Study Found Some Potential Safety Issues With Airbag Restraint Systems

After adopting the safety study Airbag Performance in General Aviation Restraint Systems on January 11 the NTSB is issuing six safety recommendations to the FAA to address issues concerning airbag restraint systems, and shoulder harnesses, as well as capturing and recording crash dynamics information relating to airbag deployment, and tracking aircraft safety equipment installations. Information supporting these recommendations is discussed in this letter and in the safety study.

In 2003, airbags were first certificated for pilot and copilot seats on general aviation (GA) aircraft, and as of January 2011, they have been installed in nearly 19,000 seats in over 9,000 GA airplanes. Airbags in GA aircraft are installed in the lap belt or shoulder harness portions of the restraint system and are designed to deploy outward from the pilot or occupant. Sled tests conducted under controlled conditions have suggested that aviation airbags may increase survivability and reduce injury in actual aviation accidents; however, no systematic evaluations had been conducted to evaluate their efficacy in real-world scenarios. Therefore, in 2006, the NTSB initiated an exploratory case series study to assess airbag performance in GA accidents.

Two goals of the study were to examine the effectiveness of airbags in mitigating occupant injury in GA accidents, and to identify any unintended consequences of airbag deployments.

During the course of its investigations, the study team discovered two potential safety issues associated with the misuse or incorrect adjustment of restraint systems. One issue involves occupants reversing restraints in Cessna airplanes. After the February 27, 2007, Cessna T182T accident in Athens, Texas,3 the accident pilot stated that at the beginning of the flight, the left front seat passenger had attempted to use the restraint for the right seat. In the Cessna T182T, both of the front seatbelts hang from the ceiling between the two seats. The pilot, who was also a certified flight instructor, noted that there had been other occasions when his students had inadvertently used the wrong restraint in either the Cessna 172 or Cessna 182.

The NTSB concludes that the 3-point restraint systems in certain Cessna airplanes can be reversed in such a way that the airbag and restraint systems are not used as designed and certified. For example, if a left-seated occupant fastened the right seat shoulder harness to his or her outboard buckle, the airbag system in the unused restraint would be active while the airbag in the buckled restraint would be inactive.

The NTSB is recommending that the FAA 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.

Cessna 182T File Photo

They further recommend revision of the guidance and certification standards concerning restraint systems to recognize and prevent potential misuse scenarios, including those documented in this safety study, and modification of 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.

Other recommendations include requiring 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, evaluation of 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 reviewedafter a crash to determine whether the system performed as designed, and development of 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.

FMI: www.ntsb.gov