The NTSB conclude around 55% on the crash that killed Engen. That one
appears to have been pilot error. Inadvertent spin, recovered at 45 deg
nose down, but the pilots appear to have pushed over to (or allowed the
aircraft to rotate) vertical before trying to pull out. If I recall
correctly the outer panels failed at a calculated 55% over certified load...

Co-incidently this was very close to what Schempp had stated the design
was good for.

After a recent fatality some tests were performed in SA - proving that a
cross-controlled entry into a spin from thermalling with a current
flapped 15m racer at full ballast results in an extremely rapid entry,
with a roll over often past the vertical and recovery at VNe even if you
were expecting it. The caption is to be careful out there.

One comment - the NTSB investigators did find some deviations from the
design layup in the wings - although in this instance all of them were
neutral or increased the strength.

Steve Davis wrote:

At 02:42 18 September 2003, Janus2k wrote:

John,
If you are still wondering about the 4DM breakup, read
the NTSB report.

From reading the report, the plane did not fail.

Mark

Actually the wings did fail. They presumably failed
above their design load limit. but they still failed
in flight causing the crash. A better question would
be, how much of a design cushion is there between the
load limit and actual failure of the wing?