TM 1-6625-724-13&P0071 000071 00-29TASK 4 – BALANCE TAIL ROTOR NOTETail rotor balance will be accomplished before any inflight checks are performed. The tail rotor balanceprocedure can be performed during a ground run. If thetail rotor is wired, take the measurements during thesame ground runs used for main rotor ground track andbalance.Tail Rotor Balance LimitThe tail rotor vibration limit displayed by the AVA is 0.15 ips. Tail rotor balance below 0.1 ips should be readilyachievable, and is encouraged.PROCEDURE 1: EQUIPMENT INSTALLATIONa. Remove AVA tail rotor balancing equipment from transport case. Check for possible damaged equipment andfrayed 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 usingcanvas straps and D-rings.d. Locate CADU in aircraft. Connect CADU to DAU cable (29325601) to CADU and to DAU receptacle markedCADU.PROCEDURE 2: OPTICAL RPM SENSOR INSTALLATIONa. 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 minimumof 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 tothe DAU. Ensure cables are not pinched in CPG’s door.e. Connect the optical rpm sensor cable to the DAU receptacle marked TACHO 2.NOTEIf there is any tape remaining from previous balanceroutines, this must be completely removed to ensure aclean and accurate tachometer signal to the DAU.Never apply new tape on top of existing tape. See figure13.f. Place a single, 8-inch strip of reflective tape on either outboard blade, figure 13, item 2, aligning the tape in linewith 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 busand ensure that DAU has power. With optical tachometer sensor in place rotate tail rotor so that blade withreflective tape is in front of the optical sensor. With tape in front of sensor. The red LED on back of sensorshould 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 ensuremaximum reflectivity as oils from your fingers can reduce reflection.
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