It's not that the wing is making any more lift with the flaps down, but that the lift is redistributed so more of the lift (and thus downwash) is made inboard right in front of the tail and less outboard.
sstearns2 said:It's not that the wing is making any more lift with the flaps down, but that the lift is redistributed so more of the lift (and thus downwash) is made inboard right in front of the tail and less outboard.
I wont swear to it, but....I vaguely recall something about flaps increasing the camber, AOA, and on some types, (i.e. Fowler) wing area resulting in an increse in total lift produced by the airfoil. The resultant shift of the center of pressure in relation to the CG of the aircraft causing a pitch-up or pitch-down tendancy, but maybe I'm wrong.
sstearns2 said:The previous post on drag was good, but here's a little different way of looking at it (the way I think of it anyway).
The way I think of it, there are 3 kinds of drag...
1- Parasite or 'skin friction' drag.
2 - Induced drag or the drag caused by making lift in whatever direction.
3 - Wave drag or the drag cause by air decellerating thru the speed of sound (shock waves).
They are all really the same basic thing, the acceleration of the air in some direction. Skin friction drag is caused by the entrainment of air in the boundary layer (the layer of air right next to the skin of the airplane). Basically skin friction drag is caused by the air your just dragging along with you as you fly along. Induced drag is caused by the acceleration of the air in some direction to make lift in the opposite direction. The wing accelerates the air down to make lift up.
Imagine there is a box of still air, then a glider flies thru the box of air. Now the box of air has a velocity component in the direction of the flight of the glider caused by the glider dragging (acclerating) air along with itself and there is a vertical velocity component caused by the need of the glider to accelerate air down in order to make the needed lift. The air will also be rotating some amount because of 'wing tip vorticies'. (I hate the word wing tip vortex and disagree with the book explainations, but that's another tirade.)
Wave drag is caused by the sudden deceleration of air thru a shock wave. Air cannot decelerate thru mach 1 smoothly, it will be going Mach 1.5 for example and the hit the shock wave and slow to Mach 0.75 (or so, I don't have a mach table in front of me) in a fraction of an inch. Basically there is a big wall of air being dragged along behind the shock wave that causes a huge amount of drag.
I hope this make some amount of sense.
sstearns2 said:Previous post....
>The flaps do increase lift by increasing the angle of attack. They >also add drag.
Flaps increase the ability of the wing to make lift. In order to fly staight and level lift has to equal wieght. The weight of the aircraft doesn't increase with flap extension, so the amount of lift made in straight and level flight is the same with the flaps up or down.