757-200 MAINTENANCE MANUAL SUPPLEMENT Part I 维护手册补充(8)

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The actuator drives a rotary cam via a linkage.  The cam can cause the speedbrake handle to either retract or remain stationary, depending on speedbrake lever position; the cam cannot cause lever extension.
If the speedbrake lever's position is less than 50% of the Flight Detent position, then neither activating nor deactivating the Autostow function results in the cam contacting the speedbrake control system; the lever remains stationary.
If the speedbrake lever position is greater than 50% of the Flight Detent, then the cam contacts the speedbrake control system, causing the lever to retract to the 50% Flight Detent position.
A spring provides override forces.  At the position 50% between the Down and Flight detents, the override force is 20 pounds above normal.  The increment increases to approximately 25 pounds at approx. 65. lever position.
Aviation Partners Boeing
757-200
MAINTENANCE MANUAL SUPPLEMENT
 Part I

B.  Speedbrake Autostow Controller (SAC) Module
The electronics for Speedbrake Autostow function is implemented in the Boeing Part Number 69-78576 per Aviation Partners Boeing Specification 737S3900.  The SAC module is installed on the right side of the E1 E/E rack.  Program pins are used to properly configure the SAC for any unique aircraft configurations. (Reference APB WDM Supplement, AP57.2-0615, for aircraft specific configurations.)
The SAC module assembly installation is comprised of the following:
(1)  
A single Printed Wire Assembly (PWA) comprised of the following circuit modules (CMs):

.  
Discrete Input CM

.  
EPLD CM, containing the Actel A24MX24

.  
Power Supply CM

.  
Discrete Output CM

 

(2)  
Mounted on the PWA are the following functional components:

.  
Boeing Specification 10-60450-6 relay

.  
Three Light Emitting Diode (LED) maintenance indicators

.  
Two momentary push-button maintenance switches

 

Figures 10, 11, 12 show SAC installation and location in EE bay and a view of the SAC module.
C.  SAC Internal Monitors
The SAC contains the following internal monitors:
.  
A watchdog timer (WDT) function resets the PLD if the timer does not receive a signal from the PLD within an appropriate time interval.  The watchdog function is performed in hardware.  If the watchdog timer trips, then a SAC Autostow fault is declared, the “Autostow Fault” LED on the module is illuminated, and all outputs are set to their default state.  The Speedbrake Autostow function will be disabled, and the Autostow Speedbrake indication, located in the crew compartment, will be turned on.

.  
A program pin monitor validates the airplane program at every power cycle and every time the PLD is set.  If an improper pattern of pins or an invalid airplane program is detected, a program pin fault is declared.  The “Autostow Fault” LED on the module is illuminated.  The Speedbrake Autostow function will be disabled, and the Autostow Speedbrake indication will be turned on.
　
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