Passengers in commuter airplanes and air taxis face a major risk of death or injury from fire in crashes because of inadequate fire protection equipment and uncrashworthy fuel systems, according to a Johns Hopkins study.
"Our findings underscore the compelling need to adopt the latest fire safety technology, such as crashworthy fuel systems and automatic fire extinguishing systems, in commuter aircraft and air taxis," says Guohua Li, M.D., Dr.P.H., the study's lead author and an assistant professor of emergency medicine. "Fire plays an important role in whether passengers survive crashes, so minimizing the risk of fire in these aircraft is critical to reduce the high death rate."
The Hopkins researchers note that while fire fatalities have been greatly reduced on major commercial airlines and military aircraft since the 1970s due to stricter safety requirements, they continue to be a high risk on commuter airlines and air taxis, which make more than five million flights a year in the United States. The fatal crash rates (per million flight hours) for commuter air carriers and air taxis were 10 times and 45 times higher, respectively, than for major commercial airlines, but the Hopkins study found that only 19 percent of the smaller aircraft had fire detection and fire extinguishing systems and only 38 percent of those systems were activated during fiery crashes.
The Federal Aviation Administration recently announced plans to extend the safety regulations and operational standards for major airlines to these smaller aircraft.
"The large differences in fatal crash rates, however, will not diminish unless more concrete changes, such as installation of fire protective equipment, are implemented in these smaller aircraft," says Susan P. Baker, M.P.H., a co-author and a professor of health policy and management. "Marked progress in technology and design have reduced the hazards of fire in major commercial and military aircraft, but our results indicate that fires in commuter air carrier and air taxi crashes are fairly common and that immediate action should be taken."
The Hopkins team analyzed all commuter and air taxi crashes from 1983-1988 using data from the National Transportation and Safety Board. They found that fires occurred in 17 percent of the 888 crashes. The crashes resulted in 536 deaths and 744 injuries.
Most of the fires, typically caused by the crash impact and started at the engines, occurred at night, in bad weather and in rough terrain away from airports, according to the results, which are published in the May issue of Aviation, Space, and Environmental Medicine. These same conditions also often hampered rescue and firefighting efforts. Fifty-nine percent of the fires occurred during impact or the following seconds, 17 percent after the plane stopped, 16 percent in-flight and 8 percent during ground operation. The engine was the source of the fire in 59 percent of the crashes, hot surfaces in 18 percent and short circuits and sparks in 9 percent each.
Aircraft with twin engines flying at night were more likely to have a fire in a crash than those with single engines, the study shows. Fires occurred in 5 percent of daytime crashes of single-engine planes at airports compared to 41 percent of nighttime crashes of twin-engine planes away from airports, probably because the latter accidents often involve high-speed, uncontrolled impact in rough terrain, the results suggest. The Beech 18, an older model aircraft, was the most common model involved in crashes and had more fires during crashes than other twin-engine planes (37 percent compared to 21 percent), most likely because of the more flammable fuel it uses, according to the results.
In major commercial airplanes and military aircraft, the risk of death and injury from flashfires, burns and smoke inhalation has been reduced dramatically by installation of rupture-resistant and self-sealing fuel systems, by requirements for fire-retardant interior materials and by improvements in fire sensing and extinguishing equipment, the Hopkins researchers say.
Senior author of the study, which was funded by Johns Hopkins, was Robert S. Dodd, Sc.D. Aviation Science and Technology in Bowie, Maryland, also participated in the study.