Angle of Attack
As many
may already know, the angle of attack is the angle at which the airplane wing
is directed into the air during flight.
If one thinks of an airplane wing as an air scoop, a larger angle of
attack helps divert more air downwards, thus creating more lift. If one imagines the air particles as
bullets hitting the wing of the airplane, an increased angle of attack
increases the number of air particles that will hit the bottom of the wing,
thus increasing the amount of air being “scooped” and diverted downwards.
(http://www.monmouth.com/~jsd/how/gif48/bullets.gif) However,
there is a limit to this great thing we call angle of attack. Generally any
angle greater than 15 degrees will cause the plane to stall. The stall happens because, as
discussed earlier, the viscous property of air “wants” to follow a curve, but
is limited to its level of “stickiness” to the surface of the plane. As the angle of attack increases, the
air has a harder time “sticking” to the surface and eventually simply passes
right over the wing without following the surface, resulting in the loss of
lift (a.k.a. stall).
This figure shows the
turbulence on the airfoil created by an increased angle of attack. Increased angle of attack helps create more lift by
increasing the amount of air diverted downwards, but too much of a good thing
can cause a stall. (http://ldaps.ivv.nasa.gov/Physics/Images/Engineering_Manual10.gif) |
