5.1 NOISE

The problem:

• Aircraft noise annoys communities surrounding airports
• Cruise noise could become critical
• Aerodynamic noise at landing/take off
• APU noise irritates ground personanel
• Political emphasis

Possible constraints:

• Tightening of noise regulations
• Local traffic frequency restrictions
• Night curfews
• Use of APU restricted

Conventional solutions:

• Stage II aircraft phase-out (2000 from 1990-1995)
• High bypass engines
• Intake noise attenuation
• Long duct nacelles
• Noise abatement procedures

Advanced solutions:

• Optimise flap setting for minimum thrust requirement during take off/climb out
• High thrust/weight ratio for steep climb out
• Automatic configuration control (FEW) during approach
• Minimise drag of a/c in approach configuration
• Area navigation to avoid noise sensitive areas
• Special noise attenuation devices (Inlet splinters, choked inlet, advanced mixers)
• Oversized/derated engines
• Stealth configuration (engines on upper side of wing)

Problems arising from the UHCA:

• High aerodynamic sound at take-off and landing

Advantages with an UHCA:

• The UHCA uses state of the art high bypass engines
• Aerodynamical designed gears and sliding doors to reduce aerodynamic sound 
• Fly by computer minimises thrust variations during approach