Geoff Sebesta ([info]megatexas) wrote,
@ 2009-06-06 15:10:00
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Air France 447
"The plane was awaiting replacement of a speed sensor that investigators identified as a likely contributor to the accident...The sensor, made by Thales SA, gave inconsistent readings on the speed of June 1. Airbus SAS had advised airlines more than a year ago to replace the sensors on A330 jets with models that are less vulnerable to ice.

France’s chief crash investigator today told journalists at a briefing near Paris that the failure of the air sensor to convey reliable speed data may have kicked off the chain of events that led to the deaths of all 228 people aboard.

Sensors Not Replaced

“The sensors had not been replaced” with the improved units, said Paul-Louis Arslanian, head of France’s air-accident investigation agency, at a briefing outside Paris. “But that doesn’t mean that without them the plane was dangerous.” The inconsistent speed measurements may have played a role in the crash, though it’s “too early to draw conclusions,” he added. "


Okay, based on my limited experience in the airplane field, I'm calling shenanigans. The pitot tube is not nearly as important as the static ports. However, everything we're hearing about this is consistent with static port failure, and they are part of the same system. I'm guessing right now that there was a problem deeper in the system that was showing up with the pitot tube.

The widely differing airspeed warnings, and perhaps even the autopilot and loss of cabin pressure warnings, could be caused by pitot/static port failure. But remember, a static port can function without a pitot tube, but pitot tubes can't function without static ports*.

If this is true, it is not major malfeasance on Air France's fault at all. It was a very minor issue that turned out to be major, a "for want of a nail**" situation.

*This is of course assuming the engineers and other people at the San Diego Airport told me correct information, and that I understood it when they told it to me. You know how it goes.

**If you are not familiar with this phrase, google it; you may like it.

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Too early to tell
(Anonymous)
2009-06-08 08:00 am UTC (link)
It is *incredibly* too early to start speculating about the causes of the crash. I'll remind people that in Colgate's February crash, the first speculation was icing. Now the report seems to be settling on pilot fatigue as the primary cause.

The fact is, we have absolutely no idea what could have caused it, and baring a Richard Feynman on the crash board (it was he that brilliantly, and almost instantly, identified the o-rings as the culprit in the Challenger disaster) we won't know for a long, long time. It could be things as diverse from a cargo hold fire (perhaps something flammable that shouldn't have been on board in the first place got jostled around too much turbulence, a la ValuJet), perhaps a once-in-a-lifetime lightning strike knocked the autopilot off at just the wrong time, leaving the airplane in a situation where a couple knots too slow meant stalling and a couple knots too fast meant exceeding the structural limitations), perhaps... perhaps something completely unexplored in the press.

Although I agree that no matter what the conclusion, it will definitely be "for want of a nail".

Speculation is for the 24-hour news cycle. Leave the wasted ink and words to them.

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Re: Too early to tell
[info]megatexas
2009-06-08 08:08 am UTC (link)
I'm assuming you're Kenn.

The Colgate crash, we found, was caused by the pilot's error in dealing with the icing. So.

The conflicting speed errors are precisely what happens with static port/pitot tube problems, that's why I'm mentioning it. I can already tell that if this is the problem, people are going to crucify Air France for not replacing the pitot tubes, when I (and if you are Kenn, you) know that the pitot tubes are much less important than the static ports and it was understandable that Air France did not leap to replace them -- after all, failure of that system is not automatic trouble, it's only trouble if you lose visibility. A pitot tube problem is not going to knock you out of the air. But a static port malfunction, which gives conflicting air speed and altimiter readings when in the middle of a powerful thunderstorm, could be fatal.

I disagree that speculation is for anywho and who cares. My blog is for me and I write what I want to read.

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Re: Too early to tell
(Anonymous)
2009-06-09 09:21 am UTC (link)
Oh, yeah, sorry, sorta forgot to identify myself.

Harmless, fun speculation is one thing. Participating in the general atmosphere that leads to more anxiety and agitation in passengers is another. I think speculating now as to causes leads to the latter, no matter how good the intentions.

The fact is, we don't know why there were conflicting readings. I have yet to see any news reports that actually identify the sources of these errors. Was one was GPS and the other pitot? Are there multiple pitot tubes? Were there two different ways to calculating the same airspeed? We're not privy to this info, and to speculate now is just to scare people. Flying is already difficult enough with the TSA eating away at what pilots can and cannot do. The last thing we need is passengers clamoring to have the right to get off a plane because they have, in their infinite wisdom, decided that a 100% fly-by-wire is or is not safer than a human-overridable system.

Incidentally, visibility and losing airspeed information are unrelated. As long as the gyros still work, the airplane can maintain or regain a level pitch and heading. Being able to see 10 miles out your window at 35,000 feet will not permit you to be a good judge of your speed.

The recovered the vertical stabilizer yesterday, so there's every chance the black box isn't too far behind. How in the heck did they find that, though? Was it just floating on the surface like a life raft? I somewhat doubt it, but anything is possible...

(Reply to this) (Parent)(Thread)
Re: Too early to tell
[info]megatexas
2009-06-13 07:12 pm UTC (link)
This flight crashed because of a nonfunctioning static port:

http://en.wikipedia.org/wiki/Aeroper%C3%BA_Flight_603

As you can see, there are many commonalities:

a) conflicting instrument readings and warnings
b) very survivable if not for poor conditions, but under poor conditions:
c) unable to read their altimeters or velocimeters, they went faster and faster, lower and lower, until they plowed into the sea.

"as a consequence of the pilot's inability to precisely monitor the aircraft's airspeed or vertical speed they experienced multiple stalls resulting in rapid loss of altitude with no corresponding change on the altimeter."

I've been up on the mountain, so I haven't read all the news. Have they found if the passengers had water in their lungs or not? That's the scariest thing for me -- I suspect that the crash was prolonged and terrifying for them.

from the news today:

"The problem [faulty pitot tubes] was not perceived as urgent — and, in fact, it has not yet been proven so. Regulators in Europe and the United States have not made the replacement mandatory." that's precisely my point -- if it turns out to be a static port/pitot thing, I don't want people complaining that Air France was lax, or at least massively so. After all, I am a massive Francophile.

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