A thought on BRS

Not really. For allmost every turbo equipped glider the max. total weight is
the same as the one for the pure glider, and in some cases the turbo has one
even lower. The discus 1 for example has a MTOW of 525 kg without the engine,
but with the turbo it reduced to 450 kg.

Roelant van der Bos




I simplified it a bit too much, perhaps. It would come out of the
"non-lifting parts" limit (basically the fuselage and everything in it).
Generally, the effect would be to reduce the cockpit allowed load, but
not always, depending on the exact weight of fuselage and installed
equipment. The amount of water ballast allowed would not likely change,
since it is carried by the wing (a lifting part), not the fuselage.

A glider designed to carry a motor will have a higher "non-lifting
parts" limit (perhaps from more structure, stronger lift pins, etc) than
a similar non-motorized one, in order to preserve the cockpit load.

Thanks for the explanation.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

On Wed, 28 Apr 2004 17:37:23 +0200, Roelant van der Bos
wrote:

Actually such a system is available at DG Flugzeugbau. The NOAH system
works with a compressed air cilinder and a bag located under the cushion in
the glider. It lifts to over the canopy rim and lets you just roll out of
the cockpit

See:

http://www.dg-flugzeugbau.de/noah-e.html

Roelant van der Bos

I think Roger was thinking of something like an automotive crash bag.
Unlike the DG Noah-e it would need to inflate just before impact so it
would lift the pilot off the seat and then absorb the impact forces as
it deflates.

There are problems:

- it must inflate just before the glider hits the ground, not when the
BRS deploys, but how would its inflation be triggered?

- would there be space in a closed cockpit for it to deploy?

- a cockpit is MUCH smaller than even the smallest car interior so
might it injure the pilot anyway, e.g. by breaking his eardrums as a
result of its explosive deployment in a confined space?

Its a nice idea, but I think its a non-starter inside the cockpit.

--
martin@ : Martin Gregorie
gregorie : Harlow, UK
demon :
co : Zappa fan & glider pilot
uk :

Martin Gregorie wrote in
:

....snip

I think Roger was thinking of something like an automotive crash bag.
Unlike the DG Noah-e it would need to inflate just before impact so it
would lift the pilot off the seat and then absorb the impact forces as
it deflates.

There are problems:

- it must inflate just before the glider hits the ground, not when the
BRS deploys, but how would its inflation be triggered?

- would there be space in a closed cockpit for it to deploy?

- a cockpit is MUCH smaller than even the smallest car interior so
might it injure the pilot anyway, e.g. by breaking his eardrums as a
result of its explosive deployment in a confined space?

Its a nice idea, but I think its a non-starter inside the cockpit.


I was thinking that it would be recessed in the underside of the glider,
and covered with thin material that would match the outside contour. When
it deploys it would puncture the bottom and be a big bubble on the OUTSIDE.
I don't see why it couldn't inflate at the same time as the BRS.

--
Roger Kelly
to reply replace the IP address above with cgisenior.com

Roger Kelly wrote:

Its a nice idea, but I think its a non-starter inside the cockpit.



I was thinking that it would be recessed in the underside of the glider,
and covered with thin material that would match the outside contour. When
it deploys it would puncture the bottom and be a big bubble on the OUTSIDE.
I don't see why it couldn't inflate at the same time as the BRS.

Perhaps a system that automatically extended and locked the landing gear
when the BRS activated would be simpler. The extended gear on modern
gliders is designed to absorb significant energy, so it, plus a well
designed cockpit, should be adequate to protect the pilot.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Roelant van der Bos wrote:

I simplified it a bit too much, perhaps. It would come out of the
"non-lifting parts" limit (basically the fuselage and everything in it).
Generally, the effect would be to reduce the cockpit allowed load, but
not always, depending on the exact weight of fuselage and installed
equipment. The amount of water ballast allowed would not likely change,
since it is carried by the wing (a lifting part), not the fuselage.

