Gary Evans wrote:

The ASH failures may be due to another problem that
being storage. The gates preventive maintenance manual
clearly states that the stored belts should not be
subjected to bending beyond that which is defined as
the minimum pulley diameter as it may damage internal
cording resulting in premature failure.
The belts are obviously designed to be used in a straight
line without twisting which may be the reason why twisting
is not specifically identified as something to be avoided
in the Gates manual.
The ASH drive system puts a 90-degree bend into the
belts when the engine is stowed into a relatively hot
environment. If you explained these failures to a Gates
engineer and showed them the drive design they may
point out that twisting in heated storage could be
a contributing factor.

I have no knowledge of what Schleicher's discussions with Gates have
been; however, the ASH belt breaking problem is a recent one. Older
belts don't break - it's the NEW belts that are breaking. My belt is 12
years old, the engine has 114 hours on it, and at least 600 starts. When
I discussed belt life with Martin Heide (the "H" in ASH) about 3 years
ago (which was before the current problem), he said several 26 Es had
been in the shop for the 250 hour motor inspection, and all belts were
in good condition.

It could be the twisting has become a problem due to the change in belt
construction that Schleicher says has caused the recent problems, but I
doubt it. When a belt breaks with only 5 or 10 hours on it, it doesn't
seem long enough for degradation to occur. I suspect the culprit is also
shock loading, but that's speculation on my part, since I haven't
discussed it with the factory or Gates.

In any case, a prospective buyer might want to discuss the issue with
Schleicher, and remember that a glider ordered now won't be delivered
for many months, during which the problem is likely to be solved, if it
isn't already.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org