I think the visors that the astronauats wore had a very thin film of old applied
to reduce both glare and heat. Could a similar coating be applied to canopies?
Bob Williams
Gramin@aol.com wrote:
> There is a great deal of publicity about development of flat panel displays,
> driven by the market need for advertising, brighter laptops, tv etc. Those
> that have been applied in military and commercial aviation cockpits are have
> so far been outside the price range suited to light aircraft, and are usually
> mounted in far more shielded environments. However things are improving.
> You can now buy a display for a few hundred uk pounds which will be about 3
> times brighter than your typical computer monitor.
>
> Unfortunately this is not good enough to compete with uniform skylight
> reflected around a small cockpit by day, let alone direct sunlight. A low
> wing configuration is clearly much worse than a high wing for this. The
> standard Europa tinted plexiglass helps a bit (factor of 2), but you really
> need to add an opaque film above your head, wear dark clothing (even blacken
> your face), and then add a shroud to mask light from the side.
>
> Here are some measurements from an unscreened 250 cd/sqm display system in
> the Europa cockpit (G-EMIN). It should be noted that the screen cannot be
> mounted flat against the face of the cockpit module, as the contrast falls
> when the viewing line is away from the perpendicular. However a tilted
> screen has the advantage of allowing air to circulate around it, which is
> important as they are limited at the top end to around 50C.
>
> Pointing at uniform blue sky at midday as reference .....................1000.
> Scattered light along pilot's eyeline from screen with display OFF... 15
> Typical light received from screen (in dark)........ with display ON....
8
>
> So there is around twice as much scattered light as there is light from the
> screen and the effective contrast falls to around a third. It is very
> difficult to read a map display at such a contrast. 1000+ cd/sqm screens can
> be bought at a price, but this would still be diluted down to 66% , and of
> course direct sunlight rather than skylight washes even these out. At the
> present therefore it is necessary to add a screening tunnel to use such
> displays reliably by day. Even then, the time taken to for the eye to adapt
> from viewing outside brightness is a problem, bearing in mind that attention
> should not be directed to a display for more than brief time.
>
> This situation will improve with more brightness per buck, but we really need
> a reasonably priced colour version of the b/w reflective technology already
> existing on gps screens, palmtops etc., which just love more illumination on
> them.
>
> Graham Clarke G-EMIN
>
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