Human Fallibility in Aviation II: Case Study

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.

References

[1] William Langewiesche, “The Human Factor”, Vanity Fair, October 2014. http://www.vanityfair.com/business/2014/10/air-france-flight-447-crash