Saturday, June 13, 2009

Air France 447: Weather, Technology, and Questions

"Air France Flight 447: A detailed meteorological analysis"
Weather Graphics (last updated June 9, 2009)

(If you're not all that interested in a detailed and rather technical article, scroll down a bit: I'm covering two articles in this post.)

"I received an e-mail (see the comments page) from a scientist affiliated with the NASA TRMM mission indicating that no lightning was detected during a 90-second pass of the system that affected Air France Flight 447. This agrees with evidence from the WWLL sferic lightning network for that date. A review of the literature confirms these findings and suggests that convective systems over the equatorial oceanic regions do indeed exhibit an unusual lack of lightning activity. In a 1993 paper E. J. Zipser cites 'many examples of intense mesoscale systems, such as squall lines ... extending to 13–17 km in altitude, but that nevertheless produce few reports of lightning. This reinforces the idea, based on data from other tropical ocean regions and from global satellite data, that in spite of the ubiquitous "hot towers" over tropical oceans, marine cumulonimbus produce little lightning.'..."

Still reading?

That's a pretty good sample of the page. There are diagrams and images, like the one thumbnailed here, to illustrate radar and other data that relate to the sort of storm Air France Flight 447 flew into.

This page isn't the most reader-friendly discussion you'll ever find of what happened to AF 447. But, it's the best and most complete discussion of the weather I've found, that's remotely accessible to the average reader.

Lightning or no, the Airbus A330-200 came down in very bad weather: "...Temperature trends suggested that the entire system was at peak intensity...."

The author gives a detailed summary of what might have happened, and a conclusion that we don't know everything there is to know about the flight:

"...Overall what we know for sure is weather was a factor and the flight definitely crossed through a thunderstorm complex. ... It's my opinion that tropical storm complexes identical to this one have probably been crossed hundreds of times over the years by other flights without serious incident....

"...We can almost certainly count on some unexpected surprises once the CVR is recovered...."

I appreciated the detail given by the author. A dozen airliners flying through an area of thunderstorms seems less daft now.

Another point which sets this article apart from so much news coverage is that it discusses possible equipment failures other than the Pitot tubes. For example, it's possible, if not necessarily likely, that the engines of AF 447 failed "due to precipitation or ice ingestion".
"Is Flight 447's 'Fly-by-Wire' Aircraft Technology Safe?"
FOXNews (June 12, 2009)

" As investigators search for clues to why Air France Flight 447 crashed, former pilots and aviation experts are debating whether the "fly-by-wire" technology in modern aircraft makes it difficult or impossible for a pilot to control a plane in distress.

"The Airbus A330-200 that crashed into the Atlantic on May 31 — killing all 228 people aboard — relied on electronic rather than hydraulic or mechanical systems to control the aircraft.

"It's akin to having a computer control your car, with the electronic brain doing the steering, hitting the gas and pumping the brakes as you tell it what to do.

"Some pilots claim the old way was better. In an emergency, they say, passengers are better off having a skilled pilot working all the systems.

"But planes built by Airbus, a European consortium based in Toulouse, France, give computers, not humans, the final authority on flight decisions...."

The article discusses two design philosophies, pointing out that both have something in their favor.

Airbus's fly-by-wire system has the advantage of allowing airliners to put pilots with less experience and training in control of airliners, and still get from point A to point B. And, if a pilot tries to force the airplane into a maneuver it's not designed for, the flight control system won't allow it.

Boeing's newer airliners have similar fly-by-wire technology, but Boeing includes an override, so that the pilot can take full control of the aircraft in an emergency.

As far as which design philosophy is 'right,' that's something that probably won't be decided for years.

"...In 2000, Capt. Paul McCarthy, then the group's [The Airline Pilots Association] executive air safety chairman, told the Seattle Post-Intelligencer that its pilots had 'strong opinions' on the issue.

" 'There are good arguments on both sides,' McCarthy told the paper. 'Both make legitimate points. And both sides are correct ... It's a good, healthy debate that will continue for the next five to 10 years until everyone is confident which way we should go.' " (FOXNews)

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