Cambidge 302 display polarization

On 2/13/2012 7:32 AM, JC wrote:
Hi folks,
This weekend I flew a task with a borrowed 302.We are planning to
upgrade the panel and it was a good oportunity to try it out. It was
the first time I used one and I liked it but the display blacks out
with my polarized sunglasses and the only way to read it was lifting
them or tilting my head..
Is there a fix for this?


I went to my optometrist and said that I wanted non-polarized lenses.
She said "are you a pilot?". I have a 302 that's polarized one way, and
a Filser radio that's 90 degrees different. There's only one "fix for this.

Tony "6N"

On 2/13/2012 7:32 AM, JC wrote:
Hi folks,
This weekend I flew a task with a borrowed 302.We are planning to
upgrade the panel and it was a good oportunity to try it out. It was
the first time I used one and I liked it but the display blacks out
with my polarized sunglasses and the only way to read it was lifting
them or tilting my head..
Is there a fix for this?


I went to my optometrist and said that I wanted non-polarized lenses.
She said "are you a pilot?". I have a 302 that's polarized one way, and
a Filser radio that's 90 degrees different. There's only one "fix for this.

Tony "6N"

Go to a Camera store. Get a polarized filter. The one I got was about
8in x 8 in plastic and had a cardboard frame it was used to be placed
in front of a light for stage lighting.

I had a circle cut out of it and placed it over the glass display and
taped in place. Sit in the glider and rotate the polarized plastic
until you can see the 302 screen again. Used to do this in a borrowed
DG800. It was slightly darker than ideal, but worked fine.

Sunglasses block light polarized direction A.
Instrument polarizer blocks light polarized A+90 degrees.
In series they block everything.

Why does adding a third polarizer in the middle
allow light through ?

Spoooooookkyyy ;-)

That was my first thought as well...

My only guess would be if the polarized gel filter was actually a circular polarizer (unusual for a gel filter). Circular polarizers consist of a linear polarizer layer on a 1/4 wave retarder layer that then rotates/circularizes the polarization. The coating on the C302 and other instument glasss is actually such a circular polarizer, with the linear polarizer layer outermost--bouncing off the glass changes the circular orientation handeness, back through he retarder layer again turns that circular polarization to linear but at 90 degrees to the linear polarizer layer, blocking the reflection.

If a circular polarizer film was held with the 1/4 wave layer side facing the pilot and the linear polarized side to the C302 glass and rotated so it is aligned to the linear polarizer layer on the glass then the pilot sees circular polarized light that his polarized sunglasses won't show orientation sensitivity to, but the overall image will be darkened... how is that for a hand waving guess? An obvious test is this will only work with only one side of the polarizer film facing the pilot, turn the film over and it will not work (it will go from dark to light as you rotate the filter but it won't improve problems with viewing with polarized sunglasses).

Darryl

Guess again ;-)

And I'm sticking that guess until Garret tells us the test of flipping the gel filter does not work....

Ah winter r.a.s., how are all those PW5's doing?

Darryl