Deadline Looms for Arrestor Beds

With such a bona fide success record, you would think deployment would be accelerated.

I am referring to the Engineered Materials Arresting System (EMAS), which employs specially configured concrete that slows aircraft that have overrun the runway. EMAS has been credited with seven “saves” since 1999, the most recent of which occurred 1 October 2010 at Teterboro, NJ. A Gulfstream G-IV business jet ran off the end of the runway and into the arrestor bed. The EMAS, as designed, crushed under the weight of the aircraft, providing a predictable, controlled deceleration. The Gulfstream was stopped before it could break though the airport perimeter and hurdle across Route 46, a busy highway.

Runaway corporate G-IV halted by an arrestor bed.

Runaway corporate G-IV halted by an arrestor bed.

In this fortuitous case, no one was hurt and the aircraft suffered only minor damage – mainly needing a new set of tires.

In February 2005, an overrun at Teterboro had a less happy outcome. A Canadair CL-600 corporate jet attempted take off with its center of gravity well forward of allowable limits. The airplane did not get off the ground. It crashed through the perimeter fence, crossed Highway 46 and plowed into a warehouse. No one was killed. The 11 occupants of the aircraft all survived, but the badly damaged aircraft was written off. Two people in automobiles hit as the Canadair roared across the highway were injured.

Canadair jet lodged in a warehouse after overrunning the same runway in 2005.

Canadair jet lodged in a warehouse after overrunning the same runway in 2005.

After that accident, EMAS was installed in 2006 to prevent future overruns from bursting through the fence.

The light-colored area shows the installed EMAS at Teterboro. Note close proximity of the highway.

The light-colored area shows the installed EMAS at Teterboro. Note close proximity of the highway.

A witness said of the latest incident, “Just drove by and thankfully they installed those arrestors or it would have gone straight across Route 46 again.”

EMAS is produced by NJ-based ESCO-Zodiac Aerospace. The company’s Kevin Quan said:

“Both the airport and ESCO [Engineered Arresting Systems Corp.] – Zodiac Aerospace are thrilled about the aircraft arrestment from last Friday afternoon … This is our 7th successful save with the product. Both loss of lives and millions of dollars of aircraft damage have been avoided with the use of EMAS arrestor beds. Airports that have been proactive in installing arrestor beds such as Teterboro are now seeing the benefits of this technology.”

Six previous "saves" attributed to EMAS.

Six previous "saves" attributed to EMAS.

One could quibble with Quan’s enthusiastic use of the word “proactive.” The terrible 2005 accident spurred the 2006 installation that saved the plane and lives in 2010.

There is a disturbing pattern of the Federal Aviation Administration (FAA) freeing up money for airports to install EMAS after, not before, an accident. Following the fatal overrun of an American Airlines MD-82 twinjet at Little Rock, AR, EMAS was installed.

EMAS works by increasing the resistance of the aircraft tires to rolling. A concrete surface normally decreases rolling resistance through its hard surface. But EMAS consists of aerated cement blocks. Those blocks are designed to have the same effect on the airplane’s tires as gradually deepening snow would to a moving automobile. EMAS is configured for each runway, and is intended to stop a jet moving up to 70 knots (80 mph).

Close up of the crushable concrete.

Close up of the crushable concrete.

In the latest incident at Teterboro, the jet did not show obvious signs of structural damage, although its tires and landing gear struts were buried in the fractured concrete.

According to ESCO-Zodiac, “[A] Proprietary computer model predicts aircraft performance and design for the most effective solution for each runway end.” The company is the only one that presently produces an aircraft arresting system certified by the FAA for airport runway safety areas (RSAs).

Normally, an RSA consists of a grassy area, free of obstacles, extending 1,000 feet beyond the end of each runway and about 500 feet in width. But many airports were built before the 1,000-foot RSA length was promulgated by the FAA about 20 years ago. And airport locations are constrained by highways, railroads, severe drop-off of terrain – as at Little Rock – bodies of water, and populated areas (residential, office, industrial).

Where there is insufficient area for the 1,000 x 500 foot RSA, the EMAS arrestor bed can be installed. It normally extends up to 600 feet past the end of the runway, but the design is tailored for each location and for the heaviest types of aircraft anticipated to operate at the particular airport.

Under the FAA program of airport safety improvements, all runways must feature either the full 1,000-foot RSA or the EMAS arrestor bed by 2015. For some deficient runway RSAs, grading and planting will suffice if land is available and not too costly. Where this is not possible, EMAS is employed.

According to ESCO, as of October 2010, 55 EMAS configurations have been applied to runways at 37 airports worldwide (35 U.S. airports) since 1996. This works out to an average of about four installations yearly in the U.S. According to the FAA, about 80 EMAS installations remain to be completed during 2011-2014 to meet the deadline of projects completed by 1 January 2015.

emas installed

That works out to an installation rate of about 20 EMAS per year, or four times the annual rate of installations thus far.

It is doubtful the FAA will meet its goal.

The pity here is that the EMAS installation can easily be justified on cost-benefit grounds. Assume an EMAS installation price at Teterboro of $8 million. Now assume the statistical value of a life is approximately $3 million, and there were 9 passengers and crew aboard the G-IV that was stopped by EMAS. Assume $25 million for a used G-IV. Add together the cost of airplane and lives and compare to the price of an EMAS installation:

Benefit: $27 million lives saved + $25 million aircraft saved = $52 million

Cost: $8 million EMAS

Ratio of benefits to cost: 6.5 to 1

That’s one runway, one incident. The benefits nationwide clearly are in the hundreds of millions of costs avoided.

The FAA’s support of EMAS is laudable; at the same time, the agency’s definition of a “high priority” program does not square with the 2015 deadline. An accelerated limit of 2013 would be more in keeping with the FAA’s definition of the program’s importance.