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Comment: You want you 15 minutes with that? (Score 3, Insightful) 176

by cmdahler (#41396135) Attached to: Man Pays For Cross-Country Trip Using Bacon As Currency
Of course, the fact that he's being followed around by a film crew has nothing to do with his success at bartering his bacon. That's a pretty ridiculous stunt. He might as well just go up to all these people and say, "Hey, if you'll give me decent seats to this game, I'll let my film crew here get a clip of you handing me the tickets and you might wind up on national TV!"

Comment: Re:Umm, no... (Score 1) 449

by cmdahler (#36273236) Attached to: Flight 447 'Black Box' Decoded

That's because Airbus actually trained pilots to react this way since, according to them, stalling an Airbus was impossible. To recover from an "almost stall" (which they thought was the worst that could happen), you just pull back on the stick and slam the throttles forward, and the plane would automatically maintain the maximum angle of attack without stalling. Oops, Airbus got it wrong again.

That's only in normal law - you need to research your details before you start bashing something you have no experience with. Stall protections are lost in alternate law, and recovering from a stall in alternate law is part of standard Airbus training.

Comment: Re:Actually, you're right. (Score 5, Informative) 449

by cmdahler (#36270148) Attached to: Flight 447 'Black Box' Decoded

What's most interesting in this case is that the systems warned the pilots of an impending stall, but then once they were in a stall, there was no warning at all, as if they had recovered from the stall. That's really unfortunate.

That's because once the airspeed drops below 60 knots, the input from the angle of attack vane is ignored by the flight computer. The computed angle of attack is how the flight computer determines the airplane is approaching a stall, so without a valid input from the AOA vane, the computer can't sound the stall warning. The AOA vane is just a triangle-shaped piece of metal sticking off the side of the airplane on a little lever, so the airflow naturally positions it, just like a weather vane. As the angle of attack changes, the vane moves, providing an input to the computer. Below about 60 knots, though, there isn't enough airflow to move the AOA vane to a reliable, steady position, so the information is discarded by the computer.

In this case, you're right, it was unfortunate because it provided a confusing result to the crew. They had pulled the airplane's nose up into a stall, and when the airspeed dropped below 60 knots, the stall warning stopped. At one point, the crew did lower the nose of the airplane, which caused an increase of airspeed, which is of course precisely what they needed, but as the airspeed increased beyond 60 knots, the stall warning suddenly started back up. That made them think that what they were doing was making the situation worse, not better, when in fact they were doing the right thing. They pulled the nose back up and then never got it back down until they hit the water. Even when valid, the AOA vane never indicated an angle of attack of less than 35 degrees - generally speaking, almost any general or commercial aviation wing will be well into a stall by about 15 or 16 degrees AOA.


by cmdahler (#36270046) Attached to: Flight 447 'Black Box' Decoded

Color me ignorant (I don't know much about 'planes... just enough to avoid them), but wouldn't an independently powered GPS tell which way is up? Like, uh, constantly?

No. A GPS does not provide attitude information. It merely gives you your three-dimensional position (lat/long/altitude). In any case, on a commercial airplane such as the A330, the GPS data is not generally presented directly to the crew - you can find it, but it's buried in some menus on the computer. In fact, unless you look through the menus on those computers, you have no direct indication that GPS is even installed on the airplane or not.

Comment: Re:Memory Part? (Score 4, Informative) 205

by cmdahler (#35980670) Attached to: Mystery Air Crash Black Box Found Sans Memory Part

From the article, it sounds like the flight data recorder has basically been smashed to pieces. This is usually what happens to them; they're really only useful in relatively low-speed accidents.

That's not the case at all. FDRs commonly survive catastrophic high speed accidents. For example, USAir 427 in 1994 crashed in a near vertical nose-down attitude, and pretty much all that was left of that accident was small bits and pieces. The FDR was recovered and was usable. They rolled and went nose down from 6,000 feet, and the last data on the recorder indicated an airspeed of 261 knots (300 mph, or about 135 meters per second), at a 80 nose-down attitude, virtually straight into the ground. If an FDR can survive that, it can survive damn near anything.

