V formation 

Canada Geese in V formation. Source: NASAexplores

A V formation (sometimes called a skein) is the symmetric V-shaped flight formation of flights of geese, ducks and other migratory birds. V formations are also used on military flight missions.

Aerodynamics

Flying in a V formation aids the birds in covering long distances efficiently. All the birds except the first are flying in the upwash from the wingtip vortices of the bird ahead. The birds in the formation take turns flying first. A little upwash assists the bird to support its own weight in flight in the same way a glider can climb or maintain height indefinitely in rising air. In V formation of 25 members, each bird can achieve a reduction of induced drag by up to 65% and as a result increase their range by 70%1. The birds flying at the tips and at the front are rotated in a timely cyclical fashion to spread flight fatigue equally among the flock members. The formation also makes communication easier and allows the birds to maintain visual contact with each other.

Often one side of the V formation extends beyond the other side, creating a lopsided effect. ( An example of this may be seen here).

Military flight missions

Mixed IAF and USAF aircraft in V formation during Cope India '04

Visual contact is why V formations (and the asymmetric echelon formations) are also commonly adopted by flights of military aircraft engaged on a common mission.

The basic flight formation for military aircraft in many air forces during World War II was a V formation. In the U.S. Army Air Forces the most basic formation for bombers was a three-plane "V" called an "element." Stacks of these elements were configured to form a defensive bombing formation called the "combat box".

The V formation is also common in ceremonial flyovers and airshow flights.

See also

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