Definition
The acute angle formed between the chord line of an aircraft's wing and the longitudinal axis of the fuselage. It is a fixed, built-in design angle set by the manufacturer when the wing is mounted to the airframe.
Plain English
The angle at which the wing is permanently bolted onto the fuselage, measured between the wing's chord line and the length of the airplane. It does not change in flight.
Context Anchor
Seen in aircraft design, performance, and aerodynamics discussions, especially when comparing it with angle of attack.
Derivation
From Latin 'incidere,' meaning 'to fall upon' or 'to meet.' The angle of incidence is literally the angle at which the wing 'meets' the fuselage. This original sense of 'meeting' is why the term describes a structural relationship rather than something that changes during flight.
Why Pilots Care
It sets the airplane's basic nose attitude in level flight and influences lift, drag, and stability characteristics from the moment of takeoff.
Analogy
Think of mounting a shelf on a wall with a slight upward tilt. The tilt is built in; you can place different objects on the shelf, but the shelf’s mounting angle stays the same.
Intuition Check
Do not assume angle of incidence is the same as the wing’s angle to the oncoming air. Angle of incidence is fixed by the airplane’s design; angle of attack changes as the airplane flies.
Example Sentence 1
The designers chose a small positive angle of incidence so the aircraft would cruise efficiently with the fuselage close to level.
Example Sentence 2
When the mechanic replaced the wing, he verified the angle of incidence against the maintenance manual before flight.