BRS chutes. Why doesn't everyone use them?

On Mon, 24 Jan 2011 08:26:52 -0800, Andy wrote:

What do you mean by exposed spar stubs? How are they more exposed, and
to what, in the 19 rather than say the 24, 27, 28, and 29.

I'm familiar with Discus 1, 19, 20 and Pegase innards but not with the
others, so I was restricting my comments to gliders I understand. I
didn't mention the 20 since its very likely that the mixer is exactly
where you'd want to put the BRS.

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.

The 19/20/Pegase fuselage also has a battery mount in front of the spars
that would need to be cut partly away to allow the BRS webs to come round
the front of the spar. I don't think its structural apart from supporting
the batteries, but even so making clearance for the webs may weaken it
unacceptably: you really don't want the batteries ending up sitting on
the wheel well after a 'firm' landing.


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

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.

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

On Mon, 24 Jan 2011 17:29:10 -0800, Andy wrote:

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.

Good point. The only pic I've seen of an installed BRS where I could see
what was going on was that HP installation I mentioned, so I just
extrapolated without really engaging my brain.

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.

Better have a lifting panel too, or it would still be somewhat
uncomfortable, whether the seat harness was released or not.


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

Many Pipistrel Taurus have a BRS; mine does. You can see the
installation in a shot I took at the factory - unfortunately, I don't
have a better picture handy:

http://groups.yahoo.com/group/taurus...t=21& dir=asc

or http://yhoo.it/g6IUh3

The half cylinder in front is the rocket; the larger container behind
it is the chute; the tube leading down is the exhaust route for the
rocket. Its located behind the spars, just in front of the firewall
and does not attach to the spars. Obviously, this configuration is
not relevant to a discussion about retrofitting, and because the ship
has side-by-side seating, there's a lot more room to work with than a
typical ship would have. I can easily conceive of situations where I
might also want a personal parachute, but I think having another
option is good. To me, it only made sense to order it.

I believe that Pipistrel has the same option in its touring
motorgliders and I seem to recall hearing that they had been used on a
few occasions.

- Kevin


On Jan 24, 8:05*pm, Martin Gregorie
wrote:
On Mon, 24 Jan 2011 17:29:10 -0800, Andy wrote:
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.

Good point. The only pic I've seen of an installed BRS where I could see
what was going on was that HP installation I mentioned, so I just
extrapolated without really engaging my brain.

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.

Better have a lifting panel too, or it would still be somewhat
uncomfortable, whether the seat harness was released or not.

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

Hi Bob

I have seen an ASW20 where the wings departed the fuselage together-
ripping the main spar out of the fuselage. The accident entry was
exactly the kind of situation one would typically envisage a BRS handle
being reached for. Pilot did something stupid, went way over Vne
recovering from the resulting unusual attitude. A little flutter
combined with high G pull up and structural failure.

My conclusion is that - if you were to attach the BRS bridle exclusively
to either the wing spar, or the fuselage you would have problems.
Picture the pilot plummeting vertically in his perfectly streamlined
fuselage, while the wings drift down under the BRS. Alternatively
picture the pilot after the BRS rapidly decelerated the fuselage, but
not the wings which are now displaced some feet forward of their
original fitting.

Seriously- the loads have to be designed for - and I doubt there are
many gliders that this would work on. I don't know what the design work
was on the Schempp-Hirth gliders, and I know that the BRS systems have
chokes on the shrouds to reduce the shock loading. But still...

Personally I will go with a decent personal chute, Flarm and some
dedicated use of the Mk1 eyeball.

Bruce



On 2011/01/25 12:55 AM, Bob Kuykendall wrote:
On Jan 24, 12:30 pm, Martin
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.

