Definition
The uncommanded rearward movement of a parked or taxiing aircraft caused by strong winds acting on its surfaces, particularly when brakes are released, power is reduced, or the aircraft is light. The wind effectively pushes the aircraft backward, much like wind on a sail.
Plain English
When wind is strong enough to push an aircraft backward across the ground, even though the engines aren't driving it that way.
Context Anchor
Seen in instrument procedure and air traffic control language, especially for fast aircraft that need more room to descend or slow before continuing inbound.
Derivation
From the imagery of a sailboat being pushed by wind. An aircraft's tail, fuselage, and control surfaces can act like a sail when wind pressure exceeds the forces holding the aircraft in place.
Why Pilots Care
Enables safe, low-power maneuvering on water in windy conditions and reduces risk of propeller damage or loss of directional control.
Analogy
Like letting a sailboat drift backward with the wind to line up at a dock without starting the motor.
Intuition Check
Do not read “sail back” as casual wording for simply returning somewhere. In this context, it is a specific flight maneuver: go past a navigation point, use the distance, then turn back to continue.
Example Sentence 1
During taxi in strong gusty winds, the pilot kept some power in and used proper control inputs to prevent sail back.
Example Sentence 2
During water taxi training, the instructor demonstrated sail back to show how wind can be used for positioning without added power.