Seattle Class B redesigned

If your family outgrows your home and relocating is not an option, you remodel. That metaphor applies to airspace too, which is why Seattle’s Class B airspace was recently redesigned.

“The previous Class B airspace design in the Seattle area had become outdated and resulted in an inefficient use of airspace,” said Mike Fergus, Public Information Officer for the Seattle office of the FAA. “To increase safety and maximize the efficiency of overall airspace resources, a new design was planned.”

As traffic increases, so does the possibility of conflict, noted Fergus.

While aircraft on IFR flight plans have the benefit of Flight Following from ATC, VFR pilots who do not take advantage of ATC services are on their own to maintain separation. In congested airspace, that can be a challenge. The VFR/IFR separation was a big part of the Seattle redesign, said Fergus.

“The old design allowed IFR glide slopes to exit controlled airspace and then reenter as it proceeded down to the airport,” he said. “This exposed those controlled aircraft to VFR uncontrolled flights with potential for conflict. The new design keeps the glide slope entirely inside controlled airspace.”

Some pilots in the Pacific Northwest were taken by surprise when they picked up the new charts in December and saw the changes. They shouldn’t have been, noted Fergus, as the redesign work began in 2007 and followed a formal rulemaking process.

Among the most noticeable change was the raising of the floor of the key-shaped Bravo south of Seattle-Tacoma International Airport (SEA) from 1,600 to 1,800 feet. The airspace is sandwiched between the Class Delta of Joint Base Lewis-McChord (TCM) and Tacoma Narrows Airport (TIW). In the past, pilots had the choice of flying approximately 1,000 to 1,500 feet above the Interstate, subdivisions and industrial parks or altering their course for a longer route, with careful attention paid to ground landmarks or the GPS to be sure they didn’t clip the Bravo.

“The altitude to the south of Sea-Tac that changed by 200 feet was based on the glide-slope altitude for aircraft arriving at Sea-Tac,” he explained. “That area has seen an increase in VFR traffic and we were trying to better serve the VFR pilots by allowing them an area to transit around Class B.”

Pilots who are not fans of controlled airspace will be happy to know that the redesign reduced the Class B by approximately 194 square miles, but still retains existing features familiar to local users.

“Where possible, this design aligned Class B boundaries with existing VOR NAVAIDs and geographical features, resulting in improved boundary definition,” he said, noting this makes navigating around and through the airspace easier for all pilots.

“It is important to note that existing IFR traffic — primarily SEA turbojet traffic — routes and altitudes did not change as a result of this airspace modification,” he said.

Formerly, the familiar blue lines on the sectional featured a cylindrical design that evoked an image of an upside-down wedding cake. Now it is more squared off, with local pilots saying it is reminiscent of an emerald, which some noted is fitting as Seattle is known as “The Emerald City” in some circles.

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