--
Bruce Greeff
T59D #1771 & Std Cirrus #57

On Jan 20, 7:47*am, "
wrote:
On Jan 19, 11:35*pm, Sparkorama Sparkorama.



wrote:
I'm just getting back into the sport after a long hiatus. I've seen that
a lot of glider pilots fly with parachutes (ones they wear) and I have
seen Ballistic Recovery System parachutes in planes as well. From my
layman's view, it appears that getting out of a plane using a
traditional chute after a mid-air collision seems exceedingly difficult
and time-consuming. On the other hand, BRS chutes seem to deploy very
fast and can be deployed very close to the ground. They can lower the
entire plane safely to the ground in almost any terrain, and a few
bruises to your bird or your body seems a lot better than certain death
if you can't get out of a plane after a mid-air. So if this is true, and
I am happy to say I am no expert, then why isn't everyone using these
things? I think they should be mandatory in every new glider built.
Thoughts?
Spark

--
Sparkorama

Here we go with this mandatorys stuff again!!

First of all you have at least one misconception......the aircraft is
not "lowered to the ground with only a few bruises". *The opening of
the chute is a major event, the shock can cause considerable damage by
itself. *The descent rates are high, so considerable damage upon
striking the ground. *The device is "life saving" but not "aircraft
saving".

I has strongly considered a BRS when building my homebuilt
plane......I ruled it out for a number of reasons. *The greatest
reason was that the design and structure of the aircraft wuld have had
too have been highly modified.....strengthened....coping with strong
force loads *in the oposite direction......to with stand the opening
shock of the chute............this required the doubling of the
cockpit side walls, installation of metal cross members, etc. * This
alone would have added too much weight to the aircraft, not to mention
the complications and weight of the mounting of the BRS unit
itself.........

Yeah, and then the cost...........

Now on the other hand, there are many factory built aircraft with
BRS....Like Cirrus.....a few gliders too..........these companies feel
that the BRS is a good selling point....enhanced safety and all
that....

In the world of ultralights, BRS type chutes are the "norm" * fairly
common in Light Sport aircraft too......I believe that just about ALL
hanglider guys have a ballistic chute of some type.

Cookie

Correction!

I was just taken to task by a hang glider (and sailplane) pilot
friend......

Hang gliders use "hand thrown" chutes, not "ballistic".


Cookie

Correction!

I was just taken to task by a hang glider (and sailplane) pilot
friend......

Hang gliders use "hand thrown" chutes, not "ballistic".

Cookie

Happily, everybody is right. :-) both hand-thrown and ballistic chutes
are available to the hang glider community. See
http://www.highenergysports.com/arti...ontroversy.htm for a
start

Tony LS6-b, USHPA 7826

On Jan 25, 8:05*am, BruceGreeff wrote:
I have seen an ASW20 where the wings departed the fuselage together-
ripping the main spar out of the fuselage.

As a Schleicher driver I'm interested to know what failed. How did
the wings separate from the fuselage but remain together? Did all the
lift pins fail, or did the lift pin sockets in the wing roots fail, or
was there somehow sufficient bending of the spar that the lift pins
detached without the pins or sockets failing. Maybe the whole lift
pin carry through structure detached from the fuselage but isn't it
attached to the landing gear?

I'd always assumed the spar would break before any of that could
happen but I know the 20 spar is more flexible than some.

Andy

On Tue, 25 Jan 2011 16:48:29 -0800 (PST), Andy
wrote:


As a Schleicher driver I'm interested to know what failed. How did
the wings separate from the fuselage but remain together? Did all the
lift pins fail, or did the lift pin sockets in the wing roots fail, or
was there somehow sufficient bending of the spar that the lift pins
detached without the pins or sockets failing. Maybe the whole lift
pin carry through structure detached from the fuselage but isn't it
attached to the landing gear?

Hi Andy,

Schleicher gliders have a notorious weak point: The bushings that hold
the lift pins are a little bit too short and not fixed in the shear
force tube - there have been a number of accidents where they were
twisted and ripped out of the shear force tube instead of keeping the
wing attached. (I hope I got the technical terms halfways correctly).

However, I'm not aware of such a thing happening inflight, but it
happened a couple of times after a wing hit a tree and an extremely
hard impact. I'm pretty sure that strong wing flutter exhibits forces
that are sufficient.

In Schleicher gliders, the structure that carries the wing is not
directly attached to the landing gear (as ist is the case with most
Schempp-Hirth gliders).

One thing should be mentioned: I have the impression that the
Schleicher design is - despite the problem with the bushings - one of
the strongest - in case of a crash the wings of Schleicher gliders
stay attached to the fuselage comparably often.

Andreas