51-24-20
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747-400
MAINTENANCE MANUAL

 (b)  
Make the primer thin with TL-52 up to a maximum thin ratio of four parts finish and one part thinner by volume if it is necessary.

 (c)  
Apply the spray to a dry layer thickness of 0.8 to 1.2 mils.

 (d)  
Cure a minimum of four hours at 75 |5°F before service.

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 51-24-20
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747-400 MAINTENANCE MANUAL
 SEALS AND SEALING - DESCRIPTION AND OPERATION
_____________________________________________
 1.  General
_______
 A.  Certain portions of airplane structure are sealed to prevent passage of gases or liquids through the many small gaps which normally exist at joints in fabricated structures. Sealing is accomplished by applying sealing compounds to crevices, edges and joints through which a fluid or gas might pass. The sealant used depends upon such factors as resistance of sealant to effects of fluids and temperatures.
 B.  In addition to sealing requirements contained in this section, installation drawings for specific items may require additional sealing.
 C.  Sealing definitions used in this section other than wing sealing are as follows. Wing sealing definitions are located in Fig. 6 and 7:
 (1)  
Absolute seal. All openings of any nature

_____________No leakage is allowed.
in the seal envelope, including all fasteners and seams require
 sealing.

 (2)  
Intermediate seal._________________All holes, slots, and joggles, and seams in the seal envelope require sealing.

 (3)  
Limited seal.____________All holes, slots, and joggles in the seal envelope require sealing.

 D.  Unless otherwise specified, all sealing shall be accomplished per AMM 51-31-01/201.
 2.  Structural Sealing
__________________
 A.  Most of the structural sealing on the airplane encloses the pressurized zone of the fuselage and integral fuel tanks in the outboard and center sections of the wing (Fig. 1 thru 8).
 B.  Several other local areas of structure are sealed to provide protection from, and proper drainage of, certain fluids. Examples of this are the areas below the toilets, galley, battery stowage, and air conditioning plenums.
 C.  In the area of the engines, sealant is used to isolate nacelles and pylons from the wing.
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 51-31-00
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747-400
MAINTENANCE MANUAL

CREW OVERHEAD HATCH

PRESSURE SEAL
1-A (INTERMEDIATE) 1-B (INTERMEDIATE) 1-C (INTERMEDIATE)
WEATHER SEAL 2-A (INTERMEDIATE)
AERODYNAMIC SEAL 3-A (LIMITED)
3-B (LIMITED)
LIQUID SEAL 4-A (ABSOLUTE) STA
ELECTRONIC ACCESS DOOR
520
SEALING REQUIREMENTS
-INSIDE CONTOUR
-AFT SURFACE OF STA 140 BULKHEAD
-AIRPLANE SIDE OF WHEEL WELL
-
ALL EXTERNAL GAPS AND NONBONDED SEAMS

-
ALL EXTERNAL GAPS INVOLVED IN THE AIRSTREAM NECESSARY TO MEET AERODYNAMIC REQUIREMENTS

-CAB WINDOWS SEALED PER CHAPTER 56
-UPPER SURFACES OF CONTROL CABIN FLOORS IN FORWARD OF STA 520 AND PASSENGER FLOOR IN AREA OF LAV, GALLEY, ENTRY AND BAR
Seal Index and Requirements Body Section 41
Figure 1 (Sheet 1)

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