Arrestor System Can Compensate If Runway Safety Area Is Lacking

When the safety area does not extend 1,000 feet past the paved end of the runway, an engineered materials arresting system (EMAS) may be worth considering.

According to Kent Thompson, vice president of Engineered Arresting Systems (ESCO) of Aston, Pa., which manufactures this system, the prepared bed will slow and stop an aircraft going 70 knots (about 85 mph). It's ideal for those locales where a 1,000-foot runway safety area is not available. Federal Aviation Administration (FAA) Order 5200.9, "Financial Feasibility and Equivalency of Runway Safety Area Improvements and Engineered Material Arresting Systems," states that the system, when used in conjunction with a safety area of just 600 feet, is equivalent to an overrun safety area ("stopway") of 1,000 feet.

Made of cellular cement material typically cast into four foot square blocks at the factory and shipped to the site for placement, the system may be ideal for stopping aircraft before they reach natural hazards such as steep slopes or a body of water, as well as stopping aircraft before they collide with man-made obstacles, such as highways, railroads or built-up areas.

The system is installed at New York's John F. Kennedy International Airport, and it has saved three aircraft. In January of this year a Polar Air B747 cargo jet landed on an icy runway, slid off the end and was stopped by the EMAS system with minimal damage to the aircraft and no injury to the crew or anybody on the ground.

In 2003 the arrestor stopped an MD-11. In May of 1999 the same arrestor bed stopped a Saab 340 commuter twin-turboprop. In all cases the airplanes were pulled backward onto the runway and quickly repaired. The runway was immediately reopened. Subsequent repairs to the arrestor bed took about 12 days to accomplish.

The system is presently installed at 15 airports nationwide. The installation typically is as wide as the runway. Length depends on the amount of safety area. Depth varies to arrest a range of aircraft, typically starting at six inches near the runway and increasing to between 18 and 30 inches at the far end of the system. EMAS also features side steps to facilitate access by airport rescue and firefighting (ARFF) equipment, which can drive over the pavement without deforming it. The concrete cells are computer-designed to deform when aircraft landing gear plows through it, slowing the airplane to a stop.

The system is presently installed at JFK, and the Little Rock and Burbank airports, where overruns beyond the limited safety area have occurred.

In a couple of cases where aircraft overran the runway and were stopped by the system, tires were blown; however, the damage was slight compared to the potentials - structural breakup of the airframe and fire.

"It looks like there's plenty of room to put EMAS at Toronto's Runway 24L," said Thompson. This would go far to mitigate the hazards posed by the nearby creek and highway.

"So far, we've focused on the U.S. market," Thompson said. The National Transportation Safety Board (NTSB) is participating in the Transportation Safety Board (TSB) of Canada's investigation into the overrun at Toronto, and the NTSB has recommended EMAS in past investigations as one way to compensate for insufficient runway safety areas.

How EMAS Works

The loads are placed on the aircraft landing gear and support structure as the special cellular concrete deforms, as in this case of a successful May 2003 "arrest" of an MD-11F at JFK in New York.