1. #1
    It's been a while since I thought on this topic, but I'll try to explain anyway.

    Most flap usage is intended to reduce stall speed, increase lift, and create drag.

    Stall speed is lowered due to geometery changes to the wing chord. Lift increases, but not becaues of the traditional causes of lift, pressure differences, but rather this lift is a deflection type of lift (the correct name escapes me now). And of coures drag is the consequence of enlarging the profile of the aircraft. In most cases this drag is desirable, as intended during landing.

    Now let me clarify the "lift" that most flaps generate. Wings of course produce lift by creating pressure differences above and below the wing. This type of lift is very effective at higher speeds. Lift generated by most flaps is not an extension of the pressure differences created by the wing, but rather a vertical deflection of airflow. This type of lift is economical at lower speeds, but requires very high thrust to maintain flight at high speeds (lifting body designs).

    Much the same as sticking ones hand out the car window while driving. Obviously there is no aerodynamic lift given the shape of the human hand. But, but using an increased angle of attack (as flaps do) lift can be generated simply by deflection. The high cost of this is felt as the wind pulls back against ones arm.

    I believe that most aircraft are designed for maximum lift power in wing geometry, rather than from flap deflection. In fact, excessive deflection below an airfoil can interupt the aerodynamic lift process if I remember correctly, decreasing lift performance.

    EDIT: This is also the basis of the flare at landing. By increasing the angle of attack, we are also increasing the amount of deflection lift the wings are producing, as well as increasing drag. At the same time, as the angle of attack increases to a certain point, the effectivness of the wings aerodynamic lift is reduced slightly, and we both bleed energy and lift only inches above the ground.

    I hope thats correct....

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    Message Edited on 09/27/0306:39AM by adlabs6
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  2. #2
    j145198 wrote:
    - You can climb at 3800fpm in a P-39 simply by
    - lowering combat flaps.

    Yes, I remember seeing this once. Once I was recording a track online, and when I reviewed it later, I was watching a P-39 pilot takoff. His method was to get to speed down the strip, with NO flaps lowered. Then, he pulled the plane into a steep climb, and at the same time, dropped his combat flaps for a few seconds. He then retracted flaps and climbed at speed.

    I tried this and it seems to give a nice kick to getting the plane up quickly from the strip in a hurry. I think it was v1.0, but it still may work now.



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  3. #3
    Thanks for that nice link.

    I found there that the type of deflection lift I was referring to but couldn't recall the name of is "dynamic lift". As I said, this "dynamic lift" only plays a mentionable role at lower speeds and with high flap angles combined with high AoA. Read more about it here...

    http://www.allstar.fiu.edu/aero/flight41.htm

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