Experts who study airplane accidents say the mistakes that lead to crashes are the same kinds of mistakes people make all the time, akin to locking keys in the car or forgetting an item on a grocery store shopping list.
"In an airplane, it gets you in trouble," said Scott Shappell, a professor at Clemson University who studies aviation accidents and the human errors that cause them.
Scholars say that as many as 80 percent of airplane accidents are caused by human error -- it's what experts in aviation call "human factors" and will probably be deemed one of the leading causes of the Aug. 27 crash of Comair Flight 5191, which killed 49 people. The plane crashed after trying to take off from the wrong runway at Blue Grass Airport.
Human factors are an entire field of study in aviation. It embraces not only how a cockpit is run but how mechanical repairs are made.
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Scholars at universities publish academic papers on what contributes to human errors, how to analyze them and how to prevent them. Undergraduate students at the University of North Dakota can take a class just on human factors. The Federal Aviation Administration has an entire division dedicated to the research of human factors, with a budget of $17.7 million.
Specialists in the area work not only for the FAA but as investigators for the National Transportation Safety Board and as consultants to airplane manufacturers. At Boeing, they work with engineers, pilots and mechanics to make sure the planes are designed in a way that does not encourage human errors.
Its practitioners want to prevent mistakes. But they also recognize that, sometimes, mistakes get made.
"Even though we try to design the airplane and train the air crews to zero errors, we do realize that errors do happen," said John Allen, deputy director of flight standards at the FAA. "So we design techniques and procedures so that no one error will result in an accident."
Those techniques and procedures should create a series of filters to catch mistakes before they cause a problem.
And they should have prevented the Aug. 27 crash, said Jim Hall, a former chairman of the NTSB.
"There are just so many basic things that appear, on the surface, not to have been properly followed," Hall said. "Almost every safety net that was in place was blown through."
Hall thinks the Comair crash will be studied by experts for years to come.
"It is the most significant accident of this decade," Hall said. "It has a wealth of safety do's and don'ts in it that need to be examined."
On the morning of Aug. 27, the one air traffic controller on duty at Blue Grass Airport cleared Comair Flight 5191 onto Runway 22 and then turned his back to catch up on paperwork. According to FAA policy, two controllers should have been on duty (though FAA officials dispute whether that would have made a difference in the crash).
The plane's captain, Jeffrey Clay, who died in the accident, taxied the plane into position, but instead of turning onto Runway 22, which is used by commercial flights, the plane turned onto Runway 26. That runway is unlit and only 3,500 feet long. It's meant for smaller planes.
Recent construction had changed the approach to Runway 22, and the construction was not reflected in the chart of the airport given to the pilots. In addition, the center lights on Runway 22 were not working, although lights along the edge of the runway were.
Because of those problems, James Clay, the brother of Jeffrey Clay, does not believe that blame for the crash should rest on his brother and First Officer James Polehinke, who was at the controls during take-off and was the only survivor of the crash.
"There's a lot of contributing factors," James Clay said.
To figure out what went wrong, human-factors investigators will want to know the basics, such as what the pilots were talking about in the cockpit, Shappell said. But they will also want to know when the pilots went to bed, how they slept, what they ate and drank and if they were having difficulties at home.
Some of that information will come from the plane's cockpit recorder. Some will come from relatives of the pilots, who have said that both pilots went to bed at a reasonable hour. But investigators will also want to interview Polehinke, who remains in serious condition at the University of Kentucky hospital.
Investigators will also consider the construction at the airport and the out-of-date map the pilots had. Things like Comair's bankruptcy proceedings and company staff morale may also be important.
"There's a whole host of things, and you try to identify what issues caused the accident and what issues contributed to it," Shappell said.
According to Hall, the former NTSB chairman, Comair 5191 was missing one piece of equipment that could have helped override the errors that led the plane to the wrong runway. The accident could have been prevented had the plane been equipped with an $18,000 Runway Awareness and Advisory System made by Phoenix-based Honeywell Aerospace, he said. It uses a mechanical voice to tell pilots what runway they are on and warns them if the runway is too short.
While the FAA has approved the device, it does not require airplanes to have it. Hall believes it should have been a requirement.
"Why was it not added on?" he asked. "Did the economics of the carrier have a role? That is an area of legitimate inquiry."
On the day of the crash, the pilots initially boarded the wrong airplane. That misstep could have put them behind schedule in completing their pre-flight checks, which include checking the plane's operating systems and calculating the takeoff speed, said Paul Czysz, a retired aeronautics professor at St. Louis University.
The air traffic controller could also have been in a hurry, which might explain why he had his back turned, Czysz said.
"It was just a series of mistakes that when you add them all up, it's a tragedy," Czysz said. "At any one time, if somebody would have said, 'Where am I,' it wouldn't have happened."
As Shappell imagines the morning flight, many things could have contributed to the decision to take the wrong runway: darkness, pilot fatigue, distraction in the cockpit. Both pilots had flown out of Blue Grass before the construction and the turn onto Runway 26, the shorter one, was similar to the old left turn onto Runway 22, the long one. The similarity may have confused them.
"Just out of habit, they take the wrong runway," Shappell said.
Still, several signs should have told the pilots they were on the wrong runway. Runway numbers correspond to compass directions, and the plane's compass, a routine check on takeoff, would have pointed to 260 degrees, signaling that the pilots were on Runway 26. In addition, Runway 26 didn't have any lights.
But once the pilots were on the wrong runway, another factor would have come into play, what experts refer to as "confirmation bias."
"Once you make a decision, you seek out those things that confirm your original decision and ignore everything else," Shappell said.
To prevent these kinds of errors, pilots in training take classes to help them identify what might limit their performances, and airlines are required by the FAA to train their employees in crew resource management -- a way of running the airplane designed to keep human errors from happening.
In the training, employees learn how to communicate better, plan for the flight, work as a team and manage their work loads. All of those factors contribute to pilots and other crew members having a good sense of where the plane is and what the conditions are -- what aviation experts call situation awareness.
"If the humans do have appropriate situation awareness, they make the right decisions," Allen said. "But if things start breaking down ... then you have an accident or an incident."
Crew Resource Management began in the 1980s, after a series of accidents that could have been prevented by better communication in the cockpit. In one case, a DC-8 ran out of fuel near Portland, Ore., killing 10 people. A subsequent investigation found that the pilot had been warned that the aircraft was running out of fuel.
"It was recognized that airline pilots were becoming too autocratic and not taking in communications from the rest of their crew members," Allen said.
At Comair, which has had crew resource management training since 1991, employees are trained when they are hired in five areas: building teams, communicating well, making good decisions, managing the workload and being aware of where the plane is.
Generally, the adoption of CRM, as it's called, helped change the dynamic of the cockpit. It encouraged first officers to speak up and other members of the crew to challenge the captain, Allen said.
The changes introduced have helped make flying safer, Allen said. Even counting the Lexington accident last month, since 2001, the U.S. has been in the safest period of its aviation history, an FAA official said at a congressional hearing last week.
"Pilots are actually safer on the job than when they are not at work," said Nicholas Sabatini, the associate administrator for Aviation Safety.
Shappell believes that investigators will ultimately conclude that the errors that contributed to the crash of Comair Flight 5191 are not systemic. They will be local, particular to this one flight and this one morning.
In general, commercial aviation accidents are the result of simple mistakes: pilots not paying enough attention, forgetting a step or misperceiving a distance.
"You hope it doesn't happen again," Shappell said. "But it will. It absolutely will. It's just a matter of time."