Definition
A bed of crushable, lightweight cellular concrete blocks installed at the end of a runway to safely decelerate an aircraft that overruns the paved surface. The aircraft's wheels sink into and crush the material, producing predictable drag that brings the aircraft to a stop without major structural damage to the airframe or serious injury to occupants.
Plain English
A patch of crushable blocks at the end of a runway that gently stops an airplane if it rolls off the end. The wheels sink in and the material slows the airplane down quickly but smoothly.
Context Anchor
Pilots encounter EMAS when studying runway safety, airport diagrams, and runway markings at airports where an overrun area has been installed beyond the runway end.
Derivation
"Arresting" here means stopping or halting motion, the same sense used in "cardiac arrest" or "arresting cables" on aircraft carriers. The name simply describes what it does: an engineered material that arrests (stops) an aircraft.
Why Pilots Care
Provides an additional margin of safety that can stop an aircraft with minimal damage during a runway overrun.
Analogy
Think of it like the runaway truck ramps you see on steep mountain highways — a soft, deep gravel bed that lets a heavy vehicle sink in and stop without crashing into something solid.
Intuition Check
Do not think of EMAS as extra usable runway. It is a protected stopping area beyond the runway end, meant for an aircraft that cannot stop in time.
Example Sentence 1
Because the runway at LaGuardia ends near the water, EMAS beds are installed at both ends to stop any aircraft that overruns the paved surface.
Example Sentence 2
Pilots are briefed on EMAS locations during preflight planning for unfamiliar airports.