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  • 1
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    Identification and proposed control of helicopter transmission noise at the source (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Helicopter cabin interiors require noise treatment which is expensive and adds weight. The gears inside the main power transmission are major sources of cabin noise. Work conducted by the NASA Lewis Research Center in measuring cabin interior noise and in relating the noise spectrum to the gear vibration of the Army OH-58 helicopter is described. Flight test data indicate that the planetary gear train is a major source of cabin noise and that other low frequency sources are present that could dominate the cabin noise. Companion vibration measurements were made in a transmission test stand, revealing that the single largest contributor to the transmission vibration was the spiral bevel gear mesh. The current understanding of the nature and causes of gear and transmission noise is discussed. It is believed that the kinematical errors of the gear mesh have a strong influence on that noise. The completed NASA/Army sponsored research that applies to transmission noise reduction is summarized. The continuing research program is also reviewed.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA, Washington, NASA(Army Rotorcraft Technology. Volume 2: Materials and Structures, Propulsion and Drive Systems, Flight Dynamics and Control, and Acoustics; p 1045-1065
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    An overview of rotorcraft propulsion research at Lewis Research Center (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Rotorcraft propulsion research at Lewis Research Center is discussed, stressing programs in four areas of component research: compressors, combustors, turbines and transmissions, and three developmental programs: the Small Turboshaft Engine Research (STER) Project, the Advanced Rotorcraft Transmission (ART) program, and the Compound Cycle Engine (CCE) program. The component research emphasizes special problems of turboshaft engines in the 5 lb/sec to 30 lb/sec range. The objectives of the STER program are to evaluate the application of advanced concepts to small turboshaft engine systems and to investigate system related phenomena, such as distortion effects and secondary flow phenomena. The goals of the ART program are to reduce transmission weight by 25 percent, noise generation by 10 dB and mean time between removal to 5,000 hrs. The CCE program is working to combine the airflow capacity and light-weight features of a gas turbine with the more efficient, but heavier diesel turbine.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Vertiflite (ISSN 0042-4455); 34; 24-31
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Rotorcraft transmissions (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Highlighted here is that portion of the Lewis Research Center's helicopter propulsion systems program that deals with drive train technology and the related mechanical components. The major goals of the program are to increase life, reliability, and maintainability, to reduce weight, noise, and vibration, and to maintain the relatively high mechanical efficiency of the gear train. The current activity emphasizes noise reduction technology and analytical code development, followed by experimental verification. Selected significant advances in technology for transmissions are reviewed, including advanced configurations and new analytical tools. Finally, the plan for transmission research in the future is presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Aeropropulsion 1987; p 303-313
    Format: application/pdf
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  • 4
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    Results of NASA/Army transmission research (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Since 1970 the NASA Lewis Research Center and the U.S. Army Aviation Systems Command have shared an interest in advancing the technology for helicopter propulsion systems. In particular, that portion of the program that applies to the drive train and its various mechanical components are outlined. The major goals of the program were (and continue to be) to increase the life, reliability, and maintainability, reduce the weight, noise, and vibration, and maintain the relatively high mechanical efficiency of the gear train. Major historical milestones are reviewed, significant advances in technology for bearings, gears, and transmissions are discussed, and the outlook for the future is presented. The reference list is comprehensive.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA, Washington, NASA(Army Rotorcraft Technology. Volume 2: Materials and Structures, Propulsion and Drive Systems, Flight Dynamics and Control, and Acoustics; p 769-801
    Format: application/pdf
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  • 5
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    Rotorcraft transmission (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The NASA Lewis Research Center and the U.S. Army Aviation Systems Command share an interest in advancing the technology for helicopter propulsion systems. In particular, this presentation outlines that portion of the program that applies to the drive train and its various mechanical components. The major goals of the program are to increase the life, reliability, and maintainability; reduce the weight, noise, and vibration; and maintain the relatively high mechanical efficiency of the gear train. The current activity emphasizes noise reduction technology and analytical code development followed by experimental verification. Selected significant advances in technology for transmissions are reviewed, including advanced configurations and new analytical tools. Finally, the plan for transmission research in the future is presented.
