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 B.  When the speed brake control lever is moved out of the DN position, the speed brake drum mechanism releases the auto speed brake arm switch.
 5.  Automatic Speed Brake Actuator (Fig. 2)
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 A.  The automatic speed brake actuator contains a 28v dc motor, gearset, and limit switches. The actuator is attached to structure just aft of the speed brake drum mechanism. The actuator is connected to the no-back brake ring on the speed brake drum mechanism through a linkage. When the actuator is energized to extend, it moves the forward quadrant to extend all flight and ground spoiler panels.
 B.  The actuator extends when the speed brake control lever is out of the DN position, both air/ground relays systems are in ground mode, hydraulic system 1 or 4 is pressurized, and thrust levers 1 and 3 are near idle. The actuator also extends if the control lever is in the DN position when the reverse thrust lever 2 or 4 are deployed and the other conditions are met.
 6.  Speed Brake Sequence Mechanism (Fig. 2)
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 A.  The speed brake sequence mechanism receives input through the speed brake control cables and programs outputs to the ground spoiler control valve and the spoiler differential mechanisms. The sequence mechanism is located in the right wing gear well.
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MAINTENANCE MANUAL

 B.  The speed brake sequence mechanism consists of a cable quadrant, two output cranks which connect control rods to the spoiler differential mechanisms, an output crank which connects a control rod to the ground spoiler control valve, and a housing assembly with a mechanism which programs the spoiler panels to function as speed brakes.
 C.  The output from the sequence mechanism operates in two stages. With the speed brake control lever in the ARM to FLIGHT DETENT range, the control rod to the left spoiler differential mechanism moves. With the control lever in the FLIGHT DETENT to UP range, the control rod to the right spoiler differential mechanism also moves.
 7.  Ground Spoiler Control Valve (Fig. 2)
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 A.  The ground spoiler control valve receives mechanical input from a control rod connected to the speed brake sequence mechanism. Depending on the rod position, the control valve directs hydraulic pressure through two output ports to operate the ground spoiler control packages and the flight spoiler 5 and 8 ratio changer actuators. The control valve is located below the sequence mechanism.
 8.  Ground Spoiler Control Package (Fig. 2)
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 A.  Each ground spoiler control package has three output positions controlled through two hydraulic pressure inputs. The control package is a piston type actuator with the piston end attached to the spoiler and the cylinder end attached to a trunnion pivot on the trailing edge beam. A thermal relief valve prevents damage to the control package due to thermal expansion of hydraulic fluid inside the actuator. The control packages are located below ground spoilers 6 and 7.
 B.  With the speed brake control lever at FLIGHT DETENT, the ground spoiler control packages extend the ground spoilers to 20°. With the control lever at UP, the ground spoilers are extended to 45°.
 9.  Ground Spoiler Panel (Fig. 3)
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 A.  The ground spoiler panels are located on the upper surface of each wing at the most inboard position. Each ground spoiler panel is attached to the trailing edge support beam through four hinges. The panels are raised by the ground spoiler control packages located beneath them. Ground spoiler panels No. 6 and 7 are interchangeable.
 10. Operation (Figs. 4 and 5)
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 A.  Functional Description
 (1)  The speed brake control system uses hydraulic power to extend and retract the spoiler panels. Hydraulic power is supplied through the flight control hydraulic shutoff valves on each wing. The valves are controlled by the FLT CONT HYD POWER switches on the P461 pilots' overhead maintanance panel. The flight spoilers use hydraulic systems No. 2, 3, and 4 and the ground spoilers use hydraulic system No. 4.
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