In areas surrounding most airports, there is typically an initiative undertaken by various stakeholders with the objective of mitigating noise pollution. This noise pollution can be apparent in areas in which aircraft arrive and depart on a frequent basis.
Known as Noise Abatement, it is typically delivered through a set of procedures which document and outline action air traffic can take in order to reduce noise output.
The exact noise abatement protocols differ from airport to airport. However, there are generally several common practices adapted at most major airports implementing noise abatement procedures.
Noise Abatement Technologies
Modern commercial aircraft are designed with minimal noise output in mind. Coupled with a necessity for reduced carbon emission outputs, aircraft designers have implemented these factors into the design of aircraft.
These considerations have been taken into account even more so in the last 20-30 years, with the increased attention on the aviation industry as a whole in relation to its contribution to the environment.
While modern aircraft have been designed with noise outputs that are within the legal limits, several older aircraft have required retrofits in order to continue operating.
As outlined in the Federal Aviation Administration’s (FAA) Guidance for Noise Screening of Air Traffic Actions,
there are numerous modifications available to gas turbine aircraft which contribute to reducing the noise levels emitted. One of the most common technologies in this regard are the installation of hush kits to the engines. These devices are typically installed on engines which are either turbojets or low bypass turbofan engines.
Hush kits reduce the noise levels emitted from engines by installing an exhaust gas mixer to the engine. With this device, exhaust gases are mixed with a specific level of outside air in order to reduce noise levels.
This technology has proven extremely effective at reducing noise outputs from engines however there is a fuel penalty and installation cost attached to these devices.
The requirement for hush kits to be installed on specific aircraft and engine types has been mandated in many regions of the world.
Noise Abatement Procedures
Also known as NABPs, Noise Abatement Procedures outline specific practices to be adapted by departing and arriving aircraft to an airport. ATC may also be obligated to enforce these procedures depending on the specifics to the airport.
Noise Abatement Procedures are predominantly found at airports in which there are densely populated areas in the vicinity.
The means of implementing noise abatement practices can be achieved by arriving and departing aircraft adopting a pre-determined flight path outlined by the procedures.
While all efforts should be made to outline flight paths that facilitate minimal noise pollution, these routes should also factor into consideration safe limits for aircraft.
These limits include identifying and recognizing the safe parameters (speed and altitude) in which aircraft can fly.
As a result, there should be a significant degree of flexibility implemented to noise abatement procedures in order to accommodate various aircraft types operating to/from the airport.
While all noise abatement procedures enforced should be complied with, the safe operation of the aircraft is paramount.
In addition to the noise abatement procedures related to the departure and arrival of aircraft, there is also generally a set of on-ground noise abatement procedures which aircraft can comply with.
Such procedures involve limiting the use of the Auxiliary Power Unit (APU) and restricting hours in which engine runs are permitted. Implementing these practices as part of the noise abatement procedures will contribute to reducing noise pollution.
In order to enforce these procedures and regulations, fines and regular recording of noise levels at airports have been introduced.
The recording of airport noise levels can be conducted via the utilization of a system known as ANOMS – Airport Noise and Operations Monitoring System. This system allows for the collection of noise samples at an airport followed by generating a detailed trend analysis of the noise profiles at the airport.
The noise profiles created provide an insight into the efficacy of the existing noise abatement procedures while identifying potential modifications which could be made to further reduce noise levels.
These measures help to incentivize operators to comply with published noise abatement procedures.
In conjunction with the above procedures, airport operating curfews and restricted operating hours can be found at many major commercial airports around the world today.
At airports such as London Heathrow, UK and Sydney Kingsford Smith, Australia for example, there are specific operating hours in which aircraft are not permitted to take off or land.
These operating hours typically range from approximately 11pm at night up until 6am in the morning.