From: rmiller@i88.isc.com (Richard J. Miller)
Subject: Re: Ropes and gliders
Organization: INTERACTIVE Systems Corporation, Naperville, IL
Date: Thu, 13 Aug 1992 20:56:31 GMT

>From: hagood@sabre.den.mmc.com (Dave Hagood)
>In article <10AUG199217524496@vxcrna.cern.ch>, cohler@vxcrna.cern.ch (Mike Cohler) writes:
>> ...
>> Schweizer releases...... seems to me that the basic design of the Schweizer
>> release leaves a lot to be desired.  ALL our gliders in our club ...
>> have the standard tost release, ... After the number of
>> stories posted here about Schweizer releases, I might feel inclined to
>> replace the Schweizer hook with a tost one if I had such a glider, even
>> though they cost a fair sum.
>
>While the Schweizer hook may not be a perfect design, IMHO this is a
>classic case of improper operation.  I work the line at Black Forest at least
>once a month, and had NEVER heard of this kind of systematic
>failure-to-release problem with the Schweizer hook until this thread came up.
>
>The solution to this problem is simple: don't put Schweizer and Tost
>attachment hardware on the same weak link.
...
>David M. Hagood
>
>From: milgram@eng.umd.edu (Judah Milgram)
>Same here. I've never heard of any failure of sailplane to release
>with a Schweizer hook. On the other hand I did once have difficulty
>releasing with a Tost hook, using the proper Tost ring. (Also unusual-
>it seemed to be a problem only in the particular aircraft I was
>flying).
>
>Judah Milgram

you have heard (i think), one story of failures, which was mine, and a
bunch of people talking about it. there is certainly nothing systematic
about them seeing as they happened in two different places several years
apart and all required more than just the use of the wrong ring.

as David says, the solution is to use the correct equipment. as i said
in a separate post, you must use your equipment correctly, as my wing
runners did not.

the Tost release costs something on the order of $250 or more (better
number anyone?) and requires an inspection every 2 years which is a real
pain to perform because the typical installation buries it in a place
that can't be reached easily. the Schweizer release costs less than $100
and needs to be checked for lubrication and wear occasionally, and all of
the release is hung out in the open where you can see it trivially (that
is, in fact, it's worst sin per many sailplane drivers, it's not
"aerodynamically clean"). the lubrication usually is done during the
annual. with one known exception, the thing just doesn't wear out.

the exception brought on an Airworthiness Directive that required a
piece of rubber and/or a tensioning clip to assure that a release under
heavy pressure would not allow the release arm to strike the supporting
structure. if this happened many thousand times, it tended to break
things (like the primary longeron along the bottom of the fuselage of a
2-33) (i probably saw the first case of this with serial number 2 back
about 1980). the suggested fix of the AD removed that problem entirely.

and as Judah says, the Tost has its own set of problems, notably with
off sized/shaped rings that can twist in the release and jam the release
completely (i have had one of these happen too).

you pays your money and you takes your chances ...

Rich Miller
ex-Schempp-Hirth Discus JBX and
ex-Rolladen-Schneider LS-4 TQ
rmiller@i88.isc.com