Never assume the glider is stronger than the placarded
limits. As quite rightly stated earlier, exceed them
and you become a test pilot - especially so on excess
speed where there is little margin.

A friend of mine broke the boom on a SF34 (best thing
to do to the beast, some might say;-) recovering from
an intentional spin. He's a Chief Flying Instructor
and engineer so one presumes he knows what he's doing
but even he was caught out. These things are not unbreakable
in flight.

The loads on spin recovery can be quite unpredictable,
especially if the recovery pull-up is done with some
twisting moment still present on the tail - hence we
are trained to stop the spin, unstall the wings, recover,
not one 'pot-stirring', stress-inducing manoeuvre.

Rob

At 09:12 03 October 2003, Stefan wrote:
Bill Daniels wrote:

I think gliders are just as strong as the manufacturer
says, but no
stronger

Most Gliders are built in JAR country and are certified
by JAR rules.
For the utility category, JAR requires an allowed load
of 5.3g at Vne
and 4.0g at Vm. JAR further requires that the break
load be no lower
than 1.5 times the allowed load.

Since every extra strengh comes at a price in weight
and money, the
break load of most gliders acually *is* 1.5 times the
allowed load. This
is when the glider is new. Take some turbulence, and
the safety cusion
is rather small.

As for the Eta, this may turn out to be an intriguing
case. At 31 meters it
is certainly pushing the limits.

Actually this is the whole idea of the Eta project:
pushing the limits.
Remember that the first prototype was too heavy and
extra work was
required to bring the take off mass down to 850 kg!
(The 850 kg limit is
again required by JAR as well as by contest rules.)

Stefan