Vanity Fair recently featured an excellent article on Air France
Flight 447 that crashed into the Atlantic in 2009. It is a long read, but
if you have 30 min to spare it will be a great educational investment.
The author, William Langewiesche, does a
good job at weaving multiple aspects of aeronautics, such as cockpit design,
ergonomics, the physics of flight and pilot training, into a story that is
ultimately about the role of human fallibility in a system that is governed by
automation. This is a topic that I find highly fascinating and will
only become more pertinent in the future as computers take over increasing
number of tasks in the cockpit. In fact, the psychological impact on the pilots
and the effect of automation on the piloting profession on a whole remain
uncertain.
The article features extensive coverage of the pilots’ conversation and
provides a riveting account of what transpired in the cockpit prior to the
crash. In this way the article brings to light some of the human misjudgements
that ultimately led to the catastrophe. On some occasions I found myself
cringing at the incredulity of the events that transpired, futilely hoping that
the pilots would turn the situation around and save the 228 passengers onboard, while fully aware that hindsight makes all
mistakes appear tauntingly clear.
The reason for the plane crash was a classic case of aerodynamic stall
brought on by the pilot climbing too quickly and exceeding the critical angle
of attack, depending on the operating conditions in the range of 13-16°. Even
when the angle of attack was at an incredible 41°, the aircraft was rolling
from side to side, the alarm system was screaming “STALL”, the cockpit was
shaking violently due to the turbulent flow separation over the wings and the aircraft
was losing altitude at a rate of 4,000 feet per minute, each one a tale-tell
signs of aerodynamic stall, the pilots did not know what was happening with the
airplane!
What brought the aircraft into this situation in the first place? The
pitot static tube used as sensors for the flight speed had been clogged by a
hail storm, which automatically took the fly-by-wire system out of the
auto-pilot, disabled the automatic stall recovery system and returned the
controls back to the pilots. At this point had the pilots continued the modus
operandi of keeping the aircraft at the same altitude with the engines at
constant thrust, nothing would have happened. It is ironic, that the only thing
the pilots needed to do to keep the plane safely in the air was nothing. It is
unclear why one of the pilots decided to climb to a higher altitude and
especially why this was done so rapidly, but this ultimately triggered the
aerodynamic stall of the wings.
William Langewiesche argues that
increasing automation “de-skills” pilots, essentially rendering them incapable
of flying an aircraft without support systems. I find the following section
especially interesting:
“For commercial-jet designers, there are some immutable
facts of life. It is crucial that your airplanes be flown safely and as cheaply
as possible within the constraints of wind and weather. Once the questions of
aircraft performance and reliability have been resolved, you are left to face
the most difficult thing, which is the actions of pilots. There are more than
300,000 commercial-airline pilots in the world, of every culture. They work for
hundreds of airlines in the privacy of cockpits, where their behavior is difficult to monitor. Some of the pilots
are superb, but most are average, and a few are simply bad. To make matters
worse, with the exception of the best, all of them think they are better than
they are. Airbus has made extensive studies that show this to be true.”
So how has this been dealt with in the past?
“First, you put the Clipper Skipper [daring WW II fighter
pilots] out to pasture, because he has the unilateral power to screw things up.
You replace him with a teamwork concept—call it Crew Resource Management—that
encourages checks and balances and requires pilots to take turns at flying. Now
it takes two to screw things up. Next you automate the component systems so
they require minimal human intervention, and you integrate them into a self-monitoring
robotic whole. You throw in buckets of redundancy. You add flight management
computers into which flight paths can be programmed on the ground, and you link
them to autopilots capable of handling the airplane from the takeoff through the rollout after landing. You design
deeply considered minimalistic cockpits that encourage teamwork by their very
nature, offer excellent ergonomics, and are built around displays that avoid
showing extraneous information but provide alerts and status reports when the systems
sense they are necessary. Finally, you add fly-by-wire control. At that point,
after years of work and billions of dollars in development costs, you have
arrived in the present time. As intended, the autonomy of pilots has been
severely restricted, but the new airplanes deliver smoother, more accurate, and
more efficient rides—and safer ones too.”
This essentially causes a shift in the piloting profession…
“In the privacy of the cockpit and beyond public view,
pilots have been relegated to mundane roles as system managers, expected to
monitor the computers and sometimes to enter data via keyboards, but to keep
their hands off the controls, and to intervene only in the rare event of a
failure. As a result, the routine performance of inadequate pilots has been
elevated to that of average pilots, and average pilots don’t count for
much[…]Once you put pilots on automation, their manual abilities degrade and
their flight-path awareness is dulled: flying becomes a monitoring task, an
abstraction on a screen, a mind-numbing wait for the next hotel.[…] For all
three [pilots on Air France Flight 447], most of their experience had consisted
of sitting in a cockpit seat and watching the machine work.”
We all know that automation is indispensable going forward. It is too
valuable a system and has made aviation the safe mode of transport it is today.
However, the issues raised above will need to be addressed within the near
future. Possible solutions may be requiring pilots to turn off auto-pilot for a
certain number of flights, while another approach may be to improve the
machine-human interaction in the cockpit. In either case, I think it is
important to point out that catastrophes such as Air France Flight 447 are
outliers, black swans, six-sigma events that are not likely to repeat again in
the same detail. In fact, the roots of the next catastrophe may lie somewhere
completely different and thus are impossible to predict.