Air France 447 - Bloggers Ponder Last Message From Missing Jet’s Computer

Updated | 4:37 p.m. While there is still little firm evidence of what went wrong on Air France Flight 447 on Sunday night — despite a report on Tuesday that some wreckage had been spotted in the Atlantic by Brazilian military planes — some bloggers who write about air travel and safety have tried to make sense of what the Airbus A330’s last, computer-generated signal might tell us.

As my colleagues Donald McNeil and Christine Negroni reported on Monday, the last communication from the Air France jet was “a series of automatic messages indicating it had suffered an electrical-system malfunction.”

Air safety expert David Learmount wrote in a blog post on Monday that while few details have been made public about the wireless message the plane’s computer sent to Air France mechanics just before the jet disappeared, “If the fault has been correctly interpreted as a short-circuit, that raises the specter of an electrically-caused fire, and fire is always serious in an aircraft.” He pointed out that an electrical fire is believed to have caused Swissair Flight 111 to crash off Halifax in September 1998.

Mr. Learmount added:

An event like this is the kind the aviation world hoped it would not see again, because it involves a world class carrier flying the latest generation of airliner, and it occurred en route, not during take-off or landing in difficult weather. It’s a chilling reminder that nothing is impossible, however unthinkable.

Another well-informed blogger, Ben Sandilands, who writes the blog Plane Talking, turned his attention to the malfunctioning electronic sensors on two other Airbus A330s, both operated by Qantas, which have caused the planes to make sudden, sharp drops in altitude.

In a post on Monday, after noting that “speculation so soon after an accident is almost invariably wrong,” Mr. Sandilands wrote that mechanics at Qantas must surely be asking if the electronic sensors, known as air data inertial reference units, “on the Air France jet were of the same type that failed and caused some serious control incidents with its A330-300s.” On three occasions these electronic sensors have caused problems, most recently last October when a Qantas flight was forced to make an emergency landing in Western Australia.

As The Sydney Morning Herald explained:

In October, a Qantas Airbus A330-300 from Singapore to Perth dropped twice from a height of 37,000 feet, injuring 74 passengers.

The plunges — lasting 20 seconds and 16 seconds — sent passengers slamming into the cabin’s ceiling and walls, causing serious injury in 14 people who were treated for broken bones, concussion and lacerations. The plane made an emergency landing at Learmonth air force base, north of Perth.

Air transport investigators said the incident was caused by a faulty computer component that sent “erratic and erroneous information” to the plane’s flight control system. The Australian Transport Safety Bureau’s director of aviation safety investigation, Julian Walsh, said analysis of flight data had revealed that the plane’s air data inertial reference unit — the device responsible for supplying data on air pressure, temperature and acceleration — had failed.

As a result, wrong data was sent to the flight control system, which has a key role in flying the aircraft, even with pilots in control.

One theory, which has not yet been entirely ruled out by investigators, is that the Qantas jet’s electronic inertia sensors might have been somehow confused or disrupted by electronic radio waves from a military base in Western Australia used by the United States. Just after the incident Australia’s Herald Sun reported:

Powerful signals from a secretive naval base are being probed as a possible cause of a Qantas jet plunge last week. Air safety investigators say they will look into claims signals from the base used to communication with U.S. and Australian ships and submarines may have interfered with the Qantas Airbus’s computer. [...]

The base uses powerful low frequency radio transmissions to US Navy and Australian Navy ships and submarines. It is understood to be the most powerful transmission station this side of the globe and includes 13 radio towers, the tallest of which is 387m tall.

As if to support this frightening theory, The Herald Sun’s Web site ran a somewhat spooky Google map image of the naval communications base at Exmouth in Western Australia, which does look like it was designed to appeal to people scouring the Internet for signs of hidden extraterrestrial landing sites:

View Larger Map

One of our readers writes in to point out that Google’s Street View cameras have paid a visit to this remote outpost, which makes it possible for us to get a good look at the apparently far from top secret location.

