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



An UHCA was born