![]() ![]() In-flight measurements of BVI noise were undertaken in the mid-1970s with a Bell UH-1H "Huey" as the test helicopter and an OV-1 Mohawk as the microphone platform (Schmitz, 1991). ![]() In-flight measurement of BVI noise is the primary effort of IRAP. A comprehensive review of rotorcraft noise is given in Schmitz's 1991 summary, listed on the references page. The resulting "blade-vortex interaction," or BVI, causes a distinctive type of noise: the annoying "blade-slap" of helicopters with slow-turning rotors, or a sharp fluttering noise for rotorcraft with fast-turning rotors. BVI noiseÄuring certain rotorcraft flight operations, particularly forward descents such as landing approaches, each rotor blade can run into the tip vortex shed by a preceding blade. The data acquired through IRAP is needed to validate wind-tunnel test results, or, where the results cannot be validated, to provide researchers with clues as to how to improve testing methods. Microphones on the wing tips and tail fin of the quiet NASA YO-3A Acoustics Research Aircraft measure BVI noise while the YO-3A descends in close formation with the helicopter or tiltrotor emitting the noise. The type of noise of concern is "blade-vortex-interaction," or BVI, noise. The objective of the In-Flight Rotorcraft Acoustics Program (IRAP) is to acquire rotorcraft noise data in flight for comparison to wind tunnel data. Aeronautics Directorate at Ames Research CenterĪ key part of NASA's aeronautics research is reducing noise to make helicopters and tiltrotors more acceptable to the public.Aeronautics Research Mission Directorate.Millennium Jet Inc - SoloTrek XFV Ducted Rotor Test.Full-Span Tilt Rotor Aeroacoustic Model.McDonnell Douglas Advanced Rotor Test Program.Blade Vortex Interaction Research In The 80- By 120-Foot Wind Tunnel.Wind Tunnel Evaluation of Sikorsky Bearingless Main Rotor.Full-Scale S-76 Rotor Research In The 80- By 120-Foot Wind Tunnel.Interactional Aerodynamics Assessment Using Radio-Controlled Models.UH-60A Airloads Wind Tunnel Test Summary.Rotorcraft Optimization for the Advancement of Mars eXploration.The Aerodynamic and Acousitc Rotorprop Test (AART) Program. ![]()
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