Air France 447

An Airbus A330-200, flying from Rio de Janeiro to Paris with 228 people aboard, vanished over the North Atlantic just after crossing the equator.  It’s always a tragedy when something like this happens.

Some people, including an Air France spokesman, ruled out terrorism and initially speculated that the mishap was due to lightning, which is so fatuous and misleading as to verge on intentional falsehood.

An A330 flying at a cruising altitude of FL350 or 35,000 feet has a pretty good idea of where the bad weather can be found.  First of all, it is flying above all but the highest cirrus (and cumulonimbus) clouds, so the lightning-producing convection activity of tall, anvil-topped cumulonimbus clouds stands out like a beacon.  Even when they are surrounded by other clouds, a line of thunderheads tend to be obvious and easy to spot with the naked eye.  And the A330 has weather radar, naturally, which does a good job of spotting clouds, convection and lightning activity within the storm that the Mark I eyeball might miss.

In order to even have a shot at being lost due to lightning, the pilots would have to have ignored their weather radar (or turned it off), ignored the evidence of their own eyes, and decided to fly into convective storms without trying to “thread the needle” and find a way around the worst of it.  Ignoring passenger safety and comfort along the way.  And that is not even considering the many backup systems available to the aircraft and pilots should lightning happen to fry something.

They may well have gone down due to the inherent risks involved in flying heavy at high altitudes, meaning that the aircraft had less margin of error between cruise speed and minimum safe manoeuvring speed. In the convective turbulence of a thunderstorm, you can lose a lot of airspeed due to the buffeting of the weather, and that may all add up to a rapid and unexpected departure from controlled flight.

But the only way that lightning could down an A330 and cause structural failure too fast for pilots to react is by de-bonding one of its composite empennages or flight control surfaces.  Or in layman’s terms, putting so much voltage into the carbon/epoxy vertical and horizontal stabilizers that they vaporise or explode, leaving the aircraft with no way to control its attitude or altitude.  This scenario is possible, but not overly likely, as A330s (as well as every other type of airliner with composite structures) get hit by lightning on a fairly regular basis—on average once every 3 years—without their rudders or elevators going kaboom.

This is not to say that terrorism is the answer.  But the true cause occurred so suddenly that the aircrew had no time to issue any distress calls, and the resulting condition put such stress upon the airframe that, according to ACARS automated telemetry, it came apart on the way down.

UPDATE: I should point out that a lot depends on how far apart those ten ACARS error messages were transmitted.  If the electrical failure came first, followed by the remainder several minutes later, it is reasonable to suppose a lightning strike occurred and took out some vital system (perhaps the plane’s radar, as supposed by Miles O’Brien in this Reuters post).

If all ten failures occurred within a very short time period, with no significant delay between them, then something catastrophic happened at altitude and took the plane apart.

UPDATE 022105Z JUNE 2009: Interesting unconfirmed details from the Aviation Herald website (via commenter Tailspin at Neptunus Lex).

New information provided by sources within Air France suggests, that the ACARS messages of system failures started to arrive at 02:10Z indicating, that the autopilot had disengaged and the fly by wire system had changed to alternate law. Between 02:11Z and 02:13Z a flurry of messages regarding ADIRU and ISIS faults arrived, at 02:13Z PRIM 1 and SEC 1 faults were indicated, at 02:14Z the last message received was an advisory regarding cabin vertical speed. That sequence of messages could not be independently verified.

The whole Aviation Herald post is worth checking out, lots of good information there, including airway routes and infrared weather images.

UPDATE 040909Z JUNE 2009: Reuters is reporting that the debris field included a large fuel/oil slick on the ocean surface, which in the estimation of the Brazilian Defence Minister rules out a fire or explosion.  That is pure nonsense.

I’d say it indicates that one of the wings came down more or less intact, and that’s about it.  If both wings and their tanks had come apart at cruise, the fuel would probably not be a large 20km-long slick; it would be many smaller droplets spread out over a large area.  I also don’t see how the presence of the slick would rule out, for example, a fire in the cockpit (a la Swissair 111) or detonation of an explosive near the rear pressure bulkhead, which could cause separation of the vertical or horizontal stabilisers (a la Japan Air Lines 123) and render the aircraft uncontrollable.

The A330-200 has a few variants, one with a center fuel tank and one without.  Tanks common to both variants would be inner and outer wing tanks, wingtip vent tanks, and a trim tank in the horizontal stabilisers.  Tank location diagram can be found here.

None of this is proof that a fire or an explosion did occur, but neither is it wise of the politicians to rule out such a possibility while the most significant data and materials lie on the ocean floor.

UPDATE 060404Z JUNE 2009: So basically everything you have heard about AF447 from the media is wrong.  Except that the plane was flying from Rio to Paris, didn’t make it to the destination, and 228 people died.  They are now saying that the 20km-long oil slick came from a ship, not the aircraft.  And a wooden pallet reported to be payload from the aircraft is not actually from the aircraft, either.  Well done, fellas.

UPDATE 101146Z JUNE 2009: Reader Ghost of a flea emailed this article which contains an interesting nugget of information:

Unease over the A330 was strengthened by charges from the Alter pilots’ union that Air France had covered up problems with the airspeed instruments. It emerged this week that the airline advised pilots on November 6 last year that there had been “a significant number of incidents” in which false speed readings had upset the automated flight system — in the manner that appears to have happened on Flight 447.

These incidents, from which the crew were able to recover, occurred at cruising altitude, said the two-page circular. As a result of the false readings — apparently caused by ice clogging up the pitot tubes — the automatic pilot disconnected. The data from the doomed Airbus last week reported the same sequence, but the pilots were unable to regain control. A parallel is being drawn with an incident last October in which a Qantas A330 dived inexplicably under the command of its flight system, seriously injuring several passengers. James Healy Pratt, a lawyer with Stewart Law, a London firm handling the Qantas incident, said that the sequence of events was the same, with fluctuating airspeed indications apparently causing the auto-pilot to disconnect.

— Charles Bremner.  “Air France pilots told not to fly Airbus jets after Brazil crash“, London Times, June 10th, 2009.

UPDATE 151221Z JUNE 2009: No explosion, but an in-flight structural failure.

Post mortems carried out on 16 of the first 50 bodies found floating in the sea reportedly have no trace of burn marks or smoke, supporting the theory that the accident was not the result of a blast.

…Although an explosion is unlikely, investigators believe flight AF 447 broke up in the air because of the location of victims’ bodies found in the water.

Two trails of bodies were discovered, more than 50 miles apart, which suggests the jet broke up before impact.

They had no water in the lungs – which would have indicated drowning.

— Henry Samuel.  “Bodies of Air France flight 447 victims show no signs of mid-air explosion“, London Telegraph, June 15th, 2009.

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2 Responses
  1. Chris Taylor says:

    Terrific link. The meteorology is unassailable and well thought out.
    I can see electrical failure causing departure from controlled flight fairly rapidly if they lose their instruments in a heavily turbulent area and they had no visual references for attitude.
    I am not so convinced they would blindly follow the waypoint routes, though, and not try to find a way around the worst parts of the storm. They wouldn’t knowingly fly into a dangerous situation, so whatever got them wasn’t immediately and obviously dangerous to flight.