32-43-01
 ALL  ú ú 01 Page 11 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 (2)  
To obtain autobrake system operation, the following conditions are required:

 (a)  
Autobrake power is available (AUTOBRAKE CONTR circuit breaker on P6-3 panel closed).

 (b)  
ANTISKID system switch is ON and antiskid system is
 operational.

 (c)  
AUTO BRAKE selector switch on P2-2 panel is at 1, 2, 3, MAX, or RTO.

 (3)  
Operation for landing mode

 (a)  
The system is turned on when the AUTO BRAKE selector switch is placed at 1, 2, 3 or MAX decel position. The AUTO BRAKE DISARM light will illuminate and remain illuminated only if the turn-on self-check (TOSC) detects a system malfunction. Following are conditions required to pass the self-test: 1) Both solenoid valve pressure and servo valve pressure of

 the autobrake pressure control module (V122) are less than
 1000 psi. 2) Wheel speed is less than 60 knots. 3) Airplane is in air mode. 4) No detected antiskid or autobrake circuit failures.
 (b)  
Upon successful completion of a TOSC check in about one second the system remains in a waiting state until touchdown. At touchdown, autobrake activation (autobraking) will start when following conditions are met: 1) At least one wheel on each gear is greater than 60 knots

 (based on wheel speed relay logic). 2) Average wheel velocity is greater than 70 knots. 3) Both throttles are retarded.

 (c)  
During autobraking, 28-volt dc is sent to the solenoid valve of the autobrake pressure control module (V122), admitting 3000 psi to the servo valve. Autobrake control immediately schedules an initial on-ramp pressure of 200 psi, then at 100 psi/second for 1.5 seconds to the end of the first period. A second period with a rate of pressure buildup proportional to the deceleration selected then begins which will achieve the selected deceleration within about 2.5 seconds of autobrake actuation (figure 5).

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 32-43-01
 ALL  ú ú 01 Page 12 ú Nov 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (d)  The autobrake system automatically applies brake pressure selected by the pilot as follows:
 Autobrake Brake Decel Selector Pressure Level Switch At_________ (psi)________ ____________
(ft/sec/sec)
 1 1250 4 2 1500 5 3 2000 7.2 MAX 3000 12 BELOW 80 KNOTS MAX 3000 14 ABOVE 80 KNOTS RTO FULL (Decel rate not
 PRESSURE  controlled in RTO mode, max system pressure applied without on-ramp)
 (4)  
Operation for Refuse Takeoff (RTO) mode.

 (a)  
The system is turned on when the AUTO BRAKE selector switch is placed in the RTO position. The AUTO BRAKE DISARM light will illuminate for approximately one second while the turn-on self-check (TOSC) is executed. The light will remain illuminated if the TOSC detects a system malfunction. The following conditions are required to pass the TOSC: 1) Both solenoid valve pressure and servo valve pressure of

 the autobrake pressure control module (V122) are less than
 1000 psi. 2) Wheel speed is less than 60 knots. 3) The airplane is in the ground mode. 4) Both thrust levers are retarded. 5) No antiskid or autobrake circuit failure is detected.
 (b)  
After sucessfully completing the TOSC, the system is in an unarmed waiting stage. The system will become armed if all of the following conditions are satisfied: 1) The average wheel speed is greater than 90 knots. 2) The airplane is on the ground (air ground logic is in the

 ground mode).
 3) Both throttle levers are advanced.

 (c)  
After the system has become armed, RTO autobraking can be activated. The requirements for activating RTO once the system is armed are: 1) Average wheel speed is greater than 88 knots. 2) The airplane is on the ground. 3) Both throttle levers are retarded. 4) At least one wheel on each gear is turning at greater than

 60 knots.

 (d)  
Once RTO autobraking is activated, full hydraulic system supply pressure (3000 psi) is immediately routed to all four brakes. RTO autobraking will continue until the airplane is stopped unless a disarm occurs either by a pilot action or by the failure monitoring logic.
　
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