Anyone else following this news story? I HATE flying, and stuff like this scares the crap outta me. I hate turbulence, experienced Clear Air Turbulence once and it's not very pleasant.
From what I've read, it seems like the plane literally ripped apart in mid air.
From Monday's Globe and Mail, Monday, Jun. 08, 2009 10:15AM EDT
In the still-whirling maelstrom of speculation a week after the catastrophic end of Air France's flight 447, only a few facts have emerged, all of which point ominously to a seemingly inexplicable situation.
How did it happen that highly experienced pilots flying a very sophisticated, nearly new jetliner for a world-class airline ended up in a monster thunderstorm when the wall of violent weather should have been starkly evident on the cockpit weathers radar and when the risks are well known.
Meanwhile, the last few short coded fault reports, sent automatically by the aircraft's sophisticated flights systems to Air France, paint a frightening but incomplete picture of multiple systems failing just before the catastrophic end.
A minute of two earlier there are tenuous hints that indicate failing speed sensors – perhaps iced over – could have forced the autopilot to shut off, leaving the pilots to hand-fly the big, twin-engined jetliner in the treacherous violence of a night-time thunderstorm.
No one yet knows the cause of the crash and it will take investigators months – perhaps years – to determine the chain of events, even if they manage to recover the treasure trove of detailed information from the flight data and cockpit voice recorders, now on the sea bottom.
But violent weather seems certain to have played a role, although likely only part of a sequence of the disaster. The ill-fated Airbus 330 with 228 people on board was flying a route directly into the kind of monster storms that all pilots know to avoid. Other pilots reported thunderstorms, but nothing particularly out of the ordinary.
Still, some were huge, soaring to more than 50,000 feet, with internal aircraft-flipping gusts of more than 160 kilometres per hour and vicious cold spots that can also cause severe icing. The inside of a thunderstorm can produce what is called extreme turbulence – which bears no relation to the stomach-churning bounces that has passengers white-knuckling the arm rests.
Extreme turbulence can flip an aircraft out of control. It is defined by aviation regulators as having the potential to cause “structural damage and prolonged loss of control of the aircraft.”
As night fell over the crash site Sunday, searchers had recovered half a dozen bodies from a debris field roughly 650 km northeast of the Fernando de Noronha islands off Brazil's northern coast. The area was about 60 km south of the last electronically reported position of Flight 447, but floating objects have been at the mercy of currents and winds for almost a week.
“We're sailing through a sea of debris,” said Brazilian Navy Capt. Giucemar Tabosa Cardoso said.
France sent a nuclear submarine, the United States flew specialized listening equipment that will be towed deep underwater near the crash site in an effort to detect the signals sent by finger-sized locator beacons attached to the two bright-orange recorders, often referred to as black boxes.
Finding them will be a race against time. The beacons are supposed to function for at least 30 days but only have a range of a few thousand metres. With the precise crash site still uncertain, searchers are faced with trolling for the signals over a wide area and in depths of up to 4,000 metres.
If they are recovered, the cockpit voice recorder should reveal the pilots' last half-hour of conversation, as they considered the weather and their awareness of the sequence of faults in flight systems.
From the flight's data recorder, investigators should be able to build a detailed reconstruction of the aircraft's systems, its speed, and manoeuvres.
Far less detailed, but still very useful, data is available from fault codes, automatically generated by the Airbus 330's flight computer system, which were sent by satellite. Although the pilots last radioed air traffic control with a routine position check-in about 40 minutes before the crash, they also sent a manual text message saying their were flying in heavy or hard weather (Air France hasn't released the exact text) a few minutes before the crash. Then, in the last minutes of the flight, a flurry of fault codes, including one showing the autopilot had been disconnected, were received.
One emerging, but still tentative, theory is that the airspeed sensors – known as pitot tubes and protruding into the air stream – may have iced up, a previously known problem in high-altitude cruises of Airbus 330s.
There are several pitot tubes and the autopilot depends on them being in agreement. If there are discrepancies, the autopilot would disengage and the pilots would have been alerted to hand-fly the aircraft. Icing is a known hazard in the upper reaches of thunderstorms where upwelling chilled air can create roiling turbulence.
Air France was part way through a planned upgrade of all pitot tubes after several previous cases of ice-related failures but the aircraft that crashed had not yet been upgraded. Since the crash, the airline had said it will quickly install newer-model, icing-resistant pitots.
However, ice-blocked failure of one of more pitot tubes would not, by itself, be a catastrophic problem.
However, loss of airspeed sensors – resulting in the autopilot disengaging and leaving the crew to hand-fly in the very difficult and demanding nighttime conditions if they had strayed inadvertently into a major thunderstorm or been caught by one rapidly rising from underneath them – could create extreme conditions.
Paul Louis Arslanian, the lead investigator for the French aviation-accident investigation agency probing the crash, cautioned it was too early to draw conclusions about the role of pitot tubes in the crash, saying “it does not mean that without replacing the Pitots that the A330 was dangerous.”
Nor is it clear yet whether the crew manually disconnected the autopilot, perhaps to fly around or between the thunderstorm cells that on the night of the crash towering to more than 50,000 feet, far higher than the 35,000-foot assigned cruising altitude.
If the pilots had elected a major detour – crews sometimes fly hundreds of kilometres off planned routings to avoid the well-known risks of penetrating a thunderstorm – they would have told air-traffic control to avoid conflicts with other aircraft. So it seems likely that Flight 447's pilots believed they could dodge among the thunderstorms.
Meteorologists who have conducted a painstaking review using satellite data of the conditions along Flight 447's route at the time of the disaster have found a line a huge storms, including several very severe ones welling up at about the time the Airbus was passing. But the weather, while dire, wasn't unusual for the route and avoiding the storms would have been relatively routine for highly experienced crews.