25 years passenger airbag at Mercedes-Benz

25 years ago Mercedes-Benz was the first automobile manufacturer in the world to introduce the front passenger airbag in a series-production car. The technology debuted in the S-class (model series 126) at the Frankfurt International Motor Show in September 1987.
It elevated the safety standards in Mercedes-Benz passenger cars to a new level and thus represented yet another logical step by the pioneer in passive vehicle safety in a long line of outstanding innovations.

Mercedes-Benz had already introduced the world's first fully operational driver airbag in a production vehicle in 1981 – also in a 126 model series S-class. The Supplemental Restraint System (SRS), consisting of driver airbag and belt tensioner, was available as an option for DM 1525.50. It was the result of the rigorous work undertaken by corporate research that had started in the mid-1960s. When sensors detect a collision, a propellant charge is ignited and within a few milliseconds the nitrogen produced by this process inflates a bag made out of a special woven material. The resulting cushion protects people against impacting the dashboard. While the driver airbag is housed in the steering wheel, the front passenger airbag in its early manifestations occupied the spot where the glove compartment would normally have been.

The front passenger airbag introduced in 1987 utilised the same technology as the innovative driver protection system. It went on sale as an option on S-class saloons and coupes in February 1988. Soon afterwards Mercedes-Benz also offered the front passenger airbag as an option in the mid-size model series 124. As early as 1994 the front passenger airbag became standard on all Mercedes-Benz passenger cars; the driver airbag had already been part of the standard equipment of all passenger car models since 1992. To further improve the protective effect afforded by airbags, the Mercedes-Benz engineers went on to develop additional systems such as the side airbag and the side curtain airbag in the years that followed.

Research in the interest of safety
Mercedes-Benz has shaped not only the history of the modern airbag to a significant extent, but the development of vehicle safety in general: this includes such pioneering innovations as the safety body shell with rigid passenger cell, front and rear crumple zones as well as the safety steering column. Airbag technology expanded the arsenal of passive safety by another powerful tool. Mercedes-Benz research on the airbag began in 1966, with initial practical trials starting in 1967.

Mercedes-Benz's fundamental goal was to further increase vehicle safety. The development of the airbag was also driven by plans in the United States of America to prescribe an automatic occupant protection system for all cars from 1969. Airbags that inflate during an accident were seen as a very promising technology. The principle had already been patented in the 1950s. The principal pioneers were the German Walter Linderer (Patent DE 896312 of October 6, 1951) and the American John W. Hedrik (US Patent 2649311 of August 18, 1953).

But it was a rocky road from the concept to production-ready technology. Particularly the necessary sensor systems and gas generation continued to present major challenges to the developers. This was evident in the solutions from American manufacturers, which equipped their first test fleets with compressed-air operated airbags as an alternative to seat belts: this concept led to serious injuries and in a few cases even fatalities. For this reason the engineers at Mercedes-Benz chose a different approach to arrive at the 'inflatable container in a folded state, which automatically inflates in the event of danger' (Linderer's description of his invention in the patent application): the airbag was not to replace the restraining effect of the seat belt, rather it was to supplement it. Tests showed that the airbag only achieved maximum effectiveness in combination with the safety belt. In addition, the gas was not stored under high pressure, but generated on demand by igniting a propellant charge.

The findings of Mercedes-Benz research were formulated in patent no. DE 2152902 C 2, which former Daimler-Benz AG filed on October 23, 1971. This patent application was the key document for all subsequent airbag development at Mercedes-Benz. It already described the operating principle of the new technology as it was to be implemented in series production ten years later: sensors register the particularly severe deceleration common to collisions and activate the airbag mechanism. This ignites a propellant charge (at the time consisting of sodium azide, potassium nitrate, and sand), which deflagrates instantaneously to form mainly gaseous nitrogen and every a little water and oxygen.

The airbags for driver and front passenger quickly caught on in the entire industry as a life-saving technology. As airbag modules became smaller and smaller due to the rigorous work of the engineers, it was possible to incorporate them in other areas of a vehicle to also provide comprehensive protection in the event of a side impact: in 1993, Mercedes-Benz presented a study of a side airbag; in 1995 the side airbag became available as an option, initially in the E-class. Further innovative steps were the side curtain airbag, the head-thorax sidebag and adaptive airbags that operate in different stages depending on the expected severity of the accident and provide optimal protection for the occupants.

Did you know…?
Mercedes-Benz Classic will be at the Goodwood Revival (September 14-16, 2012) with five original Silver Arrows of the 1930s – and will compete in a demonstration run with racing cars of Auto Union. It will be the biggest assembly of Silver Arrows since decades.

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