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 -------