In March Mr. Sandlilands noted on his blog that the Australian Transport Safety Bureau’s interim factual report on the October incident said that the agency had “ordered new tests to determine if electromagnetic inference from military installations” could have caused problems with the electronic sensors on Qantas A330s on three occasions.

Mr. Sandilands wrote that the A.T.S.B. report “discusses at length the electromagnetic resistance tests” the electronic sensors on the Airbus have to go through to pass for certification in both the U.S. and Europe, and the feeble strength of transmissions” from all military installations in Western Australia. The report also stated that hundreds of A330s had flown in roughly the same area over Western Australia in 2008 alone, with only one reported incident.

“Nevertheless,” as Mr. Sandilands noted, “more examination of the ways electromagnetic interference could have been experienced by the Qantas flights are to be made.”

The Los Angeles Times reported on Tuesday that aviation officials had recently warned A330 operators about possible problems with the inertia sensors used on the jets, known as Air Data Inertial Reference Units:

European aviation authorities issued an emergency airworthiness directive in January alerting A330 operators who had the unit installed on their planes to follow revised procedures for operating it. The Federal Aviation Administration issued its own directive in March, saying that the equipment failure “could result in high pilot workload, deviation from the intended flight path and possible loss of control of the airplane.”

According to my colleague Christine Negroni, “The emergency airworthiness directive issued by the European Aviation Safety Agency on the Airbus 330 inertial reference unit does include the Air France airplane that went missing Sunday night, which was A330-203.”

In an update to his most recent post, Mr. Sandilands wrote that an “unofficial but highly credible” source had told him that the type of electronic sensor unit on the missing Air France A330 “is of different design and manufacture” to the one used by Qantas. If that is true, it doesn’t necessarily rule out the possibility that a similar problem to the one that nearly downed the Qantas flight last October could have been experienced by the Air France A330 on Sunday night, but it does suggest that another blogger’s call for much more data to be sent from planes during flight is a good idea.

In a blog post on the Air France mystery, Miles O’Brien asked if it might be time to replace the on-board black box with a wireless data stream:

Why not send steady streams of telemetry from airliners to the ground all the time — a la the space shuttle? This effectively places the “black boxes,” safe and sound - on the ground. Imagine how invaluable that much data would be right now.

While that quantity of data would no doubt be useful, my colleague Ms. Negroni writes to point out that this “would require great bandwidth and storage capacity to record all the hundreds of thousands of event-less daily flights. Someday, I have no doubt this information will be transmitted to ground rather than be collected on the aircraft on flight data recorders, but that’s why we’re not there yet.”

Update | 4:37 p.m. A Lede reader named Alex pointed out after the first version of this post was published, several years ago Elaine Scarry, a literature professor at Harvard, wrote a series of articles for The New York Review of Books suggesting that three civilian air crashes off the east coast of the United States — T.W.A. Flight 800, Swissair Flight 111 and Egypt Air Flight 990 — might all have been caused by electromagnetic interference from military sources. Only the third of Ms. Scarry’s essays is available on the New York Review site for free, but in 2000, Emily Eakin wrote an article on her theory for The New York Times Magazine.

Time magazine’s Mark Thompson has more details on the investigation into what went wrong with the Qantas A330’s electronic sensors:

Following an investigation of the A330’s uncommanded dive, Australian aviation officials, assisted by U.S. and French authorities, blamed a pair of simultaneous failures for the near disaster. The plane has three air data inertial reference units (ADIRUs), which are designed to help the plane’s flight-control computer fly the plane safely. The system is intended to eliminate the possibility of electronic error: the flight computer, which is always monitoring the trio, can disregard one ADIRU if it begins relaying information that conflicts with the other two.

But that’s not what happened when one of them went awry on October 7 and began sending erroneous data spikes on the plane’s angle of attack (AOA) — the angle between its wings and the air flowing over them — to the flight control computer. “For some reason the damn computer disregarded the healthy channels,” says Hans Weber, an aviation expert who heads Tecop International, an aviation consulting firm in San Diego. “Instead, it acted upon the information from the rogue channel.” The computer, responding to the faulty data, put the plane into a dive.