Yes NADP2 saves fuel over NADP1. Simply because highliftdevices create drag. The engines deliver the same amount of power so more of that power is used to compensate for drag (less excess power to climb). You climb slower (vertical speed) with flaps and slats vs a clean aircraft (same aircraft same speed). Offcourse this is difficult to demonstrate, but it also applied to F1 departure vs F2 or F3 departure (more flaps reduces runway lenght needed but it worsens your climb performance).
So since NADP2 cleans up the aircraft about 2000 ft earlier then NADP1 (most accelerate at 1000' nowadays I believe) it is more efficient fuel burn wise.
On top of that you will reach your most efficient climb speed earlier.
Offcourse this assumes same routing, no climb restrictions, no shortcuts etc.
So simply for fuel reasons airlines prefer NADP1. Which is thus the "standard".
However in shortterm, accelerating will reduce the climb rate and climb angle over the ground. So when there is a buildup area close to the airport you can achieve a better initial climb gradient over the ground. Putting 2000ft extra air between the aircraft and the people on the ground before accelerating.
The total noise that the aircraft makes is the same, the total noise that reaches the ground is less. In that area.
Last edited by 737Jock; 22nd Jan 2014 at 09:11.