G29336
Flight Spoiler Actuator 500
27-61-0 Figure 6 Nov 15/67
Page 10
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Hydraulic power to the flight spoiler power control units is controlled by spoiler shutoff valves in the flight controls hydraulic modular packages. Switches for these electrically operated valves are located on the pilots' forward overhead panel. Hydraulic system A powers flight spoilers 3 and 6. Hydraulic system B powers flight spoilers 2 and 7.
C. Each flight spoiler actuator quadrant is bracket mounted on the actuator support fitting, and pivots on two sealed bearings. The quadrants have three cable grooves to receive wing spoiler cables. The quadrant crank is mounted on a boss around the quadrant hub and is secured in place by two shear rivets. A white painted scribe mark is provided to aid detection of shearout. Each actuator quadrant has a rigging pinhole.
D. The flight spoiler actuator is connected to the quadrant by an actuator link. The input arm on the actuator is adjustable to provide proper spoiler pickup. The input arm has two mounting locations for the actuator link. The forward position is used for the flight spoilers.
E. When the actuator is pressurized, the extension check valve is held open by pressure acting on a piston at the base of the valve. (See figure 7.) If hydraulic pressure is lost, springs reseat the extension check valve, to prevent spoiler float. A blow -down check valve located in the pressure line allows the spoilers to blow down at critical speed. Protection against actuator damage due to thermal expansion of entrapped hydraulic fluid or extreme "up " loads from the flaps is provided by a thermal relief valve and relief check valve. The thermal relief valve and the extension check valve are one unit; however the thermal relief valve is opened by actuator down pressure operating an additional piston. The thermal relief valve is set to open when a pressure of 3000 to 3600 psi is reached with hydraulic power off, and to reseat at a pressure no lower than 2500 psi. The relief check valve will also protect against damage from extreme flap up loads when hydraulic power is on. To prevent hydraulic lock when the spoilers are in the full down position, a snubber check valve is built into the piston. With the spoilers retracted and the piston in the full "down " position, an "up" signal to the control valve allows hydraulic fluid to flow to the base of the cylinder, around the piston, and through the snubber check valve to the face of the piston. The thermostat valve provides a hydraulic bleed at low temperatures to maintain warm hydraulic fluid in the actuator.
500
Nov 15/67 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 27-61-0 Page 11
G29343
Flight Spoiler Actuator Schematic 500
27-61-0 Figure 7 May 15/67
Page 12
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
6. Spoiler Control Quadrant
A. A spoiler control quadrant located in the floor beam space above the main wheel well provides a control path from the first officer's control column to the ratio changer. (See figure 4.) The quadrant shaft projects through the wheel well ceiling to connect, by two cranks, to the aileron spring cartridge and the spoiler ratio changer input rod. The quadrant is connected by cables to the transfer mechanism at the base of the first officer's control column. The quadrant shaft rotates on two ball bearings. The upper bearing is enclosed in a ball fitting, which incorporates a rotary air pressure seal. The lower crank, to which the aileron spring cartridge connects, is secured to the quadrant shaft by four shear rivets.
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