Automatic Pressure Control Module and Hydraulic Schematic 591
32-43-01 Figure 2 (Sheet 1) Nov 15/80
Page 8
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
591 Autobrake Pressure Control Module and Hydraulic Schematic
May 20/82 Figure 2 (Sheet 2) 32-43-01
Page 9
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Automatic Braking System Control Circuit 595
32-43-01 Figure 3 (Sheet 1) Jun 20/87
Page 10
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
595 Automatic Braking System Control Circuit
Jun 20/85 Figure 3 (Sheet 2) 32-43-01
Page 11
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
8. Automatic Braking System Control Inputs (Fig. 3)
A. The control inputs to the automatic braking system, furnished by wheel speed relays, air-ground sensing (inboard squat logic) relay, speed brake arming switch and engine throttle switches, are provided to the microprocessor in the antiskid module. These inputs, plus an operational antiskid system (no antiskid system fault detected) input, are condition requirements for the automatic braking system.
(1)
Four wheel speed relays (K9, K10, K11, K12 in the M338 landing gear electrical module), used in the antiskid system, also provide the logic path for autobrake application when at least one wheel speed on each main gear is greater than 60 knots. The logic path enables a 28-volt dc output from the antiskid module to energize the R289 (A/B ON) relay.
(2)
The air-ground sensing relay K7, used in the landing gear lever latch and safety relay circuit, also provides a ground (inboard squat) signal (airplane in air) or an open circuit signal (airplane on ground) for automatic braking system application. The relay is located in the M338 landing gear electrical module (E3-2).
(3)
The automatic speed brake arming switch S276 (operated by the speed brake handle, Ref 27-62-0), provides a signal to disarm the automatic braking system through the microprocessor in the antiskid module. The switch signal is 28 volt dc when the speed brake handle is raised, and an open circuit when the speed brake handle is stowed. When both the autobrake system and the auto-speed brake system are armed, the 28 volt DC signal to the autobrake microprocessor sets a disarm trigger. Then, when the speed brake handle is stowed removing the signal, the autobrake will disarm.
(4)
A total of four engine throttle actuated switches, two (S139 and S283) for left engine throttle and two (S133 and S140) for right engine throttle, provide logic signals to the antiskid module for autobrake operation. To initiate autobraking during landing, both throttles (all four throttle switches) must be in the retard position (switches close) to provide four logic highs to the microprocessor in the module. The autobrake system will disarm if either throttle is advanced (switch open) for more than three seconds with wheel speed greater than 60 knots. Switch retard position occurs when the throttle is moved aft to between 12.5 and 8.5 degrees. Switch open position occurs when the throttle is advanced forward to between 11.5 and 13.5 degrees.
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