[Ashir]

Originally Posted by Chethan B G

Fantastic thread! Thanks for the information!!

Does the car / engine become immobilized, after the airbags are deployed? OR if the impact is minimal in nature (only shell damage), but good enough to deploy airbags, can the car be driven to the nearest safe place / service center?

Thanks in advance!!

As far as I have read, there is no connection with deployment of Airbags and engine. The engine might immobilize upon impact with same and/or different sensors but nothing related to deployment of Airbags. Thus the car can be driven if damage permits.

[saket77]

Thanks to all of you who read this thread and a bigger thanks to those who have made up their mind that their next car will have air bags.

Also, thank you for all the kind comments and valuable information that many others have shared. That is the essence of TEAM BHP!

Originally Posted by Chethan B G

Does the car / engine become immobilized, after the airbags are deployed? OR if the impact is minimal in nature (only shell damage), but good enough to deploy airbags, can the car be driven to the nearest safe place / service center?

Dear Chethan,

As Ashir has already answered, airbags are not connected to the engine in any way. So, if the damage permits the car to be driven safely, the car will drive normally. However, prefer giving some time to the interiors of the car to clear the smoke and residual stuff which come as a result of airbag deployment. There can be temporary discomfort because of it and people with respiratory problems are more prone to discomfort.

Thanks!
Saket

[Gaur]

Great work Saket.

Just to add to it a few points.

1-- The Sensors are placed at multiple locations at the bumper and not just at the corners. for the side impact at sill and pillars.

2-- Calibrating the airbag for side impact is particularly tricky as there is very little space available for deployment in case of a side crash.
A term called as belt-line velocity plays a very important role in deciding the deployment of side airbag. Belt-line velocity is the velocity experienced at the door side intrusion beam, it should be less than 8-10 kmph (depends on vehicle), if it is higher it implies there is higher intrusion and hence less space available for the airbag to deploy.

3--The average deceleration measured by the sensors is taken as an input for triggering the airbag. i.e if one of the sensor experiences an exceptionally high pulse and others don't the airbag wont inflate if the average is low.

4-- sensor calibration is a very tricky issue, care has to be taken that it does not trigger the airbag just by hitting an pedestrian or an animal.
It is one of the reasons why average of sensor pulse is taken instead of output from a single sensor. eg a car hitting a dog at high speeds one of the sensors directly getting impacted senses a high pulse enough to trigger the airbag deployment. Hence the averaging.

5-- Earlier airbags had porus surfaces which allowed gas to escape but this caused burning of occupant face in some cases, now airbags are being designed such that the vents are located in a way to dissipate the gas away from the face of the occupant. The folding pattern are also decided such as to aid the gas dissipation.

6-- A mixture of Argon and helium is also being used to provide a relative less hot gas for inflating the airbag.

7-- A safety feature is also incorporated in some cases which allows for the airbag to automatically inflate in case of a fire in the vehicle . this is done as a precaution to prevent the airbag charge to explode due to fire.

8-- In USA FMVSS regulations require cars to be tested with belted and unbelted dummies.

9-- Generally around 12-15g of acceleration pulse is the triggering criteria, again the vehicle stiffness plays a important role in it.

[RocketRaccoon]

This was a really informative post Saket. I would just like to add what I have read on airbags. Usually driving 101 teaches us to hold the steering in a 10-2 position, many people now recommend following the 9-3 position to allow room for deployment in case of a mishap. Though this change is relatively small, it can bring a big change if the unforeseen eventually happens. You can follow this link for more information -
http://at.progressive.com/everything...ive-safe-today

[PearlJam]

Excellent thread, thanks for the detailed information!

I had a question opposite to what many of the others have asked - is it possible (and what are the chances) that the airbags deploy even without any accident, due to some malfunction? If so, that would be tragic, and would negate the unquestionable benefits of airbags.

[Thad E Ginathom]

is it possible (and what are the chances) that the airbags deploy even without any accident, due to some malfunction? If so, that would be tragic ...

It could be, if the shock caused the driver to have an accident, but I don't see how unexpected deployment would necessarily be tragic as I understand it which if of causing death or major injury.

From what I have gathered, the inflation/deflation is pretty quick, and, in a non-accident sitution, you are not going to be hurtling towards the airbags as they inflate.

Nothing is going to be perfect. I guess the manufacturers can only offer us a very very low probability that would ever happen. I'd bet their lawyers insist that they make it very, very low!

