PROCEDURE 3: OPTICAL RPM SENSOR INSTALLATION
a. Remove the two screws from the center of the 90-degree tail rotor gearbox fairing on the side of the tail rotor.
Ensure arrow on optical RPM sensor mounting bracket
is pointing aft.
b. Mount optical RPM sensor mounting bracket (29198700) over the holes on the tail rotor gearbox fairing, figure
10, with arrow on bracket body pointing aft. Secure the bracket with screws long enough to pass through the
mating fasteners and extend a minimum of two threads.
c. Mount optical RPM sensor (29314700) to the bracket, figure 10, and secure with a jam nut.
d. Route the optical RPM sensor cable the same as the accelerometer cable (procedure 2).
e. Connect the optical RPM sensor cable to the DAU receptacle marked TACHO 2.
If there is any tape remaining from previous balance
routines, it must be completely removed to ensure a
clear and accurate tachometer signal to the DAU.
f. Place a single, 3-inch strip of reflective tape on the inside of one of the tail rotor blades parallel to the spanwise
axis of the tail rotor blade at the approximate location as the beam of the optical interrupter, see figure 10. This
becomes the target (TGT) blade.
g. Proper alignment of the tape can be verified by applying AC power to the DAU and rotating the tail rotor until the
taped blade passes in front of the optical RPM sensor. A red LED on the back of the sensor will light if the
sensor picks up a return from the reflective tape.
PROCEDURE 4: PERFORM TAIL MEASUREMENT
a. Operate aircraft at 100% Nr, flat pitch.
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, then press DO.
f. Use cursor keys to highlight aircraft type based on table 2, then press DO.
g. Tail Number is highlighted. Press DO.
h. Use cursor keys to highlight a tail number or enter a new one (up to seven digits), then press DO.
i. Flight Plan is highlighted. Press DO.
j. Use cursor keys to highlight Tail. Press DO.
k. Enter the Measure mode by pressing F1. Verify that Test State FPGTL is highlighted.
I. Press DO when the aircraft is stable at the highlighted selection. Re-verify that the aircraft is at the required
Test State and press DO again. The AVA will acquire balance data and return to the selections menu.
m. After the measurement is completed, press DO on Finish, then press DO on Diagnostics. If measurements are
within specified limits, press QUIT to Main Menu and go to step r.
n. If measured values exceed specifications, press DO to calculate a solution. Evaluate the improvements
obtainable through recommended corrections. Perform all corrections as shown, ensuring that you display all
screens of a multiple screen solution.
o. Do not use a partial set of adjustments. If changes to the recommended corrections are desired, use the Edit
Adjustables and Edit Defaults options. The AVA will calculate a new set of corrections, use view predictions to
compare the new set of adjustments to the default solution to ensure the vibration is being reduced. Use all of
the new corrections.
p. After corrections are installed, repeat task 5, procedure 4 to re-check the vibration.
q. After more than one measurement has been taken, trend flights to verify if the tail vibration is being reduced.
r. Remove test equipment and make appropriate log entries.