TASK 7 - VIBRATION ABSORBER TUNING
The following procedures provide instructions for the testing and tuning of the vibration absorbers of the UH-60
helicopters using the Aviation Vibration Analyzer (AVA) equipment. This procedure can be accomplished in
conjunction with the Main Rotor Diagnostics.
Forward cabin and nose absorber will be tuned whenever any forward cabin or nose absorber maintenance has
Forward cabin and nose absorber tuning will be checked when a test flight reveals that 4/REV vertical vibration
in cockpit exceeds limits, or if vibration causes pilot or copilot discomfort.
PROCEDURE 1: PREPARATION
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 extending
beyond the plate.
Figure 16. Pilot Heel/Cabin Vertical Accelerometer Mounting Plate (P/N 29317300)
To prevent damaging the overhead frames, the
portion of the C-clamp that actually touches the
airframe should be padded.
c. Clamp plate horizontally to the overhead frame at station 308, buttline 0, just forward of the absorber location
using C-Clamp (NSN 5120-00-180-0905). See figure 17.
d. Connect accelerometer cable (29105600) to the accelerometer and to DAU receptacle marked ACC4.