Pilots Mistake Taxiway for Runway at Sea-Tac

At least eight times since December 1999, experienced pilots from five different airlines have mistaken Taxiway Tango for Runway 16R.

The first-known instance of a pilot mistaking Tango for Runway 16R occurred two months after Tango opened. In an anonymous report filed with a voluntary federal air-safety database, the pilot of a 737-800 said he lined up to land on the taxiway "because of the intense glare from the sun where the taxiway was clearly visible and the other landing surfaces were not able to be seen."

When he realized his mistake, the pilot executed a "sidestep," lined up with Runway 16R and landed safely. At least one other pilot -- in the 757 just ahead of the 737 -- made the same mistake that day, but that incident was not formally documented.

The most recent incident happened in January. The pilot of a Southwest Airlines 737 was just 500 feet above the ground when he realized he was about to land on Taxiway Tango. He executed a "go-around" at 250 feet and landed on Runway 16R.

Elements of Tango's design add to pilots' confusion.

Both the taxiway and Runway 16 Right are made of concrete, which has a white-ish appearance from the air. Runway 16 Left is made of asphalt, which looks dark.

"16L just kind of blends in because it's black, and looks like the ramp area" in front of the main terminal, said the senior pilot who spoke on condition of anonymity.

The dimensions of Tango and Runway 16R are similar as well. Counting the landing surface and the adjacent shoulders, Runway 16R is 200 feet wide, close to Tango's 180-foot span. Runway 16L is much wider at 250 feet across.

Additionally, Tango is just 400 feet from Runway 16R. Runway 16L is 600 feet from 16R.

Seattle's geography and weather complicate matters further.

Each of the erroneous approaches has involved planes flying from the north toward the southern sun. And they've occurred between December and March, when the sun is low on the horizon and most likely to be shining into pilots' eyes.

Several also took place on days when rain showers doused the runways, followed by bright sun breaks.

"If the sun is peeking below the clouds and the surface is wet, you're going to see one heck of a glare," said Tom McRae, regional safety coordinator for the Air Line Pilots Association and an Alaska Airlines captain.

Sea-Tac officials have tried several strategies to keep pilots from landing on Taxiway Tango.

In May 2000, they placed a small "X" on the ground about 200 feet north of the taxiway.

It didn't do the trick.

About six months later, a 14-passenger Cessna 208 operated by Harbor Air became the first plane to land on Taxiway Tango.

The problem got more attention after the heavily loaded American Airlines MD-80 landed on Taxiway Tango on March 14, 2003. The NTSB, FAA, Sea-Tac officials and pilots formed a working group to study the problem.

Soon after, in May 2003, Sea-Tac installed the yellow 25-foot-by-25-foot "X" near the end of the taxiway.

Also, an audio warning about Taxiway Tango was added on the weather and conditions radio broadcast that pilots check before landing at Sea-Tac. Yet the incidents continued, most notably the Air Canada Jazz landing on Tango in January 2004.

Seher, the captain, could not be reached for comment. But he told NTSB investigators neither he nor his co-pilot saw the X during their final approach, though they knew it was there.

"Despite the airport's efforts, flight crews continue to mistake Taxiway T for an active runway," the NTSB wrote in June 2004.

Sea-Tac in late 2004 added runway end identifier lights (REILs) to draw pilots' attention toward the two runways.

But the lights "were very disappointing," admitted Bob David, manager of FAA's airport-safety and operations divisions. One problem: REILs are easy to see when a plane is lined up on the runway, but not when the plane is off to one side.

The flight crew of the Southwest Airlines 737 that lined up on Taxiway Tango in January 2005 told NTSB investigators they did not see the REILs until after they aborted the first landing.

More recently, the FAA persuaded the publishers of flying charts and maps for Sea-Tac to include written warnings about the Taxiway Tango situation.

In June 2004, the NTSB recommended the FAA allow Sea-Tac to paint "TAXI ONLY" or "TAXIWAY" repeatedly on Tango, along with a serpentine center line.

Other airports have used such markings with good results.

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