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Old 1st May 2008, 13:33   #1
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Default Air Bag Deployment ? What are the required conditions?

I have posted a related post a few days back, but never got any replies from anyone, hence initiating a new thread on this topic.

I think this is interesting, when/how the airbags get deployed ? As far as I know, there is one or more sensors, under the bumper, radiator grills , A Pillar etc which detect rapid de-acceleration and get activated in case of an impact. But off late I have seen few cars where the speed was not much, in one case the car got scrapped from the side and no frontal collision happened, but still the Airbags were deployed. I tried to look for any damage to interiors of the car including the dash, windscreen, A Pillars etc. but they seemed in perfectly OK condition.

Is this on the expected lines? Somehow I had the impression that the airbags get deployed on impact at a high speed (>80 kmph), is that correct? Some of the sources I found on googling mention that even a frontal collision at 20 kmph will cause the airbags to deploy, if it does...what is the use/need or justification ?

I don't think anyone is going to get hurt (Physically) in a collision at 20 kmph? Ofcourse financial hit will be there since the replacements will cost >50k and insurance won't cover 100% anyway.

I think some of these Qs may appear silly to the experts on board but it will be great if they share their opinion, experiences.
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Old 2nd May 2008, 14:02   #2
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No replies even after 43 views?
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Old 2nd May 2008, 14:48   #3
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Air bags do not get deployed in case of rear collision, narrow front collision (car hits a street lamp) etc. If the air bags get deployed on such occasions, then there is some problem in the sensors etc. However, air bags do get deployed even when car is going down a slope and hits the ground or gets into a deep pit. In such case there might not be any damage to the A pillar etc. Some of the scenarios you mention do not warrant the deployment of airbags. Airbags should definitely not be deployed under 20 km, but it really depends on the impact of the collision. Your car might be going at 20 km, but some vehicle might hit you at 100 km!!!
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Old 2nd May 2008, 14:52   #4
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Quote:
Originally Posted by Shankyz View Post
even a frontal collision at 20 kmph will cause the airbags to deploy.
I dont think airbags are meant for that..... I beleive if you all strapped up with your seat beats.. a frontal collision of 20kmph should be taken care just by the seat belts.

Airbags are defintely meant for much higher speeds.
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Old 2nd May 2008, 15:12   #5
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Originally Posted by leadf00t View Post
I dont think airbags are meant for that..... I beleive if you all strapped up with your seat beats.. a frontal collision of 20kmph should be taken care just by the seat belts.

Airbags are defintely meant for much higher speeds.
Thanks for replying, I know that already and was surprised to see the airbags deployed while there was not much damage (visible), asked the owner who was standing nearby (Perfectly alright, with not a hint of injury anywhere). This guy says, he was going at 40ish and hit another car at the crossing. the other car was a Sumo, which got hit on the side, and there was just a small dent on the side door. Nothing else... look below for the damage to SX4
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Old 3rd May 2008, 00:15   #6
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Good thread Shankyz. There are very logical and solid answers to all your questions :

Quote:
Originally Posted by Shankyz View Post
I don't think anyone is going to get hurt (Physically) in a collision at 20 kmph?
Firstly, the car manufacturer is not willing to take any chances, even if only 0.001% of people really needed an airbag to help them at a 20km/h collision they will design it to deploy in that situation. If they dont, theres a possibility for millions of dollars lost in law suits and bad publicity.

Secondly, your car might be going at 20km/h, but a bus might be coming at you at 50km/h on the wrong side of the road. The combined collision speed is much higher than 20km/h!

Thirdly, dont underestimate the damage that can be caused by a very sudden stop from 20km/h.

Quote:
Originally Posted by Shankyz View Post
I had the impression that the airbags get deployed on impact at a high speed (>80 kmph), is that correct? Some of the sources I found on googling mention that even a frontal collision at 20 kmph will cause the airbags to deploy, if it does...what is the use/need or justification ?
The airbags deployment doesnt really have much to do with speed. Maybe it only activates after a certain speed (10-20km/h?) but the DEPLOYMENT happens purely due to the rate of DECELERATION that the sensors detect.
- If you drive into a pile of sponge at 100km/h, the airbags wont deploy since the deceleration will be at a fairly low rate.
- If you drive into a bunch of bushes at 30km/h it might not generate enough sudden deceleration for the airbags to deploy
- If you drive into a solid wall at 15km/h the airbags might deploy!

See the triggering conditions here for more info:
Air bag - Wikipedia, the free encyclopedia

cya
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Old 3rd May 2008, 00:18   #7
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Are airbags covered 100 % by insurance ?
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Old 3rd May 2008, 00:29   #8
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Quote:
Originally Posted by Shankyz View Post
Thanks for replying, I know that already and was surprised to see the airbags deployed while there was not much damage (visible), asked the owner who was standing nearby (Perfectly alright, with not a hint of injury anywhere). This guy says, he was going at 40ish and hit another car at the crossing. the other car was a Sumo, which got hit on the side, and there was just a small dent on the side door. Nothing else... look below for the damage to SX4
well i really wont say that the damage on a SX4 is from a 20km/h collision..... i have seen accidents on the mumbai bangalore highway(after the expressway gets over on the katraj bypass ) where cars doing close to 80 rear ending Call centre sumos and still sustaining much lesser damage...

Well I personally feel in accidents, drivers tend to quotes the speeds around 20km/h less than they were actually doing. just a way to be safe or keep the blame less on their heads.

