Description (AMM 27-62-00)

 

A- The speed brake control system actuates the flight and ground spoilers on both wings to increase drag and reduce lift. The ground spoilers are used only on the ground to aid braking after touchdown. The flight spoilers are used for lateral control (Ref 27-61-00, Flight Spoiler Control System), reducing airspeed and to aid braking after touchdown.

 

The spoiler panels are numbered 0 thru 9 from left to right. The flight spoilers 2, 3, 6, and 7 are located outboard of the engines. Ground spoilers 0, 1, 8, and 9 are located outboard of the flight spoilers. Ground spoilers 4 and 5 are located inboard of the engines (Fig. 1). With lateral controls in neutral, application of speed brakes will cause the corresponding flight spoilers on both wings to raise equally. When speed brakes are applied on the ground, the ground spoilers will also raise.

 

B- System control is applied to a speed brake control lever located on the captain's side of the control stand (Fig. 2). Moving the speed brake control lever operates control rods which rotate a speed brake forward drum mechanism. The forward drum mechanism is connected by cables to a speed brake quadrant in the right wheel well. The speed brake quadrant operates a ratio changer and provides an input to a spoiler mixer.

 

The spoiler mixer directs the speed brake signals to a ground spoiler control valve and to flight spoiler actuators. A ground spoiler interlock valve is installed in the hydraulic line between the up ports of the ground spoiler actuators and the ground spoiler control valve.

 

The interlock valve is operated by a push-pull cable from the right main gear upper torsion link. With the airplane airborne, the shock strut is extended and the upper torsion link positions the push-pull cable to close the valve. When the airplane touches down, the shock strut is compressed and the push-pull cable opens the valve to actuate the ground spoilers.

 

C- System control also may be applied by a speed brake lever actuator. The actuator electrically drives the speed brake control lever to cause the speed brakes to raise or lower. Placing the speed brake control lever in an ARMED detent will prepare the actuator for operation. When the main gear wheels begin rotation at touchdown, the actuator will move the speed brake control lever to full up position raising the ground and flight spoilers. If either engine thrust lever is positioned 25 degrees forward from engine idle position, the actuator will move the speed brake control lever into the DOWN detent, lowering the ground and flight spoilers.

 

Indicator lights are provided on the center instrument panel to verify that the system is properly armed. On airplanes with speed brake test switches three pushbutton test switches are provided on the center instrument panel. Actuating the switches will test the indicator light control circuit and the actuator circuit.

 

Operation (AMM 27-62-00)

A- The speed brakes are activated by moving the speed brake control lever aft. This is done manually or by the speed brake lever actuator (Fig. 2). Initially, the control lever must be raised to release the lever latch. As the lever is moved aft, lever motion is transferred through control rods to release the lever brake and rotate the speed brake forward drum. Cables from the forward drum transfer speed brake signals to the speed brake quadrant at the spoiler ratio changer.

 

Motion the speed brake quadrant operates the ratio changer. The speed brake quadrant transfers motion to the spoiler mixer, driving both mixer output drums in the spoiler up direction. This causes flight spoilers 2, 3, 6, and 7 to raise equally. The motion of the spoiler mixer positions the ground spoiler control valve.

 

B- When the airplane is airborne, the right main gear shock strut is extended and the push-pull cable closes the ground spoiler interlock valve. The valve blocks pressure from the ground spoiler control valve causing the ground spoilers to remain faired. The speed brake lever may be rotated aft to the FLIGHT detent. This is the maximum in flight speed brake setting. A double-acting lever brake in the speed brake drum mechanism retains the lever at the selected setting between DOWN and the FLIGHT detent. With the speed brakes in use, rotation of the aileron control wheels will cause further operation of the flight spoilers.

 

Rotating the control wheels will lower the flight spoilers on the wing going up and raise the flight spoilers on the wing going down. As speed brakes are applied, the ratio changer reduces the amount of roll control input to the spoiler mixer for a given control wheel position. This reduces the angular change in spoiler position for a given roll control input.

 

C- When the airplane is on the ground, the right main gear shock strut is compressed and the push-pull cable opens the ground spoiler interlock valve. The valve then connects the ground spoiler control valve to the up side of the ground spoiler actuators. When the speed brake control lever is rotated approximately 29 degrees aft from the DOWN position, the speed brake control valve directs hydraulic pressure through the interlock valve to cause all the ground spoilers to extend 60 degrees. On the ground, the speed brake lever may be rotated aft to the UP position. In this configuration, all the ground spoilers will be raised 60 degrees and all the flight spoilers will be raised 40 degrees.