Airbag Performance in General Aviation Restraint Systems
In 2003, airbags were first certificated for pilot and copilot seats on general aviation (GA) aircraft, and as of August 2010, they have been installed in nearly 18,000 seats in over 7,000 GA aircraft.
In 2006, the National Transportation Safety Board (NTSB) initiated an exploratory case series study to consider airbag performance in GA accidents. The goals of the study were (1) to examine the effectiveness of airbags in mitigating occupant injury in GA accidents, (2) to identify any unintended consequences of airbag deployments, and (3) to develop procedures to assist investigators in documenting airbag systems in future investigations.
During the 3-year data collection period, researchers tracked 145 notifications of events involving airbag-equipped airplanes which yielded 10 airbag-equipped GA airplane accidents that met the study criteria and were subjected to a full review and analysis by a multidisciplinary team.
There were no unexpected deployments or unintended consequences identified during the study period. When adjusted correctly, the deployment of the airbag systems did not result in any negative outcomes, and in certain cases, deployment mitigated the severity of occupant injuries.
The NTSB concluded that aviation airbags can mitigate occupant injuries in severe but survivable crashes in which the principal direction of force is longitudinal. During the course of the study, the study team also became aware of several potential issues that may compromise occupant safety associated with use, adjustment, or design of restraint systems.
The report discusses steps that could be taken to address these safety issues and suggests future research directions in the area of GA occupant protection. Finally, as a result of the study, guidance for NTSB investigators was developed and disseminated, including a formal process for gathering data about airbag installations and deployments in accident aircraft.
- Based upon investigations of 10 accidents, there were no cases in which the airbags were expected to deploy but did not.
- Based upon investigations of 10 accidents, there were no cases that involved airbags deploying under unexpected circumstances, and there was no evidence of airbags hindering egress, fueling postcrash fires, or interfering with rescue attempts.
- Aviation airbags can mitigate occupant injuries in severe but survivable crashes in which the principal direction of force is longitudinal.
- Based upon investigations of 10 accidents, the NTSB concludes that when occupants adjusted the restraint systems correctly, the airbag systems did not cause any negative outcomes, and in some cases with airbag deployment, they were associated with reductions in the severity of occupant injuries.
- Some general aviation occupants have misused or incorrectly adjusted their restraints in ways that could reduce the protection conveyed by the restraints or lead to injuries.
- The 3-point restraint systems in certain Cessna Aircraft Company airplanes can be reversed by occupants in such a way that the airbag and restraint systems are not used as designed and certified.
- Certain aviation airbag restraint configurations do not provide optimal protection for occupants whose anthropomorphic characteristics are substantially dissimilar to those of the anthropometric test dummy required for restraint testing.
- Lap belt/shoulder harness combinations provide significant protection beyond a lap belt alone, and fatalities and injuries would be reduced if lap belt/shoulder harness combinations were used in all small airplanes.
- The understanding of aircraft crash dynamics and occupant safety would be improved if airbag-equipped aircraft recorded, at a minimum, data concerning crash dynamics and airbag deployment criteria.
- Future evaluations of the effectiveness of occupant protection features, such as restraint systems, airbags, and parachutes, would benefit from the establishment of a system to provide information about what aircraft safety equipment is installed on individual aircraft.
As a result of this safety study, the National Transportation Safety Board makes the following recommendations:
To the Federal Aviation Administration:
- Require Cessna Aircraft Company and other manufacturers whose restraint system designs permit an occupant to use an inactive airbag restraint system not intended for use in his or her seat to modify their restraint system designs to eliminate that possibility, and require them to modify restraint systems in existing airplanes to eliminate the possibility of misuse.
- Revise the guidance and certification standards concerning restraint systems to recognize and prevent potential misuse scenarios, including those documented in this safety study.
- Modify the special conditions for the installation of inflatable restraints on general aviation airplanes (at Federal Register, vol. 73, no. 217 [November 7, 2008], p. 66163) to provide specific guidance to manufacturers as to how they should demonstrate that the protection is effective for occupants that range from the 5th percentile female to the 95th percentile male.
- Require the retrofitting of shoulder harnesses on all general aviation airplanes that are not currently equipped with such restraints in accordance with Advisory Circular (AC) 21-34, issued June 4, 1993.
- Evaluate the potential safety benefits and feasibility of requiring airbag-equipped aircraft to have the capability to capture and record, at a minimum, data concerning crash dynamics and airbag deployment criteria that can be reviewed after a crash to determine whether the system performed as designed.
- Develop a system to track individual aircraft information about aircraft safety equipment, such as restraint systems, airbags, aircraft parachutes, and other specific aircraft equipment, designed to improve crash outcomes.