(6)
AIRPLANES WITH THE -122 AND SUBSEQUENT YAW DAMPER MODULES; A module fault on the YDM causes a YDM fault message to be recorded.
(7)
AIRPLANES WITHOUT THE -122 AND SUBSEQUENT YAW DAMPER MODULES; A module fault on the YDM latches the YDM faultball. A module fault on the SAM latches the SAM faultball. If an amber light comes on, the applicable faultball(s) will latch for the specific malfunction. The EICAS display shows the YAW DAMPER advisory message to indicate a failure.
(8)
In addition to faultballs for fault indication, the RRC module contains a BITE test switch. By placing the switch from NORMAL to TEST, hydraulic power is applied to extend the RRC actuator in 15 seconds. The IN TEST light on the module comes on and stays on for 15 seconds. The TEST FAIL faultball latches if the test fails.
(9)
Power Supply Module (PSM)
(a)
All PSM outputs are continuously monitored. When 115v AC is applied and an output is out of tolerance, its monitor will set the fault on the PSM and enable the EICAS message L(R) FLT CONT ELEC.
(b)
In a CSEU shelf, removal of either PSM also activates the EICAS message L(R) FLT CONT ELEC and sets the MODULE fault on the installed PSM.
(c)
After power up, the PSM will continuously monitor its outputs for power failures.
(d)
For a +5v dc output power loss the internal monitor circuitry will shut down the module, set PSM "MODULE" fault, and enable L(R) FLT CONT ELEC message on EICAS.
(e)
For a |15v dc output power loss the internal monitor circuitry will set PSM "MODULE" fault, and enable L(R) FLT CONT ELEC message on EICAS.
(f)
For a 26v ac output power loss the internal monitor circuitry will transfer control to standby module, set PSM "MODULE" fault, and enable L(R) FLT CONT ELEC message on EICAS.
(g)
Pushing the reset button on the PSM front panel will reset the monitor circuits and the MODULE fault.
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27-09-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
(10)
Stabilizer Trim/Elevator Asymmetry Limit Module (SAM)
(a)
The SAMs continuous built-in test equipment (BITE) monitors enable it to detect abnormal conditions and set the applicable faultball, STAB TRIM message, and light indicator. These eleven faultballs are used to identify internal faults and interfacing line replaceable units (LRU) faults: 1) SAM
a) The SAM faultball is set when the SAMs arm, or when the control channels disagree, or when the internal control processing unit fails. The SAM faultball is reset by the RESET switch, and will remain reset if there are no faults.
b) When the SAM faultball is set, the other faultballs and fault annunciations are inhibited. c) A SAM fault inhibits these modes:
Autotrim Mach/Speed Trim Aileron Lockout Rudder Ratio Changer Elevator Asymmetry Limit
2) FCC
a) The FCC faultball is set by the SAMs FCC input monitors. The left SAM monitors inputs from left and center FCCs and the right SAM monitors inputs from right and center FCCs. FCC fault is cleared on the ground if valid FCC data is received. FCC faults are cleared in air if valid FCC data is received for two seconds.
3) ADC
a) The ADC faultball is set if the primary or secondary computed mach number or computed airspeed from the ADC's disagree. ADC fault is cleared on the ground if valid ADC data is received. In the air mode, valid ADC data received for at least 30 seconds will clear the ADC fault.
4) COL TRIM SW
a) The COL TRIM SW faultball is set when the input coincidence monitor detects a fault in the thumb switch inputs.
5) MAN LEVER SW
a) The MAN LEVER SW faultball is set when its input monitor detects a fault in the manual input controls on the center control stand for the alternate manual trim mode. If the control is closed, or the control is out of detent for longer than 30 seconds, and the hydraulic pressure is high on either system the MAN LEVER SW faultball will be set. This faultball can be cleared by the RESET switch.
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