En gros, les ailes du 787 (et du 77 et d'autres Boeing) sont rallongées et courbées vers le haut MAIS ça revient grosso modo au même que de mettre des winglets.Raked wingtips are a feature on some Boeing airliners, where the tip of the wing has a higher degree of sweep than the rest of the wing. The stated purpose of this additional feature is to improve fuel efficiency and climb performance, and to shorten takeoff field length. It does this in much the same way that winglets do, by increasing the effective aspect ratio of the wing and interrupting harmful wingtip vortices. This decreases the amount of lift-induced drag experienced by the aircraft. In testing by Boeing and NASA, raked wingtips have been shown to reduce drag by as much as 5.5%, as opposed to improvements of 3.5% to 4.5% from conventional winglets.
While an equivalent increase in wingspan would be more effective than a winglet of the same length, the bending force becomes a greater factor. A one-foot increase in span has the same bending force as a three-foot winglet, which has the same performance gain as a two-foot wing extension.
For this reason, the short-range Boeing 787-3 design currently calls for winglets instead of the raked wingtips featured on all other 787 variants.
Raked wingtips are or are planned to be employed on:
Boeing P-8 Poseidon
Boeing 747-8 Freighter
Boeing 747-8 Intercontinental
Boeing 767-400ER
Boeing 777-200LR
Boeing 777-300ER
Boeing 777 Freighter
Boeing 787-8
Boeing 787-9
Partout, quelques soient les sources, les Winglets ou dispositifs assimilés semblent avoir un effet bénéfique (les chiffres varient, mais restent positifs).
Je pense franchement que c'est efficace. Sinon les compagnies n'en feraient pas rajouter sur leurs avions, elles ne dépenseraient pas de l'argent pour rien.
