On Fri, 05 Jun 2020 07:13:58 -0700, WB wrote:

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).

Look at the belly of a Std Libelle to see this setup (s/n 110 or earlier).

There's now a UK annual inspection requirement to check that the guide
spacing is in tolerance.

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.



--
Martin | martin at
Gregorie | gregorie dot org