FAA Flight Instructor Airplane (FIA)Performance, Weight and BalanceMedium
According to a typical POH short-field takeoff procedure, using the manufacturer's recommended intermediate flap setting instead of a no-flap configuration generally has which effect on takeoff ground roll?
- AIt increases ground roll because the added flap drag must be overcome before acceleration can occur
- BIt decreases ground roll because the added lift allows liftoff at a lower groundspeed
- CIt decreases ground roll to zero because flaps eliminate the need for airspeed at liftoff
- DIt has no measurable effect since flaps are only effective for landing configurations
Show answer & explanationAnswer & explanation
Correct answer: B. It decreases ground roll because the added lift allows liftoff at a lower groundspeed
Extending flaps to the recommended short-field takeoff setting increases the wing's lift coefficient at a given airspeed, allowing the airplane to reach the lift-off angle of attack and become airborne at a lower speed, which shortens the ground roll despite a small increase in drag.
Why the other options are wrong
- A. While flap drag increases slightly, the net effect on ground roll (shorter liftoff distance) is a decrease, not increase, for the recommended setting.
- C. Flaps reduce but do not eliminate the required liftoff airspeed.
- D. Flaps are explicitly used in many short-field takeoff procedures to reduce ground roll.
Flap Effect on Takeoff Distance
Extending flaps to the recommended short-field setting increases lift at lower speeds, reducing takeoff ground roll, though excessive flap deflection can increase drag and reduce climb performance after liftoff.
- Recommended flap setting balances lift increase against drag increase
- Too much flap can shorten ground roll but hurt climb gradient over obstacles
- POH performance charts specify the exact flap setting for short-field procedures
Memory trick: A little flap gets you off the ground fast, but too much flap slows the climb at last.