Monday, May 18, 2009

Crash of Flight 3407: The Human Factor

Last February 12, a Continental Airlines regional flight 3407, operated by Colgan Air, crashed short of the Buffalo, New York runway it was headed for, killing all 49 aboard and one person on the ground. At the time I wrote about it shortly afterward, speculation centered on how well the deicing systems were working, since icy conditions had been reported in the area. But after a three-day hearing on the crash held by the National Transportation Safety Board last week, it looks like human error may be the root cause of the crash.

Working with voice-recorder transcripts and flight data from the "black boxes" recovered from the crash, NTSB investigators painted a picture of the last minute or so of the flight which did not show pilot Marvin Renslow and his 24-year-old copilot Rebecca Shaw in a good light. During their final approach, when FAA regulations prohibit nonessential communications in the cockpit, the pair are heard chatting about careers and the co-pilot's lack of experience flying in icing conditions. Renslow himself had only three months of experience flying the particular Dash-8 involved in the crash, and had failed several flight simulator tests in the last few years. Besides these factors, fatigue may have further dulled the crew's responses. Shaw had joined the flight after commuting all night from her home in Seattle, where she lived with her parents. Her raising the plane's flaps without a command from the captain compounded the already critical situation the pilot found himself in when the plane lost airspeed and began to stall. Under these conditions an automatic system activates a "stick-shaker" intended to alert the pilot to the danger. The proper response is to move the stick forward to regain airspeed, but records indicate Renslow pulled it back. After stalling, the plane rolled and crashed.

The impressive and improving safety record of U. S. air travel says that on balance, nearly all pilots do the right thing in critical moments nearly all the time. But the fact that the safety record for smaller regional carriers such as Colgan is not as good as for the major carriers flying larger aircraft says there may be something about the difference in working conditions between long-range and regional carriers that bears watching, to say the least. A lot of the news coverage of the NTSB hearing centered on co-pilot Shaw's meager annual salary, which was less than $17,000 (not counting extra flying time). Deregulation of the airline industry plus the recent recession has brought intense competitive pressure to regional operators, who may be cutting corners and hiring inexperienced pilots with less-than-stellar records simply because they're cheaper. The Federal Aviation Administration has regulations about minimum standards for pilot training, performance, work hours, and rest breaks, but these things are human rules, and rules can be bent or broken without automatic penalties coming into play. At least, until something bad happens.

The loss of any life in an engineered system is a tragedy. But if the publicity surrounding the accident and its investigation result in corrective action, we can look forward to further improvements in safety procedures and their enforcement.

At last week's hearing, a NASA expert in cockpit communications acknowledged that more could be done to give pilots even earlier warning of potential stall conditions than the stick-shaker provides. This is a problem in what is called human-factors engineering: how to effectively interface a machine to a person so that the person has the right information at the right time in order to take the right action. By the time the stick-shaker went off, the pilot's options were very limited. If an earlier warning had been provided, the crew might have snapped out of their inattentive mood sooner and realized their difficulties in time to avert the accident. We will never know about this particular case, but if the investigation results in improved cockpit instrumentation that saves other inattentive crews from getting into the same fix, something good will have come from this crash.

The current federal administration seems to be more interested in regulation than deregulation, and there may be areas where such a change is appropriate. One reason that co-pilot Shaw's low pay got so much attention was that it is such a contrast to the typical popular perception of airline pilots: distinguished-looking former military flyers with some dignified gray around their temples (nearly always men), good pay, and years of flying experience. Stereotypes are made to be broken, and my hat is off to any young woman who goes through the arduous process of becoming a commercial pilot, but in the bad old days of high airfares and closely regulated airlines, the companies could afford to hire the very best pilots available, and generally did. The case of Shaw may indicate that inexperienced crews are being pushed too fast into positions of great responsibility without adequate training, or even sleep.

As sad as this accident was, we are starting to see the feedback system of engineering work. I don't mean the stick-shaker; I mean the corrective process that learns from mistakes, errors, and tragedies, and does things to make them less likely in the future. This kind of work takes place out of the spotlight, in quiet offices and labs around the world, but it is the reason that air travel is as safe and reliable as it generally is. And as long as we pay attention to the rare cases when something goes wrong, and have the courage to fix problems—whether mechanical or human—it will keep on getting even safer.

Sources: Two good reports on last week's NTSB hearings may be found at,0,5946950.story and My article "The Crash of Flight 3407: Better Deicing Needed?" appeared on Feb. 16, 2009.

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