Well if you ask me the damage to the SX4 is "big"

@rehaan great explaination.... Thanks... Its your knowledge because of which you guys wear the moderator's cap
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Old 3rd May 2008, 12:30   #9
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In this thread i would like to post a question:

If your car flips around and the roof gets damaged and you are not wearing a seat belt --- will the air bags open or not?
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Old 3rd May 2008, 20:02   #10
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Quote:
Originally Posted by adityamunshi View Post
Are airbags covered 100 % by insurance ?
50%, insurance companies treat air bags as plastic ..thanks to IRDA

I wonder what is the justification for treating airbags as plastic?

And why 50% depreciation starting from day1 for plastic parts?

Does it mean that a brand new bumper is equivalent to a 2/3/4 yr old bumper and 50% depreciation applies in both cases ?

What is the logic of defining different categories and assigning different depreciation % to them? In my opinion, the depreciation % should be directly related to the age of the vehicle irrespective of whether is's plastic, metal, glass or whatever.

Thanks Rehaan,

I understand and agree with the impact due to a collision being higher in case the other vehicle/object is at a faster pace, I was scared and worried after seeing few cars with the airbags deployed, especially the one which had no frontal damage but was scraped very badly on the side (Driver side I think).

As long as the airbags deploy when there is a real chance of injury, I'm happy with it but can't imagine the airbags getting deployed if I hit a rick @20kmph or a side collision @20-30 kmph in traffic. That'd be totally unexpected and a expense I'd not like to incur.

Last edited by Shankyz : 3rd May 2008 at 20:07.
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Old 3rd May 2008, 20:39   #11
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Rather Than Speed, Airbags work on Principal of Force Applied per unit area.


Regarding Airbag deployment, car is designed to take of its passengers.

Take cases of Old age People Driving or Pregant Ladies, The impact of crash at 20kmph would set game for them.
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Old 15th May 2012, 16:40   #12
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Default Re: Air Bag Deployment ? What are the required conditions?

Hyundai car probed after air bag cuts owner's ear!

Quote:
The US National Highway Traffic Safety Administration said on Monday on its website that it's investigating to see if the problem will recur in about 123,000 Elantras from the 2012 model year.
In a complaint filed with the agency, the Elantra owner said the driver's side curtain air bag inflated in a crash on April 7, and a metal bracket came with it, slicing the owner's ear. The owner gave the agency photos showing a metal component sticking out from the car above the driver's seat.

Hyundai car probed after air bag cuts owner's ear - The Times of India
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Old 15th May 2012, 18:34   #13
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Default Re: Air Bag Deployment ? What are the required conditions?

Let us get two things straight:

1. Airbags are provided to protect the OCCUPANTS, not the vehicle itself! So the extent of damage on the vehicle need not explain whether or not the airbags should have deployed: it is the extend of damage that WOULD HAVE occurred to the occupants that is taken into account.

2. There is NO MINIMUM SPEED for the deployment of airbags: If we watch Die-Hard 4, the kid in the movie hit a BMW 5 in the parking lot with a baseball bat (in ignition on condition), and the airbags deploy!

So now that we are clear with these two points, let us move on to some more things:

The SRS control units (ECUs) are "taught" various crash patterns that have been recorded throughout history, as studied by forensic teams sent by the airbag unit manufacturers (For eg: Autoliv, Bosch etc.) to study actual crashes. (All SRS ECUs store crash information, similar to the black-box in an aircraft. This information is collected and accumulated by the forensic team).

In addition to this, mock accidents in crash test labs (with occupant dummies) are also studied. These crash test dummies are fitted with sensors that study the impact forces that occur on occupants in the event of these accidents. This would be generating a characteristic curve of impact force vs time in milliseconds and deceleration vs time in milliseconds. All these impact force patterns are fed into the SRS ECUs, which would then be on the look-out of such crash patterns with the vehicle running in real life.

The "impact sensors" fitted on different positions of the vehicle are "accelerometers": they monitor the DECELERATION of the vehicle at all times, as long as the ignition is in on condition. Deceleration refers to the "rate of reduction in speed" of the car, and this is of primary concern to the safety of the occupants. For if the car decelerates rapidly, that is, its speed reduces too rapidly, the driver and passengers would (with their inertia or tendency to continue in their state of motion) still continue to move forward at the initial speed of the vehicle, while the car has actually slowed down, or stopped moving. This would throw out the occupants towards the dashboard/steering wheel, thereby injuring them.

So, in short, even a small dent on the vehicle could be fatal to the occupants if that impact has caused the vehicle to decelerate too fast.

Hope that this has cleared some doubts regarding the science of airbag deployment. Or have I managed to further pile on to all this confusion?
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Old 15th May 2012, 19:26   #14
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Default Re: Air Bag Deployment ? What are the required conditions?

Ah.. that's scary. I was always afraid of airbags since I watched airbag deployment causing the driver's death in one of those "Final Destination" movies :(. Well, but those hollywood movies highlight the extreme situations. In reality, I believe the cost by airbag inflation would be way cheaper than the cost occur to you otherwise (at hospital). Also, I heard from someone that the passenger's airbag would be deployed only if the seatbelt is fastened. Any ideas?
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Old 16th May 2012, 16:05   #15
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Default Re: Air Bag Deployment ? What are the required conditions?

Quote:
Originally Posted by rajni View Post
Also, I heard from someone that the passenger's airbag would be deployed only if the seatbelt is fastened. Any ideas?
that depends upon the manufacturer.
in most modern cars (in North America) - there is an indicator on dashboard to show the status of passanger airbag (activated, or deactivated). if no one is sitting on the passanger seat, the airbag remains in OFF mode; if you put a weight (let us say 20 Kg) on the passanger seat, it will prompt for seat belt and would turn on the airbag when seat belt is buckled on. all this is achieved by a sensor called
Passanger Presence Detection (PPD).
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