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 ALL  ú ú 01 Page 803 ú Feb 10/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
 STRUT DRAINS AND SEALANT - DESCRIPTION AND OPERATION
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General (Fig. 1)
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 A.  The strut drain system provides a means for disposal of accumulated fluids leaking from system plumbing routed through the strut. Sealant applied to the firewall and the interior of the nacelle strut is intended to prevent the leakage of accumulated fluids between strut compartments, or onto the engine.
 B.  The strut drain system consists of tubes which route fluids from sealed strut compartments to overboard drains. Entry screens are installed at all strut drain tube inlets. Sealant is applied at certain bulkheads and spars to provide sealed strut compartments.
 C.  Inboard and outboard strut drain systems are functionally similiar, although drain tube routing and sealant application differ due to structural differences.
Sealant
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 A.  Sealant is applied to the upper spar, midspar, lower spar, forward engine mount bulkhead, NAC STA (241) bulkhead above the midspar, torque bulkhead, vapor barrier, and wing front spar. Sealed compartments created by application of sealant include the forward strut compartment, aft strut compartment, and strut dry bay. The area aft of the torque bulkhead, vapor barrier, and wing front spar is sealed from the strut torque box area.
 B.  Leveling compound is applied to certain areas in the strut to provide proper flow of fluids to drain tube inlets. This ensures that no fluids accumulate in low points of strut compartments without means of disposal.
Drain Tubes
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 A.  Drain tubes are installed at low points in each sealed strut compartment and route fluids to either an overboard drain or the next lower compartment. The strut dry bay has a condensate drain at the low point in the compartment.
 B.  Entry screens are installed at all strut drain tube inlets to prevent debris from entering and plugging drain tubes.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
DRAIN INLETS DRAIN INLETS SEE A SEE A
AFT FAIRING 
DRAIN 
AFT MIDSPAR 
DRAIN TUBE 
STRUT DRY BAY 
CONDENSATE DRAIN 
OVERBOARD  OUTBOARD STRUT 
DRAIN 
DRAIN INLETS 
SEE  A 
DRAIN INLETS 
SEE  A 

AFT FAIRING DRAIN
AFT MIDSPAR DRAIN TUBE
STRUT DRY BAY CONDENSATE DRAIN
DRAIN INLETS WITH
ENTRY SCREENS
OVERBOARD
DRAIN INBOARD STRUT
TYPICAL DRAIN INLET 
A 
Nacelle Strut Drain 
Figure 1

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 STRUT DRAINS AND SEALANT - MAINTENANCE PRACTICES
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 1.  General_______
 A.  This procedure has these thirteen tasks:
 (1)  
Outboard Strut, Forward Tube - Leak Check (T1)

 (2)  
Outboard Strut, Aft Tube - Leak Check (T2)

 (3)  
Outboard Strut, Forward Midspar - Leak Check (S1)

 (4)  
Outboard Strut, Forward Upper Spar - Leak Check (S2)

 (5)  
Outboard Strut, Upper Spar Inlet - Leak Check (S3)

 (6)  
Outboard Strut, Closure Spar - Leak Check (S4)

 (7)  
Inboard Strut, Forward Tube - Leak Check (T1)

 (8)  
Inboard Strut, Aft Tube - Leak Check (T2)

 (9)  
Inboard Strut, Forward Midspar - Leak Check (S1)

 (10)
 Inboard Strut, Forward Upper Spar - Leak Check (S2)

 (11)
 Inboard Strut, Upper Spar Inlet - Leak Check (S3)
　
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