Leading Edge Uncommanded Motion
The FSEU provides protection from uncommanded motion by the LE devices or
TE flaps.
Uncommanded motion is detected when no TE flap position or autoslat command
is present and:
- Two LE flaps move on one wing, or
- Two or more slats move on one wing.
The FSEU shuts down the LE control and illuminates the amber LE FLAPS
TRANSIT light.
In addition, to prevent uncommanded motion from occurring on the LE devices
during cruise, the FSEU maintains pressure on the retract lines and depressurizes
the extend and full extend lines.
Autoslats
At flap positions 1, 2 and 5 an autoslat function is available that moves the LE
slats to full extended if the airplane approaches a stall condition.
The autoslat system is designed to enhance airplane stall characteristics at high
angles of attack during takeoff or approach to landing. When TE flaps 1 through
5 are selected, the LE slats are in the extend position. As the airplane approaches
the stall angle, the slats automatically drive to the full extended position prior to
stick shaker activation. The slats return to the extend position when the pitch
angle is sufficiently reduced below the stall critical attitude.
