Runway Overrun System
Works, But It’s Not Cheap
Ninety percent of airplanes that run off the end of runways
are traveling at less than 60 knots when they exit, according to FAA data. Most
of these airplanes came to a stop within 1,000 feet of the end. Although most
modern airport designs include a 1,000-foot runway safety area (RSA) for overrun
protection, old airport design standards allowed obstacles, such as bodies of
water, highways, railroads, populated areas, or even a severe terrain gradient,
to be located at the runway end. Because of this, many airports are not able to
qualify for the full standard RSA. Hence, the need for a little help. One
solution comes in the form of an engineered materials arresting system (Emas) to
provide the safety edge needed to prevent an overrun from becoming a tragedy.
Emas is made of high-energy absorbing materials, and is similar in concept to
the runaway-truck exit ramps made of sand and gravel that adjoin some steep
highway gradients. The system is normally placed in the RSA and varies in size
and height based on site-specific requirements. And Emas works. A 400-foot-long
Emas can stop a DC-9 or Gulfstream G550 within the confines of the system, even
if the aircraft leaves the runway at 75 knots. What does make some communities
catch their breath, however, is the price tag. A typical Emas often costs north
of $5 million.
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