E. The Autobrake Card
(1)
Power to the autobrake card is supplied by 28 vdc Bus 4 through a circuit breaker on the P180 DC Power Distribution Panel.
(2)
The autobrake card supplies the logic for automatic braking. It contains microprocessor circuits which receive input signals, evaluate data and respond with signals determined by software programmed into the system. Autobrake and RTO arming logic, application logic, deceleration control, and disarm logic are supplied by this card. Airplane longitudinal deceleration signals are supplied by the IRS.
F.
Brake Torque Limiting Control Card
(1)
Power for the 4 brake torque limiter cards is supplied by DC Bus 1, 2, 3, or 4. Power for each card is supplied separately through a circuit breaker on the P180 DC Power Distribution Panel in the electrical and electronics compartment. Each card supplies power for 4 brake torque limiter circuits as shown below:
~......................................................... | CIRCUIT BKR | WHEEL | BUS | ........................................................... | C10082 | 1, 5, 9, 13 | 28 vdc Bus 1 | ........................................................... | C10083 | 2, 6, 10, 14 | 28 vdc Bus 2 | ........................................................... | C10084 | 3, 7, 11, 15 | 28 vdc Bus 3 | ........................................................... | C10085 | 4, 8, 12, 16 | 28 vdc Bus 4 | 2......................….................…................1
(2)
Each brake-torque-limiter-control card supplies brake torque limiting protection for one wheel on each landing gear truck. Torque signals are supplied from the brake torque sensor installed on each brake equalizer rod. The brake torque signal is a dc voltage. A microprocessor on each card calculates the torque based on the input signal and sends a brake release signal to the applicable antiskid valve driver when any brake torque is more than a specified limit.
G.
System BITE Card
(1)
Power for the system BITE card is supplied by the 28 vdc Bus 4 throuh a circuit breaker in the P180 DC Power Distribution Panel.
(2)
The system BITE card monitors the operation of the antiskid cards, the brake torque limiting cards, and the autobrake card. The BITE has two modes of operation: the continuous monitor tests and tests started from the central maintenance computer. The continuous monitor tests operate whenever power is supplied to the BITE card.
(3)
The BITE card gets fault signals from the individual circuit cards it monitors and sends the signals to the data aquisition BITE card for storage and to the EICAS display. The BITE can isolate faults to the affected line replaceable unit (LRU) or to the brake control unit.
(4)
The system BITE card supplies redundant data for the EICAS displays.
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32-42-00
ALL ú ú 01 Page 7 ú Oct 10/96
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
H. Data Aquisition BITE Card
(1)
Power for the data aquisition BITE card is supplied by the 28 vdc Bus 2 through a circuit breaker on the P180 DC Power Distribution Panel.
(2)
The data acquisition BITE card monitors the system BITE card, the main wheel cards, the brake torque limiting cards and the autobrake card for these failures:
-Signal interrupt
-port failure
-Read Only Memory failure
-Random Access Memory failure
-Valve Bias failure
-Indicator failure
-LRU failures
-Card failures.
(3)
Analog to digital converters supply voltage values to the data aquisition BITE from all valves, transducers and card power supplies. The voltages are compared to specified limits. Voltages which are out of limit for a specified time limit will be registered as a fault or malfunction. Data on malfunctions is stored in a nonvolatile memory for recall using the CMC.
(4)
The data acquisition BITE card supplies primary data information to the EICAS displays.
I.
BRAKE INDICATION DISABLE Switches
(1)
Two BRAKE INDICATION DISABLE switches are installed on the front of the brake system control unit.
(2)
The BRAKE INDICATION DISABLE switches:
(a)
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