Vibration and Elevator Loads Survey Tests of the UH-1M Helicopter with the Forward-Looking Infrared (FLIR) System Installed
Final rept. 9 Sep 1970-25 May 1971
ARMY AVIATION SYSTEMS TEST ACTIVITY EDWARDS AFB CA
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Main rotor vibration characteristics and elevator loads were determined both with and without the FLIR system installed. Nine parameters of vibration and six channels of elevator loads were evaluated to determine military specification compliance, and to provide mission suitability information for inclusion in technical manuals and other publications. The elevator loads and vibration characteristics were generally unaltered by the installation of the FLIR system, except for the vertical vibration magnitudes at a frequency of 4rev. The magnitude of the 1rev vertical vibration was irritating to the flight crew and exceeded the limit as specified in the military specification, MIL-H-8501A, when operating at or near the forward cg limit at low airspeed less than 65 knots calibrated airspeed. The 4rev vertical vibration levels exceeded the specification limit and were generally greater with the FLIR system installed. The amplitude of the 8rev vertical vibration was higher than the limit specified in paragraph 3.7.1b of MIL-H- 8501A during diving flight. Analysis of the elevator beam bending loads data without the FLIR system installed indicated that there was some increase when compared to contractor test results of the standard UH-1CM21 helicopter.
- Fluid Mechanics