[time-nuts] Boeing 787 GPS reception trouble

[Jim Lux]

On 6/2/14, 1:55 AM, Tom Van Baak wrote:

> Has anyone else noticed this? Or know about this? Please respond only if you have real information. I can speculate as well as anyone; so it's solid technical, RF, EMF, or composite carbon fiber engineering info I'm looking for.
>
I haven't noticed it myself, but when Beechcraft was making their pusher 
twin with carbon fiber, there was a whole raft of stuff they did to make 
sure it could take a lightning strike, including adding a conductive 
layer to the skin.  It doesn't have to be all that thick, since it's not 
structural.  This is a very real concern for carbon fiber components.

And, as you note, since the windows have electric shutters, there's 
probably an Indium Tin Oxide or similar coating on them, which would 
make an effective shield.
(http://gizmodo.com/5829395/how-boeings-magical-787-dreamliner-windows-work)

The basic rule on shielding is that holes where the perimeter is >1/2 
wavelength will pass some amount of RF, and when the perimeter is >1 
wavelength (e.g. a slot half wavelength long) will pass virtually all of 
it.  So your speculation about the windows in the plane being the 
pathway through which cell/gps/etc signals pass is a good one.


See also
http://www.boeing.com/assets/pdf/commercial/airports/acaps/787.pdf