On the
evening of May 31, 2009, 216 passengers and 12 crew
members boarded an Air France Airbus 330 at Antonio
Carlos Jobim International Airport in Rio de Janeiro,
Brazil. The flight, Air France 447, departed at 7.29pm
local time for a scheduled 11-hour flight to Paris. It
never arrived. At 7 o’clock the next morning, when the
aircraft failed to appear on the radar screens of air
traffic controllers in Europe, Air France began to
worry, and contacted civil aviation authorities. By
11am, they concluded that their worst fears had been
confirmed. AF447 had gone missing somewhere over the
vast emptiness of the South Atlantic.
How, in the
age of satellite navigation and instantaneous global
communication, could a state-of-the art airliner
simply vanish? It was a mystery that lasted for two
years. Not until earlier this year, when autonomous
submersibles located the airliner’s black boxes under
more than two miles of water, were the last pieces of
the puzzle put together. What doomed the 228 men,
women and children aboard Air France 447 was neither
weather nor technological failure, but simple human
error. Under pressure, human beings can lose their
ability to think clearly and to properly execute their
training—a well-known failing that has proven all too
difficult to eliminate.
Over
at Popular Mechanics I’ve
got a long piece offering a detailed blow-by-blow
account of how one of the co-pilots of the Air France
jetliner managed, in the course of just five minutes,
to take a perfectly operational airplane from an
altitude of nearly seven miles down to impact with the
ocean. Here, I’d like to offer a nutshell summary of
what happened, and what our understanding implies for
the future of air safety.
Air France
447 was operating with three pilots: a captain, who
was the most senior crewmember, and two co-pilots. At
any given time, two of them were required to be in the
cockpit, seated at the pair of seats equipped with
controls. Four hours into the flight, the captain went
to take a nap, leaving the flying of the plane to the
more junior of the co-pilots, Pierre-Cédric
Bonin. Sitting beside him was the other co-pilot,
David Robert.
The crisis
began mere minutes later, when the plane flew into
clouds roiling up from a large tropical thunderstorm,
and the moisture condensed and froze on the plane’s
external air-speed sensors. In response, the autopilot
disengaged. For a few minutes, the pilots had no way
of knowing how fast they were going, and had to fly
the plane by hand—something, crucially, that Bonin had
no experience doing at cruise altitude.
The proper
thing for Bonin to have done would have been to keep
the plane flying level, and to have Robert refer to a
relevant checklist to sort out their airspeed
problems. Instead, neither man consulted a checklist,
and Bonin pulled back on the controls, causing the
airplane to climb and lose airspeed. Soon, he had put
the plane into an aerodynamic stall, which means that
the wings had lost their ability to generate lift.
Even with engines at full power, the Airbus began to
plummet toward the ocean.
As the
severity of their predicament became more and more
apparent, the pilots were unable to reason through the
cause of their situation. Despite numerous boldfaced
clues to the nature of their problem—including a
stall-warning alarm that blared 75 times–they were
simply baffled. As Robert put it, after the captain
had hurried back to the cockpit, “We’ve totally lost
control of the plane. We don’t understand at all…
We’ve tried everything.”
Psychologists
who study performance under pressure are well aware of
the phenomenon of “brain freeze,” the inability of the
human mind to engage in complex reasoning in the grip
of intense fear. It appears that arousal of the
amygdala causes a partial shutdown of the frontal
cortex, so that it becomes possible to engage only in
instinctive or well-learned behaviour.
In the case
of Air France 447, it appears that Bonin, in his
panic, completely forgot one of the most basic tenets
of flight training: when at risk of a stall, never
pull back on the controls. Instead, he held back the
controls, in a kind of panicked death-grip, all the
way down to the ocean. Ironically, if he had simply
taken his hands away, the plane would have regained
speed and started flying again.
Compounding
the problem was a peculiar feature of the Airbus’s
cockpit layout. Unlike a Boeing jet, in which one
pilot’s movement of the control yoke moves the other
pilot’s yoke as well, an Airbus features
“asynchronous” controls, meaning that moving one
control doesn’t cause the other to move as well.
Bonin’s colleagues probably never knew that he had the
controls all the way back—perhaps because they never
imagined that any certified airline pilot could engage
in such a misguided response.
Perhaps the
most tragic moment of the entire transcript occurs in
the final moments, when Bonin at last tells the others
that he has had the controls back the entire time.
“No, no, no,” says the captain. But by then it is
already too late.
What can we
learn from AF447? Above all, the tragedy reinforces an
unfortunate truth about air travel that many
passengers do not appreciate: that the most dangerous
component of a modern commercial jetliner is the brain
of the pilot at its controls. The majority of fatal
airline accidents (vanishingly rare though they may
be) are due to pilot error.
One way that
airline manufacturers have tried to work around this
problem is to increase the amount of automation, so
that planes can largely fly themselves. But this
tendency has had an ironic effect: the more pilots
rely on automation, the less practiced they are at
flying a plane by hand when an emergency requires it.
As a pilot
myself, I love taking the controls of an airplane and
through it finding a perfect freedom of movement in
the sky. I would never want a computer to take that
away from me. But the practical reality of moving
passengers in perfect safety from point A to point B
requires a different perspective. As technology
improves, and flight control systems become more
sophisticated, the relative inadequacy of we
two-legged mammals will only become more apparent.
Ultimately, the idea of a relying on a human being in
the cockpit may come to seem a sentimentality too
expensive to afford.
UPDATE: I’ve
added another post, explaining what the flight’s final
minutes probably felt like from the passengers’
perspective, here.