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A
747-400 MAINTENANCE MANUAL
SINGLE CRACK
DUAL CRACK
B
A
B A
CLAM SHELL
GROWTH LINES
INITIAL SCRATCH/CRAZING MARKS
VIEW OF WINDOW SURFACE
OUTER SURFACE  INITIAL SCRATCH/ 
INITIAL SCRATCH/  OF PANE  CRAZING MARK 
CRAZING MARK 

DUALSINGLE CRACK CRACK
A-A  B-B
NOTE: THESE SECTIONS AND ILLUSTRATIONS ARE MADE LARGER TO SHOW THE CRACK DEVELOPMENT MORE CLEARLY.
Window Surface Crack Development - Example
(Outer Pane Stretched Acrylic)
Figure 601

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MAINTENANCE MANUAL

A-A
CRACKS AND/OR CRAZING

0.30 MINIMUM

NOTE: ALL DIMENSIONS ARE IN INCHES. NOT TO SCALE

REPLACE THE MIDDLE PANE IF
THERE ARE CRACKS OR CRAZING.

Passenger Window Inspection (Outer Pane Crazing) Figure 602
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A 747-400 MAINTENANCE MANUAL
 (2)  S 216-003Examine the window panes for erosion. (a) Erosion or chipping of the window forward edge can occur on windows in the nose area.
 NOTE:____ Structurally, this is permitted. If the appearance is not satisfactory, you can repair the window to remove the rough areas (AMM 56-21-01/801).
 (3)  S 216-004Examine the window panes for in-plane cracks. (a) Replace the outer pane when you can see the edge of an in-plane crack with the window installed (AMM 56-21-01/401).
 NOTE:____ A part should not be installed if the in-plane crack has more than 0.55 inch maximum extension from the edge. This also applies when the pane is removed for a different cause and in-plane cracks are seen after the removal.
 (b)  Replace the pane if the chips have a maximum depth of more than 0.05 inch (AMM 56-21-01/401).
 NOTE:____ In-plane cracks of the outer pane, at any other location than the edges, usually occur with chips. The distance between defects is not very important.
 (4)  S 216-005Examine the window panes for scratches. (a) Remove the scratches from the surfaces of the panes with the procedures and limits of Passenger Compartment Windows (AMM 56-21-01/801). (b) Replace the pane if the scratches have a depth greater than 0.05 inches.
 (5)  S 216-006Examine the window panes for chips. (a) Replace the pane if the chips are more than a depth of 0.05 inch.

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 S 216-007
 (6)  Examine the window panes to see if they are concave.
 (a)  When a window is concave, the outer pane bows in and the middle pane bows out.
 NOTE: The replacement of the window is not necessary when the
____
 window is concave.

 1) The correct clearance between the two panes is 0.27 inch. 2) Put a straightedge across the small width of the outboard surface of the outer pane. 3) If there is a clearance between the straightedge and the center of the pane, the window is concave.
 NOTE: Windows which often fog are usually concave.
____
 4)  Do a check of the seals for leakage into the window cavity between the outer and middle pane.
　
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