EVALUATION OF LAMINATED ELASTOMERIC BEARINGS IN THE UH-1 HELICOPTER TAIL ROTOR
BELL HELICOPTER TEXTRON INC FORT WORTH TX
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Phase I of the program involved fabrication and bench testing of the bonded-type elastomeric bearings. Bench tests showed that two thrust bearings of this type would be required per grip to carry the blade centrifugal force. An experimental tail rotor assembly utilizing the radial and thrust bearings was designed and fabricated. Whirl and shake tests were conducted to determine rotor natural frequencies, dynamic spring rates, and bearing durability. Phase II of the program consisted of flight testing of the bonded-thin-layer-type bearing tail rotor. During the latter part of the program, molded-type elastomeric thrust and radial bearings were designed and fabricated. Results from both configurations compared favorably with standard UH-1 tail rotor data except for higher Sta. 21.6 blade oscillatory loads. The higher oscillatory loads, which would limit the allowable blade useful life, were attributed to tail rotor natural frequencies occurring near the helicopter operating three- per-rev. resonance. The second configuration is more attractive from a hardware, assembly, and flight operation characteristics standpoint. The molded-type elastomeric bearings were found to be marginally satisfactory for this application.
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