TMCS -FUNCTIONAL DESCRIPTION -A/T SERVO MOTOR
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777 AIRCRAFT MAINTENANCE MANUAL
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TMCS -TMCF FUNCTIONAL DESCRIPTION -BITE AND FAULT MONITORING
General
The TMCF has internal and external fault monitors. The TMCF records BITE faults into TMCF memory. It sends faults to the central maintenance computing function (CMCF) and causes fault messages to show on the EICAS display. BITE logic removes the A/T and thrust limit modes when TMCF BITE detects an internal or external failure.
Internal Fault Monitors
The TMCF does these checks:
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Compatibility
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Miscomparisons
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Active TMCF selection
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Cross cabinet synchronization checks.
The TMCF does these checks when the core processor module (CPM) and cabinet level BITE is valid, the back plane bus is valid, and the input/output (I/O) modules are valid.
The TMCF does these compatibility checks:
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Operational program software (OPS)/hardware
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Engine/airframe
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Operational program configuration (OPC)/OPS
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Engines/ratings
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Ratings/thrust limit data base (TLDB)
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Left and right engine ratings disagree.
EFFECTIVITY
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The TMCF stores BITE disagree data into BITE history. With a BITE disagree, the TMCF causes all outputs to go invalid and prevents thrust limit calculation (TLC) and autothrottle engage.
At power up, the TMCF does these cross-cabinet miscomparison checks:
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OPS
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Engine/airframe data bases
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OPC
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TLC database.
When a disagree occurs, the TMCF BITE stores each miscompare in BITE history and the TMCF operation shuts down.
AIMS Cross-Cabinet Synchronization
Continuous cross-cabinet synchronization occurs between the active and inactive TMCF. This ensures common modes of operation, A/T commands, and engine trim commands do not change when there is a master TMCF transfer.
External Fault Monitors
The TMCF also monitors these external interfaces for the autothrottle ASMs:
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Servo
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Power removal or no power
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Tachometer feedback, scheduled or zero
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TMCS -TMCF FUNCTIONAL DESCRIPTION -BITE AND FAULT MONITORING
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Servo rate within 2 degrees/second
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Stopper, detects inability to remove power from servo during takeoff less than 50 knots.
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TMCS -TMCF FUNCTIONAL DESCRIPTION -BITE AND FAULT MONITORING
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TMCS -SYSTEM TESTS
General
These are the servo loop system tests for the left and right TMCF:
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Left cabinet servo loop test
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Right cabinet servo loop test.
Servo Loop Test
The servo loop test makes sure that the TMCF in the left and right AIMS and the autothrottle servomotors (ASMs) operate correctly.
The thrust levers on the P10 control stand move during the test.
This test does a test of the ASM rate drive. It also does a test to find if the TMCF can remove power from the ASMs.
The test has four steps. The first step is the initial command. The initial command has a thrust lever angle (TLA) rate of -8 degrees/second for 7 seconds. It also moves the thrust levers aft to the mechanical stop. There is no pass/fail for this first step.
The second step is the throttle stopper test. This test makes sure the TMCF removes power from the ASMs and that the ASMs do not drive in the autothrottle HOLD mode.
The third step is the forward command. This test has a TLA rate of 8 degrees/second for 5 seconds. During the thrust lever movement, the average tach feedback must be between +6 and +10 degrees/second.
The fourth step is the reverse command. This test has a TLA rate of -8 degrees/second for 5 seconds. During the thrust lever movement, the average tach feedback must be between -6 and -10 degrees/second.
The TMCF provides pass/fail information for each servo loop test to show on the MAT.
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