g. If Nose/Cabin absorbers are within limits remove AVA test equipment and return the aircraft to a flight-ready
PROCEDURE 4: TUNE FORWARD CABIN ABSORBER (Cantilever Spring Type)
Refer to procedures in TM 1-1520-237-MTF (Vibration
Absorber Check and Tuning) when performing forward
cabin absorber tuning.
a. If cabin absorber is a Box Frame type absorber go to procedure 5.
b. Turn on DAU.
c. Turn on CADU.
d. Press QUIT on the CADU until all selections are undefined.
e. Use cursor keys to highlight Aircraft Type, and then press DO.
Use cursor keys to highlight UH-60, and then press DO.
g. Tail Number is highlighted. Press DO.
h. Use cursor keys to highlight a tail number or enter a new tail number (up to seven characters), then press DO.
Flight Plan is highlighted. Press DO.
Use cursor keys to highlight ABTUNE. Press DO.
k. Enter the Measure mode by pressing F1. Verify that Test State NR96 is highlighted.
The aircraft may be flown in Engine Control Unit (ECU)
LOCKOUT only when ECU LOCKOUT procedures in TM
1-1520-237-MTF are followed.
Press DOES when the aircraft is stable at the highlighted selection. Verify that the aircraft is at the required
Test State and press DO again. The AVA will acquire vibration data and return to the selection menu.
m. After the measurement is completed, the ABTUNE Test States display indicates the measured Test State as
"done" and the next Test State (Nr) is highlighted.
n. Repeat steps m and n for the remaining Test States. For the Test States above 100% Nr (101% Nr, 102% Nr
and 103% Nr) the aircraft must be operated in ECU or DEC lockout.
o. After all measurements are completed press DO on Finish, then press DO on Diagnostics. If the absorber is
tuned correctly (tuned to 100%), press QUIT to return to the Main Menu.
p. If the absorber needs tuning, a weight adjustment will be displayed. Perform the recommended weight
adjustment action according to TM 1-1520-237-23-2 (Chapter 2, Airframe Maintenance AVUM), and repeat
q. When the cabin absorber is tuned correctly (tuned to 100%), perform the FLIGHT plan (task 4) to check
cockpit main rotor 4/REV vibration and nose absorber tuning.
r. Make appropriate logbook entry when all main rotor 4/REV work is done.
s. Remove AVA test equipment and return aircraft to a flight-ready condition.
PROCEDURE 5: IN-FLIGHT CHECK OF ABSORBERS (Box Type)
This flight plan does not have a diagnostic routine in the
AVA. Once all data has been measured, perform the