MERCEDES-BENZ AND THE LATE 1980S INTRODUCTION OF PASSENGER-SIDE AIRBAGS: A CHAPTER IN RECENT AUTOMOTIVE HISTORY

Driver's and front-passenger airbag in the Mercedes-Benz SL sports car, model series R 129.

Vehicle safety at Mercedes-Benz is an issue that is relevant not only to the driver of a vehicle, but also to their passengers. And it was for this very reason that the Stuttgart-based brand launched the front-passenger airbag, back in September 1987. It was a further important innovation in passive safety, following the driver's airbag that had first been presented in March 1981. From February 1988 the front-passenger airbag became available in the S-Class and, from the autumn of that same year, in the 124 series, a precursor of today's E-Class. As early as 1994, it then became a standard feature in numerous Mercedes-Benz vehicles.

Stuttgart. The glove compartment is the home of the new dimension of safety for the front passenger: in the place of this small stowage compartment, the engineers from Mercedes-Benz were able to accommodate an airbag – one of the new features presented by the brand at the International Motor Show (IAA) in Frankfurt am Main from 10 to 20 September 1987. This innovation represented an important building block to complement the established scope of restraint systems at Mercedes-Benz, the driver's airbag and the belt tensioner. With the additional airbag for the passenger, the Stuttgart brand provided a form of occupant protection that at the time was not offered by any other manufacturer worldwide.

The front-passenger airbag initially made its debut in the S-Class Saloons and Coupés of the 126 model series. They were available to order from model year 1988 with the new equipment option, which was only available in conjunction with the driver's airbag, at a price of DM 4617 in Germany. The driver's airbag could be ordered on its own at DM 2348.40.

And so this generation of the Mercedes-Benz S-Class, built from 1979 until 1992, finally became the trailblazer for the airbag. The driver's airbag itself was also first offered for the 126 model series. This pioneering passive safety solution was presented by Mercedes-Benz from 5 to 15 March 1981 at the International Motor Show in Geneva. The Stuttgart brand thus became the first manufacturer in the world to introduce the airbag system, registered for patent back in 1971, in series vehicle production. The driver's airbag was combined with a belt tensioner for the passenger. The driver's airbag featured in the price list from July 1981, when it was offered for the model series 126 at a price of DM 1525.50. By January 1982 the system was already available for all Mercedes-Benz passenger car models, at a price of DM 1570.70. And then finally, with effect from October 1992, the driver's airbag and the anti-lock braking system ABS formed part of the standard equipment for passenger cars sporting the three-pointed star.

The front-passenger airbag presented 30 years ago at the IAA also became available from September 1988 in the model series 124 - which subsequently became the E-Class. It soon proved its worth in terms of passive safety as an effective protective device and, in August of 1994, became part of the standard specification of many Mercedes-Benz passenger cars, along with head restraints in the rear. From the very beginning the manufacturer emphasised that the front-passenger airbag was there to supplement the protective effect of the three-point seat belt, but was in no way to be seen as a substitute for it. At that point wearing seat belts had been compulsory since 1976, with fines imposed for any failure to comply from 1984 on.

The combination of these two protective systems led to significant improvements in passive safety, as experiments with test dummies showed: the combined system of seat belt with belt tensioner and front-passenger airbag could reduce the risk of injury to the chest and head area by about a third compared with the performance of the seat belt with belt tensioner alone. The tests evaluated in particular the impact of the accident on soft tissue (Viscous Tolerance Criterion, VTC) and head (Head Injury Criterion, HIC).

Five kilos of safety

Compared with the three-kilo weight of the driver's airbag, accommodated within the steering wheel, the front-passenger airbag unit in the S-Class models in the model series 126, installed in the place of the glove compartment, weighed five kilos. This was largely due to the fact that, because of the greater distance between the airbag and the passenger in the seat, the volume of the life-saving air cushion had to be almost trebled: the volume in the S-Class was 170 litres compared with 60 litres on the driver's side.

In essence, however, the technology behind the innovation that was presented in 1987 was the same as that for the tried and tested driver's airbag: If the crash sensor mounted above the transmission detects a serious accident, it triggers the two gas generators in the airbag. A solid propellant in pellet form ignites to generate a gaseous mixture that inflates the airbag immediately. The shape of the airbag is such that it protects the front passenger from impact with both the instrument panel and the A-pillar.

The triggering device is able to detect collisions and identify their severity according to two pre-set thresholds. If the first threshold is exceeded, the device begins by triggering the belt tensioner. Should the higher threshold be reached, the front-passenger airbag is activated. The two gas generators ignite 15 milliseconds apart, ensuring that the airbag cushion, which is made out of a rubber-lined polyamide fabric, inflates steadily at a controlled rate of pressure. The on-board electronics also check whether the passenger seat is occupied or not, so that if the sensors in the seat and the seat-belt buckles report that the seat is empty, the front-passenger airbag is not triggered in the event of an accident.

Ongoing research in the interests of safety

The front-passenger airbag is an important building block in the ongoing process of safety development at Mercedes-Benz. The first tests of comparable restraint systems for the front-seat passenger were initiated by the Stuttgart-based brand almost two decades before such systems were introduced in series production. As far back as 1971, for example, Hans Scherenberg, Member of the Board of Management of the then Daimler-Benz AG and Head of Overall Development and Research, reported on the tests being undertaken at the time in the development department: "In the case of the front-seat passenger, who was protected by a lap belt and an inflatable cushion, the requirements specifications were met in full." Serving as a reference here were the US-American Federal Motor Vehicle Safety Standards, the first provisions of which came into effect on 1 March 1967 for the 1968 model year. At the IAA in Frankfurt am Main in 1975, Mercedes-Benz then presented the current status of its airbag research activities: an "air cushion for the driver and front-seat passenger as a possible supplementary system to the seat belt".

The airbag gains acceptance

Airbags for drivers and front passengers soon gained industry-wide acceptance as life-saving technology. Since the airbag modules became ever smaller on account of the continuous work by the engineers, it was also possible to place them elsewhere in the vehicle, for example in order to achieve comprehensive protection in the case of a side-on collision: In 1993, Mercedes-Benz presented a side airbag as a prototype. In 1995 the sidebag initially came on to the market as an optional extra in the E-Class. Further innovations included the windowbag (1998), the head/thorax sidebag (2001), the kneebag (2009), the thorax/pelvis sidebag, the beltbag and the cushionbag (2013) as well as adaptive airbags for the driver and front passenger with two-staged time-delayed deployment, depending on the detected severity of the impact and the selected seating position. In this way, Mercedes-Benz passenger cars protects its drivers and passengers with a sophisticated system of up to twelve airbags.

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