[ltp] Re: Linux-Thinkpad digest, Vol 1 #632 - 27 msgs

[morpheus]

As I said, I'm a pilot, not an RF engineer.  As I recall, though, the
report used a particular model of Nokia phone and noted that at maximum
output it drew 4 amps of current, so that's the number that stuck in my
head.  Thanks for pointing out my mistaken use of a unit of measure,
however, it is incidental to the main point that the CAA did a
controlled study with cellphones at maximum output on a real airplane
and found no danger, except when the avionics installed are pre-1970s
equipment.

You are correct that Swissair lost an MD-11 with 229 passengers and crew
off the coast of Nova Scotia on September 2, 1998.  Arcing from a wire
likely sparked the fire, but the CTSB found that the high flammability
of insulaitng materials was the direct cause of the crash.  A wire from
the inflight entertainment system was discovered to have signs of
arcing, but it was impossible to tell if that was the primary ignition
event or whether it occurred after the fire started due to melting
insulation.

The full report of the Canadian TSB can be found here:
http://www.tsb.gc.ca/en/reports/air/1998/a98h0003/a98h0003.asp

At any rate, clearly this was not caused by RF interference...

-m

On Sat, 2004-10-02 at 07:57, James Knott wrote:
> morpheus wrote:
> > A few years ago British Airways lent an airplane to the British CAA, who
> > placed multiple transmitters (to simulate electronic devices) throughout
> > the airplane and then checked the signal strength at various locations
> > where avionics are installed.  The conclusion was that even at very high
> > signal output (4 amps) and at frequencies close to avionics frequencies
> > (they tested at 400 MHz and 900 MHz), the signal strength recorded was
> > well within the tolerances of the interference specifications to which
> > modern avionics have been designed since the 1970s.
> 
> Power, RF and other, is specified in watts, not amps.  Specifying amps, 
> without a corresponding voltage or impedance, is meaningless.
> > 
> > And let's also consider one other fact: cell phones, PDAs and laptops
> > have been around for 15 years.  I know we've all accidentally left our
> > cell phone on in our carry-on bag only to discover it when we land.  I'm
> > sure we've all once or twice left the 802.11 transmitter on our laptops
> > on during flight.  Now multiply that by millions of passenger-miles per
> > day, over fifteen years...if there were a dnager, we'd have more than
> > one story by one Delta pilot to show for it.
> > 
> > Folks, avionics are designed to exacting standards and can handle all
> > kinds of interference.  Your humble little cell phone, PDA or laptop is
> > not going to crash the plane.  The fact that Lufthansa is offering WiFi
> > service on their airplanes in flight should prove this.
> > http://wifi.weblogsinc.com/entry/9390742317552618/
> 
> Then again, IIRC, Swiss Air had built in game systems, which brought 
> down one plane, off Nova Scotia a few years ago.  The crash was caused 
> by electrical failure leading to fire.