ENGINE CONTROL SYSTEM - DESCRIPTION AND OPERATION
1. General
A. The engine control system for each engine is divided into three subsystems: the forward thrust control system, the reverse thrust control system, and the start control system (Fig. 1).
B. The forward thrust control system consists of a thrust lever assembly for each engine, connected to each engine fuel control unit by control cables, a push-pull cable, and a rod linkage. The forward thrust control system regulates the engine fuel flow, and hence forward thrust.
C. The reverse thrust control system consists of a reverse thrust lever for each engine connected to each engine fuel control by the same control cables, push-pull cable, and rod linkage used to control forward thrust. However, the reverse thrust control system causes cable travel in the opposite direction and actuates the thrust reverser. The system regulates fuel flow to the engine, and hence reverse thrust. A lockout mechanism prevents simultaneous motion of the forward and reverse thrust levers.
D. The start control system consists of a start lever assembly for each engine, connected to each engine fuel control unit by control cables, a push-pull cable, and a rod linkage. The start control system controls energizing the ignition system and initiating fuel flow to the engine.
E. On GJ ALL EXCEPT B-2509, B-2510, drum and friction brake assemblies are installed in the throttle control cable runs. The brake assemblies are located between floor beams at the aft end of the electronic equipment compartment. On GJ B-2509, B-2510, integrated autothrottle servomechanisms are installed in the throttle control cable runs. The servomechanisms are located between floor beams at the aft end of the electronic equipment compartment. In the autothrottle mode, the system is controlled by the autothrottle computer and the throttle levers are driven through the servomechanisms (Ref Chapter 22, Auto Flight).
F. A drum and shaft assembly for each engine is mounted on the forward face of the front wing spar. It extends through the horizontal firewall into the engine nacelle strut and transmits engine control cable travel to the push-pull cable assemblies. A stop pin in the drum-and-shaft assembly stops start drum travel when the start lever on the control stand is in the CUTOFF position.
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Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 76-11-0 Page 1
G. Each engine start lever is connected by cables to the drum-and-shaft assembly. A push-pull cable assembly connects a crank on the start shaft to a crank on the engine cross shaft. A linkage rod connects a crank on the right end of the cross shaft to a lever on the fuel control unit.
H. The thrust lever assembly, drum and friction brake assembly, or autothrottle servomechanism, and drum-and-shaft assembly are cable connected. A push-pull cable assembly connects a crank on the drum-and-shaft assembly to a crank on the engine cross shaft. A linkage rod connects a crank on the right end of the cross shaft to the power control shaft crank on the fuel control unit.
I. Actuation of the thrust lever assembly regulates fuel flow in the fuel control unit. For reverse thrust, the lever assembly movement actuates the thrust reverser before increasing fuel flow. It should be noted that the direction of travel of the thrust control cables and drums is the same for decreasing forward thrust as it is for increasing reverse thrust. When reverse thrust is increased, a temperature indicating detent is encountered. The detent serves as a caution to the captain and first officer that it is possible to exceed allowable engine temperature limits if the reverse thrust lever is held in a position beyond the detent.
K92399 K92414
Engine Control System Component Location 5C8
76-11-0 Figure 1 (Sheet 1) Jun 20/85
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5C8 Engine Control System Component Location
Jun 20/85 Figure 1 (Sheet 2) 76-11-0
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