Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!decvax!harpo!seismo!hao!hplabs!sri-unix!SHOLAR@cmu-cs-c
From: SHOLAR@cmu-cs-c@sri-unix.UUCP
Newsgroups: net.micro
Subject: Portables on airplanes
Message-ID: <1880@sri-arpa.UUCP>
Date: Tue, 7-Jun-83 22:44:44 EDT
Article-I.D.: sri-arpa.1880
Posted: Tue Jun  7 22:44:44 1983
Date-Received: Sat, 11-Jun-83 18:55:31 EDT
Lines: 38


Aircraft navigation receivers are much more sensitive than any
television receiver (which is why the navigation receivers start at
several thousand dollars, and typically cost tens of thousands of
dollars), so an RFI test using a TV receiver is not a very
good measure of what is safe for use on airliners.  

Suppose your view through automobile windshield were a projected
image, and that one of your back seat passengers was using a device
that caused your image to be shifted a few degrees to one side -- but
you didn't know it.  How long before you have an accident?

You might think a bit before you avoid asking a pilot about using your
portable computer just because you think he might refuse arbitrarily.
At cruise altitudes and speeds, think about what even 1 degree of
error in radio navigation indications might imply -- when headed for
Hawaii, for example.  When landing -- not the best time for hacking --
the matter becomes even more interesting.  Next time you ride an
airliner, watch for signs along the taxiway before you take off.
Quite a distance before you get to the end of the taxiway, there will
be a sign saying "ILS Critical Hold Area".

Beyond this point, the "passive" electronics on an aircraft on the
ground are sufficiently active as to cause disturbances to the
instrument landing systems on incoming aircraft.  If a different
aircraft's receivers, a half mile or more away, are sufficient to
deflect the needles on instruments of a landing aircraft, an Osborne
or Kaypro in seat 13D might be expected to do interesting things to
the instruments.

Imagine the thrill of barrelling along at 140 miles per hour,
approaching the ground at 1000 feet per minute, and discovering when
you emerge from the clouds and fog at only 200 feet above the ground
that your flight path is perpendicular to the runway!

Bill Sholar

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