[PDF] Aircraft Propeller Vibration Measurement System eBook

Author : Richard C. Dorshimer
Publisher :
Page : 138 pages
File Size : 33,27 MB
Release : 1969
Category :
ISBN :

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A slip ringless propeller-mounted data system was designed, fabricated and tested for the measurement of propeller blade strain during flight and ground operation of an instrumented aircraft. This data system is self-powered through the rotary motion of the test propeller, employs a 16 channel constant bandwidth Frequency Modulated (FM) Multiplex and signals are capacitively coupled from the propeller to the aircraft. The FM Multiplex consists of 17 channels of information including propeller rpm and 16 strain gage channels containing information from dc to 1 kHz. An environmentally protected strain gage installation was also a consideration of this program. The FM Multiplex is split into four groups of signals with a frequency translation process in order to conserve bandwidth and/or recording time on an airborne tape recorder. Seven additional data channels are provided on board the aircraft for inclusion of parameters needed to define the aircraft operating conditions. The data system was demonstrated for a period of 50 hours on an engine test stand during which the demodulated signals were observed and additional data were obtained relative to the system stability. (Author).

Author : S. J. Miley
Publisher :
Page : 192 pages
File Size : 44,75 MB
Release : 1985
Category : Airframes
ISBN :

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A literature survey was performed to identify and review technical material applicable to the problem area of propeller propulsion system integration. The survey covered only aerodynamic interference aspects of the problem, and was restricted primarily to propeller effects on the airframe. The subject of airframe aerodynamic interference on the propeller was limited to the problem of vibration due to nonuniform inflow. The problem of airframe effects on propeller performance was not included. A total of 1121 references are given. The references are grouped into the subject areas of Aircraft Stability, Propulsive Efficiency, Aerodynamic Interference, Aerodynamic Interference-Propeller Vibration, and Miscellaneous.

Author :
Publisher :
Page : 37 pages
File Size : 15,65 MB
Release : 2007
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The dynamic characteristics and human perception of higher frequency multi-axis vibration associated with a military propeller aircraft environment were investigated. Triaxial accelerations were measured at the interfaces between the occupant and aircraft seat surface (seat pan and seat back) to evaluate and compare the effects of the aircraft seat fitted with different cushions. While all cushions showed a significant reduction in the X-axis seat pan vibration as compared to the original operational seat cushion at the blade passage frequency (BPF~73.5 Hz), the associated accelerations remained significantly higher than the floor input accelerations. Transmissibility data confirmed these seat system characteristics at higher frequencies. A body region perception survey suggested that the subjects were most sensitive to the BPF component of the operational exposure in contrast to the results for the weighted acceleration levels (ISO 2631-1: 1997). Effective multi-axis vibration mitigation strategies depend on the relationships between the location, direction, magnitude, and frequency of vibration entering the occupant and human perception of the exposure. Current human exposure guidelines may not optimally reflect these relationships for assessing higher frequency propeller aircraft work environments.

Author : Fritz Liebers
Publisher :
Page : 44 pages
File Size : 15,80 MB
Release : 1932
Category : Propellers, Aerial
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On the basis of the consideration of various possible kinds of propeller vibrations, the resonance vibrations caused by unequal impacts of the propeller blades appear to be the most important. Their theoretical investigation is made by separate analysis of torsional and bending vibrations. This method is justified by the very great difference in the two natural frequencies of aircraft propeller blades. The calculated data are illustrated by practical examples. Thereby the observed vibration phenomenon in the given examples is explained by a bending resonance, for which the bending frequency of the propeller is equal to twice the revolution speed.