Definition
The difference between the steady (sustained) wind speed and the peak gust speed reported in a wind observation. Pilots use this difference to add an airspeed increment to the normal approach speed when landing in gusty conditions, helping maintain controllability if the airplane suddenly loses headwind during a gust lull.
Plain English
The extra speed between a steady wind and its strongest gust. Pilots add some of that extra speed to their landing approach speed so the airplane stays controllable if a gust dies away suddenly.
Context Anchor
Used during approach and landing planning when wind is reported with gusts, especially in turbulent air.
Derivation
Gust' comes from the Old Norse 'gustr' meaning a sudden rush of wind. 'Factor' here means a value added into a calculation. Together: the value derived from sudden wind variation that factors into approach speed.
Why Pilots Care
Applying the correct gust factor adjustment prevents sudden loss of lift when a gust subsides, reducing the risk of stalling or landing short and hard.
Intuition Check
Do not read the gust factor as the full gust speed. It is only the difference between the steady wind and the gust speed.
Example Sentence 1
With winds reported at 12 gusting 22, the pilot added half the gust factor to the normal approach speed for a more stable landing.
Example Sentence 2
On a gusty day the instructor reminded us to brief the gust factor early so we would not be caught slow on short final.