AUTOBRAKES LIGHT
AUTO AUTOBRAKES
BRAKES 2 31
4 MAX DISARM
OFF AUTO
RTO AUTOBRAKE MODULE
IN L WHEEL WELL
AUTOBRAKE SELECTOR PANEL
ON PILOTS' CENTER INSTRUMENT
PANEL (P1-3) VIA TAT + 12C
EICAS 1.28 1.50 1.8 1.8 1.50 1.52
COMPUTERS 1.4 EPR 1.0 1.4 1.0
M102 ANTISKID/AUTOBRAKE CAUTION 10.50 10.50
CONTROL UNIT & WARNING N1
750 750
EGT
AUTOBRAKES
FWDTRANSDUCER EICAS DISPLAY UNITSIN AXLE (P2)
Autobrake System
Figure 2
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757 MAINTENANCE MANUAL
(d)
Thrust levers position (advanced or not advanced) signal (Ref 76-11-00)
(e)
Spoiler handle position (fully extended or not fully extended) signal (Ref 27-61-00)
E.
An antiskid/autobrake control unit provides all the monitoring and control, including arming, disarming and self test of the system. The unit consists of seven microprocessor-based subsystem circuit cards. Four identical cards are for antiskid control, each providing control for two wheels. One card is for autobrake control. One card is for antiskid and autobrake monitoring. One card is for Built-In Test Equipment (BITE).
F.
The antiskid/autobrake system consists of the following components (quantity shown in bracket):
(1)
Transducer (8)
(2)
Antiskid module, normal system (2)
(3)
Antiskid module, alternate system (2)
(4)
ANTISKID fault light on P5 (1)
(5)
Antiskid shuttle valve module (2)
(6)
Antiskid/autobrake control unit, M102 (1)
(7)
Autobrake selector switch on P1-3 (1)
(8)
Autobrake module (1)
(9)
Autobrake shuttle valve assembly (2)
(10)
AUTOBRAKES light on P1-3 (1)
2. Component Details
_________________
A. Antiskid/Autobrake Crew Control Panels and Annunciators (Fig. 1, Fig. 2)
_______________________________________________________
(1)
ANTISKID fault light (Fig. 1)
(a)
An amber ANTISKID fault light on panel P5 illuminates to signal antiskid system fault when any of the following faults exists. At the same time the ANTISKID advisory message appears on the EICAS display. 1) 28 volt/5 volt antiskid control unit power supply out of
tolerance 2) Antiskid transducer wiring open or short 3) Antiskid module (normal or alternate) valve wiring open or
short, or valve driver failure
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(2)
(3)
(4)
757 MAINTENANCE MANUAL
4) Antiskid control unit card failure
5) Parking brake valve not fully open when the parking brake
is released.Five antiskid fail relays in P36 panel control ANTISKID Light functions and the related EICAS message display. When the control unit lamp driver output signal is a ground (no fault in antiskid system), the relay energizes. The light extinguishes and no EICAS message appears. When the lamp driver output signal is an open circuit (fault in antiskid system), the relay de-energizes. The light illuminates and the related EICAS message appears. Four relays each control antiskid failure indication for two wheels. One relay controls alternate antiskid failure indication.Autobrake selector switch (Fig. 2)
(a) The switch, located on pilots center instrument panel P1-3, is a rotary, magnetic-latching eight position switch. The switch performs the following functions: 1) Provide 28 v dc power to the antiskid/autobrake control
unit. 2) Select 1, 2, 3, 4 or MAX AUTO airplane deceleration level,
or RTO.
3) Arm or disarm the system.
4) Turn on or turn off the AUTOBRAKES light.
(b)
A positive detent between the DISARM and OFF positions ensures that when the switch moves to the DISARM position, it does not overshoot to OFF and prevent the AUTOBRAKES light from illuminating.
(c)
By turning the switch counterclockwise from OFF to RTO, the autobrake system operates in the RTO mode. When the average wheel speed is above 85 knots and both engine thrust levers are moved to the idle position, full hydraulic pressure (3000 psi) applies automatically to the brakes.
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