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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
(b)
(c)
(d)
(e)
(f)
(g)
A
747-400
MAINTENANCE MANUAL
When the switch is set to RTO, the autobrake system is armed
for refuse takeoff. The system will supply full pressure (3000
psi) to the brakes if the average wheel speed is above 85 knots
and all engine thrust levers are moved to idle.
IRS inputs
1) Longitudinal deceleration and airplane pitch angle a) The IRS longitudinal deceleration and pitch angle are used to calculate the actual body axis deceleration. This deceleration is compared with the deceleration selected by the pilot. The difference between the two is used to calculate a pressure application signal to the the servo valve in the autobrake pressure control module.
Antiskid transducers
1) These supply wheel speed signals for the autobrake spinup latching logic.
Landing gear air/ground signals (2 signals from the PSEU)
1) Ground mode (Alternate or Primary) - closed circuit Air Mode (Alternate or Primary - open circuit.
2) These signals are used to detect a touchdown for autobrake operation logic and to detect a take off for RTO disarming logic.
Thrust lever signals
1) Thrust Levers #1 and #3 not advanced - open circuit Thrust levers #2 and #4 not advanced - 28 vdc Thrust levers #1 and #3 advanced - ground Thrust levers #2 and #4 advanced - open circuit
2) Thrust lever signals come from a switch pack installed in the control stand forward of the thrust levers. The switch pack contains four switches for autobrake operation. Each switch is connected to a different thrust lever linkage by a plunger assembly.
3) If a malfunction of the autobrake system is isolated to a thrust lever switch, the switch pack may be removed and replaced (Ref 76-11-03/201). Each switch may be adjusted independently without removing the switch pack from the control stand. This is done by loosening a jam nut on the plunger and turning the plunger.
4) The signals from the thrust lever switches permit autobrake operation when they indicate that all thrust levers are in idle at touchdown. They also permit RTO automatic braking during a takeoff roll when the trust levers are pulled to idle. They disarm the autobrake if any one of the switches indicate a thrust lever advanced during autobrake operation.
Spoiler lever position signal
1) Spoiler handle armed - open circuit Spoiler handle not armed - ground
2) These signals are part of the logic to arm and disarm the autobrake system.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
32-42-00
ALL ú ú 05 Page 46 ú Feb 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(h)
Brake metered pressure switches
1) Brakes applied (left or right) - open circuit
Brakes released (left or right) - ground
2) The brake metered pressure switches permit the flight crew to disarm the autobrake system by manually operating the brakes. Either switch will disarm the system when it goes to the open circuit condition. These switches do not disarm the autobrake system when it operates in the RTO mode.
(i)
Brake pedal bus switches
1) Brakes applied (left or right) - open cicuit
Brakes released (left or right) - ground
2) These switches operate only in the RTO mode. They supply a smooth transition from RTO brake operation at full 3000 psi to manual brake operation.
(2)
Autobrake logic and control
(a)
The autobrake system automatically supplies hydraulic pressure to operate the brakes. The maximum pressure supplied to the brakes is set by the deceleration selection made by the flight crew.
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本文链接地址：747-400 AMM 飞机维护手册 起落架 LANDING GEAR 6(138)
