Definition
The rate of change of velocity with respect to time. In aviation, acceleration occurs whenever an airplane changes speed, direction, or both — including speeding up, slowing down, climbing, descending, or turning.
Plain English
Any change in how fast or in what direction the airplane is moving. Speeding up is acceleration, but so is slowing down, turning, or pitching up.
Context Anchor
In the Airplane Flying Handbook’s discussion of feel, acceleration is one of the motion cues a pilot can sense through the seat, controls, and body as the airplane changes speed or direction.
Derivation
From Latin 'accelerare', meaning 'to hasten' or 'to quicken'. In everyday English it usually means speeding up, but in physics and aviation it covers any change in motion — faster, slower, or a change in direction.
Why Pilots Care
Pilots feel acceleration through their seat and controls. Recognising it is part of developing the feel of the airplane — sensing pitch changes, bank changes, and airspeed changes before reading the instruments.
Grounding Statement
If the airplane’s motion changes in speed or direction, acceleration is happening.
Intuition Check
Do not assume acceleration only means speeding up. In aviation, slowing down and turning are also forms of acceleration because the airplane’s motion is changing.
Example Sentence 1
As the pilot smoothly applied full power on the takeoff roll, the acceleration pushed them firmly back into the seat.
Example Sentence 2
Reducing power in level flight produces deceleration that the pilot feels as a slight forward pitch tendency.