Tost release failure

I've seen a few fail to release. All of them were either the result of
using incorrect (homemade, worn, deformed, etc.) rings (see Tost's website,
which has considerable documentation on this), lack of maintenance
(corrosion related to pee tubes, extremely wet fields, and dirt jamming the
moving parts) and even illegal maintenance (involving readjusting the
overcenter to compensate for beak wear, the owner won't be doing that
again!). Also seen a few broken springs under 2000 launches, but these were
due to operators having a different checklist, using the release 6 times
per flight, and only 10.000 actuations are allowed.

Tost failures other than these are pretty rare, and should be brought to
the attention of the manufacturer.


At 14:18 20 August 2012, Bill D wrote:
For the first time in my life I heard a 1st person story of a release
failu=
re. =20
The story follows:
=20
The glider, an ASK-21, was jerked forward by the tug so the front wheel
rol=
led over the rope at the start of an aero tow. The slack was then taken
ou=
t and the tow was launched without inspecting the hook and release. The
wo=
rking theory is that this somehow cocked the ring set in the hook so it
fai=
led to release even with pilot and passenger pulling on the release
knobs.
=
The pilot eventually got a successful release by yawing the glider
strongl=
y. =20

AFAIK, the hook in question had not reached it's 2000 tow life limit nor
is=
there any history of repair or maintenance in the hook area. There had
be=
en cases where a commercial operator had insisted on providing tows using
a=
chain link instead of a Tost ring set. We think it possible this had
dama=
ged the hook in some way.

Operationally, should a roll-over happen again, we will release the rope
an=
d re-attach before proceeding with a launch. The release will get
special
=
attention in the annual inspection later this month. No chain links will
b=
e allowed for any purpose.