BMW Airbags Offer Head Protection

Understand components and operation of BMW's Head Protection System.

Rescue and extrication personnel are rapidly becoming aware of the increased presence of side-impact airbags in many vehicles. With over 34 models of 1998 vehicles having these systems, it will soon become the norm, not the exception, for responders to encounter side airbags at crash scenes.

Until the model year 1998, side-impact airbags had been designed to protect only the torsos of occupants during collisions. Now, the world's first head protection system is here. Introduced as standard equipment on the 1998 BMW 7 Series sedans built after June 1997, it is currently the only airbag system that helps protect the head of the driver and front-seat passenger during side-impact collisions. The BMW side impact Head Protection System( HPS) is also known by the acronym ITS or Inflatable Tubular Structure by its' manufacturer, Simula Automotive Safety Devices, Inc.

EMS responders realize how critical head protection is during side crashes. The Insurance Institute for Highway Safety (IIHS), a research and safety organization, states that one-third of all fatalities we see each year at crash scenes involve side-impacts. Statistics reveal that people killed in side crashes typically have a high incidence of head and neck injuries. Another IIHS study showed that 64 percent of occupants on the side of the collision and 82 percent of those seated opposite the impact side receive head injuries.

Until recently, side impact protection for occupants focused on reducing the degree of intrusion into the vehicle being struck. Reinforced door collision beams, improved door latches and padded interiors all work to cushion passengers during the impact. With the introduction of side impact airbags to the US market in Volvo's 1995 model year, the emphasis shifted to actively putting a cushion between the side of the vehicle and the occupant. Side impact airbags are specifically designed to protect the occupant's chest, abdomen, and pelvic region. Now we realize however, that even as side airbags deploy from doors or seats, the occupant's head and neck remain vulnerable to injury.

The HPS System

The new HPS tubular shaped airbag is specifically designed to protect and reduce injuries to the two body areas that are most vulnerable in side impacts, head and neck .

This author witnessed two 20 mile per hour side-impact crash test demonstrations where the forces on the head of the dummy went from being a fatal injury when no HPS was present to being a minor blow to the head of a dummy in an HPS-equipped BMW.

The main component of the new HPS system is an inflatable airbag tube.

This tube is anchored to the car structure at two points: at the front end to the bottom of the A-pillar ( bottom left of windshield window frame) and at the rear end to the roof headliner behind the B-pillar ( at the side of the roof behind the door frame).

The complete HPS airbag and the nylon straps sewn into each end of the bag is stowed inside the trim of the A-pillars and behind the headliner trim over each side window of the car. The HPS system, when 'loaded', is detectable only by the letters 'HPS' imbedded in the trim cover at the top of front A-pillars.

Located at the A-pillar end of the system is the gas generator. The canister which flows the nitrogen gas into the HPS airbag is located below the bottom of the A-pillar area inside the end of the firewall area in front of where the door hinges are located.

The HPS airbag is unlike any others that rescuers have ever encountered. The tubular bag consists of a specially designed material weaved in a pattern reminiscent of the Chinese finger toy where you put a finger in each end and pull apart.

As the toy stretches, the weave tightens around the tips of the person's finger. With the HPS bag, a similar looking weave pattern expands as the bag deploys to form an airtight elongated tube. The bag has a length of 38 inches and a diameter of five inches. Nylon web strapping is sewn to each end of the HPS bag. Occupants are not exposed to vented airbag gases because the airbag is non-venting. Its' design also represents no potential for any heat or chemical burns.

Deployment

When a sensor unit inside the passenger compartment of the BMW detects the energy of a 12-mph or greater side collision, two of the six airbags in the car deploy. BMW's door-mounted side impact airbag on the crash side will deploy. It inflates along the inner door trim area, covering an area about the size of a sheet of standard notebook paper.

While the sidie door airbag is inflating, the HPS airbag tears out of the A-post and headliner and is drawn tight across the driver and passenger front windows. It is on a diagonal, higher behind the front seat passengers, lower towards the base of the A-post.

The HPS remains firmly inflated to offer head protection from rebound forces common in side-impacts and rollovers. The airbag can actually remain inflated for hours after the collision although it will soften slightly.

The primary function of the tubular structure is to prevent the occupant's head and neck from colliding with interior vehicle components, particularly the A-pillar, the B-pillar, and the roof rail structure. In addition, the HPS tube is firm enough to serve as a structural barrier that prevents the occupant's head from striking or being propelled out of the window. It also helps keep the intruding object from entering the passenger compartment through the window. Due to its deployment across the side window, the HPS bag will prevent unrestrained occupant ejection.

Crash Scene Protocols

At a crash scene, if the front door of a '98 BMW with a deployed HPS airbag is opened, the bag will remain across the window area...it is not mounted on the door. The five inch diameter bag will remain inflated longer than any other bags in the car.

BMW also has door-mounted side-impact airbags in each front door along with the dual front bags. Any side impact door-mounted airbag that deploys will already be deflated by the time emergency responders arrive on scene. Rescue personnel however, can cut the HPS bag free by severing either the nylon strap at the dashboard/A-post area or along the headliner behind the B-pillar. The bag can also be deflated by puncturing or cutting it directly.

A BMW auto with an HPS airbag system, actually has six airbags in the car. A frontal collision can deploy one or both frontal airbags but will not deploy any of the other four bags. If only one person is in the BMW and has a headon crash, the passenger front bag will not deploy. Remember, these are 'SMART' airbags. The passenger bag will not deploy if no one is sitting in the front passenger's seat. A side collision will only deploy the door airbag and the HPS airbag on the impact side. In a crash there will always be at least one HPS airbag and one door-mounted side airbag that will not deploy. You will always have a 'loaded' airbag somewhere inside the BMW.

Responders need to accept this fact and on arrival, begin to ask themselves "OK, where are the loaded airbags this time?" A- and B-pillars can be safely cut completely through even with a loaded HPS airbag present without accidentally deploying the bag. If rescuers access the battery and take away the power properly, the capacitor for any loaded front or side door airbags will drain within one second. Normal extrication and medical protocols may be followed at that time. Rescue work near a loaded HPS gas generator, located low in the A-pillar near the hinge and firewall area, should proceed with caution. Do not crush or cut into the generator unit. A deployed generator is essentially an empty canister, of no concern to rescuers.

Summary

The inflatable tubular structure presented by BMW represents a breakthrough in vehicle safety-a new idea that not only addresses the high fatality rate from side impacts but also shows how occupants can walk away from a potentially fatal incident. BMW's television promotion of the HPS airbags sums it up best. The announcer states at the close of the commercial "Other head protection systems may be available in 12 months. Ours is available in the next .0025 seconds."