Definition
A maintenance tool used during aircraft rigging to measure the angle of incidence of a wing — the angle between the wing's chord line and the longitudinal axis of the fuselage. The board is placed on the wing surface (or on specified rigging points) and a level or protractor on the board is read against a reference to confirm the wing is set at the correct angle specified by the manufacturer.
Plain English
A flat board with a level on it that mechanics lay across the wing to check that the wing is mounted at the correct angle relative to the fuselage.
Context Anchor
Seen in aircraft maintenance, rigging, and structural alignment work, especially when checking wing or tail surface angles.
Derivation
‘Incidence’ comes from the Latin incidere, ‘to fall upon,’ referring to how the airflow falls upon the wing. The board is the physical tool used to measure that angle. Knowing the term refers to the angle at which air meets the wing helps explain why setting it correctly matters.
Why Pilots Care
Correct incidence settings determine lift, stability, and handling qualities; an incorrect angle can produce poor climb performance or unsafe flight characteristics.
Analogy
It is like using a carpenter’s level and angle guide to make sure a shelf is mounted at the intended tilt, except the surface being checked is part of an aircraft.
Intuition Check
Incidence here does not mean how often something happens. It means the set angle of an aircraft surface compared with a reference line.
Example Sentence 1
The mechanic placed the incidence board across the wing's rigging points to verify the angle of incidence matched the manufacturer's specification.
Example Sentence 2
After replacing the horizontal stabilizer, the technician used the incidence board to verify the new angle before flight.