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6. Engine Control Drum-and-Shaft Assembly
A. An engine control drum-and-shaft assembly provides a mechanical link between the thrust and start control cables and the push-pull cable assemblies. The assemblies are located on the forward face of the wing front spar and extend through the nacelle strut firewall. The assembly consists of concentric thrust and start control drums and shafts, and a start and thrust crank. Cable travel is transferred by the drums and shafts to the cranks on the end of the shafts.
7. Engine Control Push-Pull Cables
A. A pair of push-pull cables transfer thrust and start control travel from the thrust and start cranks on the control drum and shaft assembly to the cranks on the left side of the engine cross-shaft. The cross-shaft transfers crank travel to the right side of the engine.
8. Cross-Shaft to Fuel Control Linkage
A. The cross-shaft to fuel control linkage consists of a start rod and a thrust rod. These rods make the final engine control motion transfer, from the right side of the engine cross-shaft to the fuel control unit.
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535 Thrust and Start Levers
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8. Operation
A. Advancing the start lever to the IDLE position from CUTOFF causes a start control cam on the control stand start drum to actuate a switch which energizes the intermittent duty starting ignition system (when the overhead start switch is in the ground start position) and to actuate a fuel shutoff switch which opens the engine fuel shutoff valve (when the emergency fire shutdown switch is in the IN or normal position). The lever motion is also transmitted through the drum-and-shaft assembly and control linkage to the start lever on the fuel control unit. Rotation of the start shaft opens a pilot valve in the fuel control unit to initiate fuel flow.
B. Placing the start lever in the CUTOFF position de-energizes the ignition system and closes the engine fuel shutoff valve in the wing. When the lever is returned toward the CUTOFF position, a stop pin in the drum-and-shaft assembly contacts the end of a slot in the start drum and stops system motion at the strut. Approximately 1-1/2 degrees of additional start lever travel is required to enter the CUTOFF detent. This stretches the control cable and provides sufficient load in the cable system to maintain the start lever in the CUTOFF detent, ensuring positive cutoff.
C. Advancing the forward thrust lever from the idle position, locks the reverse thrust lever in idle and rotates the thrust control shaft. As the shaft rotates, motion is transmitted to a lever on the fuel control unit which increases fuel flow to the engine. Forward motion of the forward thrust lever is terminated by a stop on the fuel control unit. Forward motion of the forward thrust levers causes cams in the drum and friction brake assembly to actuate switches which provide takeoff warning and other functions.
D. As the forward thrust levers are returned to the idle position, fuel flow is reduced and cams in the drum and friction brake assemblies or auto throttle servomechanisms actuate switches which provide landing gear warning under suitable circumstances (Fig. 3 or 4).
E. Advancing the reverse thrust lever from the OFF position locks the forward thrust lever in the idle position. The thrust control drum and thrust control shaft rotate moving a cam which activates the thrust reverser control valve. A follow-up cam stop limits further advance of the reverse thrust lever until the thrust reverser deflector doors are in the reverse thrust position. Rotation of the doors aft removes the cam and allows lever motion to continue toward the temperature indicating detent. The lever may be moved through the temperature indicating detent to full reverse thrust. As the reverse thrust lever is returned toward the OFF position a cam actuates the thrust reverser control valve to cause the doors to return to the forward thrust position. When the doors are stowed the follow-up cam moves to a position which will allow forward thrust. When the reverse thrust lever is in the OFF position the forward thrust lever is unlocked.
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