(a)  
Position of the flaps during hydraulic operation is contolled by the flap control lever on the pilot's control stand. Movement of the flap control lever positions a cable system which extends back to the flap PDU.

 (b)  
The flap cables rotate the input cam in the flap PDU, displacing the cam follower. The cam follower is linked to the hydraulic control valve and opens the control valve to supply hydraulic power to the PDU hydraulic motor.

 (c)  
Hydraulic flow causes rotation of the hydraulic motor which drives the PDU gearbox. The gearbox drives the output shafts and attached torque tubes.

 (d)  
As the PDU gearbox operates, it drives a feedback mechanism connected to the follow-up cam. Movement of the followup cam closes the hydraulic control valve, stopping the PDU.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.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

757
MAINTENANCE MANUAL

SEE A
FLAP CONTROL
LEVER
SEE B

FLAP
CONTROL
LEVER

1-UNIT DETENT (GATE)
5-UNIT DETENT
15-UNIT DETENT 0 (FLAPS UP) 20-UNIT DETENT (GATE)DETENT 25-UNIT DETENT
30-UNIT DETENT (FLAPS AND SLATS FULLY EXTENDED)
B
SEE C
A
LEADING EDGE AMBER WARNING LIGHT
TRAILING EDGE EDGE
LEADING TRAILING
EDGE
AMBER WARNING
FLAP POSITION
5
1 15 INDICATOR
20
UP FLAPS 25
30
ALTERNATE
ALTN FLAPS
FLAPS/SLATS
5
POSITION SELECTOR
1
15
SWITCH
UP 20
NORM  25 
30  TRAILING EDGE 
LE  TE  ALTERNATE DRIVE 
ARMING SWITCH 
ALTN  ALTN 

LEADING EDGE ALTERNATE DRIVE ARMING SWITCH
C
Trailing Edge Flap Controls
Figure 15

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL

 (2)  
Alternate Function

 (a)  
During alternate flap operation flap position is controlled by the alternate flap/slat position selector switch.

 (b)  
The flap system is placed in alternate control by pressing the trailing edge alternate drive arming switch.

 (c)  
After arming the alternate drive system, flap position is selected by rotating the alternate flap/slat position selector switch.

 (d)  
Signals from the position selector switch are sent to the FSEU which operates relays to run the alternate drive motor on the PDU.

 (3)  
Flap Drive System Function

 (a)  
Torque tubes attach to the output shafts of the PDU. The torque tubes extend out into each wing through gearboxes and support bearings.

 (b)  
Rotation of torque tubes is transferred through gearboxes into two transmissions mounted below the flap tracks for each flap.

 (c)  
Each transmission drives a ballscrew actuator through a universal assembly. The ballscrew actuator changes the rotational motion of the transmissions into translational movement of the flap carriages and attached flaps.

 (d)  
The flaps move rearward and downward on the flap tracks. As the flaps move the aft flap linkages are driven by their bellcranks to extend the aft flaps behind the main flaps.

 B.
Control

 (1)  
Normal Flap Operation (Hydraulic)

 (a)  
Flap position is normally controlled by the flap control lever on the pilot's control stand.

 ~.............................................................................. | Table I | | Flap Positions | ................................................................................ | Control Lever |UP | 1 | 5 | 15 | 20 *[1]| 25 |30 *[2]| ................................................................................ | Flap Angle |0° | 1° | 5° | 11° | 20° | 25° |34° | ................................................................................ | % Travel |0° | 10.32 | 51.85 | 70.46 | 80.41 | 88.13 |100 | 2................…...…...........…...........…........…........….......….......1
　
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