Definition
The ground speed at which an airplane is moved on the airport surface during taxi operations, governed by the principle that it must be slow enough to allow the airplane to be stopped promptly under normal conditions. Appropriate taxi speed depends on surface conditions, congestion, visibility, and the proximity of obstacles, other aircraft, and people.
Plain English
How fast you move the airplane while driving it on the ground. The rule is simple: never go faster than you can safely stop.
Context Anchor
Used during ground operations when moving between parking, run-up areas, taxiways, and the runway.
Derivation
Taxi' came into aviation use in the early 1900s, borrowed from the way a taxicab moves slowly through city streets looking for passengers. Pilots adopted it to describe an airplane moving under its own power on the ground, much slower than flight. The image still fits: a careful, deliberate pace, eyes outside, ready to stop.
Why Pilots Care
Maintaining proper taxi speed preserves directional control, prevents runway or taxiway incursions, and allows immediate stopping in response to traffic or obstacles.
Intuition Check
Taxi speed is not one fixed number that works everywhere. It means the safe speed for the surface, traffic, visibility, wind, and how quickly you may need to stop.
Example Sentence 1
The instructor reminded the student to reduce taxi speed when approaching the congested ramp area.
Example Sentence 2
During ramp operations the crew kept a walking-pace taxi speed to stay clear of ground vehicles and other aircraft.