Marco Leon writes:

Saw a repeat episode of Mythbusters for the first time last night about
the use of cell phones on an airplane and interference with cockpit
instruments. I know that this was mentioned in a November 2006 thread
briefly but the short of it was that they concluded cell phones really
CAN interfere with the VOR signals.

At very close range and in certain positions, yes. But that doesn't
mean that using a cell phone in a seat in the middle of the aircraft
will do anything. There's already a lot of RF noise in the air around
aircraft.

One of the tests however, was on a Hawker jet with a glass cockpit
(Honeywell I believe) with a FMS. They could not get any frequencies or
amplitude of cellphone signals to budge the instruments like they were
able to on a 1970's era NAV system. From what I understand, the FMS
relies on a number of different inputs to drive its nav systems. If
that's the case, wouldn't it switch to another source if one seemed
unreliable?

Yes, within limits.

If it does, I imagine it would be a fundamental flaw in
their experiment. The FBO manager and avionics guy being interviewed
however, gave the nod to the robust wire shielding.

I suspect the shielding is actually protecting the avionics. They
have to be shielded just to prevent interference with each other, much
less interference from cell phones.

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