An engineered materials arrestor system, engineered materials arresting system (EMAS), or arrester bed is a bed of engineered materials built at the end of a runway to reduce the severity of the consequences of an aircraft running off the end of a runway. Engineered materials are defined in FAA Advisory Circular No 150/5220-22B as "high energy absorbing materials of selected strength, which will reliably and predictably crush under the weight of an aircraft". While the current technology involves lightweight, crushable concrete blocks, any material that has been approved to meet the FAA Advisory Circular can be used for an EMAS. The purpose of an EMAS is to stop an aircraft overrun with no human injury and minimal aircraft damage. The aircraft is slowed by the loss of energy required to crush the EMAS material. An EMAS is similar in concept to the runaway truck ramp or race circuit gravel trap, made of gravel or sand. It is intended to stop an aircraft that has overshot a runway when there is an insufficient free space for a standard runway safety area (RSA). Multiple patents have been issued on the construction and design on the materials and process. FAA Advisory Circular 150/5220-22B explains that an EMAS may not be effective for incidents involving aircraft of less than 25,000 lb weight. It also clarifies that an EMAS is not the same as a stopway, which is defined in FAA Advisory Circular 150/5300-13A, Section 312. Pilots are advised, if they know the airplane is going to overrun onto an EMAS installation, to maintain directional control of the aircraft and roll straight into it. By doing this, the aircraft will come to a complete stop over a short distance, regardless of the runway conditions or braking action being experienced. As of May 2017, the International Civil Aviation Organization (ICAO) has been working on developing a harmonized regulation regarding arresting systems. Research projects completed in Europe have looked into the cost-effectiveness of EMAS. Arrestor beds have been installed at airports where the runway safety areas are below standards, and their ability to stop aircraft with minimal or no damage to the air frame and its occupants has proven to bring results far beyond the cost of installations. The latest report, "Estimated Cost-Benefit Analysis of Runway Severity Reduction Based on Actual Arrestments", shows how the money saved through the first 11 arrestments has reached a calculated total of 1.9 billion USD, thus saving more than $1 B over the estimated cost of development (R&D, all installations worldwide, maintenance and repairs reaching a total of USD 600 million). The study suggests that mitigating the consequences of runway excursions worldwide may turn out to be much more cost-effective than the current focus on reducing the already very low probability of occurrence.

United States installations

The FAA's design criteria for new airports designate Runway Safety Areas (RSAs) to increase the margin of safety if an overrun occurs and to provide additional access room for response vehicles. A United States federal law required that the length of RSAs in airports was to be 1000 ft by the end of 2015, in a response to a runway overrun into a highway at Teterboro Airport in New Jersey. At airports built before these standards were put into effect, the FAA has funded the installation of EMAS at the ends of main runways. The minimum recommended overall length of an EMAS installation is 600 ft, of which at least 400 ft is to consist of the frangible material. , ESCO's EMAS is installed at 112 runway ends at 68 airports in the United States, with plans to install three EMAS systems at two additional U.S. airports. As of 2017 the FAA reported that EMAS systems had been used 12 times, but that in some situations pilots tried to avoid the EMAS, steering to the grass sides in 30 – low-energy events in order to avoid publicity.

Non-U.S. installations

Of the 15 non-U.S. installations, eight were provided by Zodiac Arresting Systems (two in China, two in Madrid, one in Taipei, Taiwan (Songshan Airport), two in Norway and one in Saudi Arabia), six were provided by RunwaySafe (one in Switzerland, and three in overseas departments of France – one in Reunion Island, two in Mayotte), one in Japan, one in Germany, two in Brazil and one provided by Hankge (China).

FAA-approved manufacturers

, there were three recognized EMAS materials (from two manufacturers worldwide) that meet the FAA requirements of Advisory Circular 150-5220-22B, "Engineered Materials Arresting Systems for Aircraft Overruns." (The FAA must review and approve each EMAS installation.) The first EMAS was developed in the mid-1990s by ESCO/Engineered Arresting Systems Corp. (later Zodiac Arresting Systems) as part of a collaboration and technical acceptance by the FAA. The fourth generation EMAS arrestor beds are composed of blocks of lightweight, crushable cellular concrete material, encased in jet blast resistant protection, designed to safely stop airplanes that overshoot runways. Zodiac's EMAS is installed on over 110 airport runways at over 65 airports on three continents. Zodiac's EMAS has undergone aircraft test runs at speeds up 55 kn and is the only EMAS that has safely stopped aircraft in emergency overrun situations at commercial airports. Zodiac stopped production of EMAS systems as the U.S market slowed down and competition increased in the international market. The Swedish company Runway Safe AB developed an EMAS system, a foamed silica bed made from recycled glass contained within a high-strength plastic mesh system anchored to the pavement at the end of the runway. The foamed silica is poured into lanes bounded by the mesh and covered with a poured cement layer and treated with a top coat of sealant. A third manufacturer, certified by the Chinese CAAC, has a product that is very similar to the original Zodiac EMAS, but it is not FAA approved, as presented by International Civil Aviation Organization (ICAO) at 02/08/2019 in report A40-WP/331.

Incidents

Additional media coverage of EMAS statistics, installations, and general news include: