Article

2009-06-17 Europe

Flight computers at heart of Air France crash?

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Posted by Steve White 2009-06-17 00:00|| || Front Page|| [1 views ] Top

#1
Oh, yeah? I write little one-page homilies with a quality theme for my employer. Here's a piece of one that seems relevant:

In 2006, a near-miss lead to B-2 crews discovering the pitot tubes malfunctioned due to condensation. They also discovered that turning on the 500-degree pitot heat would quickly evaporate the water and the flight computer would receive normal readings.

But crews and maintainers never documented the procedure to use the pitot tube heaters to calibrate air pressure sensors. Some crews knew about the procedure, but on the day of the crash, calibration of the sensors did not include using the heaters. Three of the 24 air pressure sensors on the Spirit of Kansas fed distorted information into the flight control computer. When the aircraft reached 130 knots, the computer thought it was at the 140-knot takeoff speed and lifted off the runway for takeoff.

Not so bad, at that point, because aircraft are typically a full power on takeoff, but the sensors also indicated the bomber was in a nose-down attitude so it commanded a rapid climb that reached 30 degrees before the pilots could stop the climb about 80 feet off the runway. By this time, the low takeoff speed and high angle of attack caused the aircraft to stall. It rolled slightly to the left, and its left wing tip struck the ground. At that point the pilots ejected and survived with minimal injuries, but I fear their flying careers are over.

Ill bet you dollars to doughnuts that the B-2 takeoff checklist now includes an item about turning on the pitot tube heaters. Most rules are written in blood, or billions of dollars.

I've been re-using this lesson recently, because of the recent crash, but first wrote about it almost a year ago, prompted by a Rantburg article and video.

Posted by Bobby 2009-06-17 07:13|| 2009-06-17 07:13|| Front Page Top

#2 The pitot tube seems like the 2000s version of the square airliner window. Since pilots don't fly the plane any more, the sensor inputs are top priority. You get garbage input, and the computer happily flies the plane into a stall. This isn't the first time I've heard the word pitot tube and it's always in connection with an incident.

Posted by gromky 2009-06-17 07:41|| 2009-06-17 07:41|| Front Page Top

#3 http://en.wikipedia.org/wiki/Pitot_tubes

I got courtesy D's in math and chemistry in high school, and my eyes cross when I look at equations. So I am grateful to Rantburg U for explanations like these.

Posted by mom">mom 2009-06-17 11:58|| 2009-06-17 11:58|| Front Page Top

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