Engineered Material Arresting System (EMAS)
In the USA, the FAA requires that commercial airports, regulated under Part 139 safety rules, have a standard Runway Safety Area (RSA) where possible. At most commercial airports the RSA is 500 feet wide and extends 1000 feet beyond each end of the runway. The FAA has this requirement in the event that an aircraft overruns, undershoots, or veers off the side of the runway. The most dangerous of these incidents are overruns, but since many airports were built before the 1000-foot RSA length was adopted some 20 years ago, the area beyond the end of the runway is where many airports cannot achieve the full standard RSA. This is due to obstacles such as bodies of water, highways, railroads, and populated areas or severe drop-off of terrain.
The FAA has a high-priority program to enhance safety by upgrading the RSAs at commercial airports and provide federal funding to support those upgrades. However, it still may not be practical for some airports to achieve the standard RSA. The FAA, knowing that it would be difficult to achieve a standard RSA at every airport, began conducting research in the 1990s to determine how to ensure maximum safety at airports where the full RSA cannot be obtained. Working in concert with the University of Dayton, the Port Authority of New York and New Jersey, and the Engineered Arresting Systems Corporation (ESCO) of Logan Township, NJ, a new technology emerged to provide an added measure of safety. An Engineered Materials Arresting System (EMAS) uses materials of closely controlled strength and density placed at the end of a runway to stop or greatly slow an aircraft that overruns the runway. The best material found to date is a lightweight, crushable concrete. When an aircraft rolls into an EMAS arrestor bed, the tires of the aircraft sink into the lightweight concrete and the aircraft is decelerated by having to roll through the material.
Benefits of the EMAS Technology
The EMAS technology provides safety benefits in cases where land is not available, where it would be very expensive for the airport sponsor to buy the land off the end of the runway, or where it is otherwise not possible to have the standard 1,000-foot overrun. This technology is now in place at 18 airports with installation under contract at six additional airports. A standard EMAS installation extends 600 feet from the end of the runway. An EMAS arrestor bed can still be installed to help slow or stop an aircraft that overruns the runway, even if less than 600 feet of land is available.
Current FAA Initiatives
The Office of Airports prepared an RSA improvement plan for the runways at approximately 575 commercial airports in 2005. This plan allows the agency to track the progress and to direct federal funds for making all practicable improvements, including the use of EMAS technology.
Presently, the EMAS system developed by ESCO using
crushable concrete is the only system that meets the FAA standard. However, FAA is conducting research through the Airport Cooperative Research Program (project number 07-03) that will examine alternatives to the existing approved system. The results of this effort are expected in 2009. More information on the project can be found at the Transportation Research Board website at
http://www.trb.org/CRP/ACRP/ACRP.asp.
EMAS Arrestments
To date, there have been four incidents where the technology has worked successfully to keep aircraft from overrunning the runway and in several cases has prevented injury to passengers and damage to the aircraft.
May 1999: A Saab 340 commuter aircraft overran the runway at JFK
May 2003: Gemini Cargo MD-11 was safely decelerated at JFK
January 2005: A Boeing 747 overran the runway at JFK
July 2006: Mystere Falcon 900 airplane ran off the runway at the Greenville Downtown Airport in South Carolina
EMAS Installations
Currently, EMAS is installed at 24 runway ends at 19 airports in the United States. With plans to install 12 additional EMAS systems at seven more U.S. airports.