Definition
In a helicopter, the short delay between the moment the pilot moves the cyclic stick and the moment the rotor disc actually tilts and the aircraft responds. The lag exists because the rotor blades must travel through part of their rotation before the commanded pitch change takes full effect on the disc.
Plain English
When you push the cyclic, the helicopter doesn't react instantly. There is a small but noticeable pause before the nose or side of the aircraft starts to move in the direction you commanded.
Context Anchor
Seen when using the airspeed indicator to judge pitch control in helicopter instrument flight.
Derivation
Cyclic comes from Greek kyklos, meaning circle or wheel. The cyclic control changes blade pitch cyclically -- once per rotation -- which is why the response is not instantaneous.
Why Pilots Care
If a pilot expects an instant response and doesn't get one, they tend to add more input, then over-correct when the delayed response finally arrives. This causes pilot-induced oscillations, especially in instrument conditions where small, smooth, patient inputs are essential.
Grounding Statement
After a cyclic movement, wait for the helicopter and the airspeed indication to catch up before making another correction.
Intuition Check
Cyclic here does not just mean something that repeats in a cycle. It refers to the helicopter control used to change pitch and bank. Lag does not mean the control is broken. It means the response is delayed.
Example Sentence 1
Because of cyclic control lag, the instructor told her to make small pitch inputs and pause, rather than chasing the attitude indicator.
Example Sentence 2
Smooth cyclic movements help manage cyclic control lag and maintain stable airspeed during instrument approaches.