mechanical system that extends and retracts the flaps.
Flap position is displayed on the Primary Flight Display (PFD) and the FLIGHT
CONTROLS synoptic page.
2. Description of Subsystems, Units and Components:
A. Flap Control Handle:
(See Figure 12.)
The flap control handle provides the electrical command to the Flap/
Horizontal Stabilizer Control Unit (FCU) for required flap position. The flap
handle mechanically positions a dual Rotary Variable Differential
Transformer (RVDT) for flap control. Power for the RVDT comes from the
FCU. The flap control handle is located on the right side of center pedestal
and is labeled FLAP. The flaps can be placed in four positions: UP (0°),
10°, T/O APP (20°) and DOWN (39°).
B. Flap/Horizontal Stabilizer Control Unit:
(See Figure 10.)
The Flap/Horizontal Stabilizer Control Unit (FCU), located in the Baggage
Compartment Electronic Equipment Rack, performs control and system
health functions of the Flap/Stabilizer systems. It contains two independent
control channels: Channel A and Channel B. Each channel communicates
with the other by comparing FLAP handle RVDT position and left and right
flap resolver position to generate signals that drive the enable, extend or
retract solenoids of the Power Drive Unit (PDU). A malfunctioning channel
will be inhibited and the remaining operating channel will continue to
control the flaps and stabilizer.
To compensate for pitch trim changes during flap operation, the FCU also
monitors the horizontal stabilizer position information from the Horizontal
Stabilizer Actuator (HSA) resolver and generates signals that drive the HSA
AC motor assembly.
The FCU provides system protection by completing operational status tests
with Built-In-Test (BIT) and functional fault monitoring. The FCU performs
the tests and monitoring and communicates the data on the Aeronautical
Radio Incorporated (ARINC 429) data bus to the Crew Alerting System
(CAS) through the Fault Warning Computer (FWC) and to the Maintenance
Data Acquisition Unit (MDAU). The FCU accepts input information on the
ARINC 429 for computed airspeed and Weight-On-Wheels (WOW).
C. Power Drive Unit:
The Power Drive Unit (PDU) provides the interface between the FCU,
hydraulic power source and mechanical drive units of the flap actuation
system. Check valves located in the supply line fittings of the control valve
module isolate the Left Hydraulic System (L SYS) and Auxiliary Hydraulic
System (AUX) sources (including PTU) to the hydraulic motor. Pilot
solenoid valves are electrically energized to port hydraulic pressure to
open and close the enable/shutoff spool valve and to control hydraulic
motor direction for extension or retraction of the flaps. The PDU is located
at the forward area of the main landing gear wheel wells.
D. Flap Drive Torque Tubes:
The flap drive torque tubes transmit power from the PDU to the mechanical
flap actuators. The torque tube drive line set consists of seven torque shaft
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS2A-27-00
Page 32
May 22/01
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