(b)
When depressurization occurs for asymmetry or uncommanded motion failures, the flaps remain in the position where failure occurs.
(c)
Depressurization of the flap/slat system is commanded by
signals from FSEU-1.Uncommanded Motion (Fig. 16).
(a)
Flap uncommanded motion is defined as the failure of the flaps to be in, or driving toward the commanded position.
(b)
In the normal mode, FSEU-1 monitors uncommanded motion by comparing the output from the flap control lever resolver with resolvers at the outboard ends of the torque tubes. If the flap lever is out of any detent for more than 25 seconds, or if the flaps are stationary and out of the commanded position, or if the flaps are moving away from the commanded position, a failure condition exists.
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(c)
In the event of an uncommanded motion failure the EICAS display panel will show a TE FLAP DISAGREE message and the amber TRAILING EDGE light comes on. The FSEU commands hydraulic shutdown of the flap/slat systems as described in 27-58-00, Trailing Edge Flap System Position Indicating System -Description and Operation.
(d)
In the alternate control mode, FSEU-2 compares the rotary switch position with resolvers at the outboard ends of the torque tubes. Any uncommanded motion results in failure annunication messages only, as the slow system travel rates allow the system to be shut down in time to avoid a dangerous flight configuration.
(9)
Asymmetry (Fig. 17)
(a)
A difference of 4% in right flap travel compared to left flap travel is considered an asymmetry condition.
(b)
FSEU-1 detects flap asymmetry by comparing resolver output from each wing.
(c)
In normal control mode an asymmetry condition causes the FSEU to command hydrualic shutdown of the flap/slat systems as described in 27-58-00, Trailing Edge Flap System Position Indicating System - Description and Operation. The amber TRAILING EDGE light comes on and the EICAS display screen will show a TE FLAP ASYM message.
(d)
In alternate mode FSEU-2 detects an asymmetry condition resulting in the TE FLAP ASYM message on the EICAS display and illumination of the amber TRAILING EDGE lights.
2. Component Details
_________________
A. Flap Control Lever (Fig. 8)
(1)
The flap control lever, located on the center aisle stand, controls operation of the flaps and slats during normal operation.
(2)
The lever assembly consists of a spring-loaded telescoping handle and a cable drum.
(3)
The control stand has detents at the 0-, 1-, 5-, 15-, 20-, 25-, and 30-unit positions. The flap lever is spring-loaded to lock into each detent. Lifting the lever releases the handle to allow rotation.
(4)
If the flap lever is not in any detent or not properly seated in a detent for 25 seconds, a condition exists that results in FSEU commands to depressurize the flap/slat hydraulic systems and to move both flap and slat bypass valves to the bypass condition. The amber TRAILING EDGE light comes on and the EICAS display screen will show a TE FLAP DISAGREE message.
(5)
Gates are provided at detents 1 and 20 to prevent inadvertent movement past these positions.
(6)
Flap control lever position is electrically monitored by a resolver attached to the flap lever by linkages.
B.
Alternate Control Panel
(1)
The flap/slat systems are controlled electrically by a rotary position switch and the leading and trailing edge arming switches. The arming switches operate the hydraulic motor by-pass valves and depressurize the high lift system hydraulics.
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