This (seen at LDSB and quite common in GA) has been stated as being a bad idea because the window material gets a double dose of UV
Is there any evidence to support this?
It is obviously OK with cars because their windows are glass.
I thought windows don’t get much damage from UV, it’s the interior plastic that deteriorates?
Given the cost to replace windows in jets, if this were really true they wouldn’t use them. And they do all over the hotter areas of the world. The US litigation business would destroy the manufacturers if they caused damage.
I see this at smaller jets to prevent direct sunlight heating up the cockpit.
I have no evidence but for smaller pistons I could see how the reflection inside out might increase wear on the windows.
A lightweight, clean and thin cover (material similar to what camping tents are made of) on the outside might be better. Like this:
Most planes I rent have very think and heavy covers that are worn and very rough. Not good as they scratch the windows. They are usually wet and moldy as well, covering the plane in constant moisture. Taking them aboard instantly renders one above max take off mass.
My understanding is that what damages the plastic is the absorption of UV. The plexiglass absorb more than 90% of the UV so once the sun ray passed through the windshield it has lost most of the UV frequencies.
If a reflective surface is hung behind, the Ray should travel back through the plastic glass but this time with only 10% or less of the hazardous UV.
So in theory it doesn’t get double dose but just a bit more (maybe negligible amount) of UV.
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.
But IR makes it through almost 100 percent so does not age the glass?
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?
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.
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