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Old 27th May 2013, 14:29   #16
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by vikram_d View Post
... It just sensed high rate of deceleration and then an impact and it did what it was programmed to do. Deploy air bags.
Quote:
Originally Posted by flipsyde View Post
... The bumpers in most cars today are very flexible so there is a good chance the bumper deformed quite a bit hence activating the sensors before returning back to normal. ...
Absolutely correct, @vikram_d. Deceleration and Airbags are a bit of a non-intuitive subject. As you said, it is the rapid deceleration (profile) that caused the Airbag to trigger. As @supertinu said, it was a large dog, which would have sufficient mass to have caused the Airbag sensor(s) to react. The sensors sense Acceleration (-ive for Airbags) only, and not the distance the sensor travels or magnitude of deformation.

However, the point of impact (sort of dead center on the bumper, near where the bumper mounts are there) and the relatively small size of the dog (as compared to the bumper) would have minimized bumper distortion, as a majority of the force would have been directed to the metal nose are through the bumper mounts.

Commiserations, @supertinu, that would have been a nerve-wracking experience. By the grace of God you have come out of a rather tricky situation.

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Originally Posted by supertinu View Post
... Also the passenger seat only had few papers, a phone and a wallet on it and I am sure that wouldn't classify as enough weight to trigger false alarm in the system.
That was no false alarm - it is meant to work like that. The Passenger Airbag would have fired since the switch that indicates "No passenger" would have been in Off state (you need to switch it On if there is no passenger).

The switch is located somewhere convenient just inside the door, usually near the dash. Most people actually are unaware of this, till they are putting a child seat rear facing on the front seat. In that case, you are supposed to turn it On to prevent that Airbag from firing (will injure the child badly).
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Old 27th May 2013, 14:52   #17
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by DerAlte View Post

That was no false alarm - it is meant to work like that. The Passenger Airbag would have fired since the switch that indicates "No passenger" would have been in Off state (you need to switch it On if there is no passenger).

The switch is located somewhere convenient just inside the door, usually near the dash. Most people actually are unaware of this, till they are putting a child seat rear facing on the front seat. In that case, you are supposed to turn it On to prevent that Airbag from firing (will injure the child badly).
I have a point to make here.

I know that the inputs to decide on deployment of passenger airbag are as follows:
- Passenger Airbag OFF switch (PADS/ POS)
- Passenger occupancy status
- Passenger classification status
- Seat belt status of passenger
- Vehicle speed above the lower threshold

Hence, even if the switch was disabled allowing airbag deployment, the seat belt status should be buckled for a correct deployment. I doubt if this was the case and hence I suspect the deployment is a concern in this scenario.

The seat belt status is recorded in the black box for the exact reason. It helps decide if the airbag deployment/ no deployment was correct in the particular scenario.
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Old 27th May 2013, 15:28   #18
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by MotoNanu View Post
I have a point to make here.

I know that the inputs to decide on deployment of passenger airbag are as follows:
- Passenger Airbag OFF switch (PADS/ POS)
- Passenger occupancy status
- Passenger classification status
- Seat belt status of passenger
- Vehicle speed above the lower threshold

Hence, even if the switch was disabled allowing airbag deployment, the seat belt status should be buckled for a correct deployment. I doubt if this was the case and hence I suspect the deployment is a concern in this scenario.

The seat belt status is recorded in the black box for the exact reason. It helps decide if the airbag deployment/ no deployment was correct in the particular scenario.
Not all cars take the seat belt status for airbag deployment. For example, I know for sure in the Swift, the passenger side airbag will deploy irrespective of whether the passenger side belt is buckled or not. The Swift does not have any switch to over ride the deployment. So in this case, passenger or no passenger, buckled or not buckled the passenger side airbag will deploy.

The seat belt and passenger being present criteria are not taken into account on all cars.

In my Mondeo, the passenger seat has a weight sensor. If I remember correctly that sensor is calibrated at 40kgs. So in this car the passenger side airbag will deploy only if there is a passenger on the seat weighing more than 40kgs and he is buckled in. If the passenger is present and not buckled in the airbag will not deploy as this kind of deployment will probably kill the passenger.
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Old 27th May 2013, 15:44   #19
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by vikram_d View Post
The seat belt and passenger being present criteria are not taken into account on all cars.
Thanks Vikram! That sums it all I guess! But then I would ask the car owners to specifically check and take precautions depending on what their car has to offer.

