Decalage on a fixed-wing aircraft

Fixed-wing aircraft

A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 is the angle difference between the upper and lower wings of a biplane

Biplane

A biplane is a fixed-wing aircraft with two superimposed main wings. The Wright brothers' Wright Flyer used a biplane design, as did most aircraft in the early years of aviation. While a biplane wing structure has a structural advantage, it produces more drag than a similar monoplane wing...

, i.e. the acute angle contained between the chords

Chord (aircraft)

In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...

 of the wings in question.

The decalage is said to be positive when the upper wing has a higher angle of incidence

Angle of incidence

Angle of incidence is a measure of deviation of something from "straight on", for example:* in the approach of a ray to a surface, or* the angle at which the wing or horizontal tail of an airplane is installed on the fuselage, measured relative to the axis of the fuselage.-Optics:In geometric...

than the lower wing, and negative when its angle of incidence is lower. Positive decalage results in greater lift from the upper wing than the lower wing, the difference increasing with the amount of decalage.

External links

• National Advisory Committee for Aeronautics test reports accessed through the Cranfield University AERADE website.