TM 1-1520-238-T-4
Change 9
5–65
5–24.
ISOLATING/MONITORING OTHER VIBRATIONS USING AVA EQUIPMENT (cont)
5–24
b. Install accelerometer.
NOTE
For the AH64 program data can be acquired from six accelerometers for the
PROBES measurement (ACC 1, ACC 2, ACC 3, ACC 4, VIBLAT, and VIBVRT).
VIBLAT and VIBVRT are hard wired and come through the SPU on channels five
and six. The AH64NB program can acquire data from four accelerometers (ACC
1 – ACC 4). The FFT program can only measure from ACC 1, but has multiple
frequency ranges.
(1) Install accelerometer anywhere on airframe where an irregular or unusual vibration is detected.
(2) Connect accelerometer cable from accelerometer to DAU receptacle labeled ACC 1, ACC 2, ACC 3,
and /or ACC 4, or if FFT is used only ACC 1 is available.
(3) If the SPU is being utilized for the AH64 program and the MULTI–CH cable is connected, then
accelerometers are already installed for measuring lateral and vertical vibration. These will appear as
VIBLAT and VIBVRT on the measurement screen.
c. Perform probes or FFT measurements.
(1) Operate aircraft at desired flight condition. This should be RPM or airspeed at which the vibration is
strongest.
(2) Turn DAU ON.
(3) Turn CADU ON.
(4) Press QUIT on the CADU until all selections are undefined.
(5) Use cursor keys to highlight Aircraft Type, then press DO.
(6) Use cursor keys to highlight AH64, AH64NB if the SPU has been bypassed, or FFT if a specific
range is required, then press DO.
(7) Tail Number is highlighted. Press DO.
(8) Use cursor keys to highlight a tail number or enter a new tail number (up to seven digits), then press
DO.
(9) Flight Plan is highlighted. Press DO.
(10) Use cursor keys to highlight PROBES, or if FFT is utilized select appropriate range. Press DO.
(11) Enter MEASURE mode by pressing F1. Verify the following test states are displayed:
AH64
AH64NB
FFT
ACC 1
ACC 1
Different ranges depending on
which test plan is selected
ACC 2
ACC 2
ACC 3
ACC 3
ACC 4
ACC 4
VIBLAT
VIBVRT
