Noise Abatement Fuel Burn
For the B737NG. What is the fuel burn penalty for V2+20 climb with take-off flap from sea level to 3000 ft then clean up to 250 knots, as against flap retract at 1000 ft and attaining 250 knots by normal acceleration. Also do the CM56 series engines installed on the B737NG meet the noise abatement rules for clean up at 1000ft.
Apart from some airports where local restrictions dictate a flapped climb to 3000ft is it not more cost efficient to commence flap retract at 1000 ft rather than stagger up to 3000ft at low speed before flap retract?