# downwash

Newton’s third law says that forces come in equal and opposite pairs. This means that when air exerts lift on an airplane, the airplane also exerts a downward force on the air. This is clear in the image above, which shows a an A380 prototype launched through a wall of smoke. When the model passes, air is pushed downward. The finite size of the wings also generates dramatic wingtip vortices. The high pressure air on the underside of the wings tries to slip around the wingtip to the upper surface, where the local pressure is low. This generates the spiraling vortices, which can be a significant hazard to other nearby aircraft. They are also detrimental to the airplane’s lift because they reduce the downwash of air. Most commercial aircraft today mitigate these effects using winglets which weaken the vortices’ effects. (Image credit: Nat. Geo./BBC2)

How is the paper not being wrenched from his hand by the downwash from the rotor blades? And is his hat glued to his head?

either ct/tex or carolina/479er ?? your fics are so great and i loveeee how you write maine like shoot me now he's got so much personality ;u;

Well I already wrote a CT/Tex so here’s Carolina and 479er meeting under unexpected  circumstances. See, Carolina has this problem where the silence in her head — the parts that used to be Eta and Iota — make her hear things that aren’t there. This time, however, looks like the real deal. Maybe Chorus isn’t so bad after all. nsfw

The elegant V formations of migrating birds provide a picturesque harbinger of summer’s end, but why do the birds fly in such a precise formation? Flight creates a looping motion of air around a bird’s wings; at the wing tips this circulation forms a vortex, creating air movement that extends behind the bird. Airflow down the middle of this wake is directed downwards (the downwash; red), whereas the area outside the tip vortices is a region of upwash (blue). A bird flying behind another bird experiences the aerodynamic forces of the downwash and upwash created by the leading bird (a, side view; b, rear view). Portugal and colleagues show that northern bald ibises spatially synchronize their wing movements while flying in a V formation, such that the trailing bird’s wing moves through the area of maximum upwash created by the leading bird. This results in more-efficient lift production and energy savings.” Via.

Gonna fly with a little flap from my friends

Ever wondered why birds flying in “V formation” seem to be flapping in rhythm? Well, here’s your answer:

And where does that V shape come from? The trailing birds are lining up their left wingtip with the right wingtip of the bird in from of them (or right with left) to maximize efficiency. (In this figure, blue means “upwash” - areas in the wake of the first bird where air is moving upwards. Red is “downwash.”)

Muijres and Dickinson / Nature

The research subject of this newly published study is the Northern Bald Ibis, a nearly extinct migratory bird that is often confused with Gonzo from the Muppets.

Markus Unsöld

Researchers raise the birds from chicks, then train them to follow a lightweight plane.  The birds naturally form a flying V, and special data-loggers they wear record their exact position and movement. You can hear more about the story from Geoff Brumfiel.

Now we know scientifically why ducks stick together!

QUACK! QUACK! QUACK! QUACK! QUACK!