    Keywords: MECHANICAL ENGINEERING
    Type: Aeropropulsion '87. Session 5: Subsonic Propulsion Technology; 9 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Vibration characteristics of OH-58A helicopter main rotor transmission (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration occurred at the spiral bevel meshing frequency. Transmission speed and vibration measurement location had a significant effect on measured vibration; transmission torque and measurement direction had a small effect.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2705 , E-3368 , NAS 1.60:2705 , AVSCOM-TR-86-C-42 , AD-A180364
    Format: application/pdf
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  • 7
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    Identification and proposed control of helicopter transmission noise at the source (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Helicopter cabin interiors require noise treatment which is expensive and adds weight. The gears inside the main power transmission are major sources of cabin noise. Work conducted by the NASA Lewis Research Center in measuring cabin interior noise and in relating the noise spectrum to the gear vibration of the Army OH-58 helicopter is described. Flight test data indicate that the planetary gear train is a major source of cabin noise and that other low frequency sources are present that could dominate the cabin noise. Companion vibration measurements were made in a transmission test stand, revealing that the single largest contributor to the transmission vibration was the spiral bevel gear mesh. The current understanding of the nature and causes of gear and transmission noise is discussed. It is believed that the kinematical errors of the gear mesh have a strong influence on that noise. The completed NASA/Army sponsored research that applies to transmission noise reduction is summarized. The continuing research program is also reviewed.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-89312 , NAS 1.15:89312 , USAAVCOM-TR-87-C-2 , AD-A219535
    Format: application/pdf
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  • 8
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    Helicopter transmission testing at NASA Lewis Research Center (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The helicopter has evolved into a highly valuable air mobile vehicle for both military and civilian needs. The helicopter transmission requires advanced studies to develop a technology base for future rotorcraft advances. A joint helicopter transmission research program between the NASA Lewis Research Center and the U.S. Army Aviation Systems Command has existed since 1970. Program goals are to reduce weight and noise and to increase life and reliability. The current experimental activities at Lewis consist of full-scale helicopter transmission testing, a base effort in gearing technology, and a future effort in noise reduction technology. The experimental facilities at Lewis for helicopter transmission testing are described. A description of each of the rigs is presented along with some significant results and near-term plans.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-89912 , E-3603 , NAS 1.15:89912 , AVSCOM-TR-87-C-10
    Format: application/pdf
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  • 9
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    Helicopter transmission research at NASA Lewis Research Center (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A joint helicopter transmission research program between NASA Lewis Research Center and the U.S. Army Aviation Systems Command has existed since 1970. Program goals are to reduce weight and noise and to increase life and reliability. Reviewed are significant advances in technology for gears and transmissions and the experimental facilities at NASA Lewis for helicopter transmission testing are described. A description of each of the rigs is presented along with some significant results from the experiments.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-100962 , E-4181 , AVSCOM-TM-88-C-003 , NAS 1.15:100962 , AD-A242220
    Format: application/pdf
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  • 10
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    Advanced transmission studies (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The NASA Lewis Research Center and the U.S. Army Aviation Systems Command share an interest in advancing the technology for helicopter propulsion systems. In particular, this paper presents highlights from that portion of the program in drive train technology and the related mechanical components. The major goals of the program are to increase the life, reliability, and maintainability; reduce the weight, noise, and vibration; and maintain the relatively high mechanical efficiency of the gear train. The current activity emphasizes noise reduction technology and analytical code development followed by experimental verification. Selected significant advances in technology for transmissions are reviewed, including advanced configurations and new analytical tools. Finally, the plan for future transmission research is presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-100867 , E-4089 , NAS 1.15:100867 , AVSCOM-TR-88-C-002 , AD-A197797
    Format: application/pdf
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