AUTOBRAKES light (Fig. 2)
(a)
The AUTOBRAKES light is an amber light located near the selector switch. The light, controlled by the selector switch, comes on when: 1) The switch is at DISARM position
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2) The switch is at OFF position and the autobrake module solenoid valve output pressure switch shows presence of high pressure.
3) The switch is at 1, 2, 3, 4, MAX AUTO or RTO position and system fault (autobrake or RTO) is detected.
NOTE: The light only comes on if RTO is initiated and a
____
failure exists.
(b) When the selector switch is at 1, 2, 3, 4 or MAX AUTO, the light illuminates for a moment as the switch is moved through the DISARM. The light then goes out when the unit confirms that arming requirements are met. When the system disarms, the light illuminates until the switch is placed to OFF or the system is rearmed.
B. Antiskid/Autobrake Control Unit (Fig. 3)_______________________________
(1)
The control unit (M102) compares each wheel speed with the IRS ground speed for touchdown and hydroplane protection. A change in speed causes a change in control signal to increase or decrease hydraulic pressure to the brakes.
(2)
The unit, located in the E5 rack of the main equipment center, contains the following:
(a)
Four identical dual main wheel cards.
(b)
One autobrake card.
(c)
One BITE card.
E5 RACK
E5-2 SHELF (REF) FWD (M102) CONTROL UNIT ANTISKID/AUTOBRAKE CENTER (REF) MAIN EQUIPMENT ASEE CONTROL UNIT ANTISKID/AUTOBRAKE DOOR, 821 FWD CARGO
INBD A
Antiskid/Autobrake Control Unit Figure 3
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(d)
One interface/display card.
(e)
A front control/display panel with alphanumeric readout and BITE test switches.
(3)
The unit is an LRU and circuit cards are also LRUs. Either unit or cards can be replaced as required in maintenance.
(4)
Data links in the unit provides means of communication between cards. All cards contain logic circuits to generate the required signals for proper interface within the system. Power of 28 v dc to the card supplies the 26 v dc and the regulated 5 v dc source required for all logic circuits.
(5)
The main wheel card primary function is to change the mode of braking pressure and prevent wheel skid or lockup. Each wheel card provides skid protection for two wheels in tandem. Each wheel circuit shares a common power source line and is combined by locked wheel cross over function. A driver circuit in each card provides signal to the EICAS display via the EICAS computers when antiskid system fails.
(6)
The autobrake card performs all autobrake functions, including control, logic, interface and BITE. The card shares with wheel cards for wheel speed and system test information. A driver circuit in the card provides signal to the AUTOBRAKES light and the EICAS computers when autobrake system fails.
(7)
Both wheel cards and autobrake card contain self test and status circuits. The circuits check the system for fault and provide status to the BITE card.
(8)
The BITE card communicates with all other cards via the data link in the control unit. Its primary function is to monitor the operation of the four main wheel cards and the autobrake card. The function includes analyzing received data, examining analog voltages, performing test required, and providing fault signals to the memory. Logic circuits in the card determine BITE test switch inputs required for test.
(9)
The interface/display card contains circuits for BITE and ANTISKID light functions.
C.
Antiskid Module (Normal) (Fig. 4)
________________________
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SEEA MAIN WHEEL WELL FAIRING
RETURN STRUCTURE
(NOT SHOWN) AT STA 1060
(REF)
SEE B
TO BRAKES NORMAL ANTISKID MODULE
R HYD SYS
ALTERNATE PRESS
BRAKE METERED KEEL
PRESS BEAM WEB
ALTERNATE (REF)
ANTISKID
MODULE
NORMAL BRAKE METERED
FWD INBD PRESS
TO BRAKES LEFT WHEEL WELL SHOWN RIGHT WHEEL WELL SIMILAR
A
L HYD
SYS PRESS
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