950102_chen - NASA Technical Memorandum 110370 Acoustic...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
National Aeronautics and Space Administration Robert T. N. Chen, William S. Hindson, and Arnold W. Mueller NASA Technical Memorandum 110370 Acoustic Flight Tests of Rotorcraft Noise-Abatement Approaches Using Local Differential GPS Guidance September 1995
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
National Aeronautics and Space Administration Ames Research Center Moffett Field, California 94035-1000 NASA Technical Memorandum 110370 September 1995 Acoustic Flight Tests of Rotorcraft Noise-Abatement Approaches Using Local Differential GPS Guidance Robert T. N. Chen and William S. Hindson, Ames Research Center, Moffett Field, California Arnold W. Mueller, Langley Research Center, Hampton, Virginia
Background image of page 2
Acoustic Flight Tests of Rotorcraft Noise-Abatement Approaches Using Local Differential GPS Guidance ROBERT T. N. CHEN, WILLIAM S. HINDSON, AND ARNOLD W. MUELLER* Ames Research Center Summary This paper presents the test design, instrumentation set- up, data acquisition, and the results of an acoustic flight experiment to study how noise due to blade-vortex inter- action (BVI) may be alleviated. The flight experiment was conducted using the NASA/Army Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) research helicopter. A Local Differential Global Position- ing System (LDGPS) was used for precision navigation and cockpit display guidance. A laser-based rotor state measurement system on board the aircraft was used to measure the main rotor tip-path-plane angle-of-attack. Tests were performed at Crows Landing Airfield in north- ern California with an array of microphones similar to that used in the standard ICAO/FAA noise certification test. The methodology used in the design of a RASCAL- specific, multi-segment, decelerating approach profile for BVI noise abatement is described, and the flight data per- taining to the flight technical errors and the acoustic data for assessing the noise reduction effectiveness are reported. Nomenclature a acceleration, ft/s 2 C T thrust coefficient D diameter of the main rotor, ft g gravitational acceleration, ft/s 2 i s inherent shaft tilt angle, deg r distance from the rotor hub center to the microphone, ft t time, sec v h hover mean induced velocity (normal- ized with tip speed) v T normalized total velocity at the rotor disc center, v T =+ (29 μλ 22 12 / * Langley Research Center, Hampton, Virginia. V airspeed, knots (or ft/s) V free-stream or flight velocity of the air- craft (normalized with tip speed) ˙ V acceleration along the flightpath, ft/s 2 x horizontal distance from the center ground microphone (positive forward), ft z vertical distance from the center ground microphone (positive downward), ft α aircraft angle of attack, deg θ aircraft pitch attitude, deg γ s.s. quasi-steady flightpath angle, deg γ eff effective glidepath angle, deg β ic cosine component of the blade flapping in nonrotating system, deg β is sine component of the blade flapping in nonrotating system, deg σ rotor solidity ratio λ inflow ratio μ advance ratio χ wake skew angle, deg BVI Blade Vortex Interaction EPNL Effective perceived noise level FAA
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 01/05/2011 for the course DU 3 taught by Professor Frando during the Spring '10 term at University of Dundee.

Page1 / 38

950102_chen - NASA Technical Memorandum 110370 Acoustic...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online