Sunday, June 7, 2009

Coffin corner

Since the AF447 incident which puzzles many, there have been lots of discussions about what happened and the possible causes. The opinions have run the mill, so to speak, yet none have any more credence than any other (mind you, not saying here that some of these are not mostly pure bunk).

However, one thread of discussion led to a 'say what?' state. That is, there is an issue that has FAA's concern up (Operations above 25,000 Feet). Hey, isn't that what we see routinely with commercial airflights?

Well, these types of planes have flown for years in an almost uncountable number of flights (very large number, okay). So what gives? Of course, we've seen some accidents. These are studied for lessons to be learned (unfortunately, ex post facto). Test programs for new airplanes are organized to ensure some margin of safety with regard to known mix at the time of program delivery.

We are assured many times that design meets any extreme requirement (plus), that things are tested against these, that there is training sufficient to safely operate within problematic margins, and so forth. Yet, recent discussions remind us that a plane hitting turbulence at too much speed can break up (just how needs to be looked at further).

ABC had an expert on this am (Sunday, Miles O'Brien) who mentioned a very small gap being involved, like 30 mph. The industry has used 'coffin corner' to label the area on the flight envelope which relates to a critical region. Evidently, this margin of error is small enough to get special attention from FAA.

Ought there be some way for the flying public to know about this issue? It's great for us to trust the makers and the flyers; we have a right to know more, though, would not one think? Not that a passenger needs to know aerodynamics; there ought to be more visibility into technical issues, especially as the general populace becomes more educated.

And, delays due to weather would have more of a technical basis for explaining why; the past few months has had many examples. The list of contributing factors is very interesting, indeed.


05/28/2011 -- The black box was recovered, via technology. Now, analysis shows that the air speed indicator did freeze causing a state of mis-readings which didn't allow proper control actions on part of the crew. There are a lot of lessons here which we'll get into. However, that computational frameworks and their executional events can get similarly into this type of state, and vertigo is not inappropriate to use here. This bears much discussion.

07/02/2009 -- No black box yet, but analysis can be done on found pieces of the plane and on autopsy findings on the deceased. The plane hit the water while intact and with a 'strong vertical acceleration' according to this analysis. There is no need to retract the coffin corner information, as its suggestion generated a 'say what?' reaction and as there are conditions under which it can occur that the flying public ought to know about.

06/09/2009 -- A pilot's thoughts.

Modified: 05/28/2011

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