An Alaska Airlines passenger jet landed on Seattle-Tacoma International Airport’s central taxiway – not the runway – on Dec. 19, the fourth time a pilot has made the error in the history of the airport.
Nobody was hurt in the 8:33 a.m. incident, and the Boeing 737-990, Flight 27 from Chicago, brought all passengers to the terminal without issue.
“It landed safely and taxied to the gate,” said Port of Seattle spokesman Perry Cooper. “Most likely the passengers on board had no idea they landed on a taxiway.”
Both Alaska Airlines and the Federal Aviation Administration are investigating the incident, but neither spokesmen for the organizations would elaborate on what happened or whether any actions, if any, have been taken since.
Taxiways are essentially roads that pilots use to drive aircraft between the terminal and their points for takeoff and landing. Some Sea-Tac taxiways cross the runways, while others, such as the one taxiway where Flight 27 landed, run parallel to the runways.
Landing on a taxiway is dangerous. It could cause a collision with aircraft already on the taxiway or about to cross it.
The taxiway crossings have the equivalent of stop signs, and aircraft can’t proceed without an OK from air traffic controllers, but if a plane were already half-way across when another was coming in to land, it could result in a collision.
The Dec. 19 incident happened just days after workers finished paving Sea-Tac’s central runway, which may have led to the pilot's confusion.
The runway and taxiway are the same length – about 9,400 feet – and are only 600 feet apart. The newly paved center runway would not yet have accumulated the dark tire marks characteristic of a heavily used runway, and so the light-colored concrete may have looked similar on both.
The weather was clear on Dec. 19, so the pilot might have been using a visual approach as opposed to using instruments, Cooper said, but he was not sure that was the case.
Pilot mistakes over Sea-Tac's center taxiway, called “Tango” in aircraft control lingo, have caused years of debate between the National Transportation Safety Board, Sea-Tac officials and the FAA, according to a 2005 Seattle Times story.
“This is a pretty rare thing. These are very well marked,” Cooper said. “There’s a real distinction between taxiway and runway because of markings.”
But some of the complications are caused by the fact that pilots often approach from the north, which means that the surface can be obscured from sunlight from the south. In addition, when the runway is wet – as it often is in rainy Seattle – any runway markings can be hard to see.
The last time a jet actually landed on the taxiway– and the pilot didn't pull up just before landing after realizing his or her mistake – was in 2004, when a propeller-driven Dash 8, flown by Air Canada unit Jazz landed with 32 passengers on board. No one was injured, but the NTSB investigated and recommended the airport mark the taxiway with a giant "T" so pilots could see it when they came in for a landing.
Since then the airport has added a third runway, which changed the NTSB's assessment.
(Steve Wilhelm - Puget Sound Business Journal)