Re: Causes and solutions for window crazing.

From:         Steve Lacker <>
Organization: applied research laboratories
Date:         04 Aug 96 16:44:53 
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  or MIME structure (Pete Coe) wrote:
>Just back from my first flight in way too long.  Thanks to
>my travel agent I managed to get a window seat, but ended
>up severely dissapointed because I could barely see out of
>the window.  It was so badly scratched/crazed that it was
>more like looking out of frosted glass than a real window.

I have exactly the same complaint....

>All planes I travel on seem to have some level of scratches,
>but this was by far the worst I can remember.

Actually, I see a wide variation. The clearest windows I've had in recent
memory have been on several Delta 727's (well, the 5-month old MD-90s had clear
windows too), but what looks like a date code etched in the window (if it *is*
a date code) indicated that the windows were manufactured in circa 1987- long
after the plane itself. How often are the windows replaced, anyway? Even if
they were replaced, they seem very clear compared to other very new airplanes.
The most abraded windows I've seen were on Delta and American ships, but these
were 757's and MD 80s.

>I seem to recall that this crazing was blamed on volcanic ash,
>and the volcano blamed was the one that nearly downed a BA 747
>a decade or so back.

I seriously doubt this, since I also noticed that the abrasions tend to be near
vertical! A plane flying through ash would surely abrade in a horizontal
direction. I can only assume that the process of cleaning or
stripping/repainting the aircraft is the culprit. Actually, I would guess its
cleaning, since I've ridden American Airlines planes with windows that were
just as scratched as the Delta planes I mentioned.

>I would like to think that part of the care and maintenance of
>a plane would be the polishing and/or replacement of fuzzy windows,
>but as they are not a safety item what is the reality?

Are they not a safety item? I really wonder about this. Isn't it likely that
the scratches could eventually lead to stress fractures as the windows flex
during pressure cycles? Or is this simply not a problem in the case of the
window material?
Steve Lacker	/	Applied Research Laboratories, The University of Texas
512-835-3286	/	PO Box 8029, Austin TX 78713-8029