Special Operational Procedures and Hazards — Page 156, Lesson 242

I want to walk you through a new topic: Noise Preferential Routes and the procedures and limitations that go with them. This is part of the chapter on Special Operational Procedures and Hazards. Let me start by giving you the context. The excerpt first lists some conditions that are considered adverse operating conditions — these are situations where you would not require a reduced power take-off for noise abatement. Those conditions are: - When the crosswind component, including gusts, exceeds 28 km/h, which is 15 knots. - When the tailwind component, including gusts, exceeds 9 km/h, which is 5 knots. - When windshear has been reported or forecast, or when thunderstorms are expected to affect the approach or departure. Now, onto the main topic: Noise Preferential Routes. These are established routes designed to ensure that departing and arriving aeroplanes avoid overflying noise-sensitive areas near the aerodrome as far as is practicable. In other words, we try to keep the aircraft away from places like schools, hospitals, and residential areas when it's reasonably possible. When establishing these noise preferential routes, there are specific rules about turns during take-off and climb. Turns should not be required unless four conditions are met: 1. The aeroplane has reached a height of not less than 150 metres, which is 500 feet, above the terrain and the highest obstacles under the flight path — and it must be able to maintain that height throughout the turn. 2. The bank angle for turns after take-off is limited to 15°, except where adequate provision is made for an acceleration phase that permits attainment of safe speeds for bank angles greater than 15°. 3. No turns should be required coincident with a reduction of power associated with a noise abatement procedure — meaning you don't want to turn and reduce power at the same time. 4. Sufficient navigational guidance should be provided to permit aeroplanes to adhere to the designated route. There's an important note here from PANS OPS Volume 2. It permits turns after take-off at a lower height of 120 metres, which is 400 feet, with obstacle clearance of at least 90 metres, or 300 feet, during the turn. These are the minimum requirements for noise abatement purposes — so the 150-metre figure I just gave you is the standard, but the absolute minimum allowed by PANS OPS is 120 metres. Now, when establishing noise preferential routes, the safety criteria of standard departure and standard arrival routes — things like obstacle clearance climb gradients and other factors — must be taken into full consideration. Safety always comes first. An aeroplane shall not be diverted from its assigned route unless it has attained the altitude or height that represents the upper limit for noise abatement, or unless the diversion is necessary for the safety of the aeroplane. Let's move to Procedures. The state in which the aerodrome is located — that's the country where the airport sits — is responsible for ensuring that the aerodrome operators specify noise abatement objectives. The state of the operator — that's the country where the airline is registered — is responsible for approving the safe flight procedures developed by the aeroplane operator. Now, Limitations. Noise abatement procedures should not be selected if noise benefits cannot be expected — there's no point in doing it if it won't actually reduce noise. The pilot in command has the authority to decide not to execute a procedure if conditions preclude the safe execution of the procedure. That's a critical point: the captain has the final say, and safety overrides noise abatement. Finally, for Take-off: noise abatement procedures in the form of reduced power take-off should not be required in adverse operating conditions — and those are exactly the conditions I listed at the beginning: crosswind exceeding 28 km/h or 15 knots, tailwind exceeding 9 km/h or 5 knots, windshear, or thunderstorms affecting the approach or departure. That figure on screen shows you a visual representation of the Continuous Descent Final Approach, or CDFA, which is another noise abatement technique — but for now, focus on the noise preferential route rules I've just covered.