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Reflective covers placed inside the cockpit - rapid damage to plastic windows?

Generally light aircraft canopies are acrylic, for which the trade name Perspex or Plexiglass is often used depending on market. This has the advantage of being highly sunlight resistant over decades, as well as being amenable to scratch removal with abrasives and re-polishing. The downside is that it’s very brittle compared to Polycarbonate (Lexan) which unfortunately doesn’t share the other advantages of Acrylic.

172driver wrote:

@Peter, that may well be true, I’m referring to Cessnas. Btw, Perspex is widely used as a generic term for GA windshields here.

I googles it also but found some vastly divergent answers.

This inspired me to check the exact composition of mine. A four layer laminate of stretched acrylic-vinyl-vinyl-stretched acrylic.

EGTK Oxford

@Peter, that may well be true, I’m referring to Cessnas. Btw, Perspex is widely used as a generic term for GA windshields here.

I googles it also but found some vastly divergent answers.

Last Edited by 172driver at 13 Sep 17:22

If you get a rapid suntan, it probably means that different planes use different plastics, with Socata using some good stuff

However, a google on plexiglass UV absorption shows that almost none gets through. BTW I don’t think planes use Perspex, which is cheap flimsy stuff which cracks very easily.

Administrator
Shoreham EGKA, United Kingdom

Valtime wrote:

The plexiglass absorb more than 90% of the UV

Hmmmm…interesting. I always thought it was the exact opposite and the Perspex didn’t absorb hardly any UV. Being nicely tanned after a long fliught into the sun sems to bear this out. So – what is it ? Any plastics specialists around here?

Peter wrote:

at say FL150 the UV would be extremely strong.

If you fly regularly at those FLs you may need to upgrade from same plastic grade used in hubble telescope or space station

Paris/Essex, France/UK, United Kingdom

Peter wrote:

This is confirmed by the fact that one doesn’t get sunburnt; at say FL150 the UV would be extremely strong.

I definitely get sunburnt in the cockpit.

ELLX

Peter wrote:

You can definitely feel the heat through the window

Doesn’t that mean that the material doesn’t absorb, and thus is probably not affected?

But IR makes it through almost 100 percent so does not age the glass?

Biggin Hill

Yes; a good point about most UV being blocked so not much coming back out This is confirmed by the fact that one doesn’t get sunburnt; at say FL150 the UV would be extremely strong.

But maybe this issue applies to infra red. You can definitely feel the heat through the window, and in this case the material will get twice the dose.

Administrator
Shoreham EGKA, United Kingdom
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