TM 1-6625-724-13&P0069 000069 00-23Figure 14. Optical RPM Sensor Mounting BracketPROCEDURE 3: OPTICAL RPM SENSOR INSTALLATIONa.Remove screws identified by figure 14 from the right side of the tail rotor.b.Remove outer jam nut on optical RPM sensor (29314700) and install on tail rotor bracket (29198700). Thebody of the optical RPM sensor should be resting against the bracket. Reinstall the outer jam nut but do nottighten.c.Mount bracket on tail using the panel screws. The optical RPM sensor and bracket will be slightly upside-down with the arrow on the bracket pointing aft and up when installed correctly.d.Hand-tighten jam nut on optical RPM sensor.e.Route optical RPM sensor cable along the tail pylon (same as the accelerometer cable, task 6, procedure 2e)and connect it 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 DAU.f.Place a 4-inch strip of reflective tape on the inside of the target (TGT) tail rotor blade, figure 15, at the sameapproximate location as the beam of the optical sensor.g.Turn on DAU.h.Turn on CADU.i. Apply 28 Vdc power to the DAU.j. Rotate the tail rotor until the target blade passes in front of the optical RPM sensor. A red LED on the back ofthe sensor will light if the sensor picks up a return from the reflective tape.TrailingEdge of TailForwardRemovescrews
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