Site Navigation:
Craig's twitter feed:
Tweets by @gevmage
In my last post, I slightly oversimplified the situation about extending flaps and reducing throttle. Obviously, anything I say here is merely explanatory, and if you're learning to fly, you of course take your instructors advice and that of the airplane's flight manual, and anything here is supplemental information for your edification. [Further disclaimer: I have never formally studied aerodynamics, so this is an amateur explanation.]
Flaps are devices that extend the chord of the wing (make it longer from front to back) and increase its camber (curviness). These changes increase the amount of lift that the wing makes and also increase the amount of drag it experiences under a given set of circumstances. The increased lift means that the wing can support the airplane at a slower airspeed, and thus the stall speed gets lower. The increased drag means that you can bleed off energy faster (you can descend more rapidly without a dangerous build-up of speed).
Flaps are surfaces at the back part of the wing that swing down and/or extend (depending on their design). The position of flaps are their angle from their retracted position, sometimes spoken of in degrees. So "zero degrees of flaps" == "no flaps" == "flaps retracted", then as they are extended, "ten degrees of flaps", "full flaps", etc. The IMPORTANT THING that I ignored yesterday: As the flaps are extended, at first there's lots more lift and just a little more drag. As they're extended farther, the lift doesn't increase as much but the drag increases much more.
Operationally, what I should have said in yesterdays post, as far as flaps:
There are standard procedures for beginning a descent to landing. The Cessna 150 is the one I know: on downwind opposite the landing end of the runway: carb heat on, throttle down to 1700 RPM, flaps down to 10 degrees turning base: flaps down to 20 degrees, on the rest of the approach: lower throttle and add flaps as needed.
That's the standard procedure. What I was reminded of on Saturday was during the "as needed" phase, drop throttle first and then add more flaps when the throttle is at idle.