Quote:
Originally Posted by crmears
It is incorrect to say that "wings create lift by directing air downward." Wings create lift by using Bernoulli's principle. Check wikipedia for a detailed explanation on how it works. Some aircraft can use deflection (that which you describe) but it takes a huge amount of energy and is not practical for sustained flight in conventional aircraft.
You are correct in saying that flow should stay attached to the top of the wing. Otherwise you get a "stall" and the wing loses lift.
The bottom of a wing is not "rounded." It is flat. Bernoulli's principle explains why it is flat.
Randy
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Nope, it's a myth perpetrated by grade school textbooks that lift is created by air moving faster over the top of the wing.
Planes do fly by directing air downward-- that's why lift is adjusted by varying the pitch of the wings.
Two myths I learned in college: bathtub drains and airplane wings — The Endeavour
Same goes for helicopters, which is why rotors push air downward like big propellers. A helicopter blade is basically a wing.
The application of the "Bernoulli effect" here is the attachment of flow to the top of the wing. Air gets pulled downward applies a low pressure effect above the wing that acts on the top surface.
Likewise on the bottom of the wing, the slope pushes air down and creates an upward force.
According to this thread, planes usually cruise with the wings at 1.5-3.5 degrees pitch. At zero pitch they wouldn't be able to stay in the air.
http://forum.avsim.net/topic/126211-...during-cruise/