5 the directivity effect of the bvi noise was found

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5. The directivity effect of the BVI noise was found to be very strong. The average dBA max of the test runs mea- sured at the starboard microphone location was approxi- mately 6 dB higher than that at the port mic location (about 4.6 dB difference in SEL metric). Deceleration along the approach increased the TPP angle-of-attack, which tended to accentuate the directivity. References 1. Anon.: Fly Neighborly Guide. Helicopter Association International, 1992 2. Hindson, W. S.; and Chen, R. T. N.: Flight Tests of Noise Abatement Approaches for Rotorcraft Using Differential GPS Guidance. AHS Annual Forum, May 1995 3. Martin, R. M.; and Connor, A. B.: Wind-Tunnel Acoustic Results of Two Rotor Models with Several Tip Designs. NASA TM-87698, July 1986 4. Liu, S. R.; and Marcolini, M. A.: The Acoustic Results of a United Technologies Scale Model Helicopter Rotor Test at DNW. AHS Annual Forum, May 1990 5. Gallman, J. M.; and Liu, S. R.: Acoustic Characteris- tics of Advanced Model Rotor Systems. AHS Annual Forum, May 1991 6. Mueller, A. W.; Conner, D. A.; Rutledge, C. K.; and Wilson, M. R.: Full Scale Flight Acoustic Results for the UH-60A Airloads Aircraft. pre- sented at the AHS Vertical Lift Aircraft Confer- ence, San Francisco, Calif., Jan. 1995 7. Wilson, M. R.; Mueller, A. W.; and Rutledge, C. K.: A New Technique for Estimating Ground Foot- print Acoustics for Rotorcraft Using Measured Sound Fields. presented at the AHS Vertical Lift Aircraft Conference, San Francisco, Calif., Jan. 1995 8. Leverton, J.: Helicopter Noise Certification, Past- Present-Future. 18th European Rotorcraft Forum, Avignon, France, Sept. 1992 9. Yoshikami, S. A.; and Cox, C. R.: FAA/HAI Heli- copter Flight Operations Noise Tests and Initial Results. AHS Annual Forum, May 1985 10. Yoshikami, S.A.: Flight Operations Noise Tests of Eight Helicopters. FAA-EE-85-7, Aug. 1985 11. Rickley, E. J.; Jones, K. E.; Keller, A. S.; and Fleming, G. G.: Noise Measurement Flight Test of Five Light Helicopters. DOT/FAA-EE-93-01, July 1993 12. Jacobsen, R. A.; Rediess, N. A.; Hindson, W. S.; Aiken, E. W.; and Bivens, C. C.: Current and Planned Capabilities of the NASA/Army Rotor- craft Aircrew Systems Concepts Airborne Labo- ratory (RASCAL). AHS Annual Forum, May 1995 13. Kaufmann, D. N.: Helicopter Approach Capability Using the Differential Global Positioning Sys- tem. NASA CR-177618, Aug. 1993 14. Fletcher, J. W.; Chen, R. T. N.; and Strasilla, E.: State Estimation of Main Rotor Flap and Lead-Lag Using Accelerometers and Laser Transducers on the RASCAL Helicopter. submitted for presenta- tion at 34th AIAA Aerospace Science Meeting, Reno, Calif., Jan. 1996 15. Chen, R. T. N.: A Survey of Nonuniform Inflow Models for Rotorcraft Flight Dynamics and Control Applications. NASA TM-102219, Nov. 1989 16. Chen, R. T. N.: Effect of Primary Rotor Parameters on Flapping Dynamics. NASA TP-1431, Jan. 1980 17. Hoh, R. H.; Baillie, S. W.; and Traybar, J. J.: Deter- mination of Decision Height Windows for Decelerating IMC Approaches in Helicopters. AGARD Conference Proceeding 508, Feb. 1991 18. Bennett, R. L.; and Pearsons, K. S.: Handbook of Air- craft Noise Metrics. NASA CR-3406, 1981
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12 Table 1. RASCAL/LDGPS noise-abatement acoustic tests approach flight profiles tested Test PT Flight conditions Airspeed over mic Run # NASA 748 comparison A 250 ft level flight @ 80 kts 80 kt 1, 2, 3 B Descent 6 deg @ 80 kts (250 ft over center mic) 80 kt 4, 5, 6, 23 RASCAL/LDGPS acoustics C Descent 6 deg @ 80 kts
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