Definition
Departures of the airplane's indicated airspeed from a target or assigned airspeed during flight, particularly relevant in large airplanes where slow-speed handling, momentum, and engine spool-up time make precise speed control more demanding.
Plain English
How much the airplane's airspeed drifts above or below the speed the pilot is trying to hold.
Context Anchor
Seen during slow-speed flight, approaches, and training discussions where a pilot must hold a precise airspeed in a large airplane.
Derivation
Deviation comes from the Latin 'deviare,' meaning to turn off the road. An airspeed deviation is simply the airspeed wandering off its intended path.
Why Pilots Care
Uncorrected airspeed deviations in slow flight can lead to stall warnings or loss of directional control.
Grounding Statement
If the target airspeed is 140 knots and the airplane drifts to 132 or 148 knots, those differences are airspeed deviations.
Intuition Check
Do not read “deviation” here as only a course change or a major error. In this context, it means any noticeable difference between the airspeed you want and the airspeed you actually have.
Example Sentence 1
On final approach, the captain corrected small airspeed deviations early to avoid larger power changes later.
Example Sentence 2
Maintaining precise control helps minimize airspeed deviations when flying near stall speed.