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MAINTENANCE MANUAL
WHL SPEED
L IRS
INERTIAL REFERENCE SYSTEM R IRS
BRAKE SYSTEM CONTROL UNIT (M80)
S1887 ALT
SYS 4 PRESS SW BRK SOURCE
(STA 1371)PRESS SW (STA 1240)
R732 PRK BRK VALVE RLY (P415)
E9
ANTISKID SYSTEM INTERFACE (INPUTS)
Antiskid System Schematic
Figure 11 (Sheet 3)
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MAINTENANCE MANUAL
BRAKE SYSTEM CONTROL UNIT
THRU EIU'S
ANTISKID SYSTEM INTERFACE (OUTPUTS)
Antiskid System Schematic
Figure 11 (Sheet 4)
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MAINTENANCE MANUAL
ANTISKID OPERATION - NORMAL SYSTEM
Antiskid System Schematic
Figure 11 (Sheet 5)
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MAINTENANCE MANUAL
FWD
WHL
BRAKE
FWD
WHL
BRAKE
CONTROL B4 AFT WHL CIRCUITS 15 OR 16
ANTISKID OPERATION - ALTERNATE SYSTEM
Antiskid System Schematic
Figure 11 (Sheet 6)
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ANTISKID OPERATION - LOCKED WHEEL/HYDROPLANE/TOUCHDOWN
Antiskid System Schematic
Figure 11 (Sheet 7)
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2) When the parking brake valve is closed the antiskid valve hydraulic return lines are blocked, so the antiskid system cannot release brake pressure. ANTISKID OFF and BRAKE LIMITER advisory messages will come into view on EICAS when a parking brake disagree occurs for more than 2 seconds.
(f) Accumulator braking signal:
1) Accumulator brake operation - ground
Normal brake operation - open circuit
2) This signal is supplied by the alternate-brake-pressure switch (S1887) and the system-4-pressure switch (S1886) which are connected in series (Ref 32-41-00/001). This is an indication that hydraulic system 4, 1, and 2 are not pressurizing the brake system, and that the accumulator is the only source of brake pressure in the normal system. The accumulator braking signal (ground) removes the bias current from the antiskid valves. This prevents hydraulic fluid from being released into the return lines by valve response to bias current. The bias current is used by the BITE to monitor the antiskid valve for malfunctions.
(2)
Antiskid wheel control logic.
(a)
Antiskid transducer wheel speed inputs supply a signal which results in a reference velocity at wheel spinup. The reference velocity is compared to the actual wheel speed signals from the antiskid transducer. Sudden changes in wheel speed cause an increase in the difference between actual and reference velocity. This difference is an error signal which goes to the valve driver.
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