[trackbird]

This was posted on Corner-carvers.com, I thought it was worth reposting here.

From National Staff
November 16, 2004.


It has been brought to the attention of SCCA Technical Services that the use of full-face or closed-face helmets while driving vehicles with active airbag restraint systems may result in injuries in the event of a crash that deploys the airbad. Because of the location of the steering wheel relative to the driver's position, the airbag axis is on a level with the driver's chin. In a crash with airbag deployment, contact with the chin area of a full face helmet can be so powerful "that the risk of fractures to the jaw cannot be ruled out" (Hubert Gramling, FIA Institute, FT3?AF, 18.5.1999). This applies to vehicles that may be used in Solo, RallyCross, High Performance Car Control Clinics, etc.


Therefore, it is highly recommended that full-face helmets not be used in vehicles with functional airbag systems. Potentially more restrictive language is currently being considered for 2005, which could appear in an early 2005 issue of FasTrack. If you have any questions, please contact the SCCA at 800.770.2055.


http://www.scca.com/_Filelibrary/Fi...bagAdvisory.pdf

[sgarnett]

I assume that what happens is, the airbag acts on a large area of rigid helmet. This exerts a very large force (pounds per square inch times square inches) on the helmet, which shoves it back or up hard against a relatively small area of the chin.

The airbag alone can deform around the contours of your face and distribute the pressure evenly. That doesn't mean you won't still break your glasses or maybe even your nose.

In other words, the closed helmet acts to collect and focus a large amount of energy on a small part of your face (IMG:http://www.frrax.com/rrforum/style_emoticons/default/smile.gif)

Of course, that depends to some extent on how well the helmet fits, but they are all designed to protect against impact with things like pavement and rollbars, not a giant angry amoeba.