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Storms Jostle Flight Routes

August 7, 2008

By Ted Jackovics, Tampa Tribune, Fla.

Aug. 7–UPDATED: 32 MIN. AGO

TAMPA — On a recent stormy Friday, a 30-mile band of severe weather centered over Gainesville blocked a major commercial airline corridor from the Northeast and Midwest into Tampa International Airport.

Pilots changed flight plans over southeast Georgia to join a conga line of airliners along the Gulf Coast. That added extra minutes to inbound flights, but kept air traffic flowing into TIA and other major Florida airports.

The previous day, airline conditions had been worse. Thunderstorms directly over TIA forced air traffic controllers to delay takeoffs. They also directed inbound aircraft into a race-track shaped holding pattern over Pasco and Hernando counties until a pathway opened in the storm. Air traffic controllers later launched what’s called a “cap and tunnel” strategy to get inbound and outbound jetliners moving.

Inbound aircraft were directed to fly lower than usual. That allowed outbound aircraft to overfly them along the same path with at least 1,000 feet vertical separation. At any moment during such busy periods, controllers might guide a dozen inbound and dozen outbound aircraft through gaps in bad weather in the vicinity of TIA.

The examples highlight strategies used by the Federal Aviation Administration to keep commercial air traffic from backing up during Florida’s summer thunderstorm season.

Guiding commercial aircraft safely around big storms is anything but routine, experts say.

Tampa International Airport normally uses five arrival and five departure corridors for aircraft, but the number of corridors available to aircraft can shrink when big thunderstorms roll into the Tampa area.

“Thunderstorms block arrival and departure corridors, so we often are forced to use one corridor,” said Mark Kerr, a senior Federal Aviation Administration controller at Tampa International.

“That makes it much more intense, getting a pilot through a gap in the weather.”

It’s not so much the lightning and heavy rain that concerns pilots and air controllers. Rather, it’s the violent updrafts and downdrafts from thunderstorms that worry pilots, for they create the most dangerous flying hazards.

The FAA says it put its Severe Weather Avoidance Plan, or SWAP, in effect at Tampa International on 25 of 30 days in June and generally employs the plan frequently in the Tampa area through mid-September.

Guiding aircraft loaded with passengers safely around storms creates its own kind of stress for pilots and air traffic controllers.

Individual controllers respond differently to the stress, said Rob Draughon, the FAA’s traffic management supervisor for the Jacksonville Air Route Traffic Control Center in Hilliard, one of 20 FAA regional centers.

“Some handle it very well, while for others it is more stressful,” he said. “It is the supervisor’s discretion of who they assign where. They are familiar with a controller’s comfort level.”

Avoiding Thunderstorms

Pilots avoid thunderstorms, although commercial aircraft are designed to take lightning strikes. Lightning hits are not unusual, with each aircraft struck, on average, 1.5 times a year, a 2004 U.S. Department of Transportation report found. The majority are reported in Florida.

The major danger to aircraft in a thunderstorm is violent and suddenly shifting wind that can cause a pilot to lose control of the aircraft, either at low altitude near landing or takeoff or heading to and from cruising altitude.

Thunderstorms produce updrafts and downdrafts that can exceed 100 mph, and some thunderstorms can reach altitudes higher than the 30,000 to 40,000 cruising altitude of jet airliners.

A low-level phenomenon called wind shear, with air drafts strong enough to push an airliner on approach to landing into the ground, was responsible for the crash of a Lockheed L-1011 in 1985. The accident, just a mile from the end of a runway at Dallas/Fort Worth International Airport, killed 134.

TIA is equipped with wind sheer detection radar to warn controllers and pilots of potentially hazardous conditions.

No commercial airline crashes have been blamed on a thunderstorm since a 1999 accident in Little Rock, Ark., that killed 10 passengers and one crew member on a night landing during severe thunderstorms and heavy crosswinds. However, nine small airplanes have crashed in storms since 2003, U.S. Department of Transportation reports show.

“We generally steer well clear of thunderstorms, which always present problems for us,” said Larry Newman, a Boeing 757 pilot, Lithia resident, and chairman of committee for the Air Line Pilots Association, a Washington-based industry group.

“Thunderstorms take out a lot of area in Florida, where you also have to take in account the military training areas off both Florida coasts,” he said referring to Air Force and Navy flight operations. “That doesn’t leave a lot of airspace.”

Although air traffic control can suggest flight patterns, pilots have the ultimate responsibility and final say on where they fly.

They rely on their own airline’s dispatchers who monitor weather patterns nationwide, sophisticated weather radar displays in their cockpits, and communications with FAA controllers to avoid thunderstorms.

Controllers work with pilots’ requests to deviate flights around storms based on the weather displayed on their cockpit radar, said Laurie Zugay, air traffic manager at Tampa Tower/TRACON.

Some pilots may request specific deviations, and others will ask the controller for other pilot reports on weather conditions, she said. Bad weather requires more transmissions and coordination between pilots and controllers, Zugay said.

Controlling Florida Airspace

Air traffic controllers at regional centers at Miami and at Hilliard near Jacksonville and controllers at airport towers and airport radar control rooms, such as at TIA, work as a team to control air traffic.

The FAA uses multiple procedures to monitor the performance of its controllers, including equipment that can reproduce screen grabs of air traffic situations at any particular moment.

Tampa International generally ranks among the top 20 airports nationwide in on-time performance during the summer thunderstorm season. The airport ranked eighth in August 2007 with 75.8 percent of arrivals on-time and fifth with 80.2 percent of on-time departures.

New York’s three major airports ranked last in August for performance on arrivals last year, and Atlanta ranked last in performance for departures.

“First and foremost, we have professional controllers who make it work,” said Kerr, the TIA controller. “It is beneficial that Tampa is not a hub airport, so we don’t have situations where we are inundated.”

The FAA’s severe weather procedures typically double the controllers’ workload to handle the same number they do during good weather, when multiple arrival and departure corridors are available.

“Work is more intense during SWAP, but air traffic controllers in Tampa, Orlando and Jacksonville are awfully good at it,” said Draughon at the Jacksonville regional control center.

“Tampa and Orlando are nationally recognized for thunderstorm activity, but compared with New York or Washington, the only time air traffic stops in Central Florida is when thunderstorms are right over the field.”

The FAA is installing more sophisticated equipment at its regional centers to provide high-resolution, three dimensional displays of weather information and forecasts in its regional control centers and airports, including TIA.

The Air Line Pilots Association also hopes improved aircraft separation standards can be developed to expedite flights when the FAA’s satellite-based Next Generation Air Transportation System is introduced. That multibillion-dollar program is still years off. It will replace most current radar operations.

Reporter Ted Jackovics can be reached at (813) 259-7817 and tjackovics@tampatrib.com.

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