LATCH MECHANISM
SEE E
FWD
LATCH SUPPORT CLIP SEE B
A
Bulk Cargo Door Figure 1 (Sheet 1)
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A
747-400
MAINTENANCE MANUAL
TYPICAL STOPS
D
Bulk Cargo Door Figure 1 (Sheet 2)
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A
747-400
MAINTENANCE MANUAL
LATCH FITTING (2 PLACES)
LATCH ROLLER (2 PLACES)
ROD ASSEMBLY (2 PLACES)
LATCH PROBE (2 PLACES)
OPERATING
SHAFT OPERATING
HANDLE (INNER)
AFT
INBD
LATCHING MECHANISM
E
Bulk Cargo Door
Figure 1 (Sheet 3)
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MAINTENANCE MANUAL
3. Balance Mechanism (Fig. 1)
_________________
A. Door balance is maintained by a constant tension system composed of compression springs, a cable drum, and a cable attached to the interior side of the door. The cable grooves in the cable drum have a decreasing radius in order to provide a constant balance of the door as the door is opened and closed. The balance mechanism is arranged so that when the door is closed the springs are compressed; when the door is opened, the springs expand to assist in raising the door to the open position.
4. Snubber (Fig. 1)
_______
A. The snubber is a self-contained hydraulic actuating unit installed between the door and overhead structure to slow door closing.
5. Operation
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A. Functional Description
(1)
The outer operating handle is pulled from its recess and rotated approximately 46 degrees counterclockwise to unlatch the door. Rotation of the handle actuates the two rod assemblies which withdraw the latch rollers from their latch fittings. As the latch rollers withdraw, the bulk cargo door warning switch (Ref 52-71-00) is actuated. This causes the DOOR BULK CARGO message to show on EICAS. The handle is released as soon as the door has moved clear of its latch fittings. Springs on the probe assemblies and within the handle cause the handle to return to its normally locked and recessed position. With little or no manual effort, the door is swung open until the spring-loaded mechanical latch on the lower edge of the station 2000 floor beam engages with the latch support clip on the lower end of the door. Inward movement of the door causes the cable attached to the door to be drawn into the balance mechanism housing around the cable drum by the expanding compression springs. A snubber attached to the fuselage structure and the lower end of the forward hinge prevents any sudden movement of the door and ensures a smooth transition from closed to open.
(2)
The door may also be opened from inside the airplane, using the nonretracting inner handle. The procedure is similar except that rotation of the handle appears clockwise to the operator. Access to the inside handle is obtained by pulling aside the cargo net which extends from the ceiling to the lower edge of the door.
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