Only yesterday I was shocked by the number of recorded deaths and injuries due to burning and exploding phones. I hope subsequent posts don't bring me a similar experience with airbags.

[DriveTrain]

Renault calls their system SRP (System for Restraint and Protection) and not SRS. Does anyone know the exact differences between a SRS and SRP system, if any ?

Here are some links to SRP :
http://www.renault.co.uk/safety/inno...ct/restraints/

http://www.autoworld.com.my/ads/rena...ultsafety4.asp

[amanomics]

Very informative Saket and others.

I have a question on the deployment. How exactly the airbags pop-out? The pressure from the gases is so high that they make the steering lid pop-out?

And what about the passenger side? The dash board cover doesn't look so loose. What happens if one clips the cover off? The cover easily comes off? The airbags deploy or I can only see the airbag sitting in deflated state because the SRS did not trigger (no crash scenario).

[ajmat]

Originally Posted by amanomics

Very informative Saket and others.

I have a question on the deployment. How exactly the airbags pop-out? The pressure from the gases is so high that they make the steering lid pop-out?

And what about the passenger side? The dash board cover doesn't look so loose. What happens if one clips the cover off? The cover easily comes off? The airbags deploy or I can only see the airbag sitting in deflated state because the SRS did not trigger (no crash scenario).

There are segments in the steering wheel boss / dashboard which have a thinner edge. These edges give way under the airbags explosive pressure. This normally means a replacement of part of the dashboard or entire steering boss.

[PearlJam]

Originally Posted by Thad E Ginathom

I don't see how unexpected deployment would necessarily be tragic as I understand it which if of causing death or major injury.

If the airbags deploy without reason (especially on a highway if going at a good speed) - that itself would be the cause of death or a serious accident, due to loss of visibility, control, and surprise/shock.

I'm not in any way trying to downplay the use of airbags. They are invaluable. Rather, I'm concerned about possible malfunctions - especially if it has been known to happen frequently in the past.

Originally Posted by Thad E Ginathom

I'd bet their lawyers insist that they make it very, very low!

Well, I wouldn't bank on that! We all know how manufacturers try skimping on safety features. Add to what Mr.Bhargava said about airbags. Trusting them to always do what's good for consumers is too much to expect.

[saket77]

Originally Posted by PearlJam

If the airbags deploy without reason (especially on a highway if going at a good speed) - that itself would be the cause of death or a serious accident, due to loss of visibility, control, and surprise/shock.

The possibility of such a happening is pretty low. Should be a rarest of the rare case but it should not cause death. As stated in the opening post, the front airbags deflate pretty quickly after the action -under 1/10th of a second so that visibility is not impaired. However, overcoming the surprise shock is on the driver. Also since there is no crash in first place, so the occupants would not be forced on the airbags, hence airbags sustained injuries should not be a concern as they would be sitting far away from even deploying airbags. Subsequent loss of control may be, but that rests on the driver.

Originally Posted by PearlJam

I'm not in any way trying to downplay the use of airbags. They are invaluable. Rather, I'm concerned about possible malfunctions - especially if it has been known to happen frequently in the past.

It may malfunction like any other system like the brakes, engine, etc., but as stated, it is a rare occurrence. That should not deter us in choosing them. No two ways that they save lives in majority of cases.

Originally Posted by PearlJam

Well, I wouldn't bank on that! We all know how manufacturers try skimping on safety features. Add to what Mr.Bhargava said about airbags. Trusting them to always do what's good for consumers is too much to expect.

Makes the case even stronger for choosing a car with airbags. Manufacturers, in absence of proper safety regulations, will see the bottom-line of their company first. Sad state of affairs!

Regards,
Saket

[nikhiljaipurkar]

Originally Posted by RocketRaccoon

This was a really informative post Saket. I would just like to add what I have read on airbags. Usually driving 101 teaches us to hold the steering in a 10-2 position, many people now recommend following the 9-3 position to allow room for deployment in case of a mishap. Though this change is relatively small, it can bring a big change if the unforeseen eventually happens. You can follow this link for more information -
http://at.progressive.com/everything...ive-safe-today

Thanks for the link. I personally prefer the 9-3 position over the 10-2 one as it provides good control over the steering and at the same time allows for a more relaxed posture of the shoulders & arms.

