Porsche introduced its driver and passenger airbag passive restraint system on the U.S. 1987 944 Turbo, making it the first vehicle with driver and front passenger airbags fitted as standard equipment. This system, standard on all 944 Turbos destined for the U.S., was also available here as an option on 1987 944s and 944Ss. By the 1990 model year, dual airbags were standard on all Porsches, as they have been on every production Porsche since.
Stuttgart was well ahead of the curve. Airbags with shoulder belts for the driver and front passenger were mandated by the National Highway Traffic and Safety Adminstration Act of 1991, requiring these systems to be installed in all vehicles manufactured after September 1, 1997. Porsche didn’t rest on its laurels: Its two-seat Boxster got door-mounted side-impact airbags for 1998, which were replaced for 2005 by seat-mounted airbags augmented by “curtain” airbags rising out of the tops of the doors to protect occupants’ heads, another first.
Because airbags are a critical safety component, because airbags are largely ignored in Porsche media, and because many airbags are getting older, they’ll be the subject of this Tech Forum, the first by Tony Callas and Tom Prine.
Performance of airbags and related safety systems is defined in the Federal Motor Vehicle Safety Standards Section No. 208, Occupant Crash Protection. The main dynamic performance requirement in FMVSS No. 208 is a “Successful” test rating using a 50-percentile (average height/weight) adult male dummy built to measure impact loads at specific areas of the body. The tests require impacts into rigid barriers (an instantaneous stop) from speeds up to 30 mph and at all angles between perpendicular and 30º to either side of perpendicular.
Some “Successful” test results require that the dummy’s measured Head Injury Criterion (HIC) be rated at 1,000 or less. (For reference, an HIC of approximately 1,850 is generally considered not survivable). Deceleration measured at the chest must not exceed 60 g, and compressive deflection of the sternum (pushed in towards the spine) cannot exceed 76 mm. Additionally, forces transmitted axially through each upper leg cannot exceed 2,250 pounds.
Clearly, these are tremendous loads for our bodies to endure. Airbags are a critical advantage, allowing a somewhat gradual deceleration of the head and upper body over an additional fraction of a second. They can be the difference between walking away with bruises and sustaining far more serious injuries.
Porsche’s first airbags, like others, were designed to function in a frontal or near-frontal impact. A collision to the side or rear is not recognized and should not deploy the airbags. The system is meant to be used in conjunction with other passive-restraint systems, including a properly adjusted three-point seatbelt and Porsche’s integrated headrests. The system consists of two front impact sensors, a control unit with safety sensor, airbags with gas generators, ignition pills in both front-seat positions, and a system monitor lamp in the instrument cluster.
When an airbag-equipped car sustains a frontal impact, sensors immediately measure the impact force. Airbags are not designed to deploy at a specific vehicle speed but rather at a set threshold of vehicle deceleration based on the vehicle’s design. If the forces meet or exceed the set threshold, the sensor switch closes, the control unit receives this signal and, if the internal safety sensor also closes, the control unit sends voltage to the airbag’s pyrotechnic charge, which ignites and deploys the airbag.