76-11-00
ALL ú ú C01 Page 8 ú Mar 15/96
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
9. Operation
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A. Advancing the start lever to IDLE from CUTOFF position causes start control cams 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 in the wing (when the emergency fire shutdown switch is in the IN or normal position). The lever motion is also transmitted through the start control drum and push-pull cable to the shutoff lever on the main engine control. Movement of the shutoff lever opens the fuel shutoff valve in the main engine control to initiate fuel flow.
B. Placing the start lever in the CUTOFF position de-energizes the ignition system and closes the fuel shutoff valve in the main engine control and the fuel shutoff valve in the wing. When the lever is returned toward the CUTOFF position, the pin in the start control drum connecting the cable quadrant to the push-pull cable contacts a stop. Approximately 1-1/2 degrees of additional start lever travel is required to enter the CUTOFF detent. This stretches the control cable to preload the lever in the detent to prevent lever "buzz".
C. Advancing the forward thrust lever from the idle position, locks the reverse thrust lever and transmits motion through the thrust control system to the power lever on the main engine control which increases fuel flow to the engine. Forward motion of the forward thrust lever is terminated by a stop on the main engine control. Forward motion of the forward thrust levers also causes cams in the integrated auto throttle servomechanism and in the control stand 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.
E. Advancing the reverse thrust lever from the OFF position locks the forward thrust lever in the idle position and closes a switch in the thrust lever which moves the thrust reverser directional control valve to the deploy position. Translation of the thrust reverser sleeves causes rotation of the feedback cams in the thrust control drum through the thrust reverser feedback push-pull cables. When the feedback cams no longer block movement of the rollers on the throttle gear, the reverse thrust lever can be moved further aft. As the reverse thrust lever is returned toward the OFF position, a cam on the control stand thrust drum actuates switches which actuate the thrust reverser directional control valve to cause the thrust reverser sleeves to return to the stowed position. As the reverser sleeves move toward the stow position, the interlock cams are repositioned to allow motion of the forward thrust lever.
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76-11-00
ALL ú ú C01 Page 9 ú Jun 25/84
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
ENGINE CONTROL SYSTEM - MAINTENANCE PRACTICES
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1. General
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A. This section gives a method to change the thrust lever angle, in degrees, to arc length at the control stand cover, in inches.
B. The linear dimension is used to position the thrust levers when this is required for an adjustment/test.
C. To make the linear measurement, a flexible scale is used that will conform to the contour of the seal retainer along the top of the control stand cover, adjacent to the thrust levers.
(1)
The thrust lever angle is measured from the lever contact surface on the idle stop to the aft surface of the thrust lever.
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