Definition
The clinging force between an aircraft's tires and a soft surface (such as mud, wet grass, soft sand, or snow) that resists the tire's rolling motion and increases takeoff roll distance.
Plain English
The way soft ground sticks to the tires and slows the airplane down as it tries to roll forward.
Context Anchor
Encountered during soft-field and rough-field takeoff discussions, especially when explaining why the pilot should keep weight off the wheels as much as practical during the takeoff roll.
Derivation
From the Latin 'adhaerere', meaning 'to stick to'. The same root gives us 'adhesive'. In a soft-field takeoff, the ground is literally sticking to the tires.
Why Pilots Care
Managing adhesion determines whether the wheels roll freely or bog down, directly affecting acceleration distance and the risk of propeller strike on soft surfaces.
Analogy
It is like trying to roll a bicycle through soft mud instead of across pavement. The wheels still turn, but the surface grabs them and makes forward movement harder.
Grounding Statement
On a soft field, adhesion is the “sticking” between the tires and the ground that makes the airplane resist rolling freely.
Intuition Check
Adhesion does not mean the airplane is glued to the runway. It means the tires and surface are sticking enough to create extra drag during the takeoff roll.
Example Sentence 1
On the soft, muddy strip, adhesion was so strong that the airplane needed nearly twice its normal takeoff distance.
Example Sentence 2
Lower tire adhesion on the muddy surface increased the distance needed to reach rotation speed.