Post-crash fires are the single most important hazard to survivors of helicopter crashes. Even though crash-resistant fuel systems have been almost 100 percent effective in survivable crashes of military helicopters, manufacturers and regulators of civil aircraft have been slow to implement the technology in civil helicopters, explained Dennis F. Shanahan, MD, MPH, corresponding author of the study and an associate in the Johns Hopkins Bloomberg School of Public Health's Department of Health Policy and Management. "In 1994, civil regulations were implemented. They were based on the military regulations, but are not as strict as the military requirements. They also applied only to newly certificated helicopter models."
The researchers examined National Transportation Safety Board data of civil helicopter crashes from 1982 to 2004. They compared Bell 206 helicopters with crash-resistant fuel systems to Aerospatial-350 helicopters, which did not have crash-resistant fuel systems. They also looked at Bell 206 helicopters before and after crash-resistant fuel systems were implemented. The Aerospatial-350 helicopters, made after 1981, had the highest proportion (11 percent) of crashes with post-crash fires. Fewer than four percent of the Bell 206 helicopter crashes had post-crash fires. Early Bell 206 models had a higher risk of post-crash fire, when compared to models built after 1982, which is the year Bell Helicopter voluntarily implemented crash-resistant fuel system standards similar to the civil regulations that wouldn't be formally mandated for another 12 years.
Fuel containment and isolation of fuel from ignition sources is critical to surviving a crash. Uncontained fuel turns into a mist, which when exposed to an ignition source, produces a fireball, typically before the helicopter comes to rest. This makes it more difficult for occupants to survive a crash.
"Post-crash fires are a serious issue that doesn't often get the attention it deserves. We should be doing everything possible to increase helicopter crash victims' chance of survival," said Susan P. Baker, MPH, a professor in the Bloomberg School of Public Health's Department of Health Policy and Management and Center for Injury Research and Policy.
Co-authors of the study are Mark S. Hayden, Dennis F. Shanahan, Li-Hui Chen and Susan P. Baker.
"Crash-Resistant Fuel System Effectiveness in Civil Helicopter Crashes" was supported by a grant from the National Center for Injury Prevention and Control at the Centers for Disease Control and Prevention.