Environmental Engineering Reference
In-Depth Information
of buying or leasing new aircraft. Airlines and aircraft leasing companies already own
large numbers of very expensive aircraft that are completely airworthy. They are under-
standably unwilling to take them out of service and invest in new models simply for
environmental reasons, although such action is becoming increasingly necessary to
ensure continuing access to noise-constrained or noise-sensitive airports.
A less costly approach would involve the retrofitting of existing aircraft with
new or 'hush-kitted' engines. This has been achieved in the past, although the noise
benefits have been far less dramatic than those that could be achieved through replace-
ment with new aircraft.
Operational improvements
A wide variety of operating practices have been developed by airlines in order to
reduce the noise generated by their flights. Continuous descent approaches reduce
arrival noise. Quiet take-off procedures, which involve throttling back the aircraft
engines once a safe height has been reached, minimize departure noise. Minimum noise
routes for arriving and departing traffic can ensure that, as far as possible, aircraft are
routed away from built-up areas. On the ground, air-traffic management procedures
can ensure that aircraft are held in locations where noise propagation does not affect
local residents.
Infrastructure developments
At airports, purpose-built engine-test facilities can contain the noise generated dur-
ing ground maintenance procedures. The construction of noise mounds or walls can
prevent localized noise exposure - for example, the domestic terminal at Copenhagen
Airport has been designed to incorporate and act as a noise wall that protects local
housing from apron noise. In the most extreme examples, entirely new airports have
been built in remote and even off-shore locations in order to address, in part, the
potential constraints caused by aircraft noise (eg Munich, Hong Kong and Kansai).
Noise charges and penalties
Differential charges based upon noise emissions encourage the use of quieter aircraft
and discourage noisy operations. This tool can be adjusted to reflect varying sensi-
tivity at different times of the day and night. Noise penalties, imposed upon aircraft
that exceed agreed noise levels on take-off or landing, also put pressure on pilots to
adopt the quietest operating procedures.
Operating restrictions and limits
Operating restrictions related to noise exposure have been introduced at airports
throughout the world. In the main, these tend to relate to night flying, where conven-
tion has it that a limit is imposed upon the numbers and types of aircraft that can take
off or land during the night-time hours. Many airports also close at night, though the
definition of what is considered 'night time' varies between countries and individual
airports. Some airports have restrictions on the use of particular runways at sensitive
times. Others have agreed to, or have been forced to adopt, movement capacity limits
during the day time, often as part of a planning agreement designed to enable future
