This videographer was filming FS scrambles when, on exit, one of the jumpers (the inside center in the light blue jumpsuit) failed to secure their chinstrap and lost their helmet! The jumper also lost the ability to see the group due to the 120 mph wind in his eyes, and ended up sinking out low on the group. Unfortunately, unable to see his altimeter — and evidently jumping without an audible backup — he deployed his main based on when he "thought" he was at the proper altitude. It turns out he was still above 6,000 feet and the cameraman, who didn't see the canopy coming at him, clipped the top of the jumper's canopy. The cameraman was worried about his legs, but he was fine and was able to keep jumping. The jumper who lost their helmet landed their main despite notable damage to the topskin.
This whole incident was the result of a jumper's failure to secure the chin strap on his helmet. While we love to have big wordy explanations that make us feel smart, it's really just that simple. Had this jumper checked to make sure the helmet was secure prior to exiting, this whole incident wouldn't have happened.
While in the the plane, everyone thinks about — or at least should be thinking about! — checking their chest strap routing, making sure their pilot chute is properly in their BOC, getting a pin check, etc. The helmet chin strap is an item that a lot of us just don't consider from a safety perspective... but it should be. This video does an excellent job demonstrating why, during your gear checks, you should take a second to check anything which — if lost — could make your jump dangerous. This seems like a very basic point, but we've been on jumps where a jumper made sure to tie their shoes real tight... and then lost their altimeter because they didn't make sure it was fastened securely.
Obviously an audible altimeter wasn't helpful in this case since the jumper lost his helmet. However, it's worth noting that some belly jumpers think that audible altimeters are a waste of money that freeflyers buy because they're bad at maintaining altitude awareness. Well, this jump shows a perfect example of why having an audible as a backup makes sense and is worth the investment. You never know when your primary write-mounted alti is going to break, you never know when someone is going to rip it off your wrist, and you never know when you're going to lose the ability to read it. At the end of the day, skydiving is an inherently dangerous activity made safe because we try to find ways to mitigate every possible danger. When you think about it that way, a backup, which allows you to know your altitude through a different form of sensory input makes a lot of sense... right!?