Class A - Take-off Climb — Page 438, Lesson 537

We're moving into the second of the two noise abatement departure procedures — this is NADP 2. In the previous excerpt we covered NADP 1, which was the procedure designed to alleviate noise close to the aerodrome. Now, NADP 2 is the one that alleviates noise distant from the aerodrome. Let me walk you through exactly how it works. The core idea of NADP 2 is that you delay the power reduction. Instead of cutting power early, you climb out at a higher speed and keep the power up longer, so the aircraft gets high and away from the community before you throttle back. That's why it's the procedure for noise distant from the aerodrome — the noise footprint is pushed further out. Here's the sequence. The procedure involves initiation of flap and slat retraction on reaching the minimum prescribed altitude. So you don't retract the flaps and slats immediately after take-off — you wait until you reach a specified minimum altitude. The flaps and slats are to be retracted on schedule whilst maintaining a positive rate of climb. That means you retract them according to the planned schedule, and throughout that retraction you must keep a positive rate of climb — the aircraft must keep climbing, never descending or even levelling off. The power reduction is to be performed with the initiation of the first flap or slat retraction, or when the zero flap and slat configuration is attained. So you have two options for when to reduce power: either you reduce power at the same moment you start the first flap or slat retraction, or you reduce power after the flaps and slats are fully retracted — that is, when you reach the zero flap and slat configuration. At the prescribed altitude, you complete the transition to normal en route climb procedures. Now the key limits. The noise abatement procedure is not to be initiated at less than 800 feet above aerodrome elevation. So you cannot start this procedure any lower than 800 feet above the aerodrome elevation — that's the height of the aerodrome above sea level, so 800 feet above that. The initial climbing speed to the noise abatement initiation point is V2 plus 20 to 40 km/h, which is 10 to 20 knots. V2 is the take-off safety speed — the speed at which the aircraft can safely climb with one engine inoperative. So you climb at V2 plus 10 to 20 knots. On reaching an altitude equivalent to at least 800 feet above aerodrome elevation, you decrease the aircraft body angle, or angle of pitch, whilst maintaining a positive rate of climb. So you lower the nose — reduce the pitch attitude — but you still keep climbing. You accelerate towards VZF. VZF is the zero flap speed — the speed at which the aircraft can fly with the flaps and slats fully retracted. Then you either reduce power with the initiation of the first flap or slat retraction, or reduce power after flap and slat retraction — those are the two options I mentioned. Then you maintain a positive rate of climb, and accelerate to and maintain a climb speed of VZF plus 20 to 40 km/h, which is 10 to 20 knots, up to 3000 feet above aerodrome elevation. So you climb at VZF plus 10 to 20 knots until you reach 3000 feet above the aerodrome. On reaching 3000 feet above aerodrome elevation, you transition to normal en route climb speed. So the contrast with NADP 1 is the timing of the power reduction. NADP 2 keeps the power high and the speed higher for longer, so the aircraft is higher and further away before you reduce power — that's what pushes the noise footprint away from the aerodrome. The figure shows this as an example of a procedure alleviating noise distant from the aerodrome. Let me summarise the key numbers: the procedure starts no lower than 800 feet above aerodrome elevation, initial climb at V2 plus 10 to 20 knots, then accelerate to VZF plus 10 to 20 knots, and transition to normal en route climb at 3000 feet above aerodrome elevation. And throughout, you maintain a positive rate of climb.