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Why computers are "A Bad Thing" [Oct. 19th, 2006|03:57 pm]
Another winner from comp.risks:
Airplanes under instrument flight rules fly from one navigation beacon to another along published standard routes. In the old days, with radio navigation receivers and pilots flying by hand, a plane wouldn't fly its clearance exactly. The airways include a tolerance for error of +/- 4 miles. If you're 4 miles to the right of course, in other words, you're still legal and safe from hitting mountains or other obstacles. Altitude was similarly sloppy. If you reached for a drink of coffee or to look at a chart, you might drift up or down 200 feet. Air traffic control wouldn't get upset.

How does it work now that the computer age has finally reached aviation? The GPS computes an exact great circle route from navaid to navaid. All GPS receivers run from the same database of latitude/longitude coordinates, so they all have the same idea of where the Manchester, New Hampshire VOR is, for example. The autopilot in the plane will hold the airplane to within about 30 feet of the centerline of the airway and to perhaps 20 feet in altitude. If two planes in opposite directions are cleared to fly on the same airway at the same altitude, a collision now becomes inevitable.

Almost any other system would be safer.


[User Picture]From: whizistic
2006-10-20 04:35 am (UTC)
You are correct. In general, even numbered altitudes indicate one way, and odd numbered indicate the other. So, FL 170 is for eastbound, and FL 180 and 160, etc, are westbound. Of course, in busy airspace, air traffic controllers overrule that standard all the time.

Apparently there's a similar problem on boats ever since GPS systems were tied into the autohelm system. Captains will key in the GPS coordinates of a channel marker, not maintain lookout, and then drive straight into the channel marker.
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[User Picture]From: searat
2006-10-20 05:04 am (UTC)
a problem with the navy as well, hense the collision involving the submarine a few years ago :) According to marine law, vessels MUST maintain a look out watch at all times, so that is the fault of a complacent captain overworking his crew. He doesn't want a look out watch because he's working his staff 15 hours a day, while the officers sit in the lounge and drink coffee. This is pretty common with Russian boats with a phillipino crew; Russian officers, and 15 phillipino slaves. It was something we were always looking out for when doing vessel inspections, but it's impossible to descover. All we can do is look at their records, which are kept by the captain, who of course isn't going to write down he's breaking the law, and talk to the crew. The crew of course isn't going to say a thing because they're easily replaced, and they don't want to be thrown over board in an "accident". It's a scary thing when computers navigate our transportation devices; a concept that people entertian for cars, and that to me is the scariest damn thing. Especially with my luck with computers, if it can go wrong, it will when I'm using it :) "So ah, how'd your car end up in a tree covered in dead sheep." "I don't know, computer went balistic" ah yes, of course, it would make for a fun story to tell years later :)
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