TM 1-6625-724-13&P
0071 00
0071 00-29
TASK 4 – BALANCE TAIL ROTOR
NOTE
Tail rotor balance will be accomplished before any in
flight checks are performed. The tail rotor balance
procedure can be performed during a ground run. If the
tail rotor is wired, take the measurements during the
same ground runs used for main rotor ground track and
balance.
Tail Rotor Balance Limit
The tail rotor vibration limit displayed by the AVA is 0.15 ips. Tail rotor balance below 0.1 ips should be readily
achievable, and is encouraged.
PROCEDURE 1: EQUIPMENT INSTALLATION
a. Remove AVA tail rotor balancing equipment from transport case. Check for possible damaged equipment and
frayed cables.
b. Installed DAU in canvas carrying case.
c. Place DAU on the outboard side of the co-pilot's left armor plate with connectors facing up and secure DAU using
canvas straps and D-rings.
d. Locate CADU in aircraft. Connect CADU to DAU cable (29325601) to CADU and to DAU receptacle marked
CADU.
PROCEDURE 2: OPTICAL RPM SENSOR INSTALLATION
a. Remove the two airframe screws located on the bottom and in the center on the tail rotor gearbox airframe panel.
See figure 13, item 1.
b. Mount optical rpm sensor mounting bracket (29198700) on tail with arrow on the bracket facing aft. See figure 13,
item 3. Secure the bracket with screws long enough to pass through the mating fastener and extend a minimum
of two threads.
c. Mount the optical rpm sensor (29314700) to the bracket.
d. Connect the optical rpm sensor to the optical rpm sensor bracket and route the cable down the tail and forward to
the DAU. Ensure cables are not pinched in CPG’s door.
e. Connect the optical rpm sensor cable to the DAU receptacle marked TACHO 2.
NOTE
If there is any tape remaining from previous balance
routines, this must be completely removed to ensure a
clean and accurate tachometer signal to the DAU.
Never apply new tape on top of existing tape. See figure
13.
f.
Place a single, 8-inch strip of reflective tape on either outboard blade, figure 13, item 2, aligning the tape in line
with the optical sensor. (The tape should be placed spanwise along the center of the blade.)
1. Verify that the red LED on the back of the optical tachometer sensor is operating. Energize the aircraft’s bus
and ensure that DAU has power. With optical tachometer sensor in place rotate tail rotor so that blade with
reflective tape is in front of the optical sensor. With tape in front of sensor. The red LED on back of sensor
should be illuminated. A sensor with a pulsating LED indicates that the signal is strong.
2. After installation of the reflective tape, wipe the tape with alcohol, contact cleaner etc. This will ensure
maximum reflectivity as oils from your fingers can reduce reflection.
