Definition
An unintended sideways deviation of the airplane from its intended direction of travel during the takeoff or landing roll, typically caused by crosswind, uneven braking, propeller effects, or pilot input that fails to keep the airplane tracking straight along the runway centerline.
Plain English
The airplane suddenly veering off to one side instead of rolling straight down the runway.
Context Anchor
Encountered during landing rollout, taxi, and takeoff roll when directional control on the ground matters.
Derivation
From Old English 'sweorfan,' meaning to wipe, scour, or turn aside. The modern sense — to turn abruptly off a straight path — captures exactly what the airplane does on the runway when directional control is lost.
Why Pilots Care
Uncorrected swerves can cause loss of directional control and lead to runway excursions.
Grounding Statement
On landing rollout, a swerve is the moment the airplane begins to drift or turn away from the runway centerline instead of rolling straight.
Intuition Check
A swerve is not any planned turn on the ground. Here it means an unwanted or sudden turn away from the intended path.
Example Sentence 1
As the crosswind gust hit during rollout, the airplane began to swerve to the left, and the pilot applied right rudder to bring it back to centerline.
Example Sentence 2
A swerve on a contaminated runway requires immediate differential braking to keep the airplane tracking straight.