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

[morpheus]

As a pilot, I can tell you that most pilots have lots of stories to tell
you, and most get exaggerated over the years.  I know more than one
pilot who will swear to God he's seen a UFO.  In cases of science, we
should never rely on anecdotal evidence.

Autopilots are electronic equipment and can fail for any number of
reasons.  There is no gurantee that the PDA was causing the problem.  I
highly doubt it since autopilot avionics are generally installed under
the cockpit floor.  As you know signal strength degrades with the square
of the distance, so even if the passenger was in the first row, we're
looking at a distance of 20 feet, and 1/2 inch of aluminum in between.
Also, remember we're talking about INTERFERENCE...the frequencies used
by 802.11 (2.4 GHz) and cellular (900MHz and up) are nowhere near the
frequencies used by avionics (360 MHz and below).  Given the weak
signals put out by PDAs, it is impossible that it could have affected
the autopilot.

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.

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/

-morpheus


On Fri, 2004-10-01 at 23:13, Brian Beattie wrote:
> On Fri, 2004-10-01 at 22:58, James McKenzie wrote:
> > Ken and Morpheus:
> > 
> > There is a documented occurance when an Delta pilot was wondering what 
> > happened to his autopilot. 
> 
> Can you supply us with this documentation?
> 
> -- 
> Brian Beattie   LFS12947 | "Honor isn't about making the right choices.
> beattie@beattie-home.net | It's about dealing with the consequences."
> www.beattie-home.net     | -- Midori Koto