Air France Flight 447 Crash Report: Airbus Autopilot to Blame?
Investigators have released their initial findings into the Air France disaster that killed 228. Aviation expert Clive Irving reports on the fearful final moments and whether autopilot handicapped the pilots.
It took only four-and-a-half minutes from the moment that the pilots of Air France Flight 447 attempted to fly the airplane manually to the moment when it hit the ocean, falling at the huge velocity of nearly 11,000 feet a minute. The picture of those four-and-a-half minutes as disclosed Friday by French investigators confirms key points:
The Airbus A330 flew into storm-generated turbulence at its cruise altitude of 35,000 feet;
The three instruments relaying the airplane’s speed to its flight management computers and pilots were giving conflicting and false readings;
With the autopilot disengaged and the pilots attempting to regain control the airplane gyrated wildly and then soared from 35,000 feet to 38,000 feet, reaching a fatal stall condition in which the wings were no longer able to provide lift—at one point the nose pitched up to the extreme angle of 40 degrees and at the same time the wings were rolling violently from side to side;
When the emergency began the captain was not on the flight deck but resting. The crisis was being handled by two copilots. The captain reappeared on the flight deck one and a half minutes after the copilots took over manually but was unable to save the situation.
However violent the turbulence, the result should have been a rough ride for a few minutes, not a plunge to an ocean grave.
What is striking about this terrifying scenario is how close it comes to confirming what many experts had suspected in the days following the disappearance of Flight 447 over the south Atlantic on June 1, 2009.
Even as they released this information the French investigators were cautioning that they were still trying to understand it. “Our role is not to assess blame, merely to determine the facts,” said Jean-Paul Troadec, the director of the agency, the BEA.
That may be what the BEA hopes, but the effect of the new four-page summary released Friday will be to intensify, not inhibit, informed speculation about what the crash says about the behavior of systems aboard the Airbus A330, about the air speed gauges that were already under scrutiny for previous failures due to icing, about the way control is passed from the automated flight management system to pilots in the middle of an emergency and about the pilots themselves—about how attentive they were to the menacing storm system they flew through and why the airplane reached a stall condition so quickly.
This is, in fact, a case where more information seems to lead to a deeper dispute among experts rather than calming it. Many pilots have expressed concerns about the so-called laws written into the software of the Airbus flight management system.
It’s a fundamental part of the Airbus philosophy about automation that pilots should not be able to assert individual control outside of a defined envelope that guarantees the stability of the airplane. As long as the autopilot and engine auto-thrust are engaged, the computers inhibit pilots from superseding the commands of the system. Boeing, in contrast, within its own version of a fully automated flight deck, has a system that allows pilots to intervene at any moment when they feel it necessary.
The Airbus system has many champions: The successful ditching of an Airbus A320 in the Hudson River is cited as a case where Captain Sullenberger’s cool decision to land on water was made feasible by the efficiency of the way the computers flew the plane even though it was without engine power.
The plight of the pilots of Flight 447, now so graphically described by the investigators, shows skilled and deeply experienced aircrew unable to regain control in what should have been, in standard airmanship manuals, a recoverable situation. However violent the turbulence, the result should have been a rough ride for a few minutes, not a plunge to an ocean grave.
And now, inevitably, there must be critical attention paid to those faulty speed gauges. The version with which Flight 447 was equipped, made by the French company Thales, was in the process of being replaced because of concerns about the effect of icing. But that change had not yet reached this particular A330.
Indeed, attention should return to a report on the crash by the BEA released in November 2009. Buried in the technical details was the revelation that there was a record of at least 53 instances in which flight crews had faced control problems directly caused by the speed gauges and “13 significant events involving five airlines operating A330/340 airplanes.” Airbus itself reported 32 incidents between 2003 and 2009 that were attributable “to the possible destruction of at least two gauges by ice.” Twenty-one of those came in a sudden cluster between 2008 and the time when Flight 447 disappeared in 2009.