Definition
The speed at which the tip of a rotating propeller blade or helicopter rotor blade travels through the air. It is the sum of the rotational speed of the blade tip and the forward speed of the aircraft, and it is the highest airspeed any part of the blade experiences.
Plain English
How fast the very end of a spinning propeller or rotor blade is moving through the air. The tip moves much faster than the rest of the blade because it is the farthest point from the center.
Context Anchor
Seen in propeller, helicopter rotor, engine power, noise, and blade design discussions.
Why Pilots Care
Excessive tip speed produces compressibility effects, noise, vibration, and loss of efficiency that limit safe operating RPM.
Analogy
On a spinning fan, the outer edge is moving much faster than a point close to the hub. Tip speed is the speed of that outer edge.
Intuition Check
Do not read tip speed as aircraft speed. It is the speed of the blade tip as it circles around the hub.
Example Sentence 1
The propeller's diameter was limited by the need to keep tip speed below the speed of sound at maximum RPM.
Example Sentence 2
Engineers selected a shorter rotor radius so tip speed stayed within safe limits at high altitude.