Definition
Portions of a Standard Terminal Arrival Route (STAR) where the published path is designed to allow the aircraft to slow down before crossing the next altitude or speed restriction, or before joining the approach. They are typically built into the procedure using path stretching, level segments, or specific speed/altitude crossing fixes that give the aircraft room and time to reduce energy.
Plain English
Parts of an arrival route that are shaped to give you space to slow the airplane down before the next required speed, altitude, or the start of the approach.
Context Anchor
Seen in discussions of Standard Terminal Arrival Routes, where the route may be designed to let aircraft slow in an orderly way before approach or landing.
Derivation
From Latin de- (down from) + celer (swift) -- literally 'taking the swiftness off.' A deceleration segment is the stretch of the arrival where that slowing-down happens.
Why Pilots Care
Proper speed reduction at these points keeps the aircraft within safe operating limits and prevents rushed configuration changes closer to the airport.
Analogy
A deceleration segment is like the part of a highway exit where you ease down from highway speed before reaching the stoplight.
Intuition Check
Do not read deceleration segments as a sudden braking action. They are planned stretches of the arrival route that give the aircraft room to slow down smoothly.
Example Sentence 1
The crew briefed the deceleration segments on the arrival so they knew where to start slowing for the 250-knot and 210-knot crossing restrictions.
Example Sentence 2
ATC cleared the flight to continue through the deceleration segments while maintaining the published speed limits.