During the development of an advanced ducted tail rotor (DTR) design, a concentrated and successful effort was made to research and incorporate the low noise features of a DTR suitable for intermediate size rotorcraft. The design, whirl stand testing, and flight evaluations of this DTR configuration are described. Results of noise testing are presented for multiple design configurations to study the parametric effects of blade spacing, tip shape, rotational speed, and inflow turbulence. The acoustic effects of each parameter are presented, and measured noise reductions are identified. Isolated model ducted-rotor configurations are described, leading to additive noise level reductions of more than ten decibels for the DTR design. Installed on a Bell Model 222U helicopter, the DTR reduces total noise during hover and forward flight by an average of 2 to 6 dBA compared to the Model 222U configured with a standard tail rotor. A dramatic improvement in sound quality was found in subjective comparison tests. The performance and handling qualities of the test helicopter with the DTR prove to be similar to those characterizing a standard tail rotor. Component loads are well within design limits. These design qualities are discussed and substantiating test data are presented.
Ducted tail rotor designs for rotorcraft and their low noise features
Ummantelte Heckrotorkonstruktionen für Drehflügelflugzeuge und ihre Geräuscharmut
1996
15 Seiten, 22 Bilder, 2 Tabellen, 7 Quellen
Conference paper
English
Ducted Tail Rotor Designs for Rotorcraft and their Low Noise Features
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