I have seen so many people with kids on the front passenger seat. A deployment can seriously injure the kids and prove fatal. Even if a child seat is used, there is no way to disable airbag

I was under the impression that if you have airbags equipped in the car, then it implicitly means the presence of a PADS/ POS allowing the deactivation of deployment (child seat/ pregnant lady/ other physical constraints of the occupants!)

A request to mods: Can something be done to address such points in the official review of the cars? As pointed, in the Swift review can it be highlighted about the absence of a PADS/ POS and the subsequent precautions for a owner?
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Old 27th May 2013, 18:43   #20
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Quote:
Originally Posted by mpksuhas View Post
I guess the golden rule in India is to keep the speed limited to sub 90 KMPH range always no matter how inviting the highway looks.
though, sometimes it's hard not yield to "how inviting the highway looks"

Quote:
Originally Posted by supertinu View Post
my main point was that I dont want to spend 1lac+ in repairs just cause I hit a dog on the road and air bags deployed.
I'm sure the Insurance would cover repair costs. Correct me if I am wrong.

Last edited by Eddy : 27th May 2013 at 20:13. Reason: Please use the edit / multiquote option instead of posting back to back posts within 30 mins on the same thread. Thanks.
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Old 27th May 2013, 22:24   #21
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Quote:
Originally Posted by MotoNanu View Post
... A request to mods: ... PADS/ POS ...
Good point.

What is PADS/POS BTW?
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Old 27th May 2013, 22:26   #22
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by MotoNanu View Post
Even if a child seat is used, there is no way to disable airbag
Some cars do provide the option to turn off the passenger airbag - for instance I can do that in my Skoda Yeti.
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Old 27th May 2013, 22:38   #23
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by DerAlte View Post
Good point.

What is PADS/POS BTW?
PADS: Passenger Airbag Deactivation Switch
POS: Passenger airbag OFF Switch

Different OEMs use different acronym for the same.

Quote:
Originally Posted by xoom View Post
Some cars do provide the option to turn off the passenger airbag - for instance I can do that in my Skoda Yeti.
I think you did not get the context. I know there is the option to disable passenger airbag and I personally believe it MUST be provided if airbags are equipped in the car. I was surprised to know that Swift has airbags but does not has a option to disable! This can be fatal in the case of passenger being a child/ pregnant lady.

If you have disabled the passenger airbag, the dashboard shall clearly indicate the same by turning on the passenger airbag deactivation indicator. It must be similar to the check engine/ seat belt not buckled indicator on the dash. I have never seen it, but this is the way the commands are issued from the Airbag Control Unit.
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Old 27th May 2013, 23:06   #24
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by DerAlte View Post
As @supertinu said, it was a large dog, which would have sufficient mass to have caused the Airbag sensor(s) to react. The sensors sense Acceleration (-ive for Airbags) only, and not the distance the sensor travels or magnitude of deformation.

Commiserations, @supertinu, that would have been a nerve-wracking experience. By the grace of God you have come out of a rather tricky situation.

That was no false alarm - it is meant to work like that. The Passenger Airbag would have fired since the switch that indicates "No passenger" would have been in Off state (you need to switch it On if there is no passenger).
I guess since there was no damage on the car's exterior I am still a bit perplexed as to why airbags deployed. I do understand how sensors work hence think it would be a case of over sensitive calibration.

You are right, the car had a manual switch to disable the driver side airbag. There were no sensors associated with seat or belt.

Quote:
Originally Posted by MotoNanu View Post
Thanks Vikram! That sums it all I guess! But then I would ask the car owners to specifically check and take precautions depending on what their car has to offer.
You are right Moto. Even in my Figo there is no way to disable the driver side airbag. And I also know for certain that there is no sensing in the seat or with the belt. So having a child on the front is absolutely forbidden. I had specifically verified this with the dealer while purchasing the car.

