1 Noise abatement procedures

Noise abatement procedures are operational measures that aim to minimize the noise exposure of communities around airports and along flight routes. They include specific instructions for pilots, air traffic controllers, and airport operators on how to optimize the flight profile, speed, thrust, altitude, and direction of aircraft to reduce noise levels. Noise abatement procedures are often tailored to the local conditions and requirements of each airport, and may vary depending on the time of day, the runway configuration, the traffic density, and the noise-sensitive areas.

2 Noise abatement for fixed-wing aircraft

Fixed-wing aircraft, such as jets and turboprops, generate the most noise during takeoff and landing, when they use high engine power and low altitude. To reduce the noise, aircraft operators can employ a variety of procedures, such as Cutback or derate, Noise Abatement Departure Procedure (NADP) 1 or 2, Continuous Descent Approach (CDA), and Area Navigation (RNAV). Cutback or derate involves reducing the engine thrust after takeoff to the minimum required for safety and performance while maintaining a steep climb angle. NADP 1 involves a higher climb rate and a thrust cutback at a lower altitude, while NADP 2 involves a lower climb rate and a thrust cutback at a higher altitude. CDA consists of descending from the cruise altitude to the runway in a smooth and continuous manner, avoiding level segments and reducing engine power and drag. Lastly, RNAV uses satellite-based navigation systems to enable more precise and flexible flight paths, avoiding noise-sensitive areas and reducing noise dispersion.

3 Noise abatement for helicopters

Helicopters generate noise primarily from their rotors, which create aerodynamic noise and blade-vortex interactions. The level of noise depends on the rotor speed, pitch angle, weight, wind speed, and direction of flight. To reduce helicopter noise, pilots should follow general guidelines to avoid flying over noise-sensitive areas and maintain a safe and courteous altitude and speed. Additionally, Helicopter Arrival and Departure Routes (HARP) are designated routes for helicopters to follow when approaching or departing from an airport or a helipad. Helicopter Approach Transition (HAT) is a specific procedure that helps helicopters transition from a high-altitude en route flight to a low-altitude approach to an airport or a helipad using a constant descent angle and reduced rotor speed.

4 Noise abatement for propeller aircraft

Propeller aircraft, such as piston or turboprop planes, produce noise mainly from their propellers, which create tip noise and harmonic noise. Factors that can influence the noise level include the propeller speed, the number of blades, the angle of attack, the weight, and the airspeed. To reduce noise levels, propeller RPM reduction can be used after takeoff or before landing to maintain a constant engine power and airspeed. Additionally, best angle of climb can be employed after takeoff to achieve the highest altitude in the shortest horizontal distance. Best rate of descent can be utilized before landing to achieve the lowest altitude in the shortest horizontal distance. Lastly, a curved approach can be implemented to avoid flying over noise-sensitive areas and to align with the runway as late as possible.