E.  
A green SPEED BRAKE ARMED light is provided on the center instrument panel. This light will be on when the control lever is in the ARMED detent and the following conditions are met: at least one of the two antiskid systems are operative, the speed brake lever actuator is in the lower position, and the four wheel rotation relays are open. If any of these conditions are not met, the light control circuit will turn off the SPEED BRAKE ARMED light and turn on an amber SPEED BRAKE DO NOT ARM light. The SPEED BRAKE DO NOT ARM light is located on the center instrument panel. The speed brakes can be lowered either manually or automatically. Manual retraction will occur when the speed brake control lever is moved to the DOWN position. The SPEED BRAKE DO NOT ARM light will go off but the circuit will not be reset for the next electrical speed brake application. Automatic retraction will occur if the speed brakes have been deployed automatically and engine No. 1 and 2 thrust lever is advanced far enough to actuate one of the thrust lever actuated switches. The speed brake lever actuator will drive the speed brake control lever to the DOWN position and all the spoilers will lower. The SPEED BRAKE DO NOT ARM light will go off and the circuit will be reset for the next electrical speed brake application.

 F.  
With the speed brake control lever in the ARMED detent, dual electrical failures in the automatic speed brake control system could raise the speed brakes. The speed brake indicating system monitors the automatic speed brake control system for electrical failures. When the first failure is sensed, the SPEED BRAKE DO NOT ARM light will come on. This warns the flight crew that the speed brakes should only be operated manually.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
 G.

H.
I.
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737-300/400/500MAINTENANCE MANUAL
AIRPLANES WITH SPEED BRAKE TEST SWITCHES; The three speed brake test switches check the speed brake indicating circuit for continuity. The test switches simulate failures that the speed brake indicating system must annunciate. This proves the speed brake indicating system is operative, but does not verify if the speed brake system is operative. If continuity exists when any of the test switches are actuated, the SPEED BRAKE ARMED light goes off and the SPEED BRAKE DO NOT ARM light comes on. With the speed brake lever in the ARMED position or thrust levers in reverse thrust actuating test switch No. 1 simulates a short-to-power failure of a wheel speed relay. This applies a voltage at a point where a subsequent failure could raise the speed brakes. Actuating test switch No. 2 simulates a failed-closed (ground on the indicating system) position of a wheel speed relay. Actuation of test switch No. 3 operates the ground speedbrake go-around relay R5. This simulates an engine thrust lever advanced far enough to actuate one of the thrust lever actuated switches. The SPEED BRAKE ARMED light goes off and the SPEED BRAKE DO NOT ARM light comes on to confirm the go-around relay operated. The thrust lever position would cause the aural warning horn to sound if the airplane is on the ground and not in takeoff configuration.If the speed brake control lever is manually placed in the up position when airplane speed is below 60 knots and both ground and air sensing relays have been in ground mode in excess of 4 seconds, the wheel rotation signal will not be sufficient to automatically extend the speed brake lever actuator and the speed brake lever actuator position limit switch will remain in speed brake down or lever down and locked position. If engine No. 1 or 2 thrust lever is subsequently advanced far enough to actuate a thrust lever actuated switch, the electrical circuit to move the speed brake lever actuator automatically to the down position will not be completed. The thrust lever position will cause the takeoff warning horn to sound. The speed brake lever must be moved manually to the down position to retract the speed brakes and silence the warning horn.The speed brakes will automatically extend during a refused takeoff (RTO) when the thrust levers are moved to idle position and the reverse thrust levers are moved to reverse thrust position, with wheel speed greater than 60 knots.
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