July 23, 2012
It seems inconceivable that a small device with no movable parts—and roots back to the 18th century—could initiate a catastrophic sequence of events that would result in the demise of a long-haul commercial transport and all on onboard. Yet this device—invented by French scientist Henri Pitot to measure rivers' rate of flow—is implicated in the fatal crash June 1, 2009, of an Air France Airbus A330-200 operating the Rio de Janeiro-Paris route as Flight 447.
Investigators determined in the early part of their analysis that the twinjet's Thales speed sensors, or “pitot tubes” (see photo), were obstructed by ice crystals and could no longer calculate and transmit correct inputs to onboard electronic systems. This failure disconnected the automatic pilot, requiring the flight crew to return to manual controls. In other words, Pitot's 200-year-old invention was the initiating cause that led to the disaster, although better training of the pilots in question could have prevented the tragic outcome.
Momentarily putting aside the BEA French aircraft accident bureau's exhaustive investigation, the ill-fated Flight 447 produced more than a wake-up call. It also injected a bit of humility to engineers and operators alike—that a tiny piece of equipment with no high-technology content can challenge the world's flight-safety community. The BEA and others do not have the luxury of time to stage philosophical debates. Every agency seems to be in accord about the sequence. The task at hand is to focus on correcting the chain of errors that resulted in the ghastly accident.
Similarly, the BEA's final report does not question the use of Pitot's invention in state-of-the-art cockpits, a genuine paradox. Lessons learned rather show that aircraft manufacturers, airline technicians and pilots blindly trust electronics and, in so doing, sometimes tend to forget that human beings can have a hard time dealing with unexpected situations. It has been confirmed that Flight 447's three pilots suffered from “a profound loss of understanding” of ongoing events and, in the absence of solid airmanship, acted in a state of great confusion. For example, they didn't respond to stall warnings because they did not realize that the A330 had entered a deep stall fall.
BEA investigators have done their best to dispassionately assess the situation. The final report, released this month, cites the surprising state of confusion in the cockpit and weak crew resource management, but does not elaborate on the pilots' obvious loss of situational awareness. Investigators are extremely cautious. Says BEA head Jean-Paul Troadec: “Another [flight] crew could have faced the same problems,” which is a diplomatic shorthand for saying inadequate training was at the heart of the crews' inability to recognize a stall and remedy the situation.
Pitot can rest in peace. Although his sensors are out of date and desperately waiting for an inventor to offer a replacement, the crash resulted from inappropriate control inputs that destabilized the aircraft's flight path. Investigators are crystal clear about this: The crew failed to identify the approaching stall, did not respond in time and exceeded the flight envelope's limits. Moreover, no action was initiated that would have made recovery possible.
The BEA sent up to 41 safety recommendations to DGAC French civil aviation authorities, the European Aviation Safety Agency, the International Civil Aviation Organization and the FAA. They focus on the need for enhanced training, reporting procedures, better oversight of airlines and fine-tuning of onboard electronics. Recommendations also suggest the addition of an angle-of-attack indicator to the flight panel, and advanced training that addresses stall recovery at high flight levels.