Angle of incidence (aerodynamics)
Fixed angle between wing chord and fuselage reference axis.
The angle of incidence, also known as the mounting angle or setting angle, is the fixed angle between the chord line of a wing where it attaches to the fuselage and a reference axis along the fuselage, such as the longitudinal axis or direction of minimum drag. It is a design parameter that, with rare exceptions, cannot be varied in flight. This term also applies to horizontal surfaces like canards or horizontal stabilizers, indicating their angle relative to the fuselage's longitudinal axis.
- Typical angle
- about 6°
- Common on
- most general aviation designs
- Also called
- rigging angle, rigger's angle of incidence
- Distinct from
- angle of attack
Lore & Background
The angle of incidence is a fixed design characteristic of an aircraft, set during construction to optimize fuselage alignment in cruising flight. Wings are typically mounted at a small positive angle of incidence, allowing the fuselage to have a low angle with the airflow. Angles of incidence of about 6° are common on most general aviation designs. The term can also be applied to horizontal surfaces such as canards or horizontal stabilizers for the angle they make relative to the longitudinal axis of the fuselage. Other terms for this concept include rigging angle and rigger's angle of incidence. The figure referenced in the article shows a side view of an airplane, with the extended chord line of the wing root making an angle with the longitudinal axis (roll axis) of the aircraft.
Reader's Guide
The angle of incidence is notable because it is a fixed geometric parameter that influences the aircraft's aerodynamic behavior, particularly in cruising flight. By mounting wings at a small positive angle of incidence, designers allow the fuselage to fly at a low angle relative to the airflow, reducing drag. This setting is distinct from the angle of attack, which is the angle the wing chord presents to the airflow in flight and can vary. The article notes some ambiguity in terminology, as some engineering texts may use either term when referring to angle of attack. On rotary-wing aircraft, the angle of incidence is separate from the angle of attack, which changes with rotor blade motion and pilot input. The angle of incidence remains constant regardless of these changes, underscoring its role as a fixed design element.
Did You Know?
- The angle of incidence is sometimes called the mounting angle or setting angle.
- The angle of incidence should not be confused with the angle of attack, though some engineering texts may use either term for angle of attack.
- On rotary-wing aircraft, the angle of incidence can remain unchanged while the angle of attack varies due to blade flapping or pilot control.
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