Flap Uncommanded Motion / Moving Away / Asymmetry
(a)
If a flap group moves when not commanded, or moves in the opposite direction of that commanded (flaps moving away), the FCU sets an uncommanded motion. If the uncommanded motion is set when the group is in primary hydraulic/pneumatic mode, the FCU switches that group to primary electric mode. If the uncommanded motion is set while the flap group is in primary electric mode, the FCU will shut down that group. The group will remain shut down until power to the FCU's is cycled off and on following the flight.
(b)
The times delays for the FCU to set an uncommanded motion are: 1) TE Hydraulic: 0.5 sec 2) TE Electric: 4.0 sec 3) LE Pneumatic: 0.3 sec 4) LE Electric: 3.0 sec
(c)
If the FCU detects an asymmetry between left wing and right wing flaps of a TE flap group, the FCU will shut down both the hydraulic and electric drives for that group.
High Lift System EICAS Messages
(a)
The EICAS caution message FLAPS PRIMARY is displayed when one or more flap groups enter primary electric mode due to a disagree.
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A
747-400 MAINTENANCE MANUAL
(b)
The EICAS caution message FLAPS DRIVE is displayed when one or more flap groups fail to move in primary electric mode due to a disagree or a shutdown.
(c)
The EICAS status message TE FLAPS appears when hydraulic TE flap operation has failed, or when there is a flap asymmetry.
(d)
The EICAS status message LE SINGLE Drive is displayed when there is a single Leading Edge Drive Mode Failure. The status message LE MULT DRIVE is displayed when there are multiple Leading Edge Drive Mode failures on one or more Drive units. A mode is either Primary Pneumatic or Primary Electric operation.
(e)
The EICAS status message FLAP SYS MONITOR is displayed when there is a failure of a LE flap power drive unit limit switch, TE flap position RVDT transmitter, or flap lever RVDT.
(f)
The EICAS status message FLAP CONTROL L, FLAP CONTROL C, or FLAP CONTROL R is displayed when there is a failure of the corresponding flap control unit. The EICAS caution message FLAPS CONTROL is displayed when there is a failure of all three flap control units, or if the ALTN FLAPS ARM switch is pressed to the ARM position.
B.
Functional Description - TE Flap Drive Train and Load Relief
(1)
In primary hydraulic mode, the FCU sends signal to the flap actuator, causing it to extend or retract until its internal RVDT agrees with flap control lever position. The flap actuator moves the flap input lever. The flap input lever then moves the input linkage to the flap control assembly of each power package, which opens the flap control valve to port pressurized hydraulic fluid to the hydraulic drive motor. The hydraulic motors each drive a torque tube system through a reduction gear train.
(2)
As the flaps move, the worm gear train drives a follow-up cam mechanism in the flap control unit. When the selected flap position is reached, the follow-up mechanism closes the control valve to stop the hydraulic motor. The hydraulic motors can fully extend or retract the TE flaps in approximately 45 seconds.
(3)
In primary electric mode, the relays which control the flap drive electric motors are activated directly by the FCU. The electric motors drive the torque tubes through reduction gears. The motors stop when the flap position RVDT's indicate to the FCU's that selected flap position has been reached. The motors can fully extend or retract the TE flaps in approximately 6 minutes.
(4)
The hydraulic motor or electric motor drives a torque tube system through a reduction gear train. The torque tubes drive two transmission assemblies at each flap. Rotary motion of the flap transmissions is changed to linear motion to drive the flaps through a system of ball screws, ball bearing nuts, and gimbal assemblies.
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