On Jan 24, 3:55*pm, Bob Kuykendall wrote:
On Jan 24, 12:30*pm, Martin Gregorie
wrote:

...
By 'exposed spar stubs' I meant that there's no obvious tunnel, or top
and bottom guide channels, that the BRS webs could could go round the
outside of so they are guaranteed to be round the spars after the glider
is rigged: you'd need something like that to keep the webbing loop open
and let the spar stubs fit easily through them...

On the surface, it seems to me that attaching the parachute bridle to
the wing main spar stubs is not the optimal way to do it. In general,
I think I'd rather attach the bridle to the aircraft structure at the
forward and aft lift pin fittings. My thinking is that the lift
fitting structure is closer to the pilot along the primary load path
between the wings and the fuselage.

At issue is that there is usually no direct structural connection
between the wings and the fuselage at the wing main spar stubs, and
there are many conceivable failure modes that could disengage the
wings from the fuselage while leaving the fuselage otherwise intact.
That being the case, I'd rather grab the fuselage directly at its
strongest points rather than grab the wings that may or may not be
attached there.

Thanks, Bob K.

That was my thinking too, which explains why I was puzzled by the spar
stub reference. For most single seat Schleichers I would have thought
that attaching to the rear lift pin carry through would be about as
good as you would get. It's clear of all control linkages and the
spars, and probably reasonably strong.

The Cirrus and perhaps other aircraft designed from the start for BRS
use a glassed in bridle that breaks out when the parachute is
deployed. No reason a glider designed from the start for BRS
couldn't do the same I suppose.

I think my ideal BRS would have the option to extract the pilot from
the fuselage as a 2 stage deployment. Stage 1 the BRS is fired and
slows the descent rate of the glider. Pilot assesses altitude,
stability, injuries, wind, terrain etc and has the option to choose
stage 2 which separates the BRS parachute from the glider and extracts
the pilot who is wearing a parachute harness attached to the BRS chute
risers. Somewhere between stage 1 and stage 2 the pilot better
release the seat belt or it could get uncomfortable.

Andy