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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
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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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(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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