Comment: Re:I'm using the 105Mbit service. The datacap is r (Score 1) 372

by cmdahler (#35839482) Attached to: Comcast's 105MBit Service Comes With Data Cap
Whatever happened to sending the kids outside to play soccer or some make-believe game? No wonder this nation is so overweight and no one knows how to socialize when people whine about not having enough bandwidth to consume this level of TV watching. I let my kids watch about an hour of TV a day, tops. Then the damn thing gets turned off. If they complain about being bored I tell them I'll happily put a puzzle together with them or get the chess board out or put on the baseball glove. If anyone is consuming 250GB a month on a regular basis with gaming and media, you need to seriously take a hard look at your life and get out the door every now and then. The ISPs in this country would do the healthcare system a serious favor if they would all put a 10GB/month cap on everyone's internet usage. (This is hilarious: I'm turning into my dad!)

Comment: Re:No. (Score 1) 1486

by cmdahler (#35746734) Attached to: Is Science Just a Matter of Faith?

However, science encourages you to disagree, debate, and question things for yourself.

Well, that pretty much rules out anyone on Slashdot as being a true scientist, then. It also rules out the vast majority of scientists themselves. There are very few people, especially in science, who take well to disagreement and debate. In fact, the general public, being far removed from a deep, intricate understanding of science, is probably far more tolerant of scientific debate and disagreement than the scientists themselves. Science, in my experience, pays a lot of lip service to encouraging debate and disagreement; the reality is generally far removed from the theory. I see no practical difference between the modern scientist and the priest.

Comment: Re:...as opposed to what? (Score 1) 148

by cmdahler (#35711550) Attached to: Robots Find Wreckage of AF447
Painting results in a smooth surface, so long as it's kept clean. Thus, the fuel savings from the reduced drag offset the cost of hauling around that extra weight in paint. For airlines like American, which go with an unpainted fuselage, they have to polish that aluminum at frequent intervals to keep it smooth, which adds up to a lot of expense and wear on the skin. I've read studies in the past saying it's basically a toss-up as to which methodology costs/saves more.


by cmdahler (#35710886) Attached to: Robots Find Wreckage of AF447

Well, so what if the airlines do have to strip the paint? The point is that the paint will get stripped, so the airframe will get tested for cracks without the paint regardless of whether the airline in question decided they wanted to go with paint or without paint during commercial operations. If the airline wants to spend the money to paint, strip, paint, strip, etc., that's their business, so long as they conduct the testing without the paint.

Most airlines don't really care about this sort of thing since eddy current testing is normally performed during heavy maintenance when the airplane is pulled out of service for weeks for such minute inspections. These "heavy checks" happen after fairly lengthy intervals after which the paint on the airframe needs to be stripped and replaced anyway just because it looks awful after a while.

It's Greg Feith, actually, and he has worked as an accident investigator for the NTSB for a long time. The NTSB (which is his background) has nothing to do with the FAA and is often at loggerheads with the FAA over this or that issue. The NTSB plays an investigatory role during accidents, incidents, etc.; they have nothing to do with the ongoing regulation or inspection requirements of the airlines, which is where this paint thing would come into play. If paint seriously got in the way of performing a proper inspection, the FAA would long ago have regulated it out of existence. Since the kind of cracks we're talking about here are not going to be visible to the naked eye anyway, there's no problem with paint so long as your testing methodology is adequate to detect the metal weakness with the paint present; if it's not, the paint has to be stripped before testing.

Bottom line, paint is not an issue.


by cmdahler (#35710282) Attached to: Robots Find Wreckage of AF447

First of all, you talked about heat from the ramp. An airliner's skin will vary from about -40 C in flight to whatever the ramp temperature is. That's a pretty wide temperature variation. Adding a few more degrees from the color of the paint isn't going to do anything to the skin. Of vastly more interest to aviation professionals is the expansion and contraction of the pressure hull during thousands of pressurization cycles. This, as well as corrosion, is what causes the fatigue-related cracks that lead to hull damage such as with the recent Southwest incident.

Airline skin tests on aluminum are done via eddy current testing. It has nothing to do with a visual inspection. The point is to find the cracks long before they become visible to the naked eye.

You were slandered because you made a statement showing your ignorance of how things operating in a particular industry, when spending two minutes doing a little online searching would have educated you. Then, you stated your willingness to judge your personal safety on your misconceptions without apparently putting even a moment's effort into educating yourself on the subject so as to make an informed decision. Thus, silly.
