Wing Configuration - Dihedral and Anhedral

Dihedral and Anhedral

Angling the wings up or down spanwise from root to tip can help to resolve various design issues, such as stability and control in flight.

• Dihedral - the tips are higher than the root as on the Boeing 737, giving a shallow 'V' shape when seen from the front. Adds lateral stability.
• Anhedral - the tips are lower than the root, as on the Ilyushin Il-76; the opposite of dihedral. Used to reduce stability where some other feature results in too much stability.

Some biplanes have different degrees of dihedral/anhedral on different wings; e.g. the Sopwith Camel had a flat upper wing and dihedral on the lower wing, while the Hanriot HD-1 had dihedral on the upper wing but none on the lower.

In a polyhedral wing the dihedral angle varies along the span.

• Gull wing - sharp dihedral on the wing root section, little or none on the main section, as on the PZL P.11 fighter. Sometimes used to improve visibility forwards and upwards and may be used as the upper wing on a biplane as on the Polikarpov I-153.
• Inverted gull - anhedral on the root section, dihedral on the main section. The opposite of a gull wing. May be used to reduce the length of wing-mounted undercarriage legs or allow a larger propeller. Two well-known examples of the inverted gull wing are World War II's American F4U Corsair, and the German Junkers Ju 87 Stuka dive bomber.
• Cranked - tip section dihedral differs from the main section. The wingtips may crank upwards as on the F-4 Phantom II or downwards as on the Northrop XP-56 Black Bullet. (Note that the term "cranked" varies in usage. Here, it is used to help clarify the relationship between changes of dihedral nearer the wing tip vs. nearer the wing root. See also Cranked arrow planform.)

• The channel wing includes a section of the wing forming a partial duct around or immediately behind a propeller. Flown since 1942 in prototype form only, most notably on the Custer Channel Wing aircraft.