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747-400
MAINTENANCE MANUAL

 SIGNAL SSM CONDITION STATUS ................................................................................. FROM ACD
________
 Calculated  NCD  Calculated airspeed less than  VALID
 Airspeed  40 kts and on ground.  DATA
 NORMAL  Offside calculated airspeed greater  INVALID
 than 40 kts and onside calculated  DATA
 airspeed is less than 40 kts.
 True Airspeed  NCD  True airspeed is less than  VALID
 105 kts.  DATA
 Mach  NCD  Mach is less than .11 and  VALID
 on ground.  DATA
 Impact  NCD  Computed airspeed is less than  VALID
 Pressure  40 kts and on the ground.  DATA
 Indicated angle  NCD  Computed airspeed is less than  VALID
 of Approach  75 kts and on the ground.  DATA
 FROM MCP________
 Mach selected  NORMAL  The mach toggle signal set.  VALID
 Speed selected  NCD  Mach toggle signal set.  DATA
 Mach selected  NCD  Mach toggle signal clear.  VALID
 Speed selected  NORMAL  Mach toggle signal clear.  DATA
 FROM IRU________
 Track angle  NCD  Ground speed less than 40 kts  VALID
 and on ground.  DATA

 (4)  The fail/warn faults shall be monitored for each LRU. If a F/W fault has occured, then that LRU will be considered failed.
 D. BITE (Built In Test Equipment)
 (1)  
The BITE will continuously monitor the FMC for internal faults. Some of these tests may fail for external faults. As a result, faults which may be externally caused are transmitted to the CMC. The faults will be recorded into non-volatile CMC memory.

 (2)  
These faults can be retreived from memory for maintenance purposes. This memory can be accessed by selecting the CMC prompt on the MENU page of the CDU. By selection of the CMC prompt, the CDU will display the CMC MENU page enabling access to all recorded fault messages. The FMC will be divided into two major groups:

 (a)  FMS BITE - Failures which are not unique to the thrust management function of the FMC.
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 (b)  ATS BITE - Faults detected in the TMS function of the FMC.
 (3)  
FMC BITE consists of 6 tests, these are:

 (a)  
Power Supply Test - Tests of the FMC internal power supply.

 (b)  
Navigation Data Base Configuration Test - Tests for identical navigation data base loaded into both FMCs when airborne.

 (c)  
Software Configuration Test - Test that compatible operational software is loaded in both FMCs.

 (d)  
Program Pin Test - Test to insure program pins are configured correctly for the stored performance data base and identically configured non-switchable pins on both FMCs.

 (e)  
Receiver Tests - Tests all the ARINC 429 receivers during normal operation.

 (f)  
Transmitter Tests - Tests all the ARINC 429 transmitters excluding the data base loader transmitter.

 (4)  
ATS BITE consists of 14 tests which are ORed together and transmitted to the CMC. These tests can be grouped as follows:

 (a)  
Autothrottle system failure

 (b)  
Servo failure

 (c)  
Autothrottle power failure

 (d)  
Autothrottle latch

 E.  Failure response
 (1)  
Failures which may result in degraded or unpredictable operations of the FMC will result in automatic shutdown of the FMC. If the failure only affects the thrust management portion of the FMC, the remaining functions will not be inhibited.

 (2)  
If asynchronus activity occurs between the two FMC and resynchronization cannot be achieved, then the slave FMC will latch or shutdown.

 11. FMC Messages____________
　
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