Definition
A horizontal tail surface whose angle relative to the aircraft's longitudinal axis can be adjusted in flight, allowing the entire stabilizer to be repositioned for pitch trim rather than relying solely on a small trim tab on the elevator. It is used on many transport-category and high-speed aircraft to provide effective trim across a wide range of speeds and center-of-gravity conditions.
Plain English
The whole horizontal tail can pivot up or down to keep the aircraft balanced in pitch, instead of using just a small tab on the elevator.
Context Anchor
Seen in high-speed flight control discussions, especially on airplanes where the whole horizontal stabilizer can move for pitch trim rather than relying only on the elevator.
Derivation
‘Incidence’ comes from the Latin incidere, meaning ‘to fall upon,’ and in aviation refers to the angle at which a surface meets the oncoming air. ‘Variable incidence’ simply means that angle can be changed, which is the key idea: the whole stabilizer's angle to the airflow is adjustable.
Why Pilots Care
Enables effective pitch control at transonic and supersonic speeds where conventional elevators lose authority due to shock waves.
Intuition Check
Incidence does not mean how often something happens here. It means the angle at which the horizontal stabilizer is set relative to the airplane.
Example Sentence 1
The jet uses a variable incidence horizontal stabilizer to trim out pitch forces as fuel burns off and the center of gravity shifts.
Example Sentence 2
In the F-86 Sabre, the variable incidence horizontal stabilizer was critical for pitch control in the transonic regime.