FWD
AIRPLANES WITH EFIS
Flap Control Lever Figure 7
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 5.  Flap Control Unit
_________________
 A.  The flap control unit contains the mechanical linkage that operates the flap control valves. The control unit consists of an input linkage, two cams connected by a shaft, and a cable drum (Fig. 8).
 B.  A flap control quadrant located directly above the flap control unit transfers cable motion through a shaft, a link, and a bellcrank to position the trailing edge flap control valve slide. Pressurized fluid from the control valve drives the flap hydraulic motor. As the hydraulic motor drives the flap system, it also drives the power unit follow-up drum. Follow-up motion is transmitted by flap follow-up cables (WFFA and WFFB) to the control valve follow-up drum. Rotation of the control valve follow-up drum transmits motion through a cam, cam roller, and link to the bellcrank. Rotary motion from the bellcrank returns the control valve to the neutral position preventing fluid flow to the flap hydraulic motor. The control valve follow-up drum also transmits motion through a second cam and cam roller to control the leading edge flap control valve.
 C.  The flap control unit is mounted on the right wheel well ceiling near the aft bulkhead. Mounted on the forward end of the follow-up shaft is an actuating cam for the flap limit switches, the landing gear warning horn switches, the takeoff warning switch, the mach trim switch, and the flap 10-degree switch.
CABLE TENSION QUADRANT
FLAP CONTROL SWITCH
INPUT SHAFT FOLLOW-UP SHAFTWFB CABLE FOLLOW-UP DRUM
WFA CABLE WFFA CABLEFLAP 10-DEGREE
SWITCH S584
BELLCRANK CAM ROLLER WFFB CABLE
TE FLAP SWITCH S245
FLAPS UP LIMIT CONTROL VALVE
STALL WARNING S856
FLAPS DOWN LIMIT
CAM
SWITCH S246
ROLLER
FLAP LOAD LIMITER
TAKEOFF WARNING SOLENOID VALVE
MACH TRIM
SWITCH S130 LANDING SWITCH S290
LE FLAP SWITCH TE FLAP CONTROL
WARNING
CONTROL VALVE S138 VALVE LINK
Flap Control Unit Figure 8
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
 6.  Flap Control Valve
__________________
 A.  The flap control valve is a mechanically-operated slide valve used to control directional movement of the trailing edge flaps. The valve is attached to the flap control unit located in the right wheel well. The control valve is driven by the control unit linkage.
 B.  The control valve consists of a housing, a sleeve, and a slide assembly. Ports are provided in the housing and sleeve for passage of fluid to and from the flap hydraulic motor. Moving the valve slide outboard from neutral position pressurizes valve port B and connects valve port A to the system B hydraulic fluid return line. This allows the flaps to retract. When the valve slide is moved inboard from neutral position, valve port A is pressurized and valve port B is connected to the return line. In this valve slide position, the flaps will extend. When the valve slide is in the neutral position, the flow of hydraulic fluid to the flap hydraulic motor is blocked.
 C.  The control valve includes a hydraulic solenoid valve activated by the flap load limiter system. The solenoid valve, when energized, repositions the flap control valve to the 30-unit position from the 40-unit position.
28V DC OFF
DC BUS NO.1
FLAP VALVES ARMED NORMAL
BY-
PASS FLAP ASYMMETRY SHUTOFF RELAY
ALTERNATE FLAPS ARM SWITCH 
BY-PASS  NORM 
TE BYPASS VALVE 
PRESSURE RETURN  FLAP POWER UNIT 

SYSTEM B
PRIORITY
VALVE
TE FLAP CONTROL VALVE
CONDITION: FLAPS EXTENDING PRESSURE
SYSTEM B RETURN
Trailing Edge Flap System Hydraulic Schematic
　
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