Definition
A specially engineered, low-strength cellular concrete designed to collapse predictably under the weight of an aircraft, used to construct Engineered Materials Arresting Systems (EMAS) installed at the end of a runway to safely decelerate an aircraft that overruns.
Plain English
A lightweight, brittle concrete that breaks apart in a controlled way when an aircraft rolls over it, slowing the aircraft down without damaging it.
Context Anchor
You may see this term in runway safety discussions, airport planning material, or descriptions of an EMAS installed beyond a runway end.
Derivation
‘Crushable’ simply means able to be crushed. The phrase highlights that this is concrete deliberately made weak — the opposite of normal structural concrete — so that it gives way under the aircraft instead of resisting it.
Why Pilots Care
It provides a passive safety system that can stop an aircraft during a runway overrun without pilot intervention beyond directional control, reducing the risk of damage or injury.
Analogy
Think of it like rolling a heavy ball onto a field of foam blocks. The blocks crumble beneath it, absorbing the energy and bringing the ball to a stop without bouncing it back.
Grounding Statement
If an aircraft cannot stop before the runway ends, its wheels can enter the crushable concrete bed, break it apart, and lose speed quickly.
Intuition Check
Do not read “crushable concrete” as damaged pavement or poor construction. Here it means a purpose-built safety material that is supposed to crush under an aircraft to help stop it.
Example Sentence 1
The runway’s overrun area is fitted with crushable concrete to safely stop an aircraft that fails to brake in time.
Example Sentence 2
Maintenance crews inspect the crushable concrete blocks regularly to ensure they will perform correctly if an overrun occurs.