Definition
Controlled flight maneuvers in which the airplane's longitudinal axis is intentionally misaligned with its flight path, produced by cross-controlling the ailerons and rudder. The pilot banks the airplane in one direction while applying opposite rudder, causing the airplane to fly partly sideways. Slips are used to lose altitude without gaining airspeed, to correct for crosswind on landing, or to maintain a desired ground track during certain ground-reference maneuvers.
Plain English
A slip is when the pilot deliberately makes the airplane fly slightly sideways by banking one way and pushing the rudder the other way. This is useful for coming down faster without speeding up, or for keeping the airplane lined up with the runway in a crosswind.
Context Anchor
Seen during ground reference maneuvers such as a rectangular course, and also during turns, crosswind approaches, and landings.
Derivation
From the everyday word 'slip,' meaning to slide sideways. The airplane is, in effect, sliding through the air rather than tracking straight ahead through it.
Why Pilots Care
Provides an immediate way to adjust ground track or lose altitude without changing power or airspeed, keeping the maneuver safe and precise.
Intuition Check
A slip is not just a small flying mistake or a loss of traction like a person slipping on the floor. In aviation, it specifically means the airplane is moving partly sideways through the air because its nose and actual path are not aligned.
Example Sentence 1
On final approach with a strong crosswind, the pilot used a slip to keep the airplane aligned with the runway centerline.
Example Sentence 2
A forward slip was entered on final to lose excess altitude while maintaining the desired airspeed.