0069 00TM 1-6625-724-13&P0069 00-26TASK 7 - VIBRATION ABSORBER TUNINGThe following procedures provide instructions for the testing and tuning of the vibration absorbers of the UH-60helicopters using the Aviation Vibration Analyzer (AVA) equipment. This procedure can be accomplished inconjunction with the Main Rotor Diagnostics.Forward cabin and nose absorber will be tuned whenever any forward cabin or nose absorber maintenance hasbeen performed.Forward cabin and nose absorber tuning will be checked when a test flight reveals that 4/REV vertical vibrationin cockpit exceeds limits, or if vibration causes pilot or copilot discomfort.PROCEDURE 1: PREPARATIONa.Install test equipment as per task 1 procedures 1, 2, and 4 steps f-h.PROCEDURE 2: ACCELEROMETER INSTALLATION (FWD CABIN)a. Lower cabin soundproofing to gain access to the forward cabin vibration absorber (TM 1-1520-237-23-series).b. Attach accelerometer (28110900) to mounting plate (29317300), see figure 16. Add washers (MS15795-810)as necessary between accelerometer and mounting plate to prevent the accelerometer stud from extendingbeyond the plate.Figure 16. Pilot Heel/Cabin Vertical Accelerometer Mounting Plate (P/N 29317300)CAUTIONTo prevent damaging the overhead frames, theportion of the C-clamp that actually touches theairframe should be padded.c. Clamp plate horizontally to the overhead frame at station 308, buttline 0, just forward of the absorber locationusing C-Clamp (NSN 5120-00-180-0905). See figure 17.d. Connect accelerometer cable (29105600) to the accelerometer and to DAU receptacle marked ACC4.
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