Quote:
Originally Posted by RSUDARSANAN View Post
I'm sure the Insurance would cover repair costs. Correct me if I am wrong.
Ohh yes the insurance will cover but my point is that would it be worth all the effort for hitting a dog and also possibly putting people inside the car in danger due to the airbag deployment. Something that was initially meant to provide safety.
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Old 28th May 2013, 10:03   #25
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Long back in Fludic Verna review thread I had seen comments that front passenger airbag deactivation switch is not present, remember some forum members commenting that their sedans has the same (I guess Vento, not sure). As far as I know the deactivation switch is for preventing deployment if passenger seat is not occupied and thus avoiding additional expense.
Seating kids in front passenger seats is illegal in European countries, I guess the age limit is 12 years for the same.
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Old 28th May 2013, 10:06   #26
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by supertinu View Post

You are right Moto. Even in my Figo there is no way to disable the driver side airbag. And I also know for certain that there is no sensing in the seat or with the belt. So having a child on the front is absolutely forbidden. I had specifically verified this with the dealer while purchasing the car.
Supertinu, till date I have never come across an option to disable DRIVER side airbag! Only the passenger side airbag can be deactivated. I am talking about the standard fitment from the OEM.

Though it is always possible to get the deactivation switch installed from authorized centers for driver side too. For this the driver should fall under some category where the risk of deployment exceeds the risk of non-deployment. Also, the permission from legal body (NHTSA/ Euro NCAP) has to be obtained.

Now am interested to know if such a option exists in India!
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Old 28th May 2013, 10:51   #27
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Additional information i would like to add for discussion.

d^2S / dt^2 = Acceleration (F=ma) so Acceleration is nothing but force
dS/dt = Delta Velocity, nothing but how much it has decelerated
S = displacement, Nothing but how much the occupant has moved due to this force.

Adding a picture to show why the bag should not have deployed when hit by a dog / deer or anything which does not cause enough deformation.

Name:  Crash_forces_deformation.jpg
Views: 1131
Size:  33.8 KB

As you see, the dog has really high force or impact but for very short duration (like clapping hands)
But crash has progressive forces that accumulate and deform the structure

Last edited by groom : 28th May 2013 at 10:53. Reason: value add
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Old 28th May 2013, 11:13   #28
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by supertinu View Post
... I do understand how sensors work hence think it would be a case of over sensitive calibration. ...
LOL no, Airbag units are calibrated on a per model basis (at vendors' test facilities; production units are not calibrated individually at car manufacturers' location), and your case is not an issue of calibration.

In your case, it was just a coincidence of a certain mass deflecting the sensor, with a peak movement of maybe 2mm, but with an acceleration that falls in the trigger region of the deceleration profile. Not sensible to do it with a live airbag system, but your accident can be easily replicated by a judicious blow of a hammer on the bumper mount.

Quote:
Originally Posted by groom View Post
... the bag should not have deployed when hit by a dog / deer or anything which does not cause enough deformation. ...
While your logic is technically plausible, you should understand that the Airbag activation is unrelated to Force or Deformation. The objective is protection of the driver and passenger(s) and prevention of head injuries, and that is unrelated with the (current or future) state of the car at the moment the decision is taken to fire the airbag. The primary decision
* depends only on deceleration profile
* is taken well before any deformation can happen
* is meant to happen before the driver's head & torso travels any significant distance (act at the same time that seat-belt pre-tensioner, if present, pulls back the belt)

Last edited by DerAlte : 28th May 2013 at 11:28.
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Old 28th May 2013, 11:35   #29
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Supertinu, the airbag sensor on my civic is located in the bonnet. Where is it located on your Mazda3?

On a lighter note, please check out this video about airbag deployment. You will definitely feel better


Last edited by sharc_biker : 28th May 2013 at 11:44.
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Old 28th May 2013, 11:47   #30
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Quote:
Originally Posted by supertinu View Post
Will like to hear inputs from folks on the forum.
Read through this link. It may help you with some answers:
http://www.raa.com.au/page.aspx?TerID=299

I am happy that this thread is on why the airbags got deployed, rather than the opposite.

Last edited by vb-san : 28th May 2013 at 11:48. Reason: quote added
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