The noise technology relating to blown-flap systems is reviewed. There are three general sources of noise: turbomachinery, airframe, and the interaction noise of the jet blowing on the flaps. The latter noise-source area is the most critical and the main subject dicussed. Characteristics of lower surface blown and upper surface blown systems are described, including noise spectra, directivity, jet velocity characteristics, aircraft geometric variation effects, and aircraft forward speed effects. Noise reduction concepts are described, including slowing down the jet flow field by devices and engine cycle modifications, structural geometry and shielding modifications, local flow field modifications of the passive and active type, and the absorption of noise. It is concluded that, while there has been considerable progress in the past several years, low noise characteristics in blown flap aircraft must be largely built in by better application of low noise principles during the design. (Author)

  • Supplemental Notes:
    • Conf-Presented at the 10TH Congr. Of Icas, Ottawa, 3-8 Oct. 1976.
  • Corporate Authors:

    Lockheed-Georgia Company

    Marietta, GA  United States 
  • Authors:
    • Gibson, J S
  • Publication Date: 1976

Media Info

  • Pagination: 12 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00151574
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: NASA-CR-145086
  • Contract Numbers: NAS1-13870
  • Files: TRIS
  • Created Date: Apr 13 1977 12:00AM