Definition
The resistive force between an airplane's tires and the surface it is taxiing on, which opposes motion and affects how easily the aircraft starts moving, rolls, and stops. Ground friction varies with surface type, surface condition (dry, wet, icy, loose), tire condition, and aircraft weight.
Plain English
The grip between the tires and the ground. More grip means the airplane stops and steers easily; less grip means it slides and is harder to control on the ground.
Context Anchor
Seen in taxiing, braking, turning, and wind-control discussions during ground operations.
Derivation
Friction comes from the Latin word fricare, meaning “to rub.” That helps here because ground friction is the resisting force created where the tires rub or press against the ground surface.
Why Pilots Care
Ground friction determines how much power is needed to start and maintain taxi speed and directly affects the length of the takeoff roll on different surfaces.
Grounding Statement
A tire on dry pavement grips well; the same tire on ice has much less ground friction and can slide more easily.
Intuition Check
Ground friction does not mean only “drag that slows the airplane down.” In taxiing, it also provides the tire grip that helps the pilot steer, stop, and keep the airplane under control.
Example Sentence 1
After the rain, ground friction on the taxiway was reduced, so the pilot taxied more slowly and used gentler braking.
Example Sentence 2
Wet pavement reduces ground friction and can lengthen the landing rollout.