2. Thrust Lever Assembly
A. Two thrust lever assemblies on the control stand control the forward thrust and reverse thrust of the engines. Each thrust lever assembly consists of a forward thrust lever, a reverse thrust lever, a reverse thrust detent mechanism, a thrust control link, a pawl and a thrust control drum (Fig. 2). The forward thrust lever, with the reverse thrust lever attached to it, is concentrically mounted with the thrust control drum. One end of the control link is riveted to the reverse thrust lever and the opposite end is attached to the thrust control drum. An autothrottle disconnect switch and a go-around (or auto-take off and go-around) switch is incorporated in the thrust lever assembly (Ref Chapter 34, Navigation).
B. As the thrust lever is advanced from the idle position, the control link rotates the thrust control drum to actuate the fuel control unit to increase thrust. The forward thrust idle position is against an idle stop on the control stand cover and full forward thrust is obtained before the lever is all the way forward. The reverse thrust lever, when in the OFF position, is against an idle stop on the forward thrust lever.
C. A lockout mechanism prevents simultaneous actuation of the forward and reverse thrust levers to assure positive forward or reverse thrust control. The ability of each lever to move depends on the position of the other lever. If the forward thrust lever is more than slightly forward of the idle position, the reverse thrust lever cannot be moved more than a small travel aft from OFF. However, if the reverse thrust lever is moved more than a small travel from OFF, the forward thrust lever cannot be moved. The lockout between the levers is a pawl, riveted to the forward thrust lever (Fig. 2). The pawl is between the thrust lever and the control link. When the forward thrust lever is in the idle position the pawl is aligned with a lockout hole in the web of the control stand thrust lever cover. As the reverse thrust lever is moved from the OFF position, the control link forces the pawl into the hole to lock the forward thrust lever in the idle position. As the reverse thrust lever is returned to the OFF position the control link pushes the pawl from the hole to unlock the forward thrust lever. When the forward thrust lever is more than slightly forward of the idle position, the pawl is not aligned with the lockout hole. The web then opposes the force of the control link on the pawl so the reverse thrust lever cannot be moved more than slightly aft of OFF.
D. The thrust lever contains reverse thrust power indicating detents.
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3. Engine Start Lever
A. Two engine start levers on the control stand are used to start the engines. Each lever controls energizing the ignition system and initiating or shutting off fuel flow to the respective engine by switch actuating cams on the start control drum. The start lever is provided with a spring-loaded detent catch which may be released by lifting the knob. A detent secures the lever in the CUTOFF and IDLE positions.
4. Engine Control Cables
A. Engine control cables consist of engine start and thrust cables which connect the drum-and-shaft assemblies at each engine to the respective engine start lever and thrust lever. The cables are routed from the control stand under the floor, thru the body shell and out the forward face of the wing front spar to the engine control drum-and-shaft assemblies. The thrust control cables also pass through the drum and friction brake assembly or autothrottle servomechanism.
5. Integrated Autothrottle Servomechanism (GJ B-2509, B-2510)
A. The integrated autothrottle servomechanism is composed of a torque switch mechanism, an actuator assembly and a throttle position sensor (Fig. 4).
(1)
The torque switch mechanism consists of input and output quadrants with an integral cam to operate switches, a mechanism to permit pilot override of the servo drive, a means of generating braking friction to prevent throttle creep in the manual mode, and a support framing with two removable control cable guards and locating dowel pins.
(2)
The actuator assembly consists of a servo motor with reduction gearing to form the prime mover, an electromagnetic clutch, a tachometer to provide servo motor speed signals, and electronic circuitry which, when controlled by the autothrottle computer, drives the output when the input has contacted a stop at the idle position.
(3)
The throttle position sensor consists of a potentiometer connected by a shaft to an input gear which is meshed with the torque switch mechanism idler gear. The throttle position sensor measures output quadrant travel and provides the position signal to the flight recorder.
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