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Concept
Formation en V
Résumé
A V formation is a symmetric V- or chevron-shaped flight formation. In nature, it occurs among geese, swans, ducks, and other migratory birds, improving their energy efficiency, while in human aviation, it is used mostly in military aviation, air shows, and occasionally commercial aviation.
Flying in the V formation is proven to improve energy efficiency. Usually, large birds fly in this formation since smaller birds create more complex wind currents that are hard for the back to take advantage of. V formations also improve the fuel efficiency of aircraft.
The V formation possibly improves the efficiency of flying birds, particularly over long migratory routes. This allows the birds after to take the upwash lift force due to the wingtip vortices at the tip of the wings of the lead bird. The upwash assists each bird in supporting its own weight in flight, in the same way a glider can climb or maintain height indefinitely in rising air. The birds are able to find the place where the uplift is the most desirable either by sight or by sensing the airflow by their feathers, scientists suspect.
Previous studies found that birds can use less than 20 to 30 percent of energy. According to a 1970 paper, in a V formation of 25 members, each bird can achieve a reduction of induced drag and as a result increase their range by 71%. In a 2001 Nature study, researchers used trackers on pelicans and yielded the results that pelicans flying alone have higher heart rate and flap their wings more frequently compare to those flying in V formation.
In a V formation, some birds prefer to fly at the left, some at the right, and some at the center. 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. Canada geese, ducks and swans commonly form a skein in V formation. Thus, the flight formation variates around a V-like shape and does not stay constant.
Flying in V formation is not only about position but also about the timing of flapping.
Source officielle
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