TOKYO – Aviation analysts are considering several factors that might have contributed to a deadly plane crash in South Korea on Dec 29, including a concrete structure near the runway that the airliner slammed into, exploding and killing 179 of the 181 people aboard.
Most airports do not have similar structures in such proximity to runways, experts said. When they do, they are typically made of softer materials designed to break apart or absorb impact with minimal damage to a plane that overruns a runway.
Details about the cause of the crash of Jeju Air Flight 2216, the worst ever on South Korean soil, are likely to remain unclear until investigators release their preliminary findings, expected in the coming month. Experts cautioned against drawing conclusions, including about the possible role of airport infrastructure, until a full review of evidence is complete.
But in the days ahead, “investigators will be looking at that wall,” said Hassan Shahidi, president of the Flight Safety Foundation, a non-profit that provides safety guidance to the aviation industry.
Barriers near runways “should break easily in the case of a runway overrun so the impact isn’t catastrophic,” Mr Shahidi said. “What we saw here was a head-on collision with a concrete wall that appears very thick,” he added.
The plane involved in the Dec 29 crash, a Boeing 737-800, had taken off from Bangkok and was landing at Muan International Airport in South Korea’s south-west. As the plane was preparing to land, the airport warned the pilot about a potential bird strike. They aborted their first attempt at landing and descended from the opposite direction, which local officials said they were allowed to do.
As the plane was landing, it did not appear to have activated its wing flaps and landing gear, touching down at a faster-than-normal landing speed. It skidded down the tarmac on its belly and rammed into a mound of earth surrounding a concrete barrier past the end of the runway. The plane then exploded into a fireball.
The regions of an airport near runways, known as runway safety areas, are meant to provide unobstructed space for aircraft in the event they run past, undershoot or veer off a runway during landing.
In the United States, the Federal Aviation Administration says that standard runway safety areas extend 1,000 feet (305 metres) beyond the runway’s end and 500 feet on the sides. Any structures within these zones should be “frangible,” FAA rules say, able to break or give way to prevent catastrophic damage.
The International Civil Aviation Organisation recommends a standard buffer zone of about 180m to 300m from the end of the runway. At Muan airport, the concrete structure surrounded by a mound of dirt sits roughly 250m from the end of the runway, according to local officials.
Determining whether a runway safety area meets regulatory requirements involves evaluating a number of factors, including local geography. Some airport runways were constructed before runway buffer zone rules took effect.
That was the case at Little Rock National Airport in Arkansas in 1999, when American Airlines Flight 1420 smashed into stanchions holding lights that directed planes just off the runway. The structures tore through the plane, which caught fire, killing 11 people and injuring 80.
At Muan Airport, the concrete structure that Flight 2216 smashed into housed a device called a localiser, an antenna array that is used to guide aircraft during their approach and landing, local officials said. These antennas are normally located beyond the departure end of the runway, and they must be placed according to specific guidelines to function correctly.
Immediately following the crash, attention was drawn to the length of the runway at Muan airport. South Korea’s deputy transport minister, Mr Joo Jong-wan, said the runway’s 2,800m length did not contribute to the accident.
Najmedin Meshkati, a professor of engineering at the University of Southern California who studies aviation safety, said he believes investigators will instead focus on the fact that the localiser antenna was mounted on a base made of a hard concrete rather than a more standard metal tower or pylon installation.
“This rigid structure proved catastrophic when the skidding aircraft made impact,” Prof Meshkati said. The crash underscores the need to implement “soft barriers” at runway ends at airports worldwide, “to dampen and minimise the impact of runway excursions, which occur with concerning frequency,” he said.
Mr Joo, the transport ministry official, on Dec 30 said that regulations regarding the concrete structure would be shared at a later date. Concrete structures are used to house localiser antennas at other airports in South Korea and elsewhere, he added.
At airports such as New York’s LaGuardia, where space is limited, a barrier known as an “engineering materials arresting system” is designed to stop a plane without significant damage. LaGuardia uses aerated beds of concrete that crumble under the weight of a plane to slow it down if it overshoots a runway.
“Absent that, a runway should have clear safety zones,” said Jeff Guzzetti, founder of Guzzetti Aviation, a safety consulting firm.
In the weeks ahead, beyond examining the size of Muan airport’s runway safety area, investigators are likely to focus on the material used in the structure that held the localiser antenna and other factors, like how firmly it was anchored to the ground, Shahidi and other experts said. NYTIMES
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