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Old June 30th 17, 12:10 AM posted to rec.aviation.soaring
Martin Gregorie[_5_]
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Default Letter to the FAA

On Thu, 29 Jun 2017 15:30:42 -0700, Waveguru wrote:

A Tost CG release is made to release with a rear load on it. Why
couldn't that release be mounted on a tow plane so that when the glider
got too high it would "back release"?

Probably because the angular difference between the rope on the ground
run and when it back-releases over the winch would be far too great to be
useful when dealing with a tug upset.

Two points:

- I don't know at what angle the cable is in relation to the glider datum
when the hook back-releases above the winch, but for sure the rope
angle during a winch launch is at least 40-45 degrees most of the time
and must increase to around 90 degrees above the winch. Don't forget
that there's bow in the cable.

- when doing release checks before the first winch launch of the day,
it can be quite difficult to pull the cable down and back under some
gliders with enough force to cause a back release. Usually this is
because the CG hook is fairly close in front of the main wheel.


Both effects are the result of the 'hook' not moving during a launch
until the pilot pulls the release. When a back release occurs its because
the rope is applying sufficient rearward force to move the guard ring
back far enough for the cable ring to fall off the end of the 'hook'.

The guard ring is on standoffs which pivot on the hook body and are held
forward by a spring. This is not very strong: when moving gliders round
the field its often easier to put the tow rope onto the CG hook by
pulling the guard ring back with a couple of fingers and slipping the
rope's ring over the rear end of the 'hook' than it is to open the canopy
and operate the release to put the rope on the nose hook.


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