Asiana 214 Survival Factors
Standards must be slipping at CNN. Early Saturday morning, they didn’t have the United 777 diversion to Midway story. I expected the network to have summoned their stadium full of talking heads to connect that incident to--what else?--Malaysian 370. I figured they could spin a couple of days of 24/7 speculation out of the Midway incident…you know, smoke in the cockpit, power failing. But not so far. Maybe I shouldn’t give them any ideas. We’ll see what develops.
Meanwhile, my attention was focused on another 777, the Asiana Airlines flight that crashed in San Francisco last July. To no one’s particular surprise, at least in the aviation community, the crew took the hit for mismanaging the airplane's vertical profile during the approach and for ignoring or not having a good understanding of the automation, especially the autothrottle modes. The full report will shed detail on other factors and it’s due for publication later this month.
My longtime friend Bill English was the NTSB investigator in charge on Asiana 214 and he stopped by the other day. We both agreed that this accident was really a GA-like accident. Break it down and it’s not much different than a Cirrus being flown into terrain on autopilot or a Cessna 210 driver getting low on the PAPI, cratering the airspeed and mushing it in. I suspect something will be made about this being another “automation accident” and while there’s some merit to that, it’s really all about consistent, basic airmanship, or lack thereof. Three qualified and trained pilots saw the PAPI going red, saw the airspeed decaying and simply rode through it. As such, I find that aspect of the accident … uninteresting. It’s a human factors fail. What else is new?
What’s more interesting, at least to me, are the survival factors related to the airplane itself. This is only the second in-flight hull loss for the 777, of about 1200 flying since the airplane entered service in 1995, almost 20 years ago. The first hull loss, recall, was at London’s Heathrow in 2008, when both engines reverted to idle power because of ice crystals in the fuel system. There were injuries, but no fatalities and no fire, despite significant damage to the aircraft. An EgyptAir Triple Seven burned at the gate in 2011 and was written off and, of course, there’s MH370, which seems less and less likely to be considered an accident. It’s unlikely to mar the type’s insurance record.
Because all but three people survived the Asiana 214 crash, it’s quite natural to think of it as just a skid down the runway, sans gear and engines. But that it definitely was not. Bill told me that when he got the go call, he was told only that a mass casualty event had occurred at SFO and an airplane had cartwheeled. He hadn’t seen any news coverage and hadn’t seen the video.
“Then I saw the photo from above. It looked like an airplane…it was canted off one side of the runway. How can it be together like that? So we were not believing the cartwheel story. In fact, I don’t think I saw the video until later the next day,” Bill told me.
The video in question came from a security camera. It yielded footage reminiscent of the United 232 crash in Sioux City, Iowa, in 1989, which also looked like a cartwheel, or close. But subsequent investigation of 214 revealed what was more likely a turning pirouette of sorts. The left wing tip scrapped, but the radome never touched pavement. Bill thinks the fact that the tail departed while the engines were spooling up in a last ditch effort to save the approach may have accounted for that. It probably had a significant upward moment at the point of impact and with the tail gone, the CG shifted rapidly forward.
Whatever the reason, the impact forces were enormous, well exceeding the 16Gs the cabin floor rails are rated to carry. “We can certainly see that the airplane survived the impact and the slide down the runway pretty much intact. The center section was completely intact, the forward section had essentially no damage. In the aft part of the airplane, the floorboards gave way, but you could certainly see why because of the enormous forces. But there was survivable space,” Bill says. The impact was violent enough to produce head injuries to people striking either adjacent seats or seat arms across the aisle
Two of the three passengers who didn’t survive appeared not to have been belted in and were ejected. It’s speculation to say they would have survived if they had been belted, but it’s hardly unreasonable speculation. One passenger was struck by a door that came off its hinges during the impact sequence and likely would not have survived. Of 307 aboard, 182 were injured, 12 critically.
Post-crash photos revealed that the hull burned, but it wasn’t a fuel-fed fire. The right engine got trapped under the wreckage and a punctured oil tank leaking onto hot components appears to have started a small fire that transferred heat into the cabin. But the fire itself didn’t penetrate the cabin and wasn’t a survival or evacuation factor. Neither were the evacuation slides, two of which inflated inside the cabin. Most passengers self-exited, but some had to be helped by rescue personnel. Despite the slowly advancing fire, they had sufficient time to rescue everyone. The failed slides had been subjected to g-forces far beyond their design loads.
The investigation revealed a powerful lateral movement to the left during the impact sequence and a high number of thoracic spinal injuries. Although the mechanism isn’t understood or at least documented, it sounds likely that passengers were simply wrenched violently to the left in their seats. Subsequent investigation may reveal more about this and perhaps inform how seats and seatbelts can be improved. Would shoulder harnesses have helped?
In the meantime, it’s fair to conclude that Boeing applied what it learned from building airplanes and investigating crashes to make a safer, stronger airliner. Crash and impact forces that were barely understood during the 1970s and 1980s were yielding to the computer-aided design used to build the 777. It hung together through a horrific impact sequence. And it hung together after that, too.
“Weeks after we had done the investigation on the airplane, the wreckage had to be moved off the airport. There’s not that much room at San Francisco,” Bill told me. “So we had to break it down into smaller pieces. It was an enormous effort. It’s not easy to break apart a Triple Seven. It looked like something out of the movie Transformers to get that center wing box apart.”
After I talked to Bill, I got wondering whether the Triple Seven has the best accident record of any transport category aircraft. It doesn’t quite, but close. According to Boeing’s own numbers (PDF) the Airbus A380, the 747-8 and the 787 have better safety records than the 777 among wide bodies, but none have close to the fleet experience, having accumulated fewer than a million departures, at least through 2012. Surprisingly, despite flying in higher risk operations—more weather, more takeoffs and landings—the CRJ-series regional jets and Boeing's own 737-800-900 series have a little better numbers than the Triple. So does the 717, but only about 150 of those are flying. The Airbus 320-class is comparable to the 777, albeit with many more hull losses.
But it’s a quibble hardly worth the pixels to describe. Modern airliners, wide bodies like the 777 included, have become exceptionally reliable and safe thanks to lessons written in flesh and blood during the 1960s and 1970s. It’s hard to imagine them improving much, but they’re very likely to do just that.
So much so, in fact, that if Bill retires from the NTSB in five years, which he might do, Asiana 214 could easily be his last major U.S. accident investigation. That notion would have been unthinkable 30 years ago. But it isn’t now.
Bill will be AirVenture with a presentation on Asiana 214 survival aspects. See him in the Federal Building on Saturday, August 2 at 11:45 a.m. and catch him on EAA Radio on Thursday, July 31 at 12:15 p.m.