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. Influencing factors include: runway length, aircraft weight, wind direction, air temperature and runway altitude. Optimising engine thrust settings reduces stress on engines, reduces risk of damage if there is a bird strike and reduces 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.
Runway length and condition determine how much reverse thrust pilots apply.
Engine Ground Running
A procedure called engine ground running allows engineers to verify that aircraft engines are working properly. This takes place after an engine problem has been found or following regular maintenance. During the procedure, engine settings are increased from idle to a higher power in order to simulate what would happen in a flight. During the procedure, engineers careful monitor the aircraft.
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.
At most airports, engine ground running locations are carefully situated away from the closest residences to reduce noise impacts. 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 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 needs less runway to slow down. During take-off, headwinds actually help aircraft take off faster. This is because air moving rapidly over the wing gives aircraft 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. Generally, an investigation would 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.