And I dare say (I know I am baiting the 'Don't Honk' brigade, but still) honking is easier too! You see I drive on narrow hilly roads in Shimla, where man and beast share the narrow single lane roads with vehicles (trucks, buses & cars), and blind curves are the norm. Honking is a necessary evil.

[dark.knight]

Originally Posted by PearlJam

If the airbags deploy without reason (especially on a highway if going at a good speed) - that itself would be the cause of death or a serious accident, due to loss of visibility, control, and surprise/shock.

Correct, your statement says it all & it has indeed happened before. A couple of such cases have been mentioned in this forum as well (both of uninitiated airbag trigger & no airbag trigger even after a substantial impact). I cannot comment on the technicalities of both the above occurrences as there might be some info missing about the actual sequence of events. It is safe to assume though that a malfunction might happen in both ways.

The other term for airbags is Secondary Restraint System (SRS). We're not in control of how it works. This forum supports safety first and so do I & there are 2 things we can do as the first line of safety i.e seatbelts & following the rules of the road. Airbags have been tested extensively & users can be assured of an almost fail-safe assembly, but when you have so many tiny electronic modules like impact sensors, gyroscopes, accelerometers, brake pressure sensors and occupant sensors each depending on various external data, you have to understand there is an extent of mis-information that could be computed.

Interesting fact : Ford tried to offer airbags as an alternative to seatbelts as they felt people who didn't feel like 'buckling in' would still be safe. Mercedes only later gave both seatbelts & airbags in their flagship as they felt the seatbelt is essential to hold the driver in place.

[Thad E Ginathom]

Originally Posted by amanomics

I have a question on the deployment. How exactly the airbags pop-out? The pressure from the gases is so high that they make the steering lid pop-out?

And what about the passenger side? The dash board cover doesn't look so loose. What happens if one clips the cover off? The cover easily comes off? The airbags deploy or I can only see the airbag sitting in deflated state because the SRS did not trigger (no crash scenario).

I suppose (hope) it that what happens to the bits of plastic, especially the larger one on the passenger side, is designed into the system. I have wondered!

Originally Posted by PearlJam

If the airbags deploy without reason (especially on a highway if going at a good speed) - that itself would be the cause of death or a serious accident, due to loss of visibility, control, and surprise/shock.

That is a very big assumption. Possible, of course, but with Saket quoting 1/10 of a second for the whole experience, it could be on a par with a violent sneeze. I can imagine what would go through my mind, and forum rules don't allow to write it, even with blanks, of which there would be several, but I think the whole thing would be over before I finished thinking it.

About the same time as it took me to grab it when my wife put her hand in front of my face to point out something on my side of the road .

Well, I wouldn't bank on that! We all know how manufacturers try skimping on safety features. Add to what Mr.Bhargava said about airbags. Trusting them to always do what's good for consumers is too much to expect.

Well, true of course, and there are certainly instances of manufacturers absolutely denying other recurring failures --- until they have to admit them.

[Gaur]

Originally Posted by Samba

Am quoting SS-Traveller from another thread for the below Fortuner accident. As you mentioned above the sensors are generally placed behind the bumpers. From the look it seems the Fortuner has rear end some high trailor .


Attachment 1344934

Attachment 1344935

The airbag sensors work by either measuring the displacement, deceleration, pressure difference or some other variable, it is generally a combination of various factors depending upon vehicle to vehicle. More the number of sensors better the protection but higher the cost, particularly the accelerometers are pretty expensive to use when compared to displacement measuring devices.

The Fortuner in the above case appears to be a offset under-run and not a full under-run crash where the sensors located in the front end don't get impacted directly and fail to trigger the airbag.

The reason for the airbags not getting deployed could be at times intentional on the part of the designer or due to some design limitations.

Talking about the design limitation part first.

In a normal frontal crash the Airbag gets inflated before the occupant strikes the airbag and by the time impact between the airbag and occupant occurs the airbag actually starts deflating, this deflating action actually provides the cushioning effect and helps in arresting the velocity of the occupant head.



When compared to a under-run crash the advantage in regular frontal crash scenario is that the crash sensors are located much ahead of the passenger cabin (in and around the bumper region to be precise)directly in the impact zone. This provides the airbag control unit enough time to analyse the input from the sensors and trigger the airbags, also there is sufficient time for the airbags to inflate as well.

Whereas in case of a pure under-run crash the sensors in the front end will miss direct impact hence wont be able to measure significant displacements.

