S 422-005
(2) Install the acoustical tiles as follows:
(a)
Install the tape on the outboard surfaces of the acoustical tiles where they will touch the structure.
(b)
In areas whre the acoustic tiles overlap, clean the exposed surface on the bottom acoustic tile with the solvent before you install the upper acoustic tile.
(c)
Press the acoustic tiles firmly to make sure the tile completely touches the skin and the stringers.
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747-400 MAINTENANCE MANUAL
AIRFRAME DRAINS - DESCRIPTION AND OPERATION
___________________________________________
General
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A. External drain holes and internal drain paths are provided to prevent water and other fluids from collecting within the airplane. Drain paths and drain holes must be inspected periodically to ensure they are clear of obstructions.
External Drains (Fig. 1 and 2)
_______________
A. Drain ports are located on exterior surfaces of body, wing, and empennage to dump fluids overboard. Leveling compound is used to ensure proper drainage in sloping areas. A removable valve assembly or a spring valve is used in pressurized areas. The valves close off ports when the airplane is pressurized and allow ports to remain open when the airplane is not pressurized. Drain ports in nonpressurized areas are always open.
B. A spring valve in catch basin, is located on the aft side of the wing center section rear spar in each landing gear wheel well. The catch basin should periodically be checked to ensure that opening to catch basin and spring loaded drain valve are not clogged.
C. The canted pressure deck has continuous overflow drain fittings and lines which are vented overboard just aft of the air conditioning ram air outlet.
D. On some airplanes, drain fittings with a removable hex cap are located in the sloping pressure deck at the intersection of the center wing section upper surface and the rear spar.
E. On some airplanes, drain fittings with a manual valve and drain tube are located in the sloping pressure deck at the intersection of the center wing section upper surface and the rear spar.
Internal Drain Paths and Drain Holes
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A. Internal structure is provided with tubes, channels, dams, and drain holes, to direct the flow of fluids toward external drainage points.
(1)
Primary body drain paths are provided in the forward lower body area (body Sta 520 to 970), in the overwing and wheel well area (body Sta 1000 to 1480), and in the aft lower body area (body Sta 1480 to 2360).
(2)
Secondary body drain paths are provided to all stringer splice locations. Drain ports in the floor at waterline 310 permit fluids to flow to the lower body skin where they drain overboard.
(3)
Internal drain paths are provided for fluid to flow down the vertical stabilizer auxiliary spar to a natural opening at the base where they drain overboard. Fluids drain through ports in the ribs near the vertical stabilizer front and rear spars to slots at the base where they drain overboard.
(4)
Fluids drain along the horizontal stabilizer auxiliary spar to a drain port near the body and drain overboard. Fluids drain along the horizontal stabilizer front spar to drain holes near each rib, forward of the spar.
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747-400
MAINTENANCE MANUAL
PROVIDED WITH LEVELING COMPOUND AT DRAIN HOLE LEVEL BETWEEN HOLE AND AJOINING FRAME.
Typical External Drains
Figure 1
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