(17)
Fault Detection and Annunciation (Fig. 20)
________________________________
(a)
Two types of failures will cause the engage relays to de-energize: a second failure in the electronic systems that affects both RRCMs or a failure in the "single thread" portion of the system. The "single thread" components are the electrohydraulic servo valve, the ratio changer actuator, the ratio changer mechanism, and the LVDT. Removal of one RRCM will activate an interlock which causes the amber RUDDER RATIO light to come on.
(b)
Ratio changer modules continuously monitor system status through open load, difference and hardover monitors, and the presence of a Vp VALID signal. Detection of failure in any monitor shifts control to the standby module. This is a single RRCM failure.
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27-21-00
ALL ú ú 02 Page 34 ú Sep 20/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
SEE A
ENTRYEMER
CARGOACCESS
DOORS
DOORS DOORS DOORS a
a
a a
L CSEU
MAINT PAGE
OPEN LOAD MON
CAPTF O
L AOA
R AOA EICAS P-2
PITOT a
PITOT a
a
a
DIFFERENCE MON
L AUX
R AUXTAT
PITOT a
PITOT a
a
FAULT
DETECTION
HARD OVER MON FAULT BALLS
STAB
MACH
AUTO
BY ANYSPOILERS
MONITOR
TRIM
SPD TRIM
SPDBRK a
a
a a
UNSCHED
RUDDER
L RATIO CHANGER MODULESTAB TRIM
SIGNAL VALIDITY (E2-1) RATIO
a
MONITOR
a
P5 OVERHEAD
FAULT BALLS
HYD PRESS MON
A SEE B
TAT + 12c+10c
D-TO
1.63 1.63
R RATIO CHANGER MODULE REV
1.81.281.80.92
RUDDER RATIO
M528 L RATIO CHANGER(E1-1)
1.4
1.4
1.0 1.0 EPR
MODULE (E4-1)
TAI
54.2 21.3
109.7
N 1
RUDDER RATIOCONTROL SHAFT
HOT
AMBER WRN LIGHT
528 825
826
FLIGHT COMPARTMENT
TO STANDBY MODULE
EGT
P-5 OVERHEAD PANEL"IN TEST"LIGHT
RUDDER RATIO
RUDDER RATIOADVISORY LEVELMODULEFAULTBALLS INTERNALS EICAS P-2SAME AS
MODULE
M528
TEST
RESET
FAULT
DETECTION
SWITCH
EICAS DISPLAY - PILOTS
R CSEU
BY ANY
MAIN PANEL
MAINT PAGE
MONITOR SEE C
B
EICAS P-2 P-32
SOLENOID DE-ENERGIZED
ACTUATOR TO LOW SPEED
L HYD PRESS CUTOFF
M529 R RATIO CHANGERMODULE (E3-1) FWD P-36
RATIO CHANGER
MODULE (TYP)
C
MAIN EQUIPMENT CENTER
Fault Detection and Annunciation
Figure 20
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ALL ú ú 04 Page 35 ú Jan 28/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
(c)
Detection of a single RRCM failure provides a signal input to the EICAS computers. The EICAS computers store a white RUDDER RATIO message for ground access only. A suitable fault ball will set on the RRCM.
(d)
Detection of a dual RRCM failure will de-energize the engage relay. The ratio changer actuator solenoid valve closes, allowing the actuator to retract to the low-speed position. Hydraulic pressure to the middle PCA is cut off.
(e)
Dual module failure causes an amber RUDDER RATIO alert message (level C) on EICAS. The amber RUDDER RATIO light on overhead panel P5 comes on and suitable fault balls set on the RRCM.
(18)
RRCM Maintenance Fault Balls
____________________________
(a)
Each RRCM contains four fault balls and a fault ball reset button. The faultball display is non-volatile and can be reset only at the module.
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