However if the vehicle is fitted with Acceleration sensors along with displacement sensors it will still be able to sense the crash as deceleration of the vehicle will be a global phenomenon and irrespective of the sensor location it will provide a input sufficient for the sensor to notice it.
However it could be possible that due to the small area of contact in the case of an under-run crash the pulse generated may not be large enough to trigger the airbag.

Originally Posted by Samba

In another example i found airbags has not deployed in this Etios crash.
This was put down by Amalji, as what Toyota showroom told him.



Attachment 1344936

In both the cases it looks like the airbag sensors were not triggered properly.

Now my question is accidents can happen from any angle. I remember a case where an i20 hit a pole (Lamp post) and airbags were not deployed due to the very same reason. Same should occur in case of a side ways crash where the front bumper is not involved. So my basic query is why the manufacturers do not increase the number of sensors and put them in few more locations like the A pillar or some place which is higher than the front bumper ? Am just asking because of the pure lack of my knowledge. Is this because it will increase the car cost or there are any other reasons?

Now talking about the intentional part for not allowing the airbags to inflate.

These could be the main reasons as per my knowledge when the designer may decide not to allow the airbags to deploy in case of an under-run

1-- If the designer feels it is not important to deploy the airbag as it may not help in reducing the injury to the occupant, he may decide against the airbag getting deployed.



(sorry for the poor image quality)
In the above case we can see a under-run crash with airbags not getting deployed, if we have a close look at the driver we will notice that he is still very much in his original driving position in spite the entire bonnet region sliding under the truck and even after the deformation of roof, A-pillar and door has started.

In this case the driver will suffer injuries by the intruding truck rear-end members and not by hitting the steering or other parts of his vehicle.
Now even if the airbags deploy the occupants will not come in contact with them, hence the designer in such case may decide against deploying the airbags.

2--In the second case the designer feels that deployment of airbag may harm the occupant more than protecting it. Hence he may decide against deployment of airbag in this case.

As i mentioned earlier, the occupants come in contact with the airbag in the deflation phase and hence the cushioning effect. As it is could be seen from the above image that the front end appears to have survived the impact without significant damage, this would have probably not generated a significant output from the sensors due to which the airbag doesn't get deployed.

Now imagine a scenario where we have sensors mounted at the A-pillar (as many members wanted to know why no sensors in the a-pillar and higher locations) these sensors will in this case definitely sense an impact and will generate a output high enough to trigger the airbag, but the problem starts here.

As the A-pillar sensors are located very close to the occupant (compared to frontal impact sensors in bumper) the time available for the control unit to evaluate the pulse from them and trigger the airbag will very less, the occupant in this case will come in contact with the airbag in the inflation stage and not during deflation stage (when compared with regular frontal impact).

Now imagine getting hit by a inflating airbag at about about 200-300 kmph, these are literally neck-breaking speeds. The forward movement of the occupants due to vehicle crash and then the impact in opposite direction by the airbag will cause severe trauma to the occupants. in such case the designer may decide against the deployment of the airbag.

The key to protect the occupants in any case is to sense the impact as early as possible.

Originally Posted by Ashir

The question is genuine. It all depends on the manufacturer where he places the sensors and how many they provide. Each assembly of airbags involves some serious engineering with estimation of motion of occupant in car during collision.

Now sensors could be mounted to A pillars and doors for detecting frontal-side or side collisions. During side collision, on rough estimation, the occupants would bang on to their side opposite to the direction of impact (inertia stuff). But if manufactures decide to omit curtain airbags (side) with sole reason of reducing costs, there won't be any use of deploying front airbags in most of the side collisions. Why omit such a safe feature ? Simply because side collisions are much less likely to happen than frontal collision.

Regarding vertical height of positioning of sensors, one might think what would be the need of height sensors since bumpers would be the first one to crash! Lets bring truck into the accident. What if one crashes into a truck from side or rear ? Yes, it would be a direct hit to A pillars for most of the cars, without touching bumper. So here comes the need of positioning sensors at height too!

@Ashir Hope i have been able to answer you doubt regarding positioning of sensors at height.

Nowadays some high end cars have pressure sensors built inside the door which sense pressure change in case of side impact and create a pulse for the control unit.
Another thing regarding Side impact, the side airbags operate on the same principles as the front airbags but they deflate very slowly when compared to frontal airbags, this is to provide continuous protection in case of a rollover.