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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: searat
2006-10-20 02:26 am (UTC)
you'd figure they'd have different planes for the planes to fly on.

Example: Planes flying north will fly at 37,000 feet. Planes flying south will fly at 37,500 feet. Planes flying East will fly at 36,500 feet. And planes fly West will fly at 36,000 feet. Planes flying NE,SW,NW,SE will fly at intervals of 100 feet beyond northern or southern routs, ie: NE 37,100', SE 37,600',ets.

you know, with an error deviation of 30/20 feet, even if both planes were flying 20 feet higher and 20 feet lower, it would still eave 60 feet between them, and if they were 30 feet left or right, there still would only be 40 feet between them. Given the parameters of error, it would be mathmatically impossible to have a mid air collosion.

I understand of course that altitude effects the ammount of time it takes to go a certain distance, and can also effect the ammount of effort the plane must exert in order to fly, which effects fuel usage and strain on the engine. May I venture to ask, how many planes actually fly according to schedule? There hasn't been a time when I traveled by air, and I do so quite ofton, that the flight plan went as, well, planned. There are always delays, just the nature of the beast.

Here's a theory I've been working on. Intergallactic Instant Travel by Partical Reassimulation, aka, IITPR. The IITPR would simply be a computer that scans the body, making note of every atomic structor and mathmadically simulates the bodies atomic readings and transfers the information to the desired location equiped with receptive capabilities and distributes the exact replication of the bodies atomic structure. The computer will then use high dossages of radiation and a small atomic blast to seperate the bodies atoms and suck it into the hard drive. Yes, I stole this idea from Star Trek. No, I don't believe they are owed rights. With a jult of lightening, a bottle of Vita Radium (suppositories), and a kick to the groin the body will be rejuvinated and brought back to life. This would probably kill every traveler and I see this as a form of population control. If you're dumb enough to go through it, than you deserve to die. Yes, that's right, die. And that is why I hate flying.
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[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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[User Picture]From: jgp
2006-10-20 06:03 pm (UTC)
I was just about to point out "that's why modern planes have TCAS", then I read the article, and someone beat me to it in the comments. *In theory*, even with full-automatic autopilots, unattentative pilots, and unattentative ATC folks, the collision-avoidance systems in the plane should have been able to override the autopilot and take care of it.

Then again, I'd wonder what the hell was going on with ATC that would make them not notice the planes going at each other, or the PIC that didn't keep his plane from hitting the other one.
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[User Picture]From: whizistic
2006-10-20 07:23 pm (UTC)
TCAS was inop for the big guy because it relies on the transponder of the little plane, which was either off or inop, depending on who you ask.

ATC in S. America is a little more "interesting times"-ish than listening to ATC in the states :)

Yeah, the part of my favorite comment is reprinted as follows:

On the main point of the post, I do agree. Here’s another way to look at it. While few like to admit it, the primary collision avoidance method for VFR flights is “big sky, little airplane,” followed distantly in effectiveness by “see-and-avoid.” If the skies were congested enough that traffic conflicts were really common, there would be midairs galore. In IMC (or at high enough altitude, where true airspeeds are very high), see-and-avoid is completely useless so ATC takes over. But ATC (and pilots’ responses to commands) is not perfect, so BS-LA makes a good backup.

However, the sky is only big because it has three dimensions! Putting lots of aircraft on the same line reduces the 3-D sky to 1-D and therefore makes its effective volume approximately zero.
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[User Picture]From: jgp
2006-10-20 08:27 pm (UTC)
Heh - I'll have to look for a crowded time in the skies down there and listen in online... I can just imagine it now "cleared to land, but hold clear of taxiway J due to burro traffic"
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