Un interessante articolo a riguardo, per chi sa l'inglese.

What happened to Air France Flight 447

By Charles Bremner,
Paris Correspondent for The Times (and pilot himself)
June 2, 2009



Here is a list of reasons why Air France Flight 447 may have fallen into the Atlantic, but first a little explanation:

Modern airliners do not just vanish in mid-flight. That was certainly the first reaction to the news of the disappearance of the Airbus en route from Rio de Janeiro to Paris yesterday. Planes missing in storms sounded like something from the old days of oceanic flight, not the world of satellite links and automated flight systems.

But the Airbus A330-200, with 228 aboard seems to have fallen victim to the same unforgiving elements that have dogged mariners and aviators throughout the ages. It's testimony to the achievement of modern aviation that the "mystery of Flight 447", as it is being called, is such an exception. The last unexplained disappearance of a big jet was in July 1996 when a TWA Boeing 747 blew up off climing away from Long Island, on a flight to Paris. The crash was blamed on an explosion in a fuel tank triggered by an electrical arc, but there is still suspicion that it could have been hit by a missile. In October 1999 a Boeing 767 of EgyptAir crashed off the northeast US coast killing 217. The flight recorder indicated that the co-pilot sent the plane into the water deliberately.

Suspicions of foul play and conspiracy theories are circulating around Flight 447 today as the search continues for wreckage between Africa and Brazil. But the reality is probably more mundane. The air is a rough place and when things go wrong there they do so very quickly.

Most plane crashes are not the result of a single event, but a chain of events, usually involving technical and human factors. Crew are taught to break the chain before it's too late. All we know is that the Air France Airbus stopped flying very suddenly when its electrical power, cabin pressure and other systems suddenly failed a few hundred miles out of Brazil. An automated data link reported the shutdown to the Air France control room at Paris airport.

No distress call was heard from the crew and the three locator beacons emitted no signal. They are independent of the other aircraft systems and are triggered by shock or extreme manoeuvres. The lack of signal suggests that something very brutal happened.

Here are the possible causes, with the most likely last:

-- A missile. Highly unlikely given the altitude.


-- Hijacking. All but ruled out because there were no suspicious passengers and the crew would have communicated.


-- A collision. Unlikely, given the separation of airliners on their oceanic airways. No other plane is missing. However a Brazilian airliner crashed in 2006 after colliding with a US business jet over the Amazon in cruising flight. A mixture of pilot and air traffic control error was blamed. Aircraft in mid-ocean are not tracked on radar.


-- A bomb. This was initially excluded but it remains a distinct possibility. Security at Rio is said by pilots to be lax. A French airliner was brought down by a bomb over Africa in 1989. Libyan agents were blamed. A blast would explain the sudden failure of all systems (see next item).

-- Accidental explosion. Unlikely but it remains a plausible possible cause. Big planes have in the past been brought down by dangerous cargo or sparks igniting fuel fumes but they are well protected now.


-- Fire. Unlikely by itself. An engine fire would be controllable and give the crew time to communicate, as would an electrical fire.


-- Lightning. Unlikely alone because airliners are often hit by bolts, which are discharged along the fuselage and off the wings. Elaborate precautions shield the flight systems. Questions are being asked, however, about the way that the composite, non-metal parts, of modern airliners conduct electricity.


-- Extreme turbulence. Likely to have been the biggest factor. Air France said the plane was flying in a zone of tropical storms. These are normal in the equatorial region and airliners use weather radar pick their way around the violent towering cumulonimbus (storm) clouds which lie in their their paths.
No crew would knowingly fly into one of these cells, which can carry the energy of nuclear explosions and are capable of throwing an airliner around like a twig in the wind.

The likely explanation is a chain of failures. Electronic problems, perhaps caused by a lightning discharge, could have interfered with the computers that control the aircraft, navigation equipment, or simply the weather radar. The pilots could also have been distracted by some other problem that let the plane fly into the heart of one of the cumulonimbus. That could have upset the plane, leading to a quick break-up.

The "black box" flight recorders can tell the story, but they may never be found at the bottom of the ocean. Perhaps data from US military survillance satellites can shed light. They may have picked up a radio transmission.

Inevitably, questions are being raised about the safety of the computers that that control modern airliners. Some pilots have doubts about the Airbus family because its "fly-by-wire" system is a little more automated than that of the rival Boeing company. Most experts discount the doubts.

Computers fly the plane unless specifically over-ridden. Pilots input their controls with little electronic sidesticks but the computers will not carry out their commands if they appear abnormal. This can be over-ridden in emergency but all the control surfaces remain electronically controlled.

The last suspicious incident involved an Australian Qantas A330 -- the same as the Air France plane. On a flight between Singapore and Perth in October last year, the system suddenly commanded a dive while the pilots had set the automatic pilot for level flight. A dozen people were seriously injured in the abrupt 600-foot descent, which has still not been explained. One theory, backed by some scientists, is that strong electromagnetic radiation -- such as an intense radio waves -- could have interefered with the flight system, causing erratic behaviour. Read this, from the New Scientist, if you want a fright.

Accident causes are usually not what they seem to be at first. This is just speculation and media do far too much of that after crashes. But pilots guess about crashes as much as everyone else and they do it from an informed point of view. I have summarized what they are saying (for new arrivals here, I have been a small-plane pilot for 25 years).

Back on an historical note, the ocean between Brazil and Africa s a graveyard of French aircraft. Several pioneers disappeared in the same area as the Airbus in the early decades of air transport. The most famous was Jean Mermoz, a colleague of Antoine de Saint Exupéry, who disappeared mid-ocean in December 1936 flying an Air France Latécoere 300 amphibious plane.

Unlike Air France 447, however, Mermoz had time to report by radio that he was shutting down a failed engine before his plane vanished.