FLIGHT CONTROLS
AIRPLANE
OPERATIONS
MANUAL
2-13-30
Page
2
Code
01
JUNE 29, 2001
FLAP SYSTEM OPERATION
The Flap Selector Lever provides five detent settings at 0°, 9°, 18°, 22°
and 45° positions. Intermediate positions cannot be selected. When
any position is selected, the selector lever signals to the Flap
Electronic Control Unit (FECU) to move the flap panels. The FECU
also monitors system failures and flap position, sending signals to the
EICAS and other related systems.
Flap Power and Drive Unit (FPDU) drive the flap panels. The FPDU is
a gearbox with two electric motors connected to that unit. Each motor
is controlled by the FECU through one independent channel. Both
motors drive all the flap actuators through flexible shafts. If a motor, or
its associated FECU control channel, or associated velocity sensor or
transmission brake fail, the affected channel is disengaged and its
associated motor actuation is interrupted. The remaining motor can
drive all flap panels at half speed. An EICAS message is presented to
indicate that flaps are being moved at a lower speed. If both motors or
control channels fail, an EICAS message is presented to indicate that
the system is inoperative.
Flap actuators are torque-limited to safeguard structure against
excessive loading should flaps or actuators jam. Velocity sensors
installed at the end of the flexible shafts detect panels asymmetry. In
such cases, the system is disabled.
On the ground a protection circuit prevents flap movement when the
airplane is energized and a disagreement is detected between flap
position and flap selector lever. To override such protection, it is
necessary to lift up and release the flap selector lever.
Two switches on the Flap Selector Lever send signals to the Landing
Gear Warning System to alert pilots any time the airplane is in a
landing configuration and the gear legs are not locked down.
Flap position is shown on the EICAS display. There are also flap marks
on the wing trailing edge, indicating 9° and 22°, which becomes visible
when flap moves to those positions.
To Next Page
Loading...
