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MAINTENANCE MANUAL
2) The MCDP displays NO PRE FLT FAULTS message when there are no previous flight faults within the 02 to 99 flight segments. When all the previous flight faults have been displayed, the MCDP displays ALL PRE FLT FAULTS DSPLY. While the MCDP can store faults for up to 99 flight segments, it can only store the last 10 fault flights (flights with recorded faults).
(9) Flight Fault Control Logic (Fig. 10)
(a) The store data bit (word 1, bit 27 of the fault data block format) must be set to logic one before the MCDP stores fault data in non-volatile memory. The store data bit is set when: the inflight flag set to logic zero, the IRU is not in functional test mode, at least one air/ground relay indicating an on ground condition, and an IRU is indicating a ground speed of less than 40 knots.
TEST ENGAGE FLAG SERVO ENGAGE FLAG
GROUND TEST REQUEST
IRS GND SPD >100 KTS AIR/GND (R) LOGIC AIR/GND (L) LOGIC 1 1
IRS IN FUNCTIONAL TEST
IRS GND SPD <40 KTS
GROUND TEST INHIBIT/SERVO
ENGAGED (WORD 1 BIT 26)
TEST REQUEST WRAP AROUND (WORD 1 BIT 29)
GROUND TEST INHIBIT/IN AIR (WORD 1 BIT 25)
IN FLIGHT FLAG GROUND FAULT DATA SET
(WORD 1 BIT 28)
STORE DATA BIT
(WORD 1 BIT 27)
LOGIC 0 IN AIR INTERNAL LOGIC, NOT RECD FROM LRU'S
Flight Fault Control Logic
Figure 10
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(b) A test request wrap-around bit is used to check the interfaces between the MCDP and FCC, FMC, and TMC. To set the test request wrap-around bit to logic one (word 1, bit 29 of the fault data block format), the following conditions must be present: autopilot servos not engaged; ground test request analog discrete signals is received by the FCC, FMC, or TMC--the store data bit is set to logic zero; and the inflight flag set is to logic zero. An interface fault is a fault that disables the interconnecting bus of two or more units.
(10) Flight Deck Effect Message Priorities (Fig. 11)
PRIORITY FCC TMC FMC
0 SPARE SPARE SPARE
1 A/P DISC A/T DISC FMC FAIL LT
2 A/P CTN SPARE FMC CTN LT
3 NO LAND 3 TMC DSPLY CDU DSPLY
4 NO A/L SPARE SPARE
5 F/D BAR SPARE
6 SPARE
7
F/S DSPLY
Flight Deck Effect Message Priorities
Figure 11
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(a) The flight deck effect messages have a priority code from one to five for each FCC, FMC, and TMC. Priority code one has the highest priority. The computers also have a priority order. The FCC has the highest priority; the FMC the lowest. The autopilot disconnect (A/P DISC) for an FCC has the highest priority and the flight director bar (F/D BAR) the lowest. Flight faults are listed in order of priority (highest to lowest). The FCC flight faults and flight deck effects are listed first, the TMC second, and FMC last.
(11) Ground Test Mode (Fig. 12)
(a)
The ground test mode augments the flight fault capability by providing tests to further isolate and verify flight faults. The ground test mode also verifies system operation after maintenance. The three ground test groups (LRU tests, system tests, and support tests) complete tests in the Autopilot/Flight Director System (AFDS) and Thrust Management System (TMS). The LRU tests provide tests of individual LRU's and require operator interaction. The system tests are used to test large sections of the AFDS and TMS at one time. The Autoland System test is both automatic and manual. The Current Fault Report System test is completely automatic. The support tests are used to test only functions that interface with the AFDS and TMS. For Ground tests selected that are not for the airplanes configuration, XX NO TEST THIS A/C CONFIG (XX = Test Number) is displayed.
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