Not that the Hudson River could be described as "pristine" at any point in the last couple hundred years. But even those used to seeing garbage flotillas between Manhattan and New Jersey got a shock in 2009 when an Airbus 320 splash-landed in the Hudson. Turns out those safety briefings were good for something after all: Everyone survived, hero pilot Chesley Sullenberger went on Letterman, and no one taking off from LaGuardia looked at birds quite the same way again.
US Airways Flight 1549 was hardly the first plane to successfully land in an emergency. In 1989, a Varig flight landed deep in the Brazilian Amazon jungle, skidding on its belly to safety. All but 13 aboard survived. In 1991, a Scandinavian Airlines flight landed in an open field near Gottrora, and all 129 people aboard survived.
So it got us wondering: Where else could a pilot land a commercial aircraft with a chance of 100% survival? We talked to Dr. George Bibel, a mechanical engineering professor at the University of North Dakota and author of Beyond the Black Box: The Forensics of Airplane Crashes. He explained what you need to be able to land a plane optimally even in the lousiest circumstances.
What do you absolutely need to land?
"A plane can land anywhere it can slide to dissipate its horizontal motion," Bibel said. If it can find a flat enough space where it can decelerate before hitting something that'll break it apart, it should be fine -- provided it lands at a slow enough sink rate.
Even when a plane finds a perfectly flat surface -- even a runway -- a fast fall will break the plane apart. A typical commercial jet descends at about 1ft per second, which is why you begin your initial descent about half an hour from your destination. It can drop faster at the beginning, obviously, but once it touches down its sink rate must be tiny. For example, those landings that feel rough or jolted hit at a mere 4ft per second. No one will survive a landing faster than 42ft per second, Bibel said.
"There was a flight in 1972 where an L-1011 fell in the Everglades at about 37ft per second," he said. "It was an absolute disaster."
A plane must also land at a minimal angle. Even if landing gear doesn't deploy, a plane landing more or less parallel to the ground will suffer limited damage, as when the jet skidded into the Amazon on its belly. But trying to descend against a rise of just 20 degrees would mean game over.
"If you hit hard enough at that angle, you'll spray fuel and create a giant fireball," Bibel said. "The whole point is to fly straight and level. But if you have to fly somewhere other than an airport, it might not be that way."
This is what happened in 1990, when an Avianca flight attempted an emergency landing on Long Island. It crashed into a hillside, killing 73 people. This is the counterintuitive advantage a water landing has: At least it's on a flat surface. Sometimes.
Rivers are far less scary than oceans
Rivers are typically calmer, easier places to stop than the open sea. Large waves, when met at the speeds airplanes travel at, might as well be solid walls. "The stormier it is, the more problematic that landing will be," Bibel said. "The waves can be like hitting hills. They'll break apart the plane and people will fall in and drown."
This was the fate of an Ethiopian Airlines flight that, after being hijacked in 1996, attempted an emergency ocean landing. The plane broke apart on impact; only 50 aboard survived.
Bibel said landing on glaciers can also be safe, so long as nobody hits a mountain. Same with fields, swamps, and other flat spots. That said, he stressed that pilots will ALWAYS try and find an airport, military base, or airstrip to land in the case of emergency. So don't assume you'll be using your seat cushion as a flotation device anytime soon.
"I spent some time with some big-plane pilots and I was pressing them about what they'd do if they had to land in a pasture in North Dakota," he said. "They said it wouldn't happen -- they'd find a runway, and never try to land anywhere else. It's only done if they're forced."
Aircraft carriers and interstates
Going purely hypothetical, we also wanted to know whether a commercial plane could land on an aircraft carrier or on a major highway.
Aircraft carriers are a big nope. While cargo planes like C-130s have landed on aircraft carriers, those planes require considerably less landing room than commercial airplanes. A 737, for example, requires about 5,000ft of runway to land in optimal conditions. The largest class of aircraft carrier -- the Nimitz class -- has a flight deck of 332.9 meters, or about 1,000ft. Nowhere close. And that's not even considering the cables and hooks on the flight deck designed to catch military planes hitting the deck at top speed to slow them down. Basically, even with a carrier handy, a commercial pilot would do better to steer for the ocean.
A popular online myth holds that one in five miles of every US interstate is straight so planes can land on them in an emergency. This is actually hogwash, and while it would, in theory, be possible for a commercial plane to land on a perfectly straight stretch of asphalt that was long enough, it has never happened. Smaller, private planes have done it, though the landing requirements for those are less onerous.
So even if your plane loses all power and has to glide to an emergency landing, hope isn't lost. Even over water, if an area is long enough and flat enough, and you fall at a slow enough rate, everyone on board might survive. The scenario isn't common, or something you ever need to worry about. But it's a small comfort to consider the next time you notice birds flocking near your runway.
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