I made a somewhat disturbing discovery at the last race, which I pass on in the hope that it might prevent someone else from having the same problem.

When I came off track at the end of the race I noticed that the strap had come undone on one side of my HANS device.  I suspect that a one-sided HANS might actually be worse than having no HANS at all, so I found this quite worrying.

Upon examining my helmet I discovered that the post on that side had somehow rotated to the wrong position.  The little tab is supposed to point toward the rear, but mine had rotated almost 180 degrees.  I have no idea how this could have happened, as the nut was still tight, but it did.  I have been using this helmet with the HANS device for two years now and I'm quite certain it was not out of position before.

One more thing to put on your checklists.