Just before Christmas, the Engineered Arresting Systems Corporation (ESCO) reported that it has produced 2,257 of the 2,436 EMAS (Engineered Materials Arresting System) blocks that will, when installed this year, enhance runway safety and the length of Runway 15/33 without making it longer. And the company sent along this photo, which shows shelves filled with just one-fifth of the blocks already produced.
Each block is made of a homogenous mixture of cellular cement that crushes in a reliable and predictable manner under an airplane’s weight. For whatever reason, when an airplane runs off the end of the runway, EMAS slows its progress, much as it does when a runner sprinting for the water at the beach crosses from the parking lot to loose sand. And like the runner, FAA testing and a number of EMAS saves with aircraft up to a Boeing 747 have resulted in little or no damage to the aircraft.
To date, EMAS is installed at 74 runways at 47 airports in the United States, and they are 9/9 on safely stopping overrunning aircraft that carried a total of 243 passengers and crew. Addison will be the second airport in Texas equipped with EMAS, Laredo International received its EMAS in 2006, and its bed was retrofitted in 2012, and the Addison EMAS should be in service this summer.
It takes four weeks to make a batch of blocks. ESCO starts with 5 cubic yards of the cellular cement mixture that weighs approximately 25 pounds per cubic foot. The blocks have a standard length and width, but their weight, strength, and rate of height increase from the runway edge to its maximum height varies on the needs of each installation. The larger blocks can weigh several hundred pounds.
Each block is coated to protect it from weather, water, and jet blast. After the site is graded, if necessary, for drainage and longitudinal slope, a concrete beam is built at the front of the arrestor bed. As the diagram shows, this beam is both a lead-in ramp and blast deflector.
The arrestor bed spans the full width of the runway, and there are shorter blocks to either side that create steps for aircraft rescue and fire fighting personal and deplaning aircraft passengers and crew. The entire installation is computer modeled to meet the FAA-approved specifications for each airport installation.
Once the bed is prepared, it is marked with a grid that shows the precise location of each block, which is held in place by a mixture of hot asphalt and cement, All joints between the blocks are sealed with extruded silicone. According to ESCO, a typical EMAS takes two to four weeks to install, and that includes training the staff to maintain the finished system. Typically that involves regular inspections and maintaining the protective seam seals and the top cover requires no repainting.
Given the weight of the engineered material of which they are made, building the EMAS out of blocks not only makes for more efficient and economical installation, it allows the replacement of blocks that have done their job of safely stopping an aircraft.