*
System set to PDU RIGHT or to PDU BOTH
*
System set to PDU FWD.
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Forward Left Guides 2 and 3 Down Position
Forward guides 2 and 3 go to the down position when all of these events occur:
*
Joystick to FWD or AFT
*
System set to PDU LEFT or to PDU BOTH
*
System set to PDU FWD.
Aft Right Guides 1 and 2 Down Position
Aft guides 1 and 2 go to the down position when the system is set to PALLETS or when all of these events occur:
*
Joystick to FWD or AFT
*
System set to PDU RIGHT or to PDU BOTH
*
System set to PDU AFT.
Aft Left Guides 3 and 4 Down Position
Aft guides 3 and 4 go to the down position when the system is set to PALLETS or when all of these events occur:
*
Joystick to FWD or AFT
*
System set to PDU LEFT or to PDU BOTH
*
System set to PDU AFT.
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CARGO HANDLING SYSTEM -FUNCTIONAL DESCRIPTION -PDU
General
For control purposes, the powered drive units (PDUs) are in two major groups, longitudinal and lateral. The longitudinal group has two minor groups, left and right. All PDUs are also grouped by location in the compartment (bays). These are PDUs by group and location for the forward cargo handling system. The aft system is almost the same.
PDU Groups and Location
Area Major Group PDUs by Row
Forward Bays Longitudinal 1L/R, 2L/R
Ball Panel Longitudinal 3L/R, 5L/R, 7L/R
Lateral 4L/C/R, 6L/C/R
Aft Bays Longitudinal 8L/R through 16L/R
Only the PDUs in a single major group operate at a given time. Within the longitudinal group, the left and right minor groups may operate independently or at the same time. You can operate all PDUs row by row. The PDUs have three conditions:
*
Erect/drive
*
Erect/brake
*
Down.
All PDUs get 115v ac, three-phase voltage from the ground handling bus. They use this ac voltage for the erection coil, motor, brake and phase reversing relays.
EFFECTIVITY
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The CSC uses inputs from these switches to set the position of the PDUs:
*
Secondary joystick
*
Cargo control joystick
*
PDU forward/aft switch
*
PDU left/both/right switch
*
Pallet/container switch
*
Bay off switches.
CSC Control
Control circuits within the CSC, use phase reversing relays in the PDUs to control when and how voltage is given to the PDU motor. The circuits also control the erection coils and brake for the PDUs in the ball panel area. PDUs forward and aft of the ball panels have their erection coils and brake active when system power is on and the PDU is not in the drive condition. CSC control circuits command PDUs to erect/drive one row at a time with a small delay between rows. This reduces inrush current demands.
The bay off switches stop the drive command for rows of PDUs. This prevents PDUs from scrubbing under ULDs that are in position. The PDU rows affected by the bay off switches are different for containers and pallets. These charts show the functions of the bay off switches for the forward cargo handling system. The aft system is almost the same.
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CARGO HANDLING SYSTEM -FUNCTIONAL DESCRIPTION -PDU
Bay Off Switches (CONTAINER Mode)
Action Sw Bay(s) Effected PDU Rows Active
Toggle On D D 8, 9
Toggle On E D, E 8, 9, 10
Toggle On F D, E, F 8, 9, 10, 11, 12
Toggle On G D, E, F, G 8, 9, 10, 11, 12, 13
Toggle On H D, E, F, G, H 8, 9, 10, 11, 12, 13, 14, 15
Toggle On I D, E, F, G, H, I 8, 9, 10, 11, 12, 13, 14, 15, 16
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