(a)
The sensor target test is used to indicate sensor target near or far status. It is activated by selecting the desired sensor number using the SENSOR CHANNEL SELECT switches and then pressing the TARGET TEST switch. Target status is shown by TARGET NEAR/TARGET FAR indicators. If a fault is detected during this test, the type of fault is shown by the SENSOR or CARD indicator. No target position indication will occur if a failed sensor is detected.
(14)
Non-volatile memory
(a)
The non-volatile memory, contained in BITE for in-flight failure data storage, can recall a minimum of 50 LRU failures. Failure data will store for 240 hours after electrical power has been removed from the PSEU.
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(15)
BITE system operation (Fig. 4)
(a)
The BITE interconnects all circuit cards, the display panel and all interfaces required for BITE function. A microcomputer in one of the BITE card provides programming and control for all BITE functions, data signal flow between cards, and self test.
(b)
When a sensor code has been selected and the TARGET TEST switch is pressed, the following is performed: 1) A check that the digits entered on the SENSOR CHANNEL
SELECT switches are valid. No test occurs if an incorrect entry exists.
2) A sensor status test to check for open/shorted sensor conditions.
3) An active BIT test conducted on the selected proximity channel to artificially simulate target near and far to verify output switching of the proximity card.
4) If no fault exists, the sensor code is displayed and after approximately 5 second delay, target near/far indication is displayed.
5) If a fault is detected, the appropriate fault code is displayed and the type of fault shown by the SENSOR or CARD indicator. No target near/far indication will be displayed.
(c) When the VERIFY switch is pressed, the BITE starts an on-ground system test which includes the following: 1) Provide BITE self test. 2) Determine target descrepancies by comparing groups of
sensors for reasonableness of position.
3) Check sensor and sensor wiring for open and short circuits.
4) Functionally test all logic and output driver circuits and
all sensor circuits for target near and target far modes.
5) Failed LRU will be shown on three-digit display by number, and by sensor, card, or target light illumination at end of test.
6) Start continuation of test whenever the VERIFY test switch is again pressed.
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7) Inhibit test when airplane is in air mode or the PRESS/TEST switch is pressed.
8) Provide flashing code CCC on the three-digit display while test is in progress.
9) Provide code 999 on the three-digit display for test completion.
(d)
The system compontnts are monitored by the BITE at all time. Any component malfunction in flight causes the PSEU to start an automatic in-flight test.
(e)
All five indicator lights on the BITE panel come on and the 3-digit display shows code 888 when the PRESS/TEST (panel lamp test) switch is pressed.
(f)
Memory contents may be recalled and displayed on the 3-digit display and the LRU identification lights by momentarily pressing the BIT switch on the BITE panel. Successive BIT switch pressing recalls the memory contents on a last in -first out basis.
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本文链接地址：757 AMM 飞机维护手册 起落架 CHAPTER 32 - LANDING GEAR 1(52)
