Rumors, Lies, Innuendo, Fear, Uncertainty, and Despair

An update on Air France flight 447 is in order.

Unfortunately, the best outcome for this tragedy would have been finding bomb residue on the few parts of the aircraft that were recovered. We’ll never know what really happened but virtually all of the other possibilities do not bode well for Air France, the operator, or Airbus Industries, the builder.

On May 31 2009, Air France 447, an Airbus A330-203 took off from Rio de Janeiro bound for Paris. The airplane was flying at 35,000 feet when the last contact from the crew, a routine message to Brazilian air traffic controllers was made at 01:33 UTC as the aircraft approached the edge of Brazilian radar surveillance over the Atlantic Ocean. The aircraft entered an area of the Atlantic where radar and air-to-ground radio were unavailable. Its next scheduled contact was due when it entered Senegalese airspace off the coast of West Africa. Forty minutes after pilot radio contact was lost, a five-minute-long series of automatic radio messages was received from the plane via satellite link, indicating numerous problems and warnings. The aircraft is believed to have been lost shortly after it sent the automated messages.

On June 6 2009, a search and rescue operation recovered two bodies and debris from the aircraft floating in the ocean 680 mi (1,090 km) northeast of the Fernando de Noronha islands off Brazil’s northern coast. This finding confirmed that AF 447 had crashed into the Atlantic Ocean on 1 June 2009, killing all 216 passengers and 12 crew members.

The so-called “black boxes,” the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) were never recovered. They, along with most of the passengers and wreckage of the aircraft, are believed to be in water about 9800 feet deep. A new search for the FDR and CVR is scheduled for March 2010.

The last messages from AF 447 were Aircraft Communication Addressing and Reporting System (ACARS) reports transmitted automatically from the aircraft to a satellite, thence to Air France maintenance personnel in Paris. ACARS was designed to transmit routine maintenance data on the aircraft so that ground personnel would be ready to service the aircraft with appropriate parts and personnel when it reached its destination. ACARS data were not intended to provide the kind of crash-related data normally recorded by the FDR.

Because the FDR was not recovered, the ACARS data became essential to determining the fate of AF 447. Within a five-minute period ACARS transmitted 5 failure reports and 19 warnings. The last of these messages was transmitted at 02:14UTC. The ACARS failures and warnings included navigation auto-flight, flight controls, cabin air-handling, and the pitot-static system; twelve warning messages with the same time code indicate that the autopilot and auto-thrust system had disengaged, that the TCAS (Traffic Collision Avoidance System) was in fault mode, and flight mode went from ‘normal law’ to ‘alternate law’; the remainder of the messages contained a fault message for an Air Data Inertial Reference Unit (ADIRU) and the Integrated Standby Instrument System (ISIS); a warning message indicated disagreement between the independent air data systems; a fault message for the flight management guidance and envelope computer was sent; one of the two final messages was a “cabin vertical speed warning.”

Sources close to the investigation confirmed that “the first automated system-failure message in a string of radio alerts from the crashed jet explicitly indicated that the airspeed sensors were faulty”. Other experts have commented that the ACARS transmissions clearly indicated an aircraft that was breaking up in flight.

According to the BEA the French agency charged with aircraft accident investigations:

• The aircraft was likely to have struck the surface of the sea in a normal flight attitude, with a high rate of descent
• There were no signs of fire or explosion
• The aircraft did not break up in flight

I have identified at least 21 enabling factors that could have contributed to the loss of AF 447. The probable cause for this loss will likely never be known but BEA, Air France, and Airbus all seem determined to claim the aircraft “did not break up in flight” and that cabin pressure could not have been lost because the oxygen masks never deployed. While it may be true that the pressure vessel of the aircraft did not break up until the hull was below 14,000 feet (the triggering point for the oxygen masks), this does not mean that the vertical stabilizer, other flight surfaces, or the engines had not earlier separated from the main body of the aircraft.

Also of significance is the fact that bodies and parts of the aircraft were found scattered over a distance of 60 miles, indicating they fell separately to the water from high altitude.

Of roughly 400 pieces, the largest single piece of wreckage recovered from AF 447 was the vertical stabilizer. It had separated fairly cleanly from the rest of the aircraft and was found floating in the ocean. Loss of the vertical stabilizer was the cause of the crash of an American Airlines Airbus A300-605R in New York in 2001. While the US National Transportation Safety Board finally attributed the loss of that aircraft to the first officer’s “unnecessary and excessive” rudder inputs, the design of the vertical stabilizer and its attachment to the aircraft were still major concerns of the investigators.

It is also true that AF 447 was flying near large thunderstorms in the inter-tropic zone at the time of the accident. Wind shear may have been an enabling factor in the crash but the fact that other aircraft passed safely through the same storm line both before and after the accident aircraft make it doubtful that weather alone caused the accident.

After the loss of AF 447, Airbus Industries accelerated a program to replace the Thales pitot probes on A330 and A340 aircraft with probes made by Goodrich. Previous incidents involving Airbus aircraft equipped with Thales pitot probes indicated the devices could ice over, generating erroneous airspeed indications.

All of this notwithstanding, Airbus engineers and executives as well as personnel operating Airbus equipment must carry some nagging doubts about the design, construction, and operation of the company’s products.

Boeing has been plagued by similar problems, such as the “rudder hard-overs”, that destroyed at least two 737’s. The problem was corrected by late 2008.

Airbus is in the unfortunate position of not knowing whether it has a real problem or is the victim of bad weather, inept piloting, or just plain bad luck.

As I said, explosive residue would have allowed a lot of Airbus people to sleep more soundly.

(Fair disclosure: my wife is a Boeing stockholder)

This entry was posted on Tuesday, March 2nd, 2010 at 4:55 PM and is filed under Commentary. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.