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Clive Irving

Picking Up Pieces From a Midair Explosion

flight 447 Roberto Candia / AP Photo From popped rivets to a shredded oxygen mask: The Daily Beast’s aviation expert decodes new evidence in the ongoing investigation of Air France Flight 447’s mysterious crash.

Piece by tiny piece, a picture emerges of what happened physically to Air France Flight 447. But not why. Debris displayed for photographers in Recife, Brazil, may appear scant, but there were two very suggestive details.

One was a curved piece of the A330’s structure about three feet long. Looked at in closeup, it reveals a row of popped rivets, with one rivet still partially stuck in place. Anyone familiar with submarine movies like The Hunt for Red October or Das Boot knows what follows when the sub sinks too deep. Outside water pressure on the hull pops bolts that fly like bullets into the crew’s air space. In an airplane suffering a sudden decompression, things work the other way round: The rivets and fasteners holding together the structure are forced outward because the air inside is at far higher pressure than at the cruising altitude of around 35,000 feet.

The angle of the rudder recovered from Flight 447 seems too acute to have been safely used at 550 miles per hour.

We know that data sent from the stricken Air France flight indicated a sudden, potentially explosive loss of cabin pressure, indicating that the airplane was breaking up.

The second detail: the torn fragments of several oxygen masks, of the kind that drop automatically from the cabin ceiling for passengers to use when cabin pressure is falling. Not put on display in Recife was the one substantial piece of the A330 yet found, its vertical stabilizer. Here, too, there was a clue that tallies with the final burst of data. The rudder was fixed at an angle indicating that the airplane was making a sharp turn to the right. There was data warning that a system to limit rudder movement had been engaged. At normal cruising speed of around 550 miles per hour, only very small rudder movements are needed. The angle of the rudder recovered from Flight 447 seems too acute to have been safely used at that speed. This might indicate that the rudder was deployed at a much lower speed, consistent with one scenario, that faulty speed-reading instruments had allowed it to slow to a dangerously unstable speed. We know from the data that the computers had given up trying to fly the airplane. We don’t know how the pilots reacted.

Perhaps of most concern, in the absence of finding the flight data recorder, or black box, is what has not been found—no other substantial section of the airframe.

The most robust part of any airplane is its center section, where the wings intersect with the fuselage and where both the landing gear and main fuel tanks are grouped. When airliners break up under extreme stress, the fuselage in front of this center section, including the flight deck, and behind it, including the tail containing the black box, sheers away. Most of the wings, including the engines, would also break up. (The engines are designed to fall away in a sharp impact and would fall like bombs.) Of these three sections of the cabin, the center remains by far the heaviest, and even though it might shed pieces on hitting water, it would sink like a stone. The two other sections could float for a brief time, but they would rapidly fill with water and sink.

Therefore the main remnants of Flight 447 were never likely to be found afloat. Finding them remains essential to explaining what all these clues—electronic and physical—are indicating, a sudden and catastrophic breakup of the A330.

Xtra Insight: Clive Irving on the Myth of the Black Box

Xtra Insight: Clive Irving on Flight 447’s Deadly Scenario

Clive Irving is senior consulting editor at Condé Nast Traveler, specializing in aviation.


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June 14, 2009 | 2:51pm
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C17Pilot

Everything mentioned in the above article is extremely true, however Mr. Irving forgets to tell you the significance of why it was important to have found the rudder deflected to such a large degree.

Now all modern day aircraft have an electronic fight control system (generally known as an EFCS). Now since these systems are extremely precise at exercising their control over the flight control surfaces (when receiving accurate altitude and speed data), they actually prevent the autopilot and the pilots from damaging the aircraft if they make too large a control input.

***Essentially the higher and faster an aircraft is going, flight control inputs (to ailerons and the rudder, etc.) need to be smaller and slower; likewise the slower and the lower to the ground an aircraft is, the larger the flight control inputs need to be so as to properly control the aircraft.***

The EFCS uses altitude and true airspeed to calculate and implement the proper amount of flight control deflection based on the current conditions. Now based off a lot of the incoming data about what was happening to the aircraft, if the EFCS system was receiving erroneous data (i.e lower altitude, slower true airspeed) than what the aircraft was actually doing, if the autopilot or pilots had attempted to turn the aircraft (say for weather avoidance) then there is an extremely good chance that the rudder/vertical stabilizer could have been severely damaged by the EFCS, since the system could have gone into FROZEN GAINS mode (where the EFCS thinks the aircraft is flying at a completely different airspeed than what the aircraft is actually doing).

---I took this from the DASH-1 (performance manual) on the C-17 in regard to what happens if the EFCS thinks the aircraft is flying a lot slower than it really is, and both of these are listed as CAUTIONS:
"The EFCS may revert to FROZEN GAINS during takeoff roll and damage the rudder/vertical stabilizer."

"While in FROZEN GAINS, airspeed increases greater than 30 KCAS may result in damage to the rudder/vertical stabilizer. Airspeed decreases of greater than 30 KCAS may result in inadequate rudder control authority." (3-125)


Therefore, it would actually be quite prudent at the minimum to lean towards a few conclusions about what really brought down this aircraft.
1) The aircraft's electronic flight control system (EFCS) suffered a malfunction due to erroneous airspeed data (the erroneous airspeed data malfunction has been VERIFIED by Airbus and Air France)

2) Erroneous airspeed data likely put the EFCS into a FROZEN GAIN mode, where the EFCS may have thought the aircraft was flying at Mach .60 or less (398mph or less), when it was actually flying its Tech. Cruising speed of Mach .82 (541mph/471knots); likewise the opposite could have been true (the aircraft was actually flying mach .60 or less, and the aircraft - EFCS - could have thought it was still flying Mach .82.

3) An EFCS/FROZEN GAIN malfunciton combined with an extremely bad storm that Air France 477 was attempting to fly through, equals a highly unsurvivable situation for an aircraft.

4) This all means that, the aircraft was most likely ripped apart by flying through a extremely turbulent storm, while the flight control system was over-stressing the aircraft because it most likely thought it was flying slower than it really was.

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5:33 pm, Jun 14, 2009

C17Pilot

again, if Mr. Irving or any of you would like a more in-depth analysis, you can reach me at: Jahara.Matisek@amc.af.mil

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8:23 pm, Jun 14, 2009

SteveStephens

Call me stupid, but it really looks like a bomb blew that plane apart, not bad weather.

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12:01 am, Jun 15, 2009

C17Pilot

Yeah, you are stupid. Here's a weather company analysis of how bad the weather was:

http://www.weathergraphics.com/tim/af447/


There is way too much evidence supporting a weather theory (to include text messages sent from the pilots and the internal computer) combined with catastrophic failures with the air data computers, which contribute data to how the engines and flight controls are supposed to behave. Combine bad weather with engines and flight controls receiving erroneous data make for an unsurvivable condition, especially for an aircraft.

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1:30 am, Jun 15, 2009
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Picking Up Pieces From a Midair Explosion

by Clive Irving

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