‘‘the AMK did make a difference. The initial fireball only heated the fuselage skin to about two hundred degrees Fahrenheit. If the fuselage hadn’t been ripped open by the cutters, the flames probably wouldn’t have gotten inside the cabin for several minutes.’’
A fuel test goes up in smoke, but proponents haven’t given up - anti-misting kerosene - Special Report: Airline Safety
Discover, Oct, 1986 by David Nolan
On Dec. 1, 1984, a four-engine Boeing 720B slammed into California’s Mojave desert and burned to smoldering rubble. Nobody was injured because nobody was aboard. The plane was remotely controlled and purposely crashed by the Federal Aviation Administration (FAA) and NASA to test a promising anti-fire fuel called AMK (anti-misting kerosene).
The unexpected conflagration sent AMK’s short-term prospects up in smoke, but proponents still believe it offers the best long-range hope for reducing the risk of killer aviation fires.
‘‘The fuel was never given a chance to display its anti-misting properties,’’ says Bill Westfield, the FAA engineer who has spearheaded the agency’s AMK research. ‘‘It actually did provide some anti-fire protection in that crash. But the forty million people who saw it on TV sure don’t believe it.’’
Although jet fuel burns reluctantly in liquid form, it’s highly flammable as a mist of tiny droplets. Reason: the ratio of surface area to mass is highest. (To check out the underlying prin- ciple, try lighting a crowbar with a match, then light a tuft of steel wool. Same material, different surface-to-mass ratio.) Which is why jet fuel is sprayed as mist into the engine’s combustion chamber. But the fuel’s volatility makes it extremely dangerous in a crash. Leaking into the air from ruptured tanks, it can quickly vaporize, and only a spark or contact with hot engine parts will transform the mist into a huge fireball.
AMK’s secret ingredient is a long-chain polymer called FM-9, developed in the early 1970s by Britain’s ICI Company. It prevents jet fuel from forming tiny droplets. Before AMK can be burned in an engine, a high-turbulence centrifugal pump must break the FM-9 polymers down into shorter molecular chains that allow the mist to form.
The FAA has been testing AMK since 1978 with satisfactory results. The final exam was to have been the remote-control crash or CID (for controlled impact demonstration). The original plan was to let the 720B sink to the ground at a rate of 40 feet per second (fps) with landing gear down, which would have provided a hard enough impact to break the wings open and assure fuel spillage. But the FAA and NASA decided to piggyback other experiments onto the CID, including seat and structural tests. These required a softer impact, so the sink rate was reduced to 17 fps and the landing gear was kept up.
To make sure the wings would be ruptured and AMK spilled, the experimenters positioned eight large cutters – giant can openers, really – at the crash site. But the NASA pilot, who was ‘‘flying’’ the 720B from the ground with a primitive, slow-to-respond remote system while watching a TV monitor, had the plane slightly off course. Rather than order it around again, he opted for a last-ditch correction, which didn’t quite work. The 720B hit about 500 feet short of the mark with its left wing down, and, yawing 13 degrees to the left, struck the cutters with its right wing and fuselage. One cutter penetrated the No. 3 engine, which instantly exploded, and in the next five seconds 2,300 gallons of fuel poured onto the hot engine. Meanwhile, the skidding fuselage was squeegeeing the spilled fuel along in front of it, feeding it right onto the flaming engine.
‘‘We had the worst possible scenario,’’ says Westfield. ‘‘That blasted yaw really killed us.’’
The FAA estimates that only 19 of the 53 simulated passengers aboard would have escaped – barely. Dense smoke totally obscured the center of the cabin within seconds after the plane ground to a halt, and seats were scattered about the aircraft.
Firefighters needed almost two hours to douse the flames, because the fuel had gone beyond the reach of their foam into a bed of rocks laid down at the crash site to ensure that the plane would be properly damaged. ‘‘We had the world’s biggest charcoal grill,’’ says Westfield.
Still, Westfield insists, ‘‘the AMK did make a difference. The initial fireball only heated the fuselage skin to about two hundred degrees Fahrenheit. If the fuselage hadn’t been ripped open by the cutters, the flames probably wouldn’t have gotten inside the cabin for several minutes.’’ He’s hoping for another crash- test by 1990.
– D.N.
COPYRIGHT 1986 Discover
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