Low noise approaches

A variety of techniques can be employed to reduce the noise impacts of aircraft as they approach an airport, including:

  • keeping the aircraft high for as long as possible (increasing the distance from the aircraft noise sources to the ground)
  • keeping the aircraft at low engine power for as long as possible (reducing engine noise)
  • keeping the aircraft in a clean aerodynamic configuration for as long as possible (reducing airframe noise)
  • minimising overflight of highly populated or sensitive areas

Continuous Descent Approaches (CDAs)

One effective technique is called Continuous Descent Approach (CDA). This technique keeps aircraft higher and at lower thrust for longer by eliminating the level segments in conventional “step down” approaches.

Graph comparing the altitudes of different descent approaches

Significant noise, fuel burn and emissions benefits can result, but there can be potential impacts on air traffic control & flight crew procedures.

'Silent' Aircraft advanced CDA flight trials

In order to investigate the potential benefits and challenges with advanced CDAs in the operational system, the SAI Operations team has been coordinating a flight trials programme involving a large number of KIC partners from airports, air traffic control, regulators, operators, and suppliers.

A set of advanced CDA procedures were developed for a regional UK airport which also incorporated other low noise “best practice” techniques of Precision Area Navigation (allowing the procedure to be programmed into the aircraft Flight Management System to optimise the approach path) and Low Power/Low Drag (to keep the aircraft in a clean aerodynamic configuration)

The procedures comprise a set of waypoints with:

  • a lateral profile to allow low population exposure to noise
  • vertical constraints which assist the achievement of a CDA vertical profile
  • speed constraints designed to achieve low power/low drag

Flight trials of the procedures have been ongoing with a variety of aircraft types.

Initial results show promising reductions of noise, fuel burn and emissions, and also indications of areas where further improvements could be sought.

Further details will be released shortly.

Last updated:05/11/06