Aeroplane seats said to have helped survival

BY ALICIA DUNKLEY Observer staff reporter dunkleya@jamaicaobserver.com

Wednesday, December 30, 2009

THE type of seats carried by the Boeing 737-800 American Airlines aircraft which was damaged beyond economic repair when it crash-landed at the Norman Manley International Airport in Kingston December 22, figured highly in the passengers surviving the impact in such good shape.

Lieutenant Colonel Oscar Derby, director general of the Jamaica Civil Aviation Authority, told the Observer that the "new generation set of passenger seats" carried by the aircraft were constructed to withstand a force, on impact, of 16 times the weight of the passengers seated in them before dislodging.

While observing the removal of sections of the plane Sunday night, Derby said that an important part of the investigation would be an assessment of the survivability of the 16G seats.

"There is a very interesting thing about this accident. Those seats you are looking at which are very much intact, are a new generation set of passenger seats which are constructed to withstand 16G-forces -- that is an impact which causes the weight to increase by 16 times the normal weight," he said. "So a passenger of 200 pounds, on impact, would have to produce a force of 16 times his or her own body weight before the seat would dislodge."

Derby said the 16G seats replaced 9G seats which were known to detach invariably in an accident and crumple towards the impact end of the accident.

"That was responsible for a lot of the casualties in air accidents. I daresay one could perhaps surmise at this point that the survivability rate [of the 16G seats] is good because all the passengers survived," he said.

The seats are also said to protect the occupant from debilitating leg and spine injuries; protect crew members from serious chest injury when upper torso restraints are used and ensures that occupants do not become trapped in their seats due to excessive seat deformation.

Airplane models introduced after 1988 were expected to have 16G seats.

Safety regulators laid down the new rules after they found that passengers might survive a crash were they not being crushed when the seats tore loose from the floor.

Meantime, Derby said contemplation of the use of an arresting system such as the EMASS (Engineered Materials Arresting System) on the runway to help reduce the speed of runaway aircraft considerably would not be without merit. He, however, said it was a question of economics and the airport's decision to make.

"It's an arresting system made of crushable concrete which can be put at the end of runways and it absorbs the shock of the aircraft and slows it down. Usually it would stop an aircraft at 70 knots over 600 feet," he said. "It is a very expensive system and an investment that some airports have made. It is a matter of economics as to whether one installs such a system or not."

He said he was not aware that such a system was being contemplated by local airport officials.

The American Airlines flight, which began at the Ronald Reagan Washington National Airport in Washington, DC, overshot the runway after landing at the airport here two Tuesdays ago. The force of its landing carried it through the perimeter fence and onto the beach across the Port Royal road where it came to a stop within metres of Kingston's outer harbour and the open Caribbean Sea.

So far, work crews have removed the jet's tail, the nose, the left wing which broke off, the engines and landing gear and the midsection.