Only two incidents, involving multiple mistakes and aircraft, were categorized as the most serious: Category A.
Most were classified as B and C errors, and some were not categorized - including a medevac helicopter that cruised too close to a Southwest Airlines plane on takeoff.
The incident was the only "near miss" reported for Philadelphia to the FAA in the last 21/2 years. It caused Philadelphia controllers to change the way private planes and helicopters are permitted to "transit the tower airspace," said Robert Niszczak, a 20-year controller in Philadelphia and staff manager of the Philadelphia tower and radar room.
Controller errors are mainly a failure to keep proper distance between airplanes. FAA regulations require that planes be separated by three miles laterally and 1,000 feet in altitude - and five miles apart in wake turbulence, the unstable air behind a larger, heavy jet.
Even if a controller makes a mistake, commercial airliners, corporate jets, and military planes have had collision-avoidance alarms since the 1990s. The alarm sounds in the cockpit when another aircraft is too close and tells the pilots to climb or descend to avoid an accident.
According to error reports, pilots often took evasive action, even if a controller did not catch what was happening.
In Philadelphia, some errors occurred when the tower changed runway direction for arriving and departing flights, or made a runway change because of maintenance.
Mistakes also were made when controller functions in the radar room were combined, which is a common practice and considered operationally safe.
Planes sometimes got too close when pilots, in helicopters and private planes, failed to heed or respond to a controller's order - such as the medevac helicopter that twice did not respond to a tower controller's warning that a Southwest Airlines plane was less than a mile away.
"One of the things we always look at - was there training in progress at the time," said Scott Dunham, air-traffic-control investigator with the National Transportation Safety Board. "Or were they newer controllers? Quite a few of these [mistakes] do involve training."
A tragic error
Philadelphia has never had a collision on the ground. The most recent midair collision here - a memorable one - occurred in April 1991, when a helicopter collided with a small plane carrying U.S. Sen. John Heinz over Merion Elementary School.
The plane carrying Heinz reported trouble with its landing gear. Two pilots in a nearby helicopter volunteered to fly near to take a closer look. While the helicopter hovered below the airplane, the two aircraft collided, killing Heinz, four pilots, and two children in the schoolyard below. The tragedy was the result of action by both crews and did not involve air-traffic control.
At the Philadelphia airport, 91 controllers handle 3,500 operations a day, including takeoffs, landings, and the flights of corporate, private, and military planes within a 60-mile radius.
Controllers' duties extend from 15 miles south of Allentown to 15 miles southwest of Wilmington, east to Cedar Lake and Woodstown, N.J., and west 10 miles beyond Pottstown. Philadelphia controllers handle two dozen satellite airports, including Wings Field in Blue Bell, Brandywine Airport near West Chester, Chester County Airport in Coatesville, and Pottstown Municipal Airport.
Nationally, in the 12 months ended Sept. 30, 2010, there were 1,887 operation errors, according to the FAA's tally. During the same period a year earlier there were 1,233 errors, and the year before, 1,349. Before 2008, the FAA used a different counting method, so a lengthier pattern is not available.
The FAA attributes the higher number of reported errors to better reporting, including a new nonpunitive system that encourages controllers to voluntarily self-report. Improved technology monitors aircraft electronically and automatically reports if planes get too close.
"I'd focus not so much on the errors, but the severity," said the NTSB's Dunham. "If you've got a lot of low-level errors, they may not be that significant. Some of the 'A' errors are wake-turbulence events, where there's probably not that much hazard. Then there are 'A' events where airplanes really do get close together."
The vast majority of errors "pose little to no safety risk," said Doug Church, spokesman for the National Air Traffic Controllers Association, whose 15,500 controllers guide 50,000 flights a day and nearly two million passengers through the country. At any one time, about 5,000 planes are in the sky.
"We take errors very seriously. Anytime there is an incident, or a loss of separation, we do a full and thorough investigation," said Niszczak, the Philadelphia controller. "Out of that, usually we get recommendations, and something is going to change."
Air-safety operations have been under increased scrutiny since several high-profile controller incidents in March and April. A supervisor - and the lone controller - working after midnight fell asleep March 23 at Washington Reagan National Airport and two passenger planes had to land without assistance.
In April, a controller in Cleveland was watching a DVD instead of his radar screen. Later that month, a plane carrying Michelle Obama aborted landing because a military cargo plane was too close in the same airspace.
Fatigue was the "largest underlying problem" contributing to controller lapses in Miami; Knoxville, Tenn.; and Seattle, when controllers dozed off while working an overnight shift, controllers' union president Paul Rinaldi testified before Congress in May.
In the last five years, 7,800 controllers - or 22 percent of the workforce - have been new, Rinaldi said. Trainees require several years to become fully certified, and high attrition from 2006 to 2009 has left the system "overwhelmed" with trainees, he said.
Twenty-two of Philadelphia's 91 controllers are currently in training. "That number is a little misleading," Niszczak said. "Some have been certified for well over a year in the tower, but they are training in the radar room. So it's not like they are brand new."
Some Phila. controller errors
June 16, 2011. A US Airways Airbus was given clearance to cross Runway 27 Right, where a Piedmont Airlines Dash-8 was taking off. (Runway 27 Right is normally an arrivals runway.) The planes came within 850 feet of each other. The Dash was originally supposed to depart from Runway 35, which was closing for maintenance. The ground controller working the US Airways flight had asked the crossing coordinator for permission to cross from a taxiway. The crossing controller said OK, but failed to get permission from the local east controller who cleared the Piedmont flight for takeoff.
June 9, 2011. A controller-in-training told the wrong US Airways plane to descend to 3,000 feet, from 6,000 feet, over Woodstown, N.J., by mixing up Flights 719 and 729. By ordering the wrong plane to descend first (both flights were landing), proper separation was lost with a Piper plane flying through at 5,000 feet. US Airways 719 and the Piper were within 400 feet vertically and 1.78 miles laterally. (Standard separation is 1,000 feet and three miles.) Both US Airways flights landed without incident; the Piper continued on its journey.
Jan. 14, 2011. Three Category A errors occurred simultaneously. A US Airways Airbus and a US Airways Boeing 737 were on approach from the south to land on Runway 27 Right. A Piedmont Dash-8 turboprop was inbound from the north to land on Runway 26. The 737, traveling 80 knots faster than it should have been, lost required wake-turbulence separation with the larger Airbus. The Piedmont plane also lost separation with the Airbus when it turned on a nine-mile final approach; it was 3.1 miles behind the larger jet. The 737, because it was going too fast, overshot the final approach course and flew underneath the Piedmont, violating that plane's airspace. The two came within 200 feet vertically and one-third of a mile laterally of each other.
April 24, 2010. Two category A errors occurred simultaneously when a controller told a military aircraft to climb to 10,000 feet near a navigation point called the "DuPont VOR." An Air Wisconsin jet was heading to the same navigation point at 10,000 feet. The planes, on a converging course, were 600 feet apart vertically and 2.1 miles laterally when alarms went off in both cockpits, instructing the military jet to climb and the Air Wisconsin plane to descend. The second error happened as the military aircraft climbed above 10,000 feet and came too close to a Colgan Air Dash-8 plane traveling at 11,000 feet.
Source: Federal Aviation Administration
Contact staff writer Linda Loyd at 215-854-2831 or firstname.lastname@example.org.