(3)  
The PDU's in the ball transfer panel area and lateral guide rail system provides the cargo handling capability for lateral and longitudinal directional changes within the compartment. The system consists of retractable PDU's and lateral guide rails, linkages and linear actuators located below the cargo supporting structure within the compartment doorway.

 (4)  
The cargo handling control system provides powered control and sequencing of the power drive systems through control switch and circuitry located adjacent to the compartment doorway.

 2.  Ball Transfer Panels (Fig. 1)
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 A.  The ball transfer panels incorporate a "pan" with mounting provisions for installation of the PDUs. Pan covers are fastened over provisional PDU mounting locations. Grounding straps are installed in the pans for immediate access when installing or removing PDUs.
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 3.  PDU/Component Channel Assemblies (Fig. 1)
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 A.  PDU/Component channel assemblies are installed at LBL and RBL 31.42 and include PDU's transport rollers and braking rollers. Mounting provisions are included in channels that have PDUs installed. Transport rollers provide the low-friction surface required for longitudinal movement of containers, and are spaced at approximately 10 inch intervals. Braking rollers provide braking and coast control for containers, if aircraft is positioned on a slope.
 4.  Power Drive Units (Fig. 1)
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 A.  Power drive units (PDUs) are located in the cargo compartment to facilitate movement of containers and pallets during loading and unloading operations. The PDUs are spaced to ensure that a minimum of one PDU is in contact with a cargo container. There are ten PDUs in the ballmat area; four mounted laterally and six mounted longitudinally. The ballmats include mounting provisions for the PDUs. PDUs are also mounted in the PDU/Component Channel assemblies for forward and aft movement of cargo containers.
 B.  The PDU uses a 200v AC, 400 Hz three phase motor to drive a self-lifting, rubber covered drive roller which transfers tractive force by means of friction to the bottom of the cargo container. The rated tractive force of the PDU is 247 lbf (1100 Nm). The drive roller retracts under its own weight when power is removed. An infra-red proximity sensor in the PDU detects the presence of a container and the signal is sent to the control system.
 5.  Guide Rail Actuator (Fig. 1)
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 A.  The linear actuators are used to extend and retract the lateral guide rails consist primarily of a motor brake assembly and an acme nut-and-screw actuator. The motor operates on 220-volt, 400 Hz, 3-phase power. Internal limit switches control the actuator stroke, which varies according to the location in which the actuator is installed.
 6.  Guide Rail Linkage (Fig. 1)
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 A.  The retractable lateral guide rail extension/retraction linkage consists of several cranks and rod assemblies that are used to connect a set of six guide rails with a linear actuator. Each rod assembly is adjustable, and may be changed in length as necessary to provide the correct retracted position of the guide rails.
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MAINTENANCE MANUAL

 7.  Lateral Guide Assembly (Fig. 1)
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 A.  Guide rails, located in the cargo compartment door areas, provide lateral guides for containers being moved into and out of the containerized cargo compartments. In addition, they provide longitudinal restraint to the containers located in the compartment. The lateral guides are spring-loaded in the up position and are raised and lowered by means of linear actuators, and related linkages. Six lateral guides are located on each side of the ball transfer panel in the forward compartment and six are located on the forward side of the aft compartment ball transfer panel. Hold-down clips are provided to retain each lateral guide in a retracted position in the event of a malfunction. Each lateral guide must be depressed and held while the clip is positioned.
　
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