. In this situation, the remedy is to add power and raise the nose.
Tailwind-to-Headwind shear
When a tailwind shears to a headwind, there will be a sudden increase in airspeed, causing an increase in pitch attitude. The usually reaction is to reduce both pitch and power, which can lead to a dangerous low-speed, low-nose configuration. This is dangerous if the aircraft suddenly experiences a downdraft and a tailwind.