Andreas Maurer wrote in message . ..
On 7 Nov 2003 23:40:26 -0800, (Slingsby)
wrote:

I still wonder if this killed the Nimbus4DM pilots in Reno.
Imagine looking at the ASI and not knowing if
you should be doing a spin recovery or a spiral recovery
(two very different things).
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What really killed them were wings which, by design, are only good for
3.5 g (+50% if the glue holds) when you get into a stall/spin
situation.


The official conclusion sounds a little different:

Quote:

The maximum maneuvering load factor limits (in units of gravity or g's) change with variations in glider speed and flap/airbrake configuration. From a "flaps up" configuration at Va to the condition of airbrakes and flaps extended at Vne, the maximum maneuvering load factor limits decrease from positive 5.3 to a positive 3.5.

Right. By design they are ONLY good for 3.5 g. Exceed that amount by a paltry 50% and the wings WILL snap off like toothpicks. Guaranteed. They will, and did, snap off together. Both wings were equally weak by design and construction technique AND, they used enough glue.

In other words: If the pilots had not extended the airbrakes, the
Nimbus would not have disintegrated.

This is what NTSB thinks about what killed them:

Quote:

The National Transportation Safety Board determines that the probable cause of this accident was the pilot's excessive use of the elevator control during recovery from an inadvertently entered spin and/or spiral dive during which the glider exceeded the maximum permissible speed, which resulted in the overload failure of the wings at loadings beyond the structure's ultimate design loads.

Remove the word "excessive" and the description becomes more realistic.

Note the term "at loadings beyond the structure's ultimate design
loads".

Bye
Andreas