When Delta Flight 4819 from Minneapolis to Toronto landed in a fiery crash that ripped off a wing and rolled the plane upside down, panicked onlookers feared the worst.

But Michael McCormick saw decades of aircraft safety improvements in action. All 80 people on board survived Monday’s crash at Toronto Pearson International Airport.

“That was absolutely phenomenal that you could see an aircraft on its back like that and have people walking away from it,” said McCormick, an associate professor at Embry-Riddle Aeronautical University.

“But my second thought was, well, that’s the design. That’s engineering. That’s the years of civil aviation research … that has enabled something like that to happen.”

Fuel tanks are mainly stored in the wings

Fiery aviation disasters of the past have taught experts that jet fuel should be stored primarily in the wings, not directly beneath the passengers.

“Back in the early days of aviation, that was where it was stored – in the belly of the aircraft,” McCormick said.

So when Delta’s Bombardier CRJ900 crash-landed Monday, tipped over and skidded down the runway, its fuel-laden right wing broke off, leaving behind a massive inferno. The plane continued skidding and rolled over.

In this incident, the wing breaking free kept the fire out of the passenger cabin, said Joe Jacobsen, an aerospace engineer who has worked for Boeing and the Federal Aviation Administration.
“Things can break … but if it’s within design requirements, then you have to see how it broke, and did it break according to design?” Jacobsen said.

The wing might have broken off due to a maintenance or design flaw, Jacobsen said. The investigation may examine those possibilities, he added.

When a wing rips off entirely due to impact, ditching potentially explosive fuel is just one benefit, McCormick said.

“We want to be able to separate the fuel from the passenger compartment, and at the same time, we want to be able to ensure that the fuselage can come to rest in a stable position,” McCormick said.

The plane ended up in a stable position – albeit upside down. But everyone survived, thanks in part to brawny seats that can withstand extreme force.

16G seats are designed for safety – not necessarily comfort

Most modern commercial aircraft are required to have what’s known as 16G seats, meaning they can withstand 16 times the force of gravity, McCormick said.

“You don’t want the seats to either fall apart or come loose in an aircraft accident – even if it’s upside down,” he said.

“So it’s not specifically designed for comfort, it’s designed for durability” in case of an accident, McCormick said. “And you know that, if you’ve been in the coach for anything more than a few hours.”

The seats include a humble yet critical safety feature: life-saving seat belts.

In this case, “without the seat belts, passengers surely would have been thrown around and would have sustained a lot more injuries,” said Hassan Shahidi, president and CEO of the Flight Safety Foundation. “That was an important factor in this.”

And if this crash had occurred a few decades ago, the outcome might have been far more grim, CNN aviation analyst Peter Goelz said.

“What’s changed is that all commercial aircraft have seats that are locked in place on the tracks as part of the fuselage that can withstand up to 16 Gs of impact,” said Goelz, a former managing director of the National Transportation Safety Board.

“That means that in a crash-landing like this, if you’re strapped in correctly, you’re going to survive the impact and have a chance to escape,” he said.

“And when you combine that with advances in fire-retardant material … you really have a good chance to make it, if you follow directions.”

Nothing can replace skilled crew members

While high-tech engineering likely helped save lives, “You cannot give enough credit to the cabin crew for the safe evacuation of that aircraft,” McCormick said.

The two flight attendants on this flight had never landed a plane upside down, said Sara Nelson, international president of the Association of Flight Attendants-CWA. But the duo had trained for many scenarios, including evacuating passengers within 90 seconds.

Despite dozens of passengers being strapped in their seats and dangling upside down like bats, the crew managed to evacuate the entire plane in less than 90 seconds.

The flight attendants “performed their jobs perfectly. They were heroic,” Nelson said.

And “hopefully this will (make) the public be more aware and more grateful for the men and women who serve as flight attendants,” McCormick said.

“They are responsible for much more than picking up trash and serving sodas. They’re trained professionals responsible for the safety of the passengers. And they did a phenomenal job.”

Source: CNN
--Agencies