Staying Alive

Survivable aircraft accidents are becoming more so, thanks to major improvements in cabin safety.

By Jerome Greer Chandler
Air Transport World, December 2005, p.36     Buy this issue

That 309 people could evacuate a torn and mangled flying machine in 2 min. with only 43 injuries was hailed as a "miracle" by the thrill-a-minute mass media. The people who built, certificated and flew the A340 knew better.

The Aug. 2 runway overrun accident of Air France Flight 358 at Toronto Pearson International was a dramatic, real-time demonstration that hard lessons learned over the past 20 years finally bore "ground truth." Things like 16g seats, fire-blocking seat cushions, fire-resistant slides and highly trained cabin crews can, in an otherwise survivable accident, save lives on a massive scale. While neither Canada's Transportation Safety Board nor Airbus will discuss survivability aspects of the accident in the midst of an ongoing investigation, a source close to the probe says, "It is no surprise to me, and no surprise to the people that I work withconsidering how bad [the accident] wasthat everybody got out." If not to the letter of the law, at least in life-giving spirit the 90-sec. rule worked. "They got out in two minutes," says the source. One of the reasons: "The [16g] seats stayed in place. That's a big thing." A big thing indeed. Computer-simulated evacuations, staged manufacturer evacs and in-your-head evacs cave in comparison to the real thing.

Less than a month after AF358, FAA published its final rule regarding crashworthiness standards for passenger and flight attendant seats. By that point it was mostly moot. All transport category aircraft type certificated after Jan. 1, 1958, and manufactured after Oct. 27, 2009 (four years from the Oct. 27, 2005, effective date), must have seats that meet the 16g standard.

First promulgated in 1988 and requiring 16g seats on all new type designs, the spirit of FAR 25.562 already reigns, almost across the board. The Air Transport Assn. estimates that 90% of the seats in the US commercial fleet are 16g compatible, up from 78% just two years ago. Retrofits and retirements are the reasons why. "It's hard to buy a 9g seat," says Rick Deweese, coordinator of the Biodynamics Research Team at FAA's Civil Aerospace Medical Institute in Oklahoma City.

One benefit of parking airplanes in the desert is that the ones you keep tend to be the newest and most compliant. That's why FAA's final 16g rule differs significantly from a Supplemental Notice of Proposed Rule Making issued Oct. 4, 2002. The final rule does not mandate retrofit of the fleet. It doesn't have to. The marketplace is taking care of that. FAA says operators have retired 23.6% of the pre-9/11 fleet1,360 assorted 727s, 737s, MD-11s, MD-80s, DC-10s and 747s. Add to that the substitution of regional jets for larger craft and fiscal forces have accomplished in a matter of months what regulators couldn't foresee happening for years.

Head Count

Integral to the 16g rule, which differs from the old 9g regulation in that seats must stay put when dynamically subjected to forces from virtually all axes, is a provision for protecting people's heads. Anywhere in the aircraft that you can strike your head must conform to a Head Injury Criteria or HIC value of 1,000. Anything below 1,000 passes; anything above fails. In most interior configurations, 16g seats themselves act as energy absorbers.

The problem was that "for certain types of seating positions, it was . . . nearly impossible to meet the Head Injury Criteria," says Tom Barth, director-research and development for Amsafe Aviation Inflatable Restraints. "FAA was granting waivers and exemptions to the rule."

With the development of inflatable seatbelts, regulatory authorities don't have to do that. "These . . . systems can lower HIC to 500, even [less]," says Deweese. Mounted on the dorsal side of two-point lap belts, Amsafe's device inflates up and out, protecting the passenger's head and chest. Primary emplacement is in bulkhead seating or in transition rows in economy where perhaps three seats are configured behind a row of five.

The belts also got a real upgrade from Virgin Atlantic Airways and found a place in Upper Class. "The thing that's unique [to Virgin]," says Barth, is that its Upper Class seats are canted at a 45-deg. angle. "They're nestled along the fuselage so you can get a longer flat [bed]," and that classifies them as "side-facing" seats. As such, not only must they meet HIC requirements but additional chest and pelvis protection criteria as well because of lateral loads passengers would face in the event of a crash.

Right now, Amsafe says some 18 international and Regional airlines employ the system, most of them European. In North America, the only major using inflatable belts is Air Canada. Amsafe says another North American carrier is waiting in the wings, as are a pair of Asia-Pacific airlines.

Time, Time, Time

Passengers can't evacuate an airplane if they are unconscious or disabled; 16g seats can prevent both. But it is not always trauma that kills. While media reports indicate that the full fury of the fire that consumed the hull of AF358 took hold only after the evacuation, fire-blocking seat cushions and fire-resistant slides can be critical. In examining a selected set of survivable accidents from 1970 to 1995 in the US, FAA found that 68% of the occupants died from post-crash fires. The numbers haven't changed significantly. "The fatality rate for Part 121 airplanes is between 40% and 60% because of post-crash fires," says Gary Frings, program manager for aircraft crashworthiness at FAA's William J. Hughes Technical Center in Atlantic City. "If there's something you can do to reduce that, it would be a big deal."

