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A
747-400
MAINTENANCE MANUAL

(TYP) (4 PLACES) HINGE SUPPORT  PISTON A 
TRAILING EDGE BEAM 
A 

PACKAGE SPOILER CONTROL 3-POSITION GROUND  EDGE BEAM TRAILING  HINGE POINT SPOILER 
45` 
20` 
UP 2  UP 1 
RETURN PRESSURE  CONTROL PACKAGE PIVOT POINT  A-A  POSITION 20-DEGREE  POSITION 45-DEGREE 

Ground Spoiler
Figure 3

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747-400
MAINTENANCE MANUAL

 (2)  
The speed brake control system is operated from the speed brake control lever on the pilots' control stand. When the lever is all the way forward in the DN position, there is no speed brake input to the spoiler control system. The spoilers only move in response to the lateral control system.

 (3)  
When the speed brake control lever is lifted and moved slightly aft to the ARM position, it enters the range of speed brake use for flight. The lever may then be moved between ARM and the FLIGHT DETENT position. The lever cannot be moved aft of FLIGHT DETENT because the lever lock solenoid is engaged when the airplane is in the air. At touchdown, the lever lock releases, and the control lever may then be also moved between FLIGHT DETENT and the UP position.

 (4)  
As the control lever is moved aft from ARM, a control rod passes the lever motion to the speed brake drum mechanism through a no-back brake. The drum mechanism passes the movement to the speed brake sequence mechanism through a pair of control cables. The speed brake sequence mechanism programs the control motion through three output rods, one to the ground spoiler control valve and one to each spoiler differential mechanism.

(6 & 7)  (8 TO 12)

1 RATIO CHANGER ACTUATORS
Speed Brake Control System Hydraulic Distribution Figure 4
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MAINTENANCE MANUAL

Lever Lock and Automatic Speed Brake Schematic
Figure 5

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MAINTENANCE MANUAL

 (5)  
Flight

 (a)  
As the control lever is moved between ARM and FLIGHT DETENT, the output rod to the left spoiler differential mechanism follows lever movement. This extends flight spoilers 3, 4, 9, and 10 from down to 45° and flight spoilers 5 and 8 from down to 20° over the ARM to FLIGHT DETENT lever range.

 (b)  
As the lever passes a point approximately 80% from ARM to FLIGHT DETENT, the output rod to the ground spoiler control valve opens one port on the valve. This extends ground spoilers 6 and 7 from down to 20° at one point of control lever travel.

 (c)  
The spoiler differential mechanisms sum the inputs from the lateral control system and the speed brake control system to provide single outputs to the flight spoiler control packages. Aerodynamic loads on the spoiler panels also affect spoiler position. Pressure relief valves in the spoiler control packages limit spoiler extension or permit spoiler blow-down as loads become excessive.

 (6)  
Ground

 (a)  
As the control lever is moved between ARM and FLIGHT DETENT, the operation is the same as in flight.

 (b)  
As the control lever is moved between FLIGHT DETENT and UP after touchdown, the output rod to the right spoiler differential mechanism follows lever movement. This extends flight spoilers 1, 2, 11, and 12 from down to 45° over the FLIGHT DETENT to UP lever range.
　
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