New Four-Letter Words for Your Aviation Vocabulary: RESA and EMAS 

by Mark Laurence, Civil Aviation Safety Inspector, Aerodrome Standards, Civil Aviation, Transport Canada

The landing overrun by Air France Flight 358, which occurred in August 2005 at Toronto’s YYZ airport, has raised the profile of runway end safety areas (RESA) and Engineered Materials Arresting Systems (EMAS) in Canada. If you have heard these terms before but were not sure exactly what they referred to, this article may shed some light on these concepts.

Essentially, a RESA is a generally flat area at the end of a runway, which provides an area free of hazardous obstacles for aircraft to decelerate and facilitates the intervention of rescue and firefighting services should an aircraft overrun the end of the runway. A RESA is also beneficial when an aircraft lands short of (undershoots) the runway. This means that there must be no cliffs, bodies of water, deep ditches, boulders, roads, or similar obstacles for a specified distance at the end of a runway.

The International Civil Aviation Organization (ICAO) standard states that the RESA should end 150 m from the end of the runway, but ICAO also recommends that the RESA end 300 m from the end of the runway. Transport Canada (TC) has recommended the application of the ICAO standard, but is now considering making it mandatory¹ at Canadian airports. In reviewing runway overruns that occurred in Canada over the past 20 years or so, TC found that in 91% of overrun cases, the aircraft stopped within 150 m of the end of the runway.

The Federal Aviation Administration (FAA) chose the longer RESA (runway safety area in FAA terms), which ends 1 000 ft (300 m) from the end of the runway. Implementing this distance in Canada would have presented a challenge at many airports that do not have the space for the RESA to end 300 m from the end of the runway due to physical obstacles (such as roads, bodies of water, and steeply descending terrain). When the physical space does not exist, it is possible to reduce the declared distances of the runway in order to create the space for the RESA or, in other words, to make the runway shorter for calculation purposes without making any physical change to the runway length. This change may affect an aircraft’s performance during takeoff and landing. For example, a shorter runway length may result in the need for greater engine thrust for takeoff or a reduced take-off or landing weight.

Overhead view of EMAS installation
Photograph of an EMAS installation. 
(The EMAS bed is the grey area under the yellow chevrons) 
Ref: TC AIM AGA 9.1

An overrun accident at New York’s JFK airport in 1984 was the catalyst for an FAA project that led to the development of EMAS.

An EMAS is a bed located at the end of a runway; it is made of a lightweight, crushable concrete. For this type of concrete, sand and gravel are replaced with air and cellulose. The material looks like concrete but weighs about the same as a dry sponge. When an aircraft rolls into an EMAS bed, its tires sink into the lightweight concrete, and the aircraft decelerates in a predictable manner because it has to roll through the material. The blocks that make up the EMAS bed are progressively taller the farther they are from the end of the runway. This produces a similar effect to driving a car into snow that becomes deeper and deeper until eventually the car is stuck, but in a much more predictable manner. A typical EMAS bed is the width of the runway and 400–600 ft in length (120–180 m), depending on the characteristics of the critical aircraft for which the bed is designed.

Information on EMAS is available from the Engineered Arresting Systems Corporation, which is currently the only manufacturer of EMAS. At the moment, there are no EMAS beds installed in Canada. There are 63 EMAS beds installed worldwide, with 58 of them in the USA as of October 2011. Recently, the FAA has established a cooperative research and development agreement with Norsk Glassgjenvinning in Norway to cooperate in the testing and evaluation of their EMAS concept called Glasopor. Finally, more information on EMAS is available in the Transport Canada Aeronautical Information Manual (TC AIM) – AGA Aircraft Arresting Systems, Section 9.1.

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1Notice of Proposed Amendment 2010-012 Runway End Safety Area

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