Truck Stop: SFO's Solution for Runaway Planes Is a Familiar One for Long-Haulers

A year ago this month, Asiana Flight 214 undershot the runway at San Francisco International Airport, clipped a seawall, and came to rest in several charred pieces. Three young passengers died and 181 more were injured.

There are two impediments that would impede the momentum of an airplane suffering the opposite scenario and overshooting the runway: Highway 101 and the bay.

And so, by mid-September, the airport plans to install barriers meant to slow a runaway plane prior to its merging or sub-merging.

SFO's solution is both high-tech and gloriously low-tech. On four of its runways, it's laying down football field-sized arrays of “engineered material arresting systems” (EMAS), emplacements of 4-foot-square blocks ranging in height from 6 inches to 2 feet. From above, installations resemble monochromatic checkerboards; runaway planes roll over the “crushable concrete,” which absorbs kinetic energy as it's pulverized and slows the jet to a stop.

The exact makeup of the “crushable concrete” is a well-kept secret and proprietary matter.

New Jersey-based Engineered Arresting Systems Corporation, the only outfit producing and installing EMAS in the United States, runs complex computer-modeling programs factoring in runway configurations, lane elevation, spatial restrictions, and the characteristics of the planes taking off and landing at any given airport.

So, that's the high-tech element. The low-tech part: EMAS is, essentially, the Federal Aviation Administration-approved equivalent of the gravel pits along mountain roads meant to save runaway trucks.

It's also about as complex to maintain as gravel. The blocks are designed to last 20 years, and, in the event of someone seeing fit to roll a plane over them, they clean up easily. T.J. Chen, the West Coast regional director for Engineered Arresting Systems Corporation — which, mercifully, goes by “ESCO” — says that only 5 to 10 percent of the blocks usually need to be replaced following a smackup. The FAA reports that the systems have made arrests of planes nine times since 1999.

Of course, no San Francisco construction project could come off without its own unique challenges. SFO predates 20-year-old FAA requirements to tack 1,000 feet of extra space on the end of every runway. SFO lacks the real estate to do this — unless runways were extended into the bay or Highway 101. In fact, SFO even lacks the space to install a standard, 600-foot EMAS field (San Francisco's vary from 373 to 438 feet). Chen, however, says no one should worry. He isn't. He lives in the Bay Area and flies out of SFO all the time. “It's a great airport,” he says. “Now it'll be even better.”

Let's hope. And let's hope its glorified gravel pits remain pristine and unsmacked.

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