(2)
When compressed, a piezoelectric crystal will exhibit a minute change in its electrical charge. This change in charge is proportional to the severity of vibration.
B. The signal conditioner receives two accelerometer signals from each engine along with the N1 and N2 tachometer signals from each engine.
(1)
Charge amplifiers within the signal conditioner convert the accelerometer signals to velocity signals (expressed in volts). The velocity signals are processed by a digital tracking filter whose center frequency is controlled by the tachometer signals.
(2)
The unit, located on the E1 shelf, provides two analog outputs for flight deck display.
(3)
It is desired to sense the amplitude of vibration of a frequency that matches the rotor speed. The filters "track" the rotor speed, and filter out any unmatched frequencies that may occur from outside sources.
(4)
The multiplexer samples each tracking filter. Software then normalizes the tracked value and transmits the highest normalized NOB or, on some airplanes, TRF sensor value for each engine to vibration indicator.
C. Continuous monitoring of the AVM system LRUs, including the signal conditioner itself, is maintained by the software in the AVM signal conditioner. All LRU and/or wiring faults are stored in a non-volatile memory.
(1)
AIRPLANES WITH A S360N021-100 OR -102 AVM; There is no LED display on the front panel of the AVM signal conditioner. The fault history and the flight history must be read with an ARINC 429 reader (AMM 77-31-00/201).
(2)
AIRPLANES WITH A S332T304 OR S360N021-201/-202 AVM; A 2-digit LED display on the front panel of the AVM signal conditioner will give the fault history and the flight history (AMM 77-31-00/201).
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
(3)
AIRPLANES WITH A S360N021-113, -114, OR -213 AVM; A 3 line, 8 character per line LED display on the front panel of the AVM signal conditioner will give the fault history and the flight history (AMM 77-31-00/201).
(4)
The signal from the AVM signal conditioner to the applicable vibration indicator will stop if one of these conditions occur:
(a)
The N1 signal or the N2 signal stops.
(b)
The two accelerometer signals stop.
(c)
High noise on the two accelerometer signals.
(d)
One accelerometer signal stops and there is high noise on other accelerometer signal for that engine.
(5)
AIRPLANES WITHOUT THE ENGINE INSTRUMENT SYSTEM (EIS); If the AVM signal for the applicable vibration indicator stops, the indicator pointer will read under zero.
(6)
AIRPLANES WITH THE ENGINE INSTRUMENT SYSTEM (EIS); If the AVM signal for the applicable vibration indicator stops, the indicator will go out of view.
(7)
To prevent false messages on startup or shutdown, a one minute delay occurs before checking for N1 or N2 loss faults.
(8)
AIRPLANES WITH A S332T304 AVM; The steps below are for the general interrogation of the AVM signal conditioner:
(a) A BITE/ERASE button on the front panel of the AVM signal conditioner permits the fault codes to be read from the storage memory. 1) A fault code will be shown when the BITE/ERASE button is
pushed.
2) This fault code will be shown until the BITE/ERASE button is pushed again.
3) The next fault code is shown and the old fault code will be erased from the storage memory.
4) The fault codes will be shown for the signal loss from the accelerometers, high noise from the accelerometers, and signal loss from the N1 and N2 speed sensors.
(b) A TEST button on the front panel of the AVM signal conditioner permits a self test of the AVM signal conditioner. Only the AVM signal conditioner is tested. The procedure to do a self test of the AVM signal conditioner is given in the adjustment/test (AMM 77-31-00/501). 1) The self test is also automatically done when electrical
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