Over the Edge: Runway overrun protections

Preventing runway excursions

August 1, 2012

runway safety area

Engineered Materials Arresting System (EMAS) overruns (above) are made of a crushable cement material and are designed to dissipate forward speed and prevent excursions from the runway safety area. EMAS is installed at 42 airports in the United States, with three more airports—at Elmira-Corning and Binghamton, New York, and Boston’s Logan Airport—scheduled to receive it by this summer.

Illustration by Kevin Hand

It’s a scary scenario to envision: A turbine aircraft on a landing rollout or an aborted takeoff, unable to stop in the remaining runway and also unable to lift off or go around. This aviation Catch-22 can quickly turn a multimillion dollar aircraft into scrap metal and bring injury or death to those inside. A number of protections have been designed into many airports and runways, with turbine aircraft operations specifically in mind.

Runway Safety Area (RSA): Surface surrounding a runway, suitable for reducing the risk of aircraft damage during an undershoot, overshoot, or runway excursion. The RSA dimensions vary, but all RSAs shall be:

  • Cleared, graded, and free of potentially hazardous surface variations;
  • Drained to prevent water accumulation;
  • Capable of supporting snow removal and fire/rescue equipment and occasional aircraft passage without causing structural damage to the aircraft;
  • Free of all objects except those necessary to be placed in the RSA because of their function. Those objects must be on low-impact-resistant supports no higher than three inches above grade.

Stopway: An area beyond the runway, centered upon the extended runway centerline and no less than the runway width, able to support an airplane during an aborted takeoff (or landing overrun) without causing structural damage to the airplane. This area must be designated by the airport authority for use in decelerating an airplane during an aborted takeoff.

Engineered Materials Arresting System (EMAS): A runway safety device that has gained wide acceptance in recent years and is being installed mainly at runways with limited or no stopways. It consists of high-energy-absorbing materials installed in the RSA. The material is designed to crush under the weight of a commercial aircraft and exert decelerating forces on the landing gear. EMAS installations are increasing steadily and for good reason.

runway diagram

A sample illustration of typical runway dimensions for an airport serving small airliners and other airplanes weighing more than 12,500 lbs MGTOW (top) shows stopways and clearways. Stopways are intended to provide extra room for stopping during aborted takeoffs and landing overruns. Clearways are terrain- and obstacle-free zones for safer approach and takeoff climb margins.

For instance, when a 737 overran its runway at Chicago-Midway on December 8, 2005, it careened through the approach lights, blast fence, and airport perimeter fence, crushing a car outside the airport property—killing a child inside the car. Had that runway had an EMAS installed, there is a high probability the 737 would have been decelerated within the airport property, thus preventing a child’s death. Yet, as pilots of smaller turbine aircraft, we must bear in mind that EMAS is designed primarily for turbine aircraft exceeding 12,500 pounds.

It may not crush under the weight of smaller aircraft (such as jets in the light and very-light categories), limiting its effectiveness on deceleration. Or it may literally tear the gear out from under such aircraft, causing significant aircraft damage and possible injury to persons onboard. Yet, even those options seem better than the alternatives at airports where significant overruns can mean striking buildings, bodies of water, or other unforgiving surfaces. EMAS may be located as close as 35 feet from a runway end and should never be taxied or driven on. It is marked with yellow chevrons, indicating a surface that’s not usable for any normal aircraft operations.

Matthew McDaniel is a 22-year professional pilot with a background in airline, corporate, and charter operations.