i was astonished to find the vehicle stopping all of a sudden from a speed of about 20 km/h with a loud noise and fumes with both the airbags deployed. To my utter surprise i discovered a manhole cover probably flipped and hit the vehicle from below. No other damage except a windshield crack.enquired with the service centre, asking to cough out around 100000. insurance cover only 50%.

Does this happen usually?

Is this the best possible option?

What if it happens again with such a minimal impact. Should i cough out 100000 every time?

Can the airbags be removed without replacement?

A sudden stop from 20kmh will set the airbags off in any car, since the crash sensor will think you have hit something. 20kmh is not a trivial speed at all, and the car is completely unaware of its surrounding. The crash sensor is mounted on the central tunnel under the centre console where it is protected, there are no external sensors (the same for any car brand).

http://www.nhtsa.gov/people/injury/airbags/airbags03/page3.html

The airbags usually deploy at 8mph (EU/US Standard) upwards, at 20kmh you were doing 12mph.

The airbag deployment is not dependent on speed. The airbags deploy at a -G EQUIVALENT to hitting a fixed, solid barrier at 8mph. You can hit an object at 25mph without deployment, if that object breaks, moves or deforms.

Mannyo is right. This is a significant impact and I would be surprised if there is no damage to the underside of the car.

Yes, I would replace the airbags. It is unlikely that you can reset the airbag controller, so this needs to be replaced too. I'm not sure if you have seatbelt pre-tensioners of load-limiters on this car. These also need to checked. People do die in this kind of accident.

A sudden stop from 20kmh will set the airbags off in any car, since the crash sensor will think you have hit something. 20kmh is not a trivial speed at all, and the car is completely unaware of its surrounding. The crash sensor is mounted on the central tunnel under the centre console where it is protected, there are no external sensors (the same for any car brand).

http://www.nhtsa.gov/people/injury/airbags/airbags03/page3.html

The airbags usually deploy at 8mph (EU/US Standard) upwards, at 20kmh you were doing 12mph.

There are several crash sensors around the car including the one in the control unit. On the Fabia two are also mounted on the floor pan under the front seats bolted to the cross member.

Under seat ones mybe side inpact ones

Yes they are, on Octavia 2 and Superb 2 they are in the doors on the front (pressure sensors) and to the side of the seats at the rear.