Definition
The column of air accelerated rearward by a spinning propeller. This air moves faster than the surrounding airflow and spirals around the fuselage, striking the tail and control surfaces with greater force than ambient wind.
Plain English
The fast-moving stream of air the propeller throws back behind itself. It hits the tail and rear of the airplane harder than the regular wind around the aircraft.
Context Anchor
Encountered during engine start, run-up, and taxi, especially when power is added while the airplane is near people, loose objects, or other aircraft.
Derivation
Slipstream comes from the idea of air slipping past or being pushed past an object. The propeller pulls air in and accelerates it rearward, creating a distinct stream of air that 'slips' along the side of the aircraft faster than the surrounding air.
Why Pilots Care
Supplies airflow over the tail surfaces at low forward speeds, directly improving directional control during taxi and early takeoff roll.
Grounding Statement
When the propeller turns, air behind the airplane can move with enough force to disturb or damage things nearby.
Intuition Check
Do not read “slipstream” as meaning the propeller is slipping or not gripping the air. Here it means the stream of air driven backward by the propeller.
Example Sentence 1
A small burst of power sent propeller slipstream over the rudder, giving enough authority to straighten the nose during the slow taxi turn.
Example Sentence 2
The student added power to increase propeller slipstream and keep the tailwheel firmly on the ground during the initial takeoff roll.