Airbags didn't deploy

[Twojjs]

This concerns a Smart Passion Cabriolet that was involved in a wreck. The car was purchased in August and was involved in an accident on November 2008.

According to the driver, she was struck directly behind her driver's door after someone ran a red light at an intersection.

Her Smart went airborne, flying into the air, flipping over and rolling down (some witnesses claim 5 times) the street and after traveling some 40 foot, landed right side up on all four tires like a cat.

She was wearing a seat belt and spent 3 days in the hospital, badly bruised, but fortunately not having any broken bones.

She believes very strongly that the cars safety cell saved her from certain death.

The car actually looks pretty good under the circumstances but, was eventually totaled by her insurance company.

She's wondering why her airbags didn't deployed, possibly minimizing her injuries?

Perhaps someone with airbag expertise, past experience or a similar encounter could explain if this is normal or not?

Thanks

[Smartfor2guy]

Airbag sensors are in the front bumper area not the side or the rear. They will only deploy in a front end collision

[andrewd]

if the airbags didnt goo off it's because they didnt need to!

the front airbags arent going to go off in a side impact.... well only if you own a hummer or something mate of cheap chinese plasticine!!

the car looks in very good shape considering the accident you describe.

[SuperGeek]

Good question... glad to hear she's relatively ok. My best guess, without claim to expertise, is that the air bags are programmed to deploy only when a certain amount of force is detected coming from directions which would benefit from the airbag. Since they use explosives to inflate, there's a certain amount of risk and they only inflate if they're really needed. That said, there is a known issue reported on the forums with seat air bags having a bad wire or loose connection, triggering a SRS warning light. My thought is if it were a bad wire, you'd see the warning light as part of the self diagnostics. I would be curious to know what exactly triggers those side air bags if not a side collision and flip. Maybe the impact wasn't hard enough (30MPH?) to trigger. Front air bags should only deploy in a frontal crash, if I'm correct.

Naturally, anyone with real expertise is welcome to supplement my thoughts based on internet and couch research.

[NCC1701]

What sets of the side impact air bags, if not a side impact??? The bags in the seats.

[NCC1701]

Originally Posted by SuperGeek

Maybe the impact wasn't hard enough (30MPH?) to trigger.
Naturally, anyone with real expertise is welcome to supplement my thoughts based on internet and couch research.

Sent the car airborne, and rolling at 30MPH? I have a hard time with that. Anyway, I thought air bags deployed at lower speeds than 30 MPH. I have been wrong before.
I'm eager for someone else to pitch in.

[mdfortwoguy]

Airbags deploy based off of a principle of deceleration.

Essentially - multiple stages of sensors have to be triggered by a rapid enough deceleration to deploy the bags. The sensors have a relatively narrow field of observation in which directions they will trigger.

In this case - the forces would have been more of a spinning force - and by the time it rolled, they would not have been in a direction where the bags would have helped. This may have been on the verge of deploying the driver's side airbag - but the forces would have had to have been closer to the front of the car.

She should be glad... you want no part of an airbag going off if you don't need it... besides the pain/noise/smell, they destroy the interior panels behind which they are mounted.

[SmartIdea]

The car does look in good shape considering the description of what happened to it.

It's good to hear that the owner although hospitalized was not seriously injured.


James.

[Periokid]

Originally Posted by Smartfor2guy

Airbag sensors are in the front bumper area not the side or the rear. They will only deploy in a front end collision

What about the side airbags?

[RedDogInCan]

Originally Posted by mdfortwoguy

Airbags deploy based off of a principle of deceleration.

Acceleration and deceleration is the same thing, its just a matter of the frame of reference.

Side airbags do deploy in side impacts as shown by the crash test videos. As the driver did not suffer serious injuries, it would be safe to assume that the deployment of the airbags was not warranted. In any case, airbags do not protect from rollovers because they inflate and deflate almost instantaneously.

Given that a smart is 20.3 feet in diameter, rolling 5 times within 40 feet would be a pretty impressive feat (I think the witness might have been mistaken)

Originally Posted by mdfortwoguy

She should be glad... you want no part of an airbag going off if you don't need it... besides the pain/noise/smell, they destroy the interior panels behind which they are mounted.

I think damage to the interior panels is a minor consideration in this case.