Special Operational Procedures and Hazards — Page 156, Lesson 246

I want to walk you through noise abatement procedures for the approach and departure phases. These are special operational procedures designed to reduce aircraft noise impact on communities near airports, while still maintaining safety. Let's start with the approach phase. For instrument approaches, the procedure requires that you permit the aeroplane to be established on final approach prior to intercepting the glide path. That means you must be fully lined up and stable on the final approach course before you begin descending along the glide slope. The key technique here is what's called reduced power/reduced drag approach — or a combination of both. This has been found to be both effective and operationally acceptable. The object of these techniques is to achieve an uninterrupted descent at reduced power and reduced drag. You do this by delaying the extension of flaps and landing gear until the final stages of the approach. Because you're keeping the aircraft clean longer, these techniques result in higher than normal gear-down and flap approach speeds — so your speeds will be higher than what you'd use on a standard approach with full configuration. Now for the landing itself: noise abatement procedures do not prevent the use of thrust reverse on landing. You are still permitted to use reverse thrust. However, if you're considering using a displaced landing runway threshold for noise abatement, that's only allowed if two conditions are met: first, the aeroplane noise is sufficiently reduced by doing so, and second, the remaining runway distance after the displacement is sufficient for all operational requirements — meaning you can still stop safely. Let's move to departure climb guidance. Two standard operating procedures have been developed as guidance for the climb, and both are considered safe in accordance with the conditions we discussed earlier under take-off. The first procedure is called NADP 1 — Noise Abatement Departure Procedure 1. Its purpose is to provide noise reduction in close proximity to the departure end of the runway — so for areas very close to the airport. The second procedure is NADP 2, which provides noise reduction to areas more distant from the runway end. The two procedures differ in one critical way: the acceleration segment for flap and slat retraction is either initiated prior to reaching the maximum prescribed height, or at the maximum prescribed height. In NADP 1, you accelerate and retract flaps earlier; in NADP 2, you delay that acceleration until you reach the maximum height. To ensure optimum acceleration performance, thrust reduction may be initiated at an intermediate flap setting — meaning you don't have to wait until flaps are fully retracted before reducing power. Now, here's a specific speed requirement. The initial climbing speed from the start of the procedure up to the noise abatement initiation point shall not be less than V2 + 20 km/h to 40 km/h, which is 10 to 20 knots. So your minimum climb speed in this segment is V2 plus 10 to 20 knots. And importantly, the noise abatement procedure is not to be initiated at less than 240 metres (800 feet) above the aerodrome elevation. You must be at or above that height before you start the noise abatement actions. Let me walk you through Figure 10.2, which shows an example of NADP 1 — the procedure that alleviates noise close to the aerodrome. Here's the sequence. You start at take-off thrust, climbing at V2 + 10 to 20 knots. At or above 240 metres (800 feet) above aerodrome elevation, you initiate power reduction. You maintain a positive rate of climb throughout. You then accelerate smoothly to en-route climb speed, retracting flaps on schedule as you accelerate. During the reduced-power segment, you maintain the reduced power setting and keep the flaps and slats in the take-off position. The procedure continues until you reach 900 metres (3,000 feet) above aerodrome elevation, at which point you complete the acceleration and flap retraction to the en-route configuration. So to summarise the key numbers: minimum initiation height is 240 metres or 800 feet, minimum climb speed is V2 plus 10 to 20 knots, and the procedure extends up to 900 metres or 3,000 feet. NADP 1 keeps you at reduced power with take-off flaps longer to reduce noise close to the airport, while NADP 2 would accelerate earlier to reduce noise further away.