The Mayor's Ambient Noise Strategy - Greater London Authority

The Mayor’s Ambient Noise Strategy Mayor of London 127
the west (the predominant mode of operation at Heathrow) the
glideslope may extend across London as far as Greenwich.
4C.19 Much of the noise produced during descent to landing is aerodynamic,
including from flaps and undercarriage. An ANMAC study (see glossary)
concluded that specific measured arrivals noise limits were not practicable.
Regular monitoring and reporting of approach noise and close working
between the airport operator, airlines and air traffic control are all
necessary to achieve improvements. Continuous Descent Approach (CDA)
is a noise abatement technique for arriving aircraft which avoids the higher
noise levels generated when aircraft descend in steps (see glossary). At
Heathrow, CDA achievement during the 2300 to 0600 period improved
from 73% in the second quarter of 1999 to 88% in the third quarter of
2001. The airport operator has a target to increase this to 90% of arrivals
by December 2004. 18 A Code of Practice has been developed to reduce
noise from each aircraft arrival. 19 Low engine power settings during CDA
reduce fuel use, and the aircraft is generally higher than in a stepped
approach. Much of the noise is from the turbofan assembly and is tonal in
quality. People tend to find tonal noise more annoying at a given level.
4C.20 Future changes to international air traffic management include integrated
‘gate to gate’ operational systems, and ‘area navigation’ procedures
(RNAV, see glossary), with the prospect of adjustments to the present
structure of departure routes. Reducing the need for entering one of the
four ‘holding stacks’ around London, would not necessarily reduce the
need for integrating different traffic streams for final approach. Airspace
management is the responsibility of the Civil Aviation Authority/National
Air Traffic Services. Air traffic controllers use a variety of rules, procedures
and practices designed to ensure the safe and expeditious separation and
sequencing of aircraft. The structure of controlled airspace over London
has been built up over a long period. Any major redesign would have
widespread ‘knock on’ implications. Aircraft positioning for approach to
Heathrow are not necessarily required to enter a holding pattern, or be
constrained to a particular standard arrival route. Aircraft may, depending
on air traffic conditions, weather conditions and other factors, be directed
and sequenced to final approach in a variety of ways.
4C.21 Aircraft manoeuvre over many parts of London, outside the most-affected
areas in south-west London. Many of these are manoeuvring across south
or north London to join the glideslope on their approach to Heathrow
Airport. There are also increasing movements to and from other airports in
and around London. It may not always be clear to people in Tower
Hamlets or Greenwich, for example, whether the aircraft they see are
using Heathrow, London City or other airports. Air traffic control