On Jun 7, 5:32*pm, Martin Gregorie
wrote:
On Mon, 07 Jun 2010 20:55:46 +0000, Martin Gregorie wrote:
On Mon, 07 Jun 2010 12:21:31 -0700, bildan wrote:

Some time back during a rainstorm our then CFI gave a talk about how
the various airframe limits are set. I remember him saying that Vwinch
is 95% of the speed at which the wing's maximum design loading is
reached when the glider is overhead the winch with the stick fully
back.

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |

Your CFI may have said that but there's no engineering data or
certification specifications to back it up.

He was talking us through JAR 22 at the time and JAR 22.583 looks pretty
prescriptive to me.

There's no chance of overstressing an airworthy glider on a winch
launch when using the correct weak link.

Maybe so but note that JAR 22.583 defines the max weak link strength as
the *lesser* of 83% of structural damage limit or max achievable lift
with full up elevator and JAR 22.585 says the hook must withstand the
larger of 125% of the weak link breaking load and the glider's MTOW.

I agree that 22.583 and 22.585 taken together guarantee no damage if the
right weak link is used, but I'd remind you that this discussion was
triggered by a question about a club that was winching with NO weak
link. JAR 22.583 has no guarantee against overstressing the glider under
those conditions because it specifically says that its OK to design a
glider for a weak link that breaks at a lower load than the wing can
generate with full up elevator. Unless there's a clause somewhere else
in JAR 22 that would prevent it, this implies that a compliant glider

* * * * * * * * * * * * * * * * * * * * * * * * * * *^^^^^^^^^^^^^^^^^^

can be broken by pulling the stick back during an overspeed if it is
* ^^^^^^
winched on an incorrect weak link.

This should read "it is possible for some compliant gliders to be".

--
martin@ * | Martin Gregorie
gregorie. | Essex, UK
org * * * |- Hide quoted text -

- Show quoted text -

Right, the point, if I'm not mistaken, is to USE A WEAK LINK (of the
correct breaking strength).