Pilots mistake taxiway for runway at Sea-Tac
At least eight times since December 1999, experienced pilots from five airlines have mistaken Taxiway Tango for Runway 16R.
Seattle Times aerospace reporter
When Roger Seher flew a 37-seat Air Canada Jazz turboprop into Seattle-Tacoma International Airport in January 2004, he was aware of the "Taxiway Tango" problem.
He'd flown into Sea-Tac many times and knew pilots arriving from the north sometimes confused the western landing strip, Runway 16 Right, with the nearby taxiway, called T or Tango. He also knew Sea-Tac had placed a 25-foot-by-25-foot "X" at the end of the taxiway to prevent potentially catastrophic landings there.
So after touching down that morning, as he later reported, Seher and his co-pilot were startled to hear from the control tower: "You have landed on taxiway."
At least eight times since December 1999, experienced pilots from five different airlines have mistaken Taxiway Tango for Runway 16R.
Three planes, including an American Airlines MD-80 carrying 111 passengers and crew members, actually landed on the taxiway. Five others — most recently in January of this year — either performed last-minute "sidesteps" to shift course and land on 16R, or aborted their landings before circling and touching down safely on the runway.
The incidents have alarmed the highest levels of the National Transportation Safety Board (NTSB), which has repeatedly warned that the confusion could cause a collision between incoming jets and planes or vehicles on the taxiway.
Acting NTSB Chairman Mark Rosenker wrote in an Aug. 8 letter to Federal Aviation Administration Administrator Marion Blakey that "the Safety Board believes the Taxiway T situation at Sea-Tac is a serious problem that has the potential to contribute to or cause a major accident, yet the FAA is unwilling to take interim steps to mark the taxiway."
FAA and NTSB — Who does what?
FAA issues and enforces regulations that apply to airlines, airports and air traffic controllers.
NTSB investigates accidents and issues safety recommendations to prevent accidents. It has no power to enforce its recommendations.
The FAA and NTSB have been feuding over the issue for years, but local FAA and Sea-Tac officials were unaware of the August letter until a reporter brought it to their attention late last month.
They disagree with the NTSB's conclusions, as did several pilots interviewed by The Seattle Times. They cite multiple steps taken in recent years to make Sea-Tac's runways more visible and to educate pilots, and they insist passengers have little to fear.
"I believe the problem's fixed," said Mark Coates, manager of operations at Sea-Tac.
"We haven't had an unsafe landing on Taxiway Tango yet. Every one of them was wrong, and every one of them should not have happened, but they were not unsafe."
The NTSB wants Sea-Tac to take additional actions that sound simple, such as painting warnings on the taxiway surface itself. But FAA and Sea-Tac officials say there is no proof those measures would work.
Confusion from the start
Taxiway Tango is lightly used, mostly by small private planes and corporate jets rolling to the general aviation hangar on the airport's west side. Those planes represent just 1 percent of the traffic at Sea-Tac.
Taxiway Tango background
Much of the material produced by the National Transportation Safety Board and the Federal Aviation Administration during their review of the Taxiway Tango situation at Sea-Tac Airport is contained in public documents.
Here are NTSB reports detailing four of the incidents when planes lined up with, or landed on, Taxiway Tango:
American Airlines, 3/14/03
Air Canada Jazz, 1/19/04
Southwest Airlines, 2/24/04
Southwest Airlines, 1/30/05
The NTSB and FAA have disagreed over how best to remedy pilots' confusion over Taxiway Tango. Here is a safety recommendation issued by the NTSB; the FAA's response and the NTSB's reaction to the FAA's response.
NTSB recommendation, 6/24/04
FAA letter, 3/5/05
NTSB letter, 8/8/05
Among the steps Sea-Tac and FAA have taken to increase pilots' awareness about the Taxiway Tango situation is to add warnings to charts for the airport. Here is one example:
Sea-Tac approach chart
Commercial jets use Tango less often, mostly to reach parking spots on the edge of the taxiway during weather delays or when overnight parking at the terminal is full.
The taxiway was completed in October 1999, an accessory to the planned third runway that has been delayed for years by court battles.
Pilots noticed it right away.
"We started having issues with that [taxiway] almost from day one," said a senior commercial pilot who has been flying into Sea-Tac since 1977. His employer allowed him to speak only on condition neither was identified.
From the air, the taxiway's pristine pavement draws the eye, pilots say.
"When you're 15 or 20 miles from the airport, you pick up this piece of concrete first because it's newer and brighter," said Jack Wilkes, an Alaska Airlines 737 captain with 34 years of experience and air-safety chairman for Alaska's pilots union.
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.
Steps taken so far
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.
What else can be done?
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.
When Palm Springs International Airport added a second parallel runway in 1991, planes began landing on the taxiway between the two landing strips. Twenty taxiway landings took place in 1995 alone, although most involved small private planes rather than commercial jets.
Steve Zehr, systems aviation director at Palm Springs International, said the airport in the late 1990s painted several "TAXI" and "TAXIWAY" labels on the taxiway and added a serpentine center line.
"The incidence of errant landings dropped dramatically," Zehr said.
Airports in Las Vegas and Tucson took similar precautions, with similar success.
But Matt Cavanaugh, manager of the safety and standards branch of the FAA's Pacific Northwest office in Renton, said: "The flight tests we've done have verified that when it's wet and shiny, you cannot see markings."
"The water on the surface will obscure those markings," agreed Alaska pilot Wilkes.
Max Tidwell, head of runway safety in the FAA's Pacific Northwest office, said such markings work best at airports where pilots fly past the airport before landing, allowing them to look down and see the taxiway.
"At this airport all you have are straight-in approaches," said Coates, manager of operations at Sea-Tac. "You don't have an opportunity to fly beside a taxiway and look out a window and say, 'What's that?' "
The FAA says it tested paint on the taxiway last February and concluded it would not be visible.
The NTSB said the FAA painted only small strips on the taxiway's dark asphalt shoulders, rather than on the bright concrete surface, and didn't try running a serpentine line down the taxiway.
"Given this information, the Safety Board questions how the FAA could determine that these measures were ineffective," the NTSB wrote in its Aug. 8 letter.
No matter how Taxiway Tango is marked, electronic instruments can guide pilots precisely to Runway 16R.
When the coordinates for Sea-Tac are dialed in to a plane's navigation system, it indicates whether the final approach is on target.
But on clear days pilots generally opt for visual approaches rather than relying on their instruments. Both airlines and air traffic controllers prefer this because it allows shorter distances between incoming planes. Kathryn Vernon, air-traffic hub manager for the FAA in Seattle, says most airlines' policy is that pilots should check their electronic guidance anyhow when doing a visual approach.
Yet even highly experienced pilots occasionally forget to look back at their instruments once they see what they think is the runway.
"You pick it up, you get locked in and you land," Wilkes said.
The FAA's Max Tidwell said the agency and Sea-Tac officials are trying to correct the taxiway problem at that early point in pilots' decision making, so they do not let their eyes deceive them.
Coates said he thinks the cumulative effect of all of the measures taken by Sea-Tac has greatly diminished the possibility of another airplane landing on Taxiway Tango. But he said he, air traffic controllers, the FAA and the NTSB will keep a close eye on the situation this winter.
Because as long as Tango remains at Sea-Tac, more errant landings remain a possibility.
"The only 100 percent solution is to remove that taxiway," Wilkes said, "and I don't believe that's going to happen."
David Bowermaster: 206-464-2724 or firstname.lastname@example.org