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Thread: Base Leg Flaps
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Old 1st Oct 2007, 19:42
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Nathan Parker
 
Join Date: Oct 2007
Location: Millington
Age: 59
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Consider what the purpose of flaps are for.
Flaps were invented to lower the stall speed in order to use less runway in takeoff and landings, yet still allow for the increasingly high cruise speeds. They are best understood in that context. However, the higher flap settings won't decrease the stall speed much; in a C172, the 40 degree setting will give you maybe a 1/2 knot reduction. This setting is purely designed to steepen the descent angle.

Removing flaps doesn't necessarily result in a descent rate at all. I have removed all of them 1 foot above the runway without any loss of altitude. Works fine as long as you increase the AOA to compensate. Since the 40 degree setting results in only a small increase in lift coefficient, you need to make almost no adjustment when you reduce the setting from 40 to 30.

The student must understand that the greater the deflection of flap the less will power exceed drag during the approach and also during a go-around.
Power doesn't exceed drag ever, since they measure different quantities. Thrust may or may not exceed drag, but on a landing approach, drag exceeds thrust, or the airplane would not be descending. The larger the flap deflection, the greater drag exceeds thrust, which steepens your approach.
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