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i just wondering, how is the performance of an aircraft if it takes
off and lands quietly. what;s the engine looks like? how's the speed?
i mean, does the velocity need to be decreased in order to produce
less sound? or it has nothing to do with the velocity at all..? and
how about the lift? the range? and is there an aircraft which is
actually dont produce much sound when it takes off and lands? how it
works? please answer me quickly. thanks..
-- naaiemah mohd esa, March 14, 2006
For takeoff noise reduction is achieved through a modified climb profile. This climb profile simply gets the noisy aircraft further above the ground in less time, reducing the noise experienced on the ground. This applies nearly exclusively to jet and turboprop aircraft. A typical profile for a turbine powered aircraft is to climb at a speed of about V2+(10-25) until acceleration altitude. Acceleration altitude is the height at which the aircraft will being to shallow its climb if all engines are operating, or level off and clean up if an engine has failed. This is typically between 1,000' and 1,500' AGL. Once the aircraft is at this alititude if it has a noise abatement climb it will continue with the same flap configuration and reduce power to climb thrust until about 3,000 AGL. Once there it will retratct flaps and continue a normal climb profile. A normal climb profile is one in which the aircraft accelerates to 250 KIAS at acceleration altitude. In a non-noise sensitive area once at accleration altitude it will shallow out to acheive 250 KIAS more quickly.
Frequently turbine aircraft also do reduced-power takeoffs. This is not a noise abatement manuever, but rather an engine life-extending action. There is nearly no noise reduced with reduced power takeoffs. Piston aircraft do not reduced power for takeoff.Landing
To reduced noise on the ground landing aircraft approach at slower speeds, which require less power. Additionally, they will delay flap extension which also reduces noise creating power.
Secondly, once on the ground jet aircraft will limit or eliminate the use of reverse thrust which is extrememly noisy. Turboprop aircraft will also limit the use of reverse.
Interestingly, places such as Frankfurt, Germany have microphones installed along the ground track of the arrival and departure corridors. They continuously monitor the noise from aircraft and the authorities are quick to fine aircraft not following their strict noise abatement procedures.
Finally, old, straight-jet aircraft have been nearly eliminated from use in the US and are seeing less service worldwide. These non-bypass engines are extrememly noisy and also fuel hungry. The newer high-bypass fans are much more quiet.
-- Bradrick Pretzer, March 15, 2006