Few these days would question the effectiveness of engineered material arresting systems (Emas) in stopping wayward aircraft, and to prove the point Key West International Airport pulled off a double last fall. In the span of four days, the airport (which had not experienced a runway overrun in 30 years) saw two business jets suffer apparent brake failures while landing in opposite directions on its 4,801-foot runway 09/27. At the east end of the runway there was an Emas; at the west end there was not.

As part of an $8 million runway safety area (RSA) project, Key West Airport had completed installation of the crushable-block Emas at the east end (the departure end of 09 and the approach end of 27) of its main runway in October 2010 to comply with FAA RSA standards. When planning for the project began in 2000, there was little practical experience with Emas systems and even experts were undecided about their proper usage. “The way winds are here, 80 percent of the time we are approaching from the west and landing to the east on Runway 09,” said Peter Horton, director of airports for Monroe County, which operates the airport. “[The FAA] was afraid that if we put an Emas at the west end [in the overrun for Runway 27] of the runway and somebody landed short on Runway 09, that that would cause some real problems.” While those fears eventually proved unfounded due to later instances of aircraft touching down in the Emas without catastrophic results, at the time they led to the decision to install a 600-foot stabilized overrun at the west end of the runway instead.

On a clear, dry Halloween night at the conclusion of a flight from Stuart, Fla., a Gulfstream G150 overran the end of Runway 27 after making what was described as a near textbook landing from east to west. The pilot told investigators that by the time he realized the aircraft’s brakes were not functioning, he could not stop the twinjet by applying thrust reversers. The aircraft quickly crossed the 600-foot overrun and struck several ditches, shearing off its nose gear in the process, before coming to a halt in a salt pond, a yard from the airport’s perimeter fence and 820 feet past the runway threshold. In addition to damage to the bottom of the fuselage, the G150 incurred a broken left wing root and a ruptured fuel tank. The four occupants suffered injuries ranging from serious to minor.

Three days later, a Cessna 550 Citation II landing on Runway 09 in daylight under clear dry conditions also experienced an apparent brake failure. In this case, the jet overran the east end of the runway and traveled just 144 feet through the 340-foot-long Emas bed before coming to a stop. While the Citation lost its nosewheel yoke and had some deformation of its main gear doors, the airframe remained largely undamaged and its five occupants were unharmed. According to Esco, the manufacturer of the system, this was the eighth time the system stopped a wayward aircraft.

Despite the higher speed at which the Gulfstream exited the runway (it was estimated at 90 knots or 30 knots faster than the Citation), and its greater weight (approximately 8,000 to 10,000 pounds more than the Citation), there is no doubt that the presence of an Emas bed at the west end of the runway would have stopped it before it suffered serious damage, according to Mike Bouchard, division head of the aerospace mechanics division of the University of Dayton Research Institute, which assisted in the development of the system. “That would have been well within Emas’s range, ” he said, since the system was designed to stop aircraft ranging in size from the Boeing 737 to those weighing 12,500 pounds.

Repair of the airport’s Emas was completed around the middle of January at a cost of $710,000, split between the insurer of the Citation operator and that of a small piston single that accidentally taxied into the bed last September and destroyed some blocks. According to Horton, when the debate first arose regarding installation of the Emas, he defended its need to detractors by informing them that he was preparing the airport for a one-in-a-million event. “Now we had one-in-a-million twice in one week,” he told AIN, adding that he has already begun the FAA grant process required to have an Emas bed installed at the west end of the runway.