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I got checked out in the G1000 172 at my flight school just so I could schedule to fly when the two steam gauge 172s were booked. I'm very impressed by the G1000, but I can't wear sunglasses when I fly the NAVIII. This is with the avionics dial on the lighting panel turned all the way up.

Does anyone else have this problem? Is it my sunglasses?

egid
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flyinghigh
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1 Answers1

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The screens are LCDs, which have a polarized filter layer over them. That layer is usually placed at a 45° so they are misaligned with your polarized sunglasses which are aligned vertically. You can confirm this is the problem by turning your sunglasses at different angles and see if the screen changes.

TomMcW
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  • Bingo! Can't wait to test this out. – flyinghigh Aug 09 '15 at 01:40
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    The polarization on the sunglasses is probably the issue. It's not a good idea to fly with polarized sunglasses on anyway. It can reduce the glare off an airplane when that glare might be the queue that saves your life. – ryan1618 Aug 09 '15 at 02:07
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    This is 100% what's up. I modified this answer to be a little more certain about things. – egid Aug 09 '15 at 02:11
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    Gratuitous extra info: A polarization filter is a key part of an LCD. Liquid crystal itself can only change the polarization of the light going through it; it's the polarization filter that then blocks some of the light making pixels appear light or dark : https://en.wikipedia.org/wiki/Liquid-crystal_display#Overview – rakslice Aug 09 '15 at 07:37
  • However, it would be easy to "de-polarize" the light coming from an LCD, so you could still read it at any angle. A plastic foil of a cigarette packet mounted on a display at the correct angle works well enough to demonstrate the effect. I don't understand why manufacturers don't spend a few cents for such a foil (of course, higher quality than the foil from a cigarette pack...) – sweber Aug 09 '15 at 07:55
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    @RyanBurnette: Ahem "cue" ;) – Lightness Races in Orbit Aug 09 '15 at 13:21
  • I read a few other sources that say flying with polarized glasses is fine. In the end we'll all make our own choice about it. – ryan1618 Aug 09 '15 at 15:00
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    @DavidRicherby: Planes are made of metal, but usually are painted, too. The paint generates polarized glare. About the LCD: Of course, polarization is the principle of work inside an LCD. But you can convert the linear polarized light coming from the display into circular polarized light, which is not affected by polarizing sunglasses. As said, a simple foil on top of the display is enough. My opinion: The blue of the sky is also partially polarized and so shaded by glasses. Clouds and other objects stay bright and are better visible, which is a clear pro for polarized glasses. – sweber Aug 09 '15 at 17:55
  • @sweber I was under the impression that the thin layer of paint wouldn't cause polarization but it seems I was mistaken. – David Richerby Aug 09 '15 at 19:10
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    @DavidRicherby, it is not the paint that causes polarization. Whenever light is reflected from a surface at an angle (not perpendicular), it is polarized. – Jan Hudec Aug 09 '15 at 21:21
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    @sweber: Polarized sunglasses are polarized so that they filter out reflections, mainly from horizontal surfaces. Most of the time that is what you want, but not when looking for other aircraft. – Jan Hudec Aug 09 '15 at 21:23
  • @JanHudec Sure, it's not paint that causes polarization per se. Rather, metals cause non-polarization and I was under the mistaken impression that painted metal had enough of the properties of metal that it would also cause non-polarization. – David Richerby Aug 09 '15 at 22:11
  • Thanks guys. Did not know what the polarization filter did in lcd's, just knew there was one. You learn something new every day. Edited answer to reflect. – TomMcW Aug 10 '15 at 01:08
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    @DavidRicherby, yes, metals don't cause polarization on reflection, but once the paint is opaque (and that's it's point) it is the paint and not the metal that reflects the light, so the reflection becomes polarized (I wonder what a metalic paint does though). – Jan Hudec Aug 10 '15 at 07:41
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    First off, metallic paints actually don't have any metal (there are some paints with high metal content to make them conductive for electronic shielding, but they're not very pretty). Metallic silver paint is just a specific shade of grey in a gloss base with mica particles suspended in it to provide that metallic glitter. So on a plane painted silver, the reflection is 100% paint. The mica flakes can cause a scatter effect on polarization because they're oriented at different angles, but it's minor compared to the reflection off the high-gloss surface. – KeithS Aug 12 '15 at 18:37