Tutorial
4. Environment
Reducing
noise and aircraft engine emissions are two major environmental challenges facing
our air transportation system. Noise affects the quality of life in communities
that surround an airport. Many airports are hemmed in by businesses and homes.
Because of this proximity, cities have placed noise and flight operation restrictions
upon airports. For example, at San Jose International Airport in San Jose, California,
airlines landing large aircraft (over 75,000 pounds) between 11:30 PM and 6:30
AM are fined for noise during this curfew. Also, at John Wayne International
Airport in Orange County, California, pilots at takeoff during the early morning
hours engage in a noise abatement takeoff procedure. This procedure consists
of holding the aircraft at the beginning of the runway and "revving"
the engines. 
The pilot then "releases the parking break" and the aircraft
moves along the runway at a much faster speed than during a conventional takeoff.
Once lift has been achieved and the airplane is at a safe altitude, the pilot
then slows the engines (which quiets them). The aircraft then quietly and slowly
cruises over the densely populated area. Once the aircraft has passed over these
residential areas, the pilot then increases power to the engines. The airplane
gains speed and flies away into the departure mode of its flight. These types
of strategies have helped to reduce noise level yet even more is being done.
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