Definition
The brief delay between a control input by the pilot and the aircraft's actual response to that input. The aircraft does not react instantly; it takes a short moment for the new control position to produce a noticeable change in pitch, roll, or yaw.
Plain English
When you move the controls, the aircraft takes a short moment to respond. That short delay between your input and the aircraft's reaction is control lag.
Context Anchor
Encountered during instrument flying when making pitch corrections and then watching the instruments to see the result.
Derivation
From 'control' (the cockpit inputs that move the aircraft) and 'lag' (from Middle English, meaning to fall behind or trail). The aircraft's response trails the pilot's input, hence 'control lag.'
Why Pilots Care
Failing to anticipate control lag leads to overcontrolling and unstable instrument flight.
Grounding Statement
Make a small pitch correction, then give the airplane a moment to show the result before deciding whether more correction is needed.
Intuition Check
Control lag does not mean the controls are broken or loose. It means there is a normal short delay between moving the controls and seeing the aircraft's response.
Example Sentence 1
Because of control lag, the student learned to make a small pitch input and pause before adding any more.
Example Sentence 2
Anticipating control lag helps the pilot make smaller, smoother inputs rather than chasing the needles.