Tuesday, December 11, 2012
The Fine Art Of Crashing
The how and why of crashing a 727 for science
Two of the "smart" dummies had been installed in successive rows, one pre-positioned in the recommended airline brace attitude—leaning forward as far as possible—and the other sitting upright.
To no one's surprise, the dummy in the braced position fared better, sustaining some theoretical injuries, but nothing major. The upright subject was deemed to have suffered significant back and head damage, the latter from slamming into the seat in front of it.
The onboard cameras suggested a second benefit of the brace position was better protection from flying debris. The unbraced dummy was hit by several pieces of the interior as portions of the aircraft disintegrated during the runout.
Another conclusion was the real benefit of sitting in close proximity to an emergency exit. The science team analyzed the difficulty of extracting dummies through the emergency exits and concluded the best seating position for safety is within five rows of any exit. Otherwise, debris, wiring and unconscious passengers could make egress difficult or impossible.
An important result was what most would have predicted after seeing news coverage of the aftermath of airline accidents. Since the majority of accidents involve uncontrolled contact with the ground in a nose-down attitude, the greatest damage occurs in the front of the aircraft, and the least damage in the rear. This simulated accident was closer to a controlled, straight-and-level emergency landing; yet, because the nose gear didn't break away, it was apparent the flight crew would have been critically injured.
The G-distribution throughout the fuselage was also consistent with that conclusion. The forward-third of the cabin sustained dangerous loads averaging about 12 Gs, while deceleration in the middle section over the wing dropped to more like 8 Gs. Crash loads in the far rear of the passenger cabin were recorded at 6 Gs, normally a survivable level.
What does this mean for passengers? MIT studied airline safety between 2000 and 2007, and concluded the odds of dying in a crash are about one in 14 million. If you trust statistics, that means a passenger who flies one flight a day would need 38,000 years before being at risk.
For general aviation pilots, the takeaway is that crash landings in any aircraft often ARE survivable, contrary to popular belief. There's nothing ghoulish or fatalistic about studying plane crashes, even airline accidents. When you need information, the more the better.
Most of us don't fly Boeings (except for a few Stearman owners), we don't always have convenient, pancake-flat desert below and we can't choose to sit in the last row of seats, but if you're smart enough to touch down straight and level at minimum speed, you have a good chance of walking away.
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