56-21-01
 ALL  ú ú 02 Page 803 ú Feb 15/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 747-400 MAINTENANCE MANUAL
 (3)  S 128-022Continue each step until you remove the marks from the step before (approximately 2-3 minutes).
 NOTE:____ Go between the horizontal and vertical direction with the vibrating sander and make sure there is a continuous flow of water.
 (4)  S 228-023Make sure the window dimensions are satisfactory.
 NOTE:____ The minimum window thickness must not be less than 0.280 inch after you repair it.
 (5)  S 168-024Remove the water spray.
 (6)  S 118-015Polish the window with the buffing compound and a clean muslin or a wool pad.
 NOTE:____ If it is necessary, use a coarse and fine compounds to get a glossy finish. If you use a buffer that turns, the speed of the wheel must be 3200 rpm for a coarse compound and 4200 rpm for a fine compound.
 (7)  S 218-026Make sure that optical quality of the window is satisfactory.
 (8)  S 118-034If the optical quality is not good, continue to repair the window.
 NOTE:____ The minimum window thickness must not be less than 0.280 inch after the repair.
 To repair the bevel edge or the seal plane, refer to the overhaul manual.
 (a) (b)  The minimum thickness of the middle window pane is 0.180 inch.The maximum depth of the damage in the inner pane (dust cover) is 0.03 inch.
 NOTE:____ To remove the damage, polish the full surface that persons look through.

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 56-21-01
 ALL  ú ú 01 Page 804 ú Oct 10/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 DOOR-MOUNTED WINDOWS - DESCRIPTION AND OPERATION
________________________________________________
 1.  General_______
 A.  All entry doors for passenger and crew have windows. Each main entry door has a rectangular window approximately 10.2 by 14.2 inches and is located near the aft edge of the door.
 B.  All entry door windows are identical to passenger fuselage mounted windows.
 (1)  
For servicing of the entry door mounted windows refer to 12-16-04/301.

 (2)  
For removal/installation of entry door mounted windows refer to 56-21-01/401.

 (3)  
For inspection/check of entry door mounted windows refer to 56-21-01/601.

 (4)  
For on airplane repair of entry door mounted windows refer to 56-21-01/801.

 2.  Main Entry Door Windows (Fig. 1)_______________________
 A.  The main entry door windows consist of outer, middle, and non-structural inner panes. The non-sturctural inner pane is and is mounted in the door lining. The outer and middle panes are each capable of withstanding the full cabin pressurization load. Fail-safe structure is ensured by the middle pane which is designed for 1.5 times the normal operating pressure at 70°F. The middle and outer panes are acrylic structural panes formed to improve resistance to crazing. The non-structural inner pane (or dust cover) is a flat sheet of polycarbonate.
 B.  The main entry door windows are plug-type windows subject only to the pressure acting on them. The outer and middle panes are secured to the window frame with spring clips. A seal/spacer ring separates the panes. The outer pane of stretched acrylic plastic, 0.35 inch thick, is rectangular in shape with rounded corners and a beveled outer edge to fit the window frame. The pane is curved to fair with the fuselage contour. The middle pane of modified acrylic plastic sheet, 0.22 inch thick is similarly shaped but with an unbeveled edge which is seated on the inboard face of the seal/spacer ring. A small breather hole is located near the bottom of the middle pane.
 C.  The seal/spacer ring positions both the middle and outer panes in the window frame and seals the outer pane to the window frame. The middle pane is mounted on the inboard face of the seal/spacer ring. The spring clips, securing the window in the window frame, compress the ring tightly against all members to form a pressure seal.
 D.  Main entry door windows are designed to preclude fogging and frosting by means of multiple pane construction with intervening cavities isolated from cabin interior air.
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