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  • 1
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    Maneuver Acoustic Flight Test of the Bell 430 Helicopter (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A cooperative flight test by NASA, Bell Helicopter and the U.S. Army to characterize the steady state acoustics and measure the maneuver noise of a Bell Helicopter 430 aircraft was accomplished. The test occurred during June/July, 2011 at Eglin Air Force Base, Florida. This test gathered a total of 410 data points over 10 test days and compiled an extensive data base of dynamic maneuver measurements. Three microphone configurations with up to 31 microphones in each configuration were used to acquire acoustic data. Aircraft data included DGPS, aircraft state and rotor state information. This paper provides an overview of the test.
    Keywords: Acoustics
    Type: NF1676L-13533 , American Helicopter Society 68th Annual Forum and Technology Display; May 01, 2012 - May 03, 2012; Forth Worth, TX; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Helicopter Acoustic Flight Test with Altitude Variation and Maneuvers (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A cooperative flight test campaign between NASA and the U.S. Army was performed from September 2014 to February 2015. The purposes of the testing were to: investigate the effects of altitude variation on noise generation, investigate the effects of gross weight variation on noise generation, establish the statistical variability in acoustic flight testing of helicopters, and characterize the effects of transient maneuvers on radiated noise for a medium-lift utility helicopter. This test was performed at three test sites (0, 4000, and 7000 feet above mean sea level) with two aircraft (AS350 SD1 and EH-60L) tested at each site. This report provides an overview of the test, documents the data acquired and describes the formats of the stored data.
    Keywords: Acoustics
    Type: NASA/TM-2016-219354 , L-20729 , NF1676L-24899
    Format: application/pdf
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  • 3
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    Maneuver Acoustic Flight Test of the Bell 430 Helicopter Data Report (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: A cooperative ight test by NASA, Bell Helicopter and the U.S. Army to characterize the steady state acoustics and measure the maneuver noise of a Bell Helicopter 430 aircraft was accomplished. The test occurred during June/July 2011 at Eglin Air Force Base, Florida. This test gathered a total of 410 test points over 10 test days and compiled an extensive database of dynamic maneuver measurements. Three microphone arrays with up to 31 microphon. es in each were used to acquire acoustic data. Aircraft data included Differential Global Positioning System, aircraft state and rotor state information. This paper provides an overview of the test and documents the data acquired.
    Keywords: Acoustics
    Type: NASA/TM-2014-218266 , NF1676L-18177 , L-20367
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Report on the Joint Eglin Acoustic Week III (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A series of three flight tests have been conducted at Eglin Air Force Base located in the Florida panhandle. The first was the Acoustics Week flight test conducted in September 2003. The second was the NASA Heavy Lift Rotorcraft Acoustic Flight Test conducted in October-November 2005. The most recent was the Eglin Acoustic Week III test conducted in August-September 2007. This series of tests have acquired acoustic data for a number of rotary and fixed wing aircraft that are used to generate noise semi-spheres used in predicting the acoustic footprint for prescribed flight operations. This extensive database can be used to determine the impact of flight operations on communities around a terminal area. Another valuable use of the semi-spheres is determining the long-range propagation of noise for civilian and military purposes. This paper will describe the third in this series of tests.
    Keywords: Acoustics
    Type: AHS Southwest Region Technical Specialists? Meeting; Oct 15, 2008 - Oct 17, 2008; Dallas-Fort Worth, TX; United States
    Format: application/pdf
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  • 5
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    Measurement and Characterization of Helicopter Noise at Different Altitudes (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents an overview of a flight test campaign performed at different test sites whose altitudes ranged from 0 to 7000 feet above mean sea level (AMSL) between September 2014 and February 2015. The purposes of this campaign were to: investigate the effects of altitude variation on noise generation, investigate the effects of gross weight variation on noise generation, establish the statistical variability in acoustic flight testing of helicopters, and characterize the effects of transient maneuvers on radiated noise for a medium-lift utility helicopter. In addition to describing the test campaign, results of the acoustic effects of altitude variation for the AS350 SD1 and EH-60L aircraft are presented. Large changes in acoustic amplitudes were observed in response to changes in ambient conditions when the helicopter was flown at constant indicated airspeed and gross weight at the three test sites. However, acoustic amplitudes were found to scale with ambient pressure when flight conditions were defined in terms of the non-dimensional parameters, such as the weight coefficient and effective hover tip Mach number.
    Keywords: Acoustics
    Type: NF1676L-22567 , American Helicopter Society (AHS) Annual Forum; May 17, 2016 - May 19, 2016; West Palm Beach, FL; United States
    Format: application/pdf
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  • 6
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    Overview of Rotorcraft Acoustic Flight Testing (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Acoustics
    Type: NF1676L-21246 , 2015 Acoustics Technical Working Group Meeting; Apr 21, 2015 - Apr 22, 2015; Hampton, VA; United States
    Format: application/pdf
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  • 7
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    Direct CFD Predictions of Low Frequency Sounds Generated by a Helicopter Main Rotor (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The use of CFD to directly predict helicopter main rotor noise is shown to be quite promising as an alternative mean for low frequency source noise evaluation. Results using existing state-of-the-art grid structures and finite-difference schemes demonstrated that small perturbation pressures, associated with acoustics radiation, can be extracted with some degree of fidelity. Accuracy of the predictions are demonstrated via comparing to predictions from conventional acoustic analogy-based models, and with measurements obtained from wind tunnel and flight tests for the MD-902 helicopter at several operating conditions. Findings show that the direct CFD approach is quite successfully in yielding low frequency results due to thickness and steady loading noise mechanisms. Mid-to-high frequency contents, due to blade-vortex interactions, are not predicted due to CFD modeling and grid constraints.
    Keywords: Acoustics
    Type: ARC-E-DAA-TN1528 , 2010 American Helicopter Society 66th Annual Forum; May 11, 2010 - May 13, 2010; Phoenix, AZ; United States
    Format: application/pdf
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  • 8
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    Examination of a Rotorcraft Noise Prediction Method and Comparison to Flight Test Data (2017)
    In:  CASI
    Details
    Publication Date: 2019-08-26
    Description: With a view that rotorcraft noise should be included in the preliminary design process, a relatively fast noise prediction method is examined in this paper. A comprehensive rotorcraft analysis is combined with a noise prediction method to compute several noise metrics of interest. These predictions are compared to flight test data. Results show that inclusion of only the main rotor noise will produce results that severely underpredict integrated metrics of interest. Inclusion of the tail rotor frequency content is essential for accurately predicting these integrated noise metrics.
    Keywords: Acoustics
    Type: NASA/TM-2017-219370 , L-20781 , NF1676L-26297
    Format: application/pdf
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