Experts say its runway layout may be a factor in the high number of “close calls.”
The latest and most comprehensive report of air traffic control problems reveals that planes flew too close to each other more often around Minneapolis-St. Paul International Airport than at most of the nation’s busier airports.
Minneapolis-St. Paul ranked 13th in plane traffic but saw more problems than nine of the 12 busier U.S. airports.
The incidents were discovered by a new safety system that stresses greater use of automation and voluntary reporting to detect and document air traffic control problems. Nationwide, reported incidents more than doubled under the increased scrutiny.
The Federal Aviation Administration (FAA) withheld details of problems at each airport when it announced the overall numbers last September. The FAA recently released a breakdown in response to a Freedom of Information Act request by the Star Tribune.
The agency didn’t offer a specific reason for the higher numbers at the Minneapolis-St. Paul tower.
“Each airport has a unique set of operational procedures and runway configurations, which may be further complicated by flight paths from surrounding airports, local noise procedures and a high density of operations,” FAA spokeswoman Laura Brown said when asked about MSP.
But current and former air traffic controllers say the airport’s layout, urban location and heavy reliance on two runways can create a more challenging environment than airports with more room to maneuver.
“It’s more of a downtown airport, that makes it more complicated,” said William Schroeder, who teaches air traffic control at the University of North Dakota’s School of Aerospace Sciences.
More trouble than Atlanta
The latest figures show the airport tower recorded 34 episodes of planes flying too close together in 2012. More than a third of them were considered significant enough to trigger a special risk analysis by the FAA.
By comparison, towers at Hartsfield-Jackson Atlanta and Chicago O’Hare, the first- and second-busiest airports in the nation with more than twice as many flights as Minneapolis-St. Paul, had only 18 and seven incidents, respectively. The towers at the next busiest airports, Dallas-Fort Worth and Denver, had nine and three incidents.
The FAA in September reported that its new system documented 4,394 instances nationwide when planes came closer than allowed by federal regulations. The agency noted that the incidents are rare when compared with the more than 132 million flights that occur annually, including 425,556 at MSP.
The higher figures for the Minneapolis-St. Paul tower emerge as the FAA rolls out new satellite technology that it says would improve safety by more precisely routing planes on narrow highways in the sky during takeoffs and landings.
The FAA decided last month to hold off on using the technology for takeoffs at MSP after nearby residents complained that it could send more planes over their homes. The FAA also rejected a proposal for using the technology for departures from some runways but not others, saying a partial deployment would be unsafe. The technology will be used for arrivals.
A closer look
The FAA revamped its reporting system in 2012 after the U.S. Department of Transportation’s inspector general criticized it for inadequate reporting of planes flying too close together.
The FAA requires minimum distances between planes and reports of any flights that get closer. When planes fly closer than two-thirds of a minimum distance, the incident triggers a special review.
Thirteen of the 34 recent incidents at MSP fell into that category.
“They need to take a look at why those errors occurred,” said Edmund Strong, who worked 24 years for the FAA and is now an air traffic control consultant. “Were they the same type? If they really want to get to the bottom of it, they need to send in an outside team.”
None of the 13 incidents analyzed was deemed high risk. Most were classified as low risk, with three as medium risk. Two of those medium-risk events involved conflicts with a nearby airport or airports. While those facilities weren’t identified in the FAA reports, the Airlake Airport in Lakeville and Flying Cloud Airport in Eden Prairie are closest to MSP.
In one event, a single-engine Cessna was flying toward a smaller airport while a 50-seat commercial airliner was departing MSP.
The Cessna “mistook the primary airport for the satellite airport,” turned toward the international airport “and entered [the airliner’s] airspace,” the analysis concluded. The severity of the event was classified as “major,” but its chances of reoccurring were considered remote.
In another medium-risk event, a 13-seat twin engine turboprop was departing southeast from MSP but “turned further west than the assigned heading,” the FAA reported. It was assigned a new direction, but “did not fly that heading either,” coming too close to a single-engine plane approaching a nearby airport.
Strong said directing air traffic at MSP “may be more complex … due to satellite airports that generate a whole lot of bug smashers and puddle jumpers all over the place.”
The FAA reported 1,895 incidents nationwide of planes coming too close together in 2011, the last year of the old reporting system. Even under the old system, the MSP tower had more planes too close together than five of 10 busier airports.
MSP handles 80 percent of its traffic using parallel runways that face northwest and southeast to take advantage of prevailing winds. They are crossed by a third runway. A newer fourth runway facing north and south handles some traffic that otherwise would use the parallel runways and fly over south Minneapolis.
Jim Swenberger, who worked for three decades for the FAA as a controller, supervisor and investigator, said MSP’s runway design creates problems for controllers if a plane cancels a landing on the new north-south runway and turns toward the parallel runways.
“They’re distracted with a crossing runway operation,” Swenberger said of the controllers. “You look at all the major airports in the country, and they are trying to avoid any crossing runway operations. And Minneapolis created it.”
He said the airport decided against building a third parallel runway because it would have sent more planes over residents already protesting airport noise. “People’s heads would explode,” he said.
But airport spokesman Patrick Hogan has said Minneapolis lacks space for a third parallel runway because it is hemmed in by highways, a shopping mall and other obstacles.
Sam Tomlin, a veteran air traffic controller at MSP, also cited the number and arrangement of runways as a factor in the older reports on errors by the FAA. Newer airports have more runways; Dallas-Fort Worth has seven, Denver has six. And more of their runways are parallel, giving controllers more opportunity to avoid conflicts.
“It offers you so much more flexibility,” Tomlin said last year.
The National Air Traffic Controllers Association last week referred to Tomlin’s explanation when asked to explain the more recent higher numbers at the airport.
“His description of the operation at MSP stands the same as he described it last year,” association spokeswoman Sarah Dunn said.
Pat Doyle • 612-673-4504