Noise Management
Managing our noise footprint is an important piece of our overall environmental strategy. We work hard to take proactive steps towards minimising our aircrafts' noise impact on communities near the airports where we fly.
Our Noise Management Strategy is based on three key areas.
1. Purchasing a Quieter Aircraft Fleet
The aircraft noise standards for new aircraft are set by the International Civil Aviation Organisation (ICAO). Over the years these standards have become more and more stringent with the most recent, Chapter 4 applicable for new aircraft types from 1 January 2006.
The Qantas fleet is certified to Chapter 3 and also meets the new Chapter 4 standards.
Our Airbus A380 is already demonstrating the advanced technology reducing the takeoff noise by half and we expect the Boeing 787 Dreamliner to provide a 50% smaller noise footprint around airports.
2. Quieter Operational Procedures
Whilst our priority is always safety, we try to operate our aircraft to minimise our noise impact on the ground.
The Qantas standard procedure for take off is also a Noise Abatement Departure Procedure. This adjusts altitude, flap position and engine thrust to minimise our noise footprint.
When we land we also try to minimise our noise. The best way for us to do that is by flying a Constant Descent Arrival (CDA). This is where our aircraft don't need to level off on approach, reducing the need for additional engine thrust and keeping the aircraft higher, both reducing the noise of the aircraft.
Navigation technology is also helping us develop procedures to minimise noise on the Group. Required Navigation Performance (RNP) procedures have been implemented at places including Canberra and the Gold Coast enabling us to avoid noise sensitive areas.
3. Engaging with our Communities
We believe the best noise outcomes are developed through consultation and engagement with the communities around airports. We continue to participate in Airport consultative committees that bring together Airservices, the Airport Lessee and local communities to discuss aircraft noise issues.
4. A Closer Look at Aircraft Noise
Take-off engine thrust
To ensure a safe take-off, we consider several factors when calculating required engine thrust levels. Factors which influence thrust levels include: runway length, aircraft weight, wind direction, air temperature and runway altitude. By optimising engine thrust settings, we reduce stress on engines, reduce risk of damage if there is a bird strike and reduce maintenance requirements.
Reverse thrust during landing
During landing, a combination of reverse thrust and wheel brakes slow aircraft down on the runway. Reverse thrust uses engine panels to direct air forwards so the engine can help in slowing down the aircraft. The length and condition of the runway determine how much reverse thrust pilots apply.
Engine ground running
The procedure 'engine ground running', during which engine settings are increased from idle to a higher power in order to simulate what would happen in a flight, allow our engineers to verify that aircraft engines are working properly. It typically takes place after an engine problem has been found or following regular maintenance.
At most airports, engine ground running locations are carefully situated away from the closest residences to reduce noise impacts. For safety purposes, engine ground running requires facing the engine into the wind. Therefore, the direction of the aircraft and its engine noise will change with wind direction. Qantas always complies with airports' engine ground running regulations.
Navigation around airports
Passenger aircraft do not use streets or houses as visual cues for navigational purposes. At most major airports, specific flight paths are documented by Air Traffic Control. These flight paths ensure aircraft safely avoid noise sensitive areas, obstacles and other aircraft. All procedures are visible on pilots' displays and combine weather information, nearby aircraft positions and navigation aids.
Determining the direction of aircraft take-off and landing
For safety reasons aircraft usually take off and land facing into the wind. By landing into the wind, aircraft can go slower over the ground and thus, need less runway to slow down. During take-off, headwinds actually help the aircraft take off faster because air moving rapidly over the wing can give it more lift.
Taking off or landing with a tailwind is not the preferred procedure. Maximum tailwind limits are set by the manufacturer and the Civil Aviation Safety Authority (CASA).
Deviation from normal flight paths
Pilots occasionally deviate from normal flight paths for safety reasons or upon a request from Air Traffic Control. Generally, this is to avoid bad weather or to avoid other aircraft. Air Traffic Control can identify aircraft that deviate without a valid reason. In this situation, an investigation would typically be conducted.
Aircraft height on approach
Aircraft normally come in for landing at a three degree angle. This three degree 'glide path' follows a line that descends about 300ft with every nautical mile towards touchdown. For safety, Air Traffic Control may give instructions for aircraft to fly lower than this to keep a safe distance from other aircraft.
Aircraft noise during take-off and landing
- Landing: During landing, aircraft noise is primarily generated from the sound of the air passing over the aircraft's landing gear and flaps that are deployed.
- Take-off: During take-off, engines at high thrust settings are the primary source of aircraft noise.
Preparing for landing
Qantas policy and industry recommended practice sets a point along its approach that aircraft must be ready to land. Aircraft must be lined up with the runway, at the right angle and speed and have the landing gear down with the flaps in the landing position. This is normally at 1000ft above the ground or about three nautical miles from the end of the runway.
