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Updated: Wed, 30 Jul 2014 05:27:53 GMT | By CBC News, cbc.ca

Plane crashes are more survivable than ever



Flight attendants were praised for their role when Air France Flight 358, carrying more than 300 people on board, ran off the runway of Toronto's Pearson International Airport and burst into flames. No one was killed in that accident. David Duprey/Associated Press

Flight attendants were praised for their role when Air France Flight 358, carrying more than 300 people on board, ran off the runway of Toronto's Pearson International Airport and burst into flames. No one was killed in that accident. David Duprey/Associated Press

Concerns prompted by the recent spate of fatal airplane mishaps overshadow the overall improvements to airplane safety over the years and the survivability of many crashes, aviation experts say.

“There are many improvements in technology to prevent the accident in the first place," said Rudy Quevedo, director of technical programs of the Flight Safety Foundation. “And beyond that, if you were to get into an accident, there have been improvements into the way aircraft have been built, vulnerability of the interiors — so that all collectively enhances the chances of survival.”

An oft-cited study conducted by the U.S. National Transportation Safety Board in 2001 looking at the survivability rates from 1983 to 2000 of U.S. air carrier flights found that in the 568 plane accidents during that time period, 95.7 per cent of the occupants survived. And of the serious accidents (26) involving fire, substantial aircraft damage or complete destruction, 55.6 per cent of the occupants survived.

Although 2014 has been a particularly bad year for airplane fatalities, last year was considered one of the safest years ever, with 19 aviation accidents  worldwide involving deaths.

Runway excursions most survivable

"One of the largest factors is the type of accident," Quevedo said. "That, to a great degree, dictates the survivability rate."

Generally, the three most common types of accidents that cause the most fatalities are classified as:

- Runway excursions. 

- Controlled flight into terrain.

- Loss of control in flight. 

The most common, and most survivable, are runway excursions, where the plane departs the surface of the runway either at the end of the runway or off to the side. 

Controlled flight into terrain occurs when a pilot still has control but the airplane impacts into some kind of terrain, whether it be land, water or some kind of structure. 

Generally the least common accident, but the type most likely to be fatal, occurs when the pilot, for whatever reason, completely loses control of the flight.

The survivability of some crashes often depends on the impact angle — how steep the plane comes in and hits the terrain — and impact velocity, said Anthony Brickhouse, associate professor of applied aviation sciences at the Embry-Riddle Aeronautical University in Florida.

"We have designed planes with structures that absorb the energy and keep the energy away from the occupants for as long as possible," he said.

Those crashes deemed to be non-survivable are those where the G-forces are too high and the structure is no longer intact, meaning the airplane just crumples and kills the people inside, Brickhouse said.

Planes designed to glide

Brickhouse noted there's a big misconception about what happens to an aircraft if it loses power, with many believing that it will just drop out of the sky.​

"That's just not true," he said. 

Planes are designed to be able to glide a certain distance, based on various factors, including weather conditions and pilot skill.

Chesley (Sully) Sullenberger, the pilot of US Airways Flight 1549, was able to glide his plane to a safe landing in the Hudson River in 2009 in the so-called "miracle on the Hudson." 

A number of changes to aircraft have been made over the past decades that have increased crash survivability. Structural enhancements to the planes, including changes to seats, have given passengers a better chance of surviving accidents. 

Twenty years ago, seats were made to withstand nine Gs before they would break from their moorings. Now they're made to withstand 16 Gs of force.

Todd Curtis, former Boeing safety engineer and founder of Airsafe.com, said all sorts of evolutionary designs with new aircraft make it less likely people die after a crash. Some passengers will survive the impact of a crash but die in a subsequent fire, but fire-resistant materials have become standard in all aircraft and are less likely to generate noxious fumes. 

Improvement of flight crew training has also made a significant difference, Quevedo said. "Without the actions of the flight attendants, thoseimprovements wouldn't be as effective." 

Flight attendants were praised for their role when Air France Flight 358, carrying more than 300 people on board, ran off the runway of Toronto's Pearson International Airport and burst into flames in August 2005. No one was killed in that crash.

"That was an outstanding example of aircraft design, procedures and just the basic understanding on the part of passengers and crew of what to do in an emergency," Curtis said. 

Emergency response to crashes is also crucial. In 1999, a China Airline flight carrying more than 300 people on board flipped upside down and caught fire at Hong Kong International Airport. But the "first rate" rapid response of the crash fire rescue service, which was on the scene quickly and able to put down the fire and get everyone out, resulted in only three passengers killed, a fatality rate extremely low considering the nature of the crash, Curtis said

Rescuers make the difference

"I can cite case after case where had the rescue people not been there, no one would have survived or there would have been far fewer survivors," Curtis said.

Accidents also lead to improvements to safety, said James Hall, a former NTSB chairman. For example, the fatal crash of US Air Flight 427 prompted the redesign of the Boeing 737 rudder; wiring changes to the McDonnell Douglas MD-11​ were implemented after the crash of Swissair Flight 111

"Each one of these tragedies is mined forcefully by the investigators in terms of survivor factors," he said.

Hall said that because many accidents are indeed survivable, passengers, including frequent flyers, should pay attention to the routine announcements before takeoff. 

"Those routine announcements, those exits those lights on the floor, paying attention to the closet exit … that’s life-saving information."

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