Data Mining Helps Identify Subtle Flaws
PHOENIX -- For decades, aviation authorities played the role of homicide detectives. When an airliner went down, they scoured the crash site and flight recorders for clues that often showed how to avert future accidents.
But with so few crashes in recent years, air carriers and regulators have been trying to find other ways to identify potentially dangerous trends. Instead of digging through debris, they now spend far more time combing through computer records, including data downloaded from thousands of daily flights and scores of pilot incident reports.
The information is stored on banks of computers, such as the server housed in a windowless office of a US
Airways hangar here. Like its counterparts at other carriers, a small team of pilots and analysts sift through thousands of records daily looking for the seeds of the next big air crash.
In recent years, the team has uncovered such potential safety problems as unsafe landing and takeoff practices and difficult landing approaches. The data have helped pinpoint areas that pose an increased risk of midair or ground collisions and have led to the discovery of a large bulge in the runway of a Vermont airport. Even after threats have been reduced, US Airways' executives and pilots say they keep monitoring the data to ensure that their new procedures work.
"We have improved our safety so much from having this data," said US Airways pilot Matt Merillat, who works on the database. "There is no doubt that by using this data we have prevented an accident."
Pilots and executives at 16 other airlines have similar data-monitoring initiatives approved by the Federal Aviation Administration that are known as flight operations quality assurance programs. The carriers scour the flight data, which is often combined with pilot reports, to identify potential "precursors," a buzzword in aviation circles used to describe events that often go unnoticed until they lead to an accident. The data are amazingly detailed -- small onboard memory discs (not the "black boxes") capture hundreds of parameters that include airspeed, pitch angles, engine temperatures and movements.
Such data initiatives have grown so extensive in recent years that the FAA has launched its own effort to mine the information in search of precursors. Seven carriers have signed on to the initiative, which began in October. The FAA, which already combs government safety databases looking for precursors, thinks the flight data will be a powerful tool when combined with other information, including pilot reports and radar plots.
More carriers are expected to join by year-end, FAA and industry officials said.
"We can use this tool to find the beginnings of a new safety threat that we don't even perceive," said Jay Pardee, director of the FAA's office of aviation safety analysis.
Outside experts and FAA officials say that such data mining is part of a new era in the industry, which is enjoying its safest stretch in history. The last major U.S. commercial aircraft crash was in August 2006.
One reason the system has become so safe is because investigators, regulators and industry executives got so good at learning from past accidents. Flights that crashed into mountains, the ground or into other airplanes led to computer warning systems that alert pilots to the dangers in enough time to take action. Crashes caused by obstinate pilots led to better cockpit communication.
"Historically, we have always taken a forensic approach to aviation safety, looking at past accidents and learning all we could," said Terry McVenes, a pilot and executive air safety chairman of the Air Line Pilots Association. "Because we don't have many accidents to analyze anymore, if we want to continue to lower the accident rate, we have to look at precursors, the near misses."
But finding them, even with all the data, isn't easy.
Robert Sumwalt, vice chairman of the National Transportation Safety Board and a strong advocate of data monitoring, likened the hunt for precursors to "reading tea leaves" because it can require imagination to tie together incidents that don't seem hazardous at first blush.
The first U.S. carriers adopted the data-monitoring measures in the mid-1990s, decades after foreign airlines implemented similar programs. They have only recently expanded across the domestic industry; 11 of the 17 U.S. carriers with such programs have started them since 2000. The growth has been fueled by the decreasing cost and increasing computing power.
Regulators and investigators, including those with the NTSB, have pushed for adoption of the initiatives. Pilot unions have eased their resistance to such projects. They play a critical role in analyzing the data, which is not supposed to be used to punish pilots for mistakes. Carriers have also realized economic benefits beyond preventing crashes: The information has helped many to reduce fuel consumption and improve maintenance reliability.
Although data monitoring is a hot topic inside the industry, some airlines have been reluctant to talk about their programs. Executives worry that they might scare passengers if they discuss potential problems, no matter how rare, or may encounter pushback from pilots unions. Representatives at United, American and Alaska airlines all declined to comment.
Southwest Airlines, which started its program in 2003, said it has mined data on more than 1 million flights to help the FAA and air traffic controllers to better understand pilot workloads at certain airports. It has even used the data to pinpoint where planes experience turbulence. The carrier hopes that this information will reduce injuries to passengers and flight attendants who get jolted in the bouncy air.
Southwest executives said one of their biggest challenges is finding ways to use the database.
"We are always asking ourselves, 'What should we be asking this data that we haven't thought of yet?' " said Don Carter, senior manager of the carrier's flight safety program.
US Airways, which was reeling from several crashes in the early 1990s, was one of the first airlines to use data to improve safety. The safety issues uncovered by the airline, which is expected to join the FAA initiative by year's end, are similar to those exposed by other airlines using the same data-monitoring techniques, according to pilot groups, regulators and airline representatives.
Just over half of US Airways' 356 jets carry recording devices that compile data from thousands of flights a week. Analysts and members of the Air Line Pilots Association at the carrier then sift through the data for a minuscule number of potential precursors.
In mid-2006, for example, US Airways' computers alerted the company to what executives and pilots considered a high rate of "unstabilized" approaches -- incidents in which planes come in too fast or sink too quickly during the final phases of landing. Such approaches are usually not dangerous unless other complications arise, such as trying to land on a short, slick runway.
Working with the pilots union and instructors, the carrier changed its landing checklists to allow better communication by pilots and co-pilots about whether the plane was stable as it neared the ground. If the plane was not stable by 500 feet, the pilots are instructed to abandon the landing attempt.
The training got pilots to focus more on landing at the right speeds and with the right rate of descent, reducing the rate of unstable approaches by more than 70 percent, the company's executives and pilots said.
"The rates were unacceptable to us," said Paul Morell, the carrier's vice president of safety, who emphasized that such incidents were rare even before the reduction. "It really boils down to this: Zero is what is acceptable to us. We don't want any of them."
An added benefit of such programs, the carrier said, is the ability to monitor changes.
Within a few months of the new approach procedures, US Airways spotted some problems in how pilots abandoned landings during unstable approaches, which is known as conducting a "go around," said Tom Lulkovich, the carrier's director of flight safety. The carrier then stepped up training to eliminate the issue.
"We want to know how effective we were at mitigating risk," Lulkovich said.
The carrier has even used the database to pinpoint unstable approaches to runways at different airports. Pilots were having trouble on one type of approach into Las Vegas's international airport, so the carrier rewrote its charts to give pilots a better sense of when to make their turns, pilots and executives said.
Two years ago, a few US Airways jets were damaged when their tails hit the ground on takeoff. Such events are exceedingly rare, especially among highly trained pilots. The company's executives were perplexed -- until they analyzed flight data, which showed their planes' average pitch rate at takeoff was too high by a few tenths of a degree.
After changing the pilot training program, the carrier recorded no further tail strikes at takeoff, executives and pilots said.
US Airways also has used the data to lobby federal regulators to make changes. It provided the FAA with detailed lists of instances in which planes' midair collision warning systems sounded near the international airport in Phoenix. The FAA used the data to help redesign the airspace around the airport, a project completed in October, to mitigate the risks of small planes colliding with jetliners.
"Everything is about identifying risk here," Lulkovich said.
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