(2)  
The flaps are controlled in 4 groups: TE inboard, TE outboard, LE group A (the 8 inboard LE flaps on each wing), and LE group B (the 6 outboard LE flaps on each wing). Each group can be independently driven by electric motors if the group fails to move under hydraulic or pneumatic power.

 (3)  
Each flap group can operate independently in the primary hydraulic/pneumatic mode, or the primary electric mode, or together in the alternate electric mode. In either of the primary operating modes, flap movement is controlled by the FCU based on the position of the flap control lever. In alternate electric mode, flap movement is controlled from the alternate flaps control switches.

 (4)  
Primary Hydraulic/Pneumatic Mode

 (a)  
The flaps are normally operated in primary hydraulic/pneumatic mode. In this mode, the flaps are controlled from the flap control lever. Movement of the flap control lever rotates the shaft of the flap control lever RVDT assembly. The electrical output of the RVDT assembly is monitored by the FCU, which moves the flaps until flap position agrees with flap control lever position.

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FLAP CONTROLLEVER GROUP AACTUATION
1
5

FLAPS UP
DETENT

FLAP CONTROLGROUP BACTUATIONDETENT (E1-2) M876 ELECTRO-PNEUMATIC DRIVE UNIT1-LEFT L.E. FLAP STA 1401

Primary Pneumatic Drive System - Simplified Schematic
Figure 4 (Sheet 1)

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MAINTENANCE MANUAL

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MAINTENANCE MANUAL

E99205
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MAINTENANCE MANUAL

 (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 a specific sequence 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. The group B LE flaps retract as soon as the inboard TE flaps retract to less than 4.5 units.
 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
　
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