G37294
500  Lever Brake Mechanism 
Nov 15/67  Figure 3 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  27-62-0 Page 7 

Brake quadrant through two diagonally opposed shoe pins producing a locking action. Forces applied to the forward drum in the opposite direction will have a locking action on the other diagonally opposed shoe pins. Motion of the input arm, caused by the speed brake lever rotation, initially unlocks the shoe assembly and then rotates the shaft. The input arm drives the shaft through flanges that contact the drive arm. When lever rotation is stopped, a compression spring in the shoe assembly returns the shoe pins to the locked position. Motion of the automatic speed brake lever actuator causes the support bracket and brake quadrant to rotate. This rotation is transmitted through the shoe assembly to the drive arm causing the shaft to rotate. The drive arm also drives the speed brake lever through the input arm. A load at the speed brake lever will unlock the shoe assembly and override the motion of the speed brake lever actuator.
C.  The speed brake lever actuator connects the lever brake mechanism support bracket to airplane structure. The actuator consists of a 28-volt dc electric motor, gearing, a displacement rod, non-jamming mechanical stops, and adjustable limit switches. The limit switches are bench adjusted to limit the stroke at the extended and retracted positions. The gearing prevents actuator motion due to external loads.
D.  The speed brake forward drum is splined to the lever brake mechanism. The drum is grooved for 1/8 -inch cables and has integral cable guards. A switch cam is provided on the aft side of the drum. A switch actuator contacts this cam when the speed brake handle is down and locked. Two switches ganged to this actuator control automatic speed brake arming and provide a speed brake input to the takeoff warning system (Ref 31-26-0, Aural Warning (Takeoff Warning) System). A detent cam is provided on the forward side of the drum to provide an armed detent and a maximum in-flight detent. A spring-loaded roller arm follows this cam and provides speed brake lever feel at these detents.
5.  Speed Brake Position Warning System
A.  An aural (takeoff) warning system is provided to warn against takeoff with the speed brakes on. An intermittent warning horn will sound if the thrust levers are advanced for takeoff and the speed brakes are raised or speed brake control lever is in the ARMED position. For complete description, Ref 31-26-0, Aural Warning (Takeoff Warning) System.
501 
27-62-0 Page 8  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/77 

6.  Ground Spoiler Control Valve
A.  A ground spoiler control valve controls hydraulic pressure to ground spoiler actuators (Fig. 2). The valve is located in the right main wheel well and is bolted to a bracket on the outboard part of the wheel well forward bulkhead.
B.  The valve consists of a piston and sleeve assembly enclosed in a valve body. Drilled passages in the sleeve are connected to five external ports on the valve body. A lever which pivots about a lug on the valve body is connected to the piston. The opposite end of the lever is connected by a pushrod to a speed brake crank on the spoiler mixer. Moving the speed brake control lever causes the speed brake crank on the spoiler mixer to transmit motion through the pushrod and lever, to position the valve piston.
C.  When the speed brake control lever is in the DOWN position, the ground spoiler control valve directs hydraulic pressure directly to the down port of the ground spoiler actuator (Fig. 5). As the speed brake control lever is moved aft, the control valve moves through a neutral position where pressure is blocked and all other ports connected to return. As the speed brake lever is moved further aft, the control valve applies hydraulic pressure to the up ports of the ground spoiler actuators, through the ground spoiler interlock valve. The down port of the ground spoiler actuator is connected to return through the ground spoiler control valve.
7.  Ground Spoiler Interlock Valve
A.  A ground spoiler interlock valve limits use of the ground spoilers to ground operation. The valve is located above the right main gear trunnion and is secured to a bracket on the aft side of the wing rear spar (Fig. 2).
B.  The valve consists of a three port housing, with passages for hydraulic fluid, and a valve slide. A bellcrank which pivots about a lug on the valve body is connected to the valve slide. The opposite end of the bellcrank connects to a ground spoiler interlock push-pull cable. The push-pull cable is routed along the right main gear drag strut and is connected to the upper torsion link.
C.  With the landing gear in the retracted position the shock strut inner cylinder is fully extended. This positions the upper torsion link to cause the valve to block hydraulic pressure to the ground spoiler actuator up ports (Fig. 5).
　
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