A glider designed to carry a motor will have a higher "non-lifting
parts" limit (perhaps from more structure, stronger lift pins, etc) than
a similar non-motorized one, in order to preserve the cockpit load.

Not really. For allmost every turbo equipped glider the max.
total weight is the same as the one for the pure glider, and in some
cases the turbo has one even lower. The discus 1 for example has a
MTOW of 525 kg without the engine, but with the turbo it reduced to
450 kg.

An increased "non-lifting parts" limit would not necessarily increase
the total allowed weight, which depends on several factors (landing gear
strength and tow hook mounting come to mind as possibilities).

I don't know why the Discus 1 turbo has such a lower MTOW, but I'd guess
the major effect is you would fly it with a lot less water ballast -
about 100 liters less! I don't think this reduction has anything to do
with the "non-lifting parts" limit, but might be related to required
climb rates or other regulation.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Andreas Maurer wrote:
On 28 Apr 2004 13:36:04 GMT, Roger Kelly ] wrote:



How about the BRS plus an automotive type air bag under your butt that
could be deployed at the same time as the BRS?


An air bag under the butt is a good idea - but where?
Between butt and fuselage shell there is not enough space, and I doubt
that an airbag under the fuselage (opening through a hatch) will work
reliably.



Bye
Andreas

It could deploy forward from the gear well. I thought it was a great idea.

Shawn

Roger Kelly wrote:

Martin Gregorie wrote in
:

...snip


I think Roger was thinking of something like an automotive crash bag.
Unlike the DG Noah-e it would need to inflate just before impact so it
would lift the pilot off the seat and then absorb the impact forces as
it deflates.

There are problems:

- it must inflate just before the glider hits the ground, not when the
BRS deploys, but how would its inflation be triggered?

- would there be space in a closed cockpit for it to deploy?

- a cockpit is MUCH smaller than even the smallest car interior so
might it injure the pilot anyway, e.g. by breaking his eardrums as a
result of its explosive deployment in a confined space?

Its a nice idea, but I think its a non-starter inside the cockpit.



I was thinking that it would be recessed in the underside of the glider,
and covered with thin material that would match the outside contour. When
it deploys it would puncture the bottom and be a big bubble on the OUTSIDE.
I don't see why it couldn't inflate at the same time as the BRS.


It wouldn't have to fill with gas either. Some type of foam, even a
fast polymerizing solid (heat could be a problem with this) could fill
the bag. Lots of possibilities.

Shawn

Shawn

The reason is quite simple. Even if it doesn't seen logical, water in the wings
increase the stresses in the spar of the wing. This because the water is
situated at the root of the wing. The effect is smaller that an increase in the
non lifting parts. The original wing of the discus was desinged to be a pure
glider. To make the turbo they had to reduce the ammount of water in the wing
by so much that the stresses in the wing would not exceed those of the pure
glider. Therefore they reduced the ammount of water you are allowed to carry by
reducing the MTOW. If you remove the turbo from the glider the MTOW goes back
to 525 kg., indicating that the wing for a Discus T is the same as the pure
glider. New glider are desinged from the start to carry turbo's because
everybody want's them in their new expensive glider. Therefore the wings of the
pure glider may be (do not read : are !) stronger then necessary. MTOW is
determined by the some factors as stall speed and landing gear forces. For
example the new DG 808B ompetition required a new landing gear to be allowed to
carry the new 600 kg MTOW. see
http://www.dg-flugzeugbau.de/dg-808-...ml#competition for more
info on that aspect. Also you can read there that they had to move the ballast
bags further out in the wing, to reduce the stresses on the wing.

Roelant

Eric Greenwell wrote:

Roelant van der Bos wrote:

I simplified it a bit too much, perhaps. It would come out of the
"non-lifting parts" limit (basically the fuselage and everything in it).
Generally, the effect would be to reduce the cockpit allowed load, but
not always, depending on the exact weight of fuselage and installed
equipment. The amount of water ballast allowