Definition
The wing on the side of the airplane opposite the direction the wind is coming from during a crosswind takeoff or landing. If the wind is blowing from the left, the right wing is the downwind wing.
Plain English
The wing on the far side from where the wind is coming from. Wind from the left means the right wing is the downwind wing.
Context Anchor
Used during crosswind takeoffs and landings when describing which wing is upwind and which wing is downwind.
Derivation
Downwind' simply means 'in the direction the wind is going.' The downwind wing is the one on the side the wind is blowing toward — the side away from the wind source.
Why Pilots Care
Uncorrected rise of the downwind wing at liftoff can cause a wingtip strike or loss of directional control.
Grounding Statement
If wind is hitting the airplane from the left, the wind is moving across the airplane toward the right, so the right wing is the downwind wing.
Intuition Check
Do not think downwind means the wing facing the incoming wind. The downwind wing is on the side the wind is blowing toward.
Example Sentence 1
As the airplane gained speed on the crosswind takeoff roll, the pilot held aileron into the wind to keep the downwind wing from lifting prematurely.
Example Sentence 2
As the aircraft accelerated, the instructor reminded the student to keep the downwind wing level until liftoff.