(b)  
To move the TE flaps by hydraulic power, the FCU activates the flap actuator in the TE flap input lever assembly. To move the LE flaps by pneumatic power, the FCU activates the shutoff valve and directional control motor in each LE flap power drive unit.

 (c)  
The flaps extend in a specific sequence as the flap control lever is moved aft from the UP detent: 1) At the 1-unit detent, the group A LE flaps extend fully,

 and the TE flaps do not move. The group A LE flaps remain
 extended as the flap control lever is moved farther aft.
 2)  At the 5-unit detent, the group B LE flaps extend fully, and the TE flaps extend to the 5-unit position. The group B LE flaps remain extended as the flap control lever is moved farther aft.
 3)  At the 10, 20, 25, and 30-unit detents, the TE flaps extend to the corresponding position. The TE flaps extend fully when the flap control lever is at the 30-unit detent.
 (d)  The flaps retract in stages as the flap control lever is moved forward: 1) At the 25, 20, 10, or 5-unit detent, the TE flaps retract
 to the corresponding position.
 2)  At the 1-unit detent, the TE flaps retract fully. When the inboard TE flaps are in a position of less than 5 degrees during retraction, the group B LE flaps retract.
 3)  At the UP detent, the group A LE flaps retract as soon as the outboard TE flaps are fully retracted.
 (5)  
Primary Electric Mode

 (a)  
If a group of flaps does not move within a certain amount of time after the flap control lever is moved, the FCU sets a disagree. The FCU then switches that flap group to primary electric mode and activates the flap drive electric motors.

 (b)  
In primary electric mode, the flaps respond to the flap control lever in the same sequence as they do for primary hydraulic/pneumatic mode. Flap movement is much slower under electric power than under hydraulic and pneumatic power. A LE flap group (group A or B) in the primary electric mode will return to the primary pneumatic mode as soon as the flap group reaches the commanded position.

 (c)  
If the FCU sets a disagree while a flap group is in primary electric mode, the FCU will continue to energize the electric motors, even though there may be no flap movement.

 (d)  
The times delays for the FCU to set a disagree are:
 1) TE Hydraulic - Extend: 7 sec

 -
Retract: 7 sec
 2) TE Electric - Extend: 25 sec

 -
Retract: 25 sec 3) LE Pneumatic - Extend: 35 sec in air, 15 sec on ground

 -
Retract: 25 sec in air, 15 sec on ground

 4)  LE Electric - Extend: 135 sec, or 5 sec to leave retracted position on ground
 -Retract: 135 sec
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 27-51-00
 ALL  ú ú 01 Page 19 ú Oct 10/95
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
 (6)

(7)

(8)

A
747-400 MAINTENANCE MANUAL
 (e)  
An additional time delay of 30 seconds for the TE flap hydraulic disagree is begun when the landing gear control lever is moved from UP to DN.

Alternate Electric Mode

 (a)  
In alternate electric mode, the flap drive electric motors are under manual control independent of the FCU's. The flaps are controlled from two switches on the pilots' center instrument panel. The ALTN FLAPS ARM switch is pressed to enable the alternate system.

 (b)  
Two of the three flap control unit inputs are from the relays R7774, ALT FLAP INBD TE, and R7775, ALT FLAP 2 OTBD. Circuit breakers TE FLAP ELEC CONT OTBD and TE FLAP ELEC CONT INBD supply power to these relays. If these two circuit breakers are pulled, the flaps will remain in the primary mode. If only one of the circuit breakers are pulled, the flaps will transition into the alternate mode. A FLAPS CONTROL EICAS caution message will be displayed when the flap system is in the alternate mode.

 (c)  
The ALTN FLAPS EXT/RET switch is placed in the EXT or RET position to activate the relays which power the electric motors. The relays are deactivated when the limit switches in the TE power packages and the LE power drive units open at flaps fully extended or retracted. The flaps may be stopped at any intermediate position by placing the ALTN FLAPS EXT/RET switch to OFF.

 (d)  
In alternate electric mode, the extend limit switches in the TE power packages do not allow the TE flaps to extend beyond the 25-unit position.
　
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