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...you witnessed. NO hook-in checker in recorded history has ever launched with a dangling carabiner. And ALL unhooked launchers - one hundred percent of them - have been one hundred percent certain they were safely connected to their gliders in the critical two second period.
The only thing we have to fear is to ever once not have the fear of launching unhooked. (I never have the first 'cause I always have the second.)
And that should also apply with respect to our buddies. On 2005/10/01 for the first (wind dummy) flight of that year's Team Challenge when Bill Priday did THIS:
06-04213
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09-05019
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10-05124
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with his carabiner dangling behind his knees there'd been SCADS of assholes who'd been concerned about whether or not he'd done an idiot hang check...
03-03107
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...in the setup area. And there was NO ONE with the slightest doubt that he was safely hooked in until his glider climbed back up without him.
http://www.youtube.com/watch?v=2mX2HNwVr9g
Hang Gliding Fail
andyh0p - 2011/04/24 - dead
03-0325 - 06-0511
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18-0919 - 21-1025
And that's all it would've taken. Just ONE PERSON not assuming that he was connected to his glider in the final seconds before his foot moved.
And as far as I can tell not ONE SINGLE INDIVIDUAL started doing, looking for, teaching, requiring hook-in checks in response to that horrifying spectacle - particularly the highly revered asshole who'd signed him off on all his ratings through his third and last. People packed up and went home, engaged in epic flame wars on the local forum, painted their carabiners orange, became really focused - and did nothing of any actual significance. Same deal with Kunio at Mingus a month shy of three years later.
You just making the declaration is a big help.