One of the most infamous survivable post-accident fires occurred at Manchester International Airport on Aug. 22, 1985, when the compression chamber on the No. 1 powerplant of an Airtours 737-200 ruptured during the takeoff roll just before decision speed. The crew rejected the takeoff, turned off the runway, and thus placed the fuselage downwind of the burning engineand of a pool of fuel that had formed on the left side of the aircraft. What resulted was a classic burn-through scenario. The blaze penetrated the skin quickly and 55 of the 135 onboard died, all of them victims of fire or smoke.

Providing passengers more time to evacuate is what drives Gus Sarkos, manager of the fire safety branch at the Hughes Technical Center. Two decades after Airtours, a new rule is aimed at breaking the back of burn-through. It takes effect Sept. 2, 2007, and covers newly manufactured aircraft. In the wake of Swissair 111, where insulation caught fire and filled the cabin with smoke, FAA developed a tough new standard for thermoacoustic insulation. In the midst of the rulemaking, Sarkos says the agency decided, "If we're going to change insulation to make it better in terms of an inflight fire, let's make them change it to make things better in terms of a post-crash fire."

The new requirement is that insulation act as a barrier to keep flames outside of the cabin for a minimum of 4 min. "If you add the time it takes to melt through the aluminum shell of an airplane, you have about five minutes protection," says Sarkos, "which is more than enough [given] all the accidents we've ever analyzed."

The insulation rule is the latest in a legacy of regulations tracing to the 1980s: Fire-blocking seat cushions, low-heat and low-smoke release interior panels, floor proximity lighting, fire-resistant evacuation slides. Each added precious time to escapefire-blocking cushions 40-60 sec., low-heat and low-smoke panels 1-2 min. Floor proximity lighting boosted evacuation rates by 20%.

In Toronto, all of this came together. "People raise the question whether these improvements had an impact," says Sarkos. "The airplane was gutted. It was loaded to the gills. Yet everyone escaped. I can't imagine they weren't a factor."

The Carbon Factor

If it takes about a minute for aluminum to burn through, it takes composites substantially longer. "We've done tests on the order of 20 minutes," says Jeff Hawk, director-government, environment and certification for Boeing's 787 program. By weight, 50% of the Dreamliner is compositenot just the empennage but wings, fuselage skin, stringers and longerons.

Sarkos is convinced of the inherent fire-blocking properties of carbon fiber. After all, the material is essentially pre-burned. His concern is that while composite material may not burn through readily, "it may outgas" and could build up toxic fumes inside the cabin. "There are issues to be addressed," he believes. Hawk says, "We've specifically been observing any fumes and smoke that's been emitted and we think we will have no difficulty passing regulatory requirements."

One requirement much on the minds of aircraft manufacturers is the 90-sec. rule mandating that a commercial aircraft be evacuated within 90 sec. with one-half of the exits blocked. The aircraft most at issue is the A380, Airbus's double-deck leviathan. The July-August 2004 edition of the Flight Safety Foundation's Cabin Crew Safety found that researchers are concerned about a Very Large Transport Aircraft's unique requirements for "a very fast evacuation resulting from the fire threat that is not found to the same level in other forms of transport, or indeed buildings."

Among issues cited by a JAA "Very Large Transport Aircraft Emergency Research Evacuation Study" are:

" Spatial disorientation during an evacuation. " Visually assessing the obstruction of aisles, cross-aisles and situations at the opposite side of the cabin. " Conducting empty cabin checks. " Visually assessing the aircraft attitude and usability of slides.

Those slides are long. Upper-deck devices on the A380 are 26.6 ft. above the ground. "While there is very little data concerning the use of upper-deck slides under certification-evacuation conditions," says the JAA document, "what data is available suggests that . . . passenger exit-hesitation delays, while slightly longer, are similar to those in standard exits."

A regulatory official close to the issue is a bit more concerned: "Trust me, there are some tricky things here. When you're now talking about someone standing at the door [almost 27 ft. above the ground] and they're looking at that long, long jump down the slide, how are you going to do that?"

To mitigate anxiety, cabin crew participating in the study suggested using fully enclosed tubes, or slides that would limit passengers' view from the top of the slide to the ground. Airbus declined to talk about either survivability or A380 certification. FAA spokesperson Alison Duquette says that for the most part, her agency will take data developed by EASA in a mid-2006 emergency evacuation test. But what kind of data?

Another official close to the certification process says, "The issue is what type of test will they do? I don't think that's been decided yet. Will it be a single evacuation of the whole aircraft or will it be by each deck? That's still being discussed."

Hearing Is Believing

What also is being discussed, at least at CAMI, is devising ways to get passengers to pay more rapt attention to safety briefings. Human Factors Specialist Cynthia Corbett says humorous safety briefs and those by celebrities may not work any better than boring monologues. "Do people tend to remember the humor or the message?" she asks. Indications are it's the former. CAMI wants to see if broadcasting safety briefs via commercial television will work, or perhaps posting them on airline websites. The latter could be computer-gamed to demonstrate interactively an understanding of, say, how to open an aircraft door. That might lead to a reward, like frequent-flier miles.

Lesson learned? Many believe AF358 was precisely thatthe culmination of a series of lessons learned. In another airplane or another era, the accident might have proven catastrophic. Call it a miracle if you will but remember, miracles can be the result of good people putting into practice lessons all too painfully learned.

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