View Full Version : 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?
GlueBall
1st Jan 2003, 23:32
A simple answer is that more flaps requires more power which translates into more noise.
john_tullamarine
2nd Jan 2003, 00:12
GlueBall,
Not quite that simple.
Ignoring the physiological niceties ... noise (more specifically sound pressure level) is a distance squared function ... the idea is to get the aircraft higher within a closer radius of the airport so that the main noise nuisance is confined to airport adjacent areas. Short of having quieter engines, which is the thrust (do pardon the pun) of improving certification standards, the only ways to reduce noise is to reduce thrust (not overly effective) or increase distance (hence a steeper close-in climb) ..... If you prefer numbers ... in the idealised situation a doubling of the distance drops the dB reading by 6. Always necessary to keep in mind that the scales are logarithmic and small changes in the numbers equal big changes in the sound levels.
Unfortunately, operational techniques are a compromise arrived at in an attempt to appease various competing factions, of which the noise lobby is but one ... no simple answer.