Avionics News March 2012 - 63

447’s loss raises significant questions about the impact of increased automation in cockpits of all sizes, along with concerns about how pilots are trained to use all that magic. It’s not a new debate, but it is one guaranteed reinvigoration by the loss of AFR447. And, although the A330’s highly automated systems seem to have performed as designed and certified, there are lessons here for the avionics industry.

NEEDLE IN A HAYSTACK
Transoceanic flight operations differ from most regions of the world in one important aspect: there is little to no ground-based radar coverage. As one result, air traffic control facilities rely on the aircraft’s crew and modern airborne navigation equipment to fly a set of dynamic routes, called tracks, when out of radar coverage, helping ensure separation from other aircraft. The system works well, but it does not provide the kind of real-time surveillance capabilities terrestrial ATC radar can. Similarly, satellitebased or high-frequency voice communications beyond VHF’s line-of-sight limitations remain troublesome. Thus, in the first hours after AFR447 disappeared, confusion was widespread. At Air France operations headquarters, contact with the flight proved impossible, even though a controller in Dakar at one point maintained he was in communication with the missing jet some three hours after it had crashed. Other ATC facilities reported controllers in Casablanca were talking to the flight six hours after it disappeared. But, it was not to be. Soon, the reality sank in, and search-and-rescue aircraft from Brazil, Spain and France headed for the flight’s last-known position, a navigation fix 351 nautical miles northeast of Brazil. During the next few days, surface vessels scoured the area, accompanied by a French submarine and U.S. Navy patrol aircraft. The first bodies were recovered June 6; the A330’s vertical stabilizer was found the next day. By June 26, some 640 items from the aircraft had been recovered and cataloged, including 51 bodies. Not among the material retrieved, however, were the all-important flight data and cockpit voice recorders – the so-called black boxes. Investigators did have some data from the flight’s last

moments with which to work: the A330’s aircraft communications addressing and reporting system, ACARS, had transmitted 24 warning or failure messages via satellite, beginning at 0210:10 UTC. The ACARS messages detailed a cascading series of problems aboard the jet, beginning with autopilot and autothrottle disengagement, plus flagged airspeed indications on the primary flight displays, concluding with the pressurization system’s inability to keep up with the airplane’s rapidly changing altitude. The Atlantic Ocean in that area is deep – up to 15,400 feet. Despite sonar-based searches by a French submarine and surface vessels towing listening devices obtained from the U.S. Navy, no trace of the pinger-equipped black boxes was found that summer. Subsequent searches also failed to find any trace of the Airbus. It wasn’t until early 2011, when deep-diving robots from the Woods Hole Oceanographic Institute using side-scan sonar discovered the flight’s debris field in a relatively flat area of the seabed. The wreckage was 6.5 nautical miles north-northeast of the flight’s last-known position, under approximately 13,000 feet of water. On May 1, 2011, 23 months after AFR447 disappeared, the flight data recorder’s memory module was retrieved and brought aboard a French vessel. Late the next day, the cockpit voice recorder was found; it was raised to the surface on May 3. Both devices miraculously survived the crash and almost two years at the bottom of the Atlantic Ocean. But, the two devices raised many more questions than they answered.

PIECES OF THE PUZZLE
According to the Bureau d’Enquêtes et d’Analyses pour la Sécurité de l’Aviation Civile, France’s analog to the U.S. National Transportation Safety Board, beginning at 0210:05 UTC and “likely following the obstruction of the pitot probes in an ice crystal environment, the speed indications became erroneous, and the automatic systems disconnected. The airplane’s flight path was not brought under control by the two co-pilots, who were rejoined shortly after by the
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Avionics News March 2012

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