Definition
A defined portion of a powered-lift or rotorcraft takeoff or landing flight path during which the aircraft slows from a higher airspeed to a lower one as part of the transition between forward flight and hover, or between hover and forward flight.
Plain English
The part of a takeoff or landing path where the aircraft is deliberately slowing down as it changes between flying forward and hovering.
Context Anchor
Seen in takeoff performance planning, especially when calculating whether the runway is long enough to stop safely after a rejected takeoff.
Derivation
From Latin 'de-' (down, away from) and 'celer' (swift) — literally 'taking away the speed.' A 'segment' is one defined piece of a longer path. Together: the piece of the flight path where speed is being taken away.
Why Pilots Care
Proper identification of the segment allows correct speed management, flap and gear timing, and compliance with published constraints.
Intuition Check
Do not think of this as the whole rejected takeoff distance. It is only the slowing-down part after the decision to stop has been made.
Example Sentence 1
During the approach, the pilot entered the deceleration segment and began reducing airspeed in preparation for the hover.
Example Sentence 2
During the deceleration segment the pilot reduced thrust and maintained the vertical path while the airspeed bled off as planned.