On Thursday, June 4, 2020 at 4:33:29 PM UTC-5, Kenz Dale wrote:
I understand that CG hooks are designed to autorelease when the angle of pull passes a certain critical angle. Is this a very reliable disconnect, or is more of an "Eh, it's nice to have but I've seen it fail too many times to trust it"?

I have never heard of a TOST CG release failing to "back release". The back "jaw" of the TOST CG hook is held closed only by light spring tension. If there is any rearward pressure on it, it has to release. The spring tension is light enough that it is easy to attach the tow ring to the hook simply by pushing the ring against the back jaw of the release. Not many ways that it can fail. A foreign body or broken part falling into the mechanism could conceivably jam it and prevent it from opening. Some of the older TOST CG releases could have a problem with the tow ring jamming sideways in the release. Gliders with those model TOST releases require installation of small metal guides to prevent misalignment of the ring. Those metal guides also act as protective skids if one forgets to extend the landing gear upon landing (one guess as to how I know this).

I think most of the "failure to release" problems for gliders launching with the CG release have not actually involve the CG release as such. Rolling over the launch cable and entangling it in the wheel have been the cause of some incidents. That is why ground launch systems MUST have some means of quickly cutting the cable.