Science / Medicine : Fleeing the Flames : Aviation: Systems exist to put out fires in buses and military tanks, but not passenger planes. Safety advocates and airlines battle over costs and other factors.

Robert Rodriguez was driving his Rapid Transit District bus along 3rd Street in Los Angeles when he heard a pedestrian yelling that the bus was on fire. Before Rodriguez could park the vehicle at the curb, an automatic fire suppression system put out the flames in the methanol-powered bus’s engine compartment.

No one was hurt. Damage totaled only about $50, despite the fuel’s high flammability. If the fire had struck in the days before the automatic system was installed, “we would have lost half the bus,” said RTD engineer Vince Pellegrin.

Yet comparable systems do not exist for airplanes. When a USAir Boeing 737 slammed into a parked SkyWest commuter plane Feb. 1 at Los Angeles International Airport, more people died from the flames and smoke that enveloped the planes than from the impact. Of the 34 who were killed, 18 died while either strapped in their seats or struggling to get out of the inferno.

That scenario has been repeated many times around the world. In many cases, more people die from fire and smoke inhalation after a crash than from the impact.

That grim fact has left aviation safety experts wondering if enough is being done to protect passengers from the highly toxic fumes and flames that follow many crashes. This is especially troubling since efficient fire-control systems now protect everything from computers in industrial complexes to combat troops in military vehicles.

For example, the same type of system that put out the fire aboard the RTD bus in October, 1989, is used to protect troops in tanks and crewmen aboard combat aircraft. But for a variety of reasons, there is no serious consideration being given to installing such a system aboard commercial airliners.

Tanks built by General Dynamics have a system that will put out a fire before it can be detected by humans.

“It’s quicker than the blink of an eye,” said a company spokesman. “Just as the fire is beginning to ignite, it is smothered. You can’t even see it before it is out.”

The military system uses infrared sensors manufactured by the Santa Barbara Research Center, a subsidiary of Hughes Aircraft, that detect emissions at infrared wavelengths in the earliest stages of combustion.

“It very, very quickly determines whether the emissions are from a fire,” said Robert J. Cinzori, manager of the program for the Santa Barbara facility.

If the computer determines that a fire is about to erupt, it floods the area with Halon gas, which instantaneously smothers the fire. The gas poses no threat to the crew, according to experts with Dupont Corp., which manufactures it, but there are other problems.

“It sounds good, but it poses a lot of questions,” said Dan Moore, technical development manager for Dupont.

Halon gas is one of the chemicals believed to be destroying the ozone layer that protects the Earth from harmful solar radiation, and under international agreements Halon is slowly being phased out. Substitutes are being developed, according to Dupont, but they are not as effective and will cost and weigh more than the gas they will replace.

Cost and weight are among the reasons that such systems are not considered cost-effective for airliners. The system on the RTD’s methanol buses costs about $7,000 for each bus, Pellegrin said. It takes about two pounds of Halon to protect each cubic foot of space, and that is expected to double with the substitutes.

Weight is no problem for a bus, in which only the engine compartment is protected. But a typical airliner has several thousand cubic feet in the passenger compartment, so the system would add thousands of pounds to the aircraft.

The most compelling objection, however, is that damage to an aircraft during a crash probably would destroy the effectiveness of the system by breaking the fuselage open and allowing the gas to escape, Moore said.

The FAA has been studying the problem for many years but has thus far rejected automated systems that would flood the airliner in the event of fire. There are some limited automatic extinguishers in engine compartments and even in the waste disposal system in bathrooms aboard commercial airliners, but there is no system that would automatically put out a fire in the passenger compartment.

Fred Farrar, an FAA spokesman in Washington, said the agency has looked at various types of sprinkler systems but is reluctant to put such a system in an aircraft to go off automatically if sensors detect a threat.

Automatic systems “sometimes go off when you don’t want them to,” he said. “Would you want that happening at 30,000 feet?”

That answer does not satisfy everyone, especially aviation safety groups that believe any system that gives passengers a few more seconds could save lives.

“There isn’t any reason why we shouldn’t have state-of-the-art systems,” said Peter Trafk of the Aviation Safety and Health Assn. in Honolulu. He maintains that passengers are not nearly as safe as they think.

“The one biggest misconception of the passenger is that when there is a fire, an oxygen mask will drop from the ceiling and that will help,” he said. “But the oxygen mask is only for rapid decompression (if the air pressure in the aircraft suddenly drops.) It will give you oxygen to keep you alive because you can’t breathe at that level, but it won’t keep out smoke or toxic fumes that can kill you.”

That has been a matter of great concern in England since a British airliner crashed and caught fire in August, 1985, and authorities have pushed for a requirement that airliners be equipped with smoke hoods that could protect passengers from toxic fumes. A transparent hood, perhaps coupled with the oxygen mask, could allow passengers to survive in a smoke-filled compartment for several minutes. The passenger could pull the light-weight plastic hood over his or her head and cinch it around the neck, thus closing off the toxic fumes.

But James Vant of Oxford University, an adviser to Britain’s Parliament, said the airline industry fought the move so fiercely that specifications initially were set so high that no manufacturer came up with equipment that would meet the requirements.

“You know how when you are waiting to take off and the stewardess up in the front of the aircraft tells you that the oxygen masks will drop from the ceiling in the event of rapid decompression?” Vant asked in a telephone interview. “No airline wants to add, ‘And if the place catches on fire. . . .’ ”

Nevertheless, last January Parliament’s Standing Committee on Transport noted that in the 1985 crash, many of the victims died because they “collapsed unconscious from smoke inhalation” while trying to get out of the burning aircraft. That led the committee to push once again for realistic specifications that would encourage manufacturers to produce the equipment.

However, like the FAA in the United States, Britain’s Civil Aviation Authority has resisted the suggestion on the grounds that passengers might spend so much time trying to put on the smoke hoods that evacuation would be slowed, thus placing them in even greater peril.

Vant argues that no evacuation is possible, however, if the passengers are overcome with smoke, and he cites the Los Angeles accident as evidence of that.

Smoke produced by burning aircraft fuel is so toxic, he said, that “within seconds you become unconscious.”

“Take three breaths and you’ve had your chips,” he said. “It also produces a film over your eyes and you can’t see where you are going, so I don’t know what good those lights along the floor do.”

During a hearing last week in Los Angeles, Rep. Mel Levine (D-Santa Monica), whose district includes Los Angeles International Airport, said he plans to introduce two bills in Congress soon that would require smoke hoods for passengers and improve emergency exits.

Levine estimated that the hoods would cost about $400 each, which he said will translate into about a 30-cent increase in the average ticket.

Critics believe those changes could help, but will airliners ever become as safe from fire as tanks in a combat zone?

Probably not, but many experts believe far more could be done to help passengers escape the fiery aftermath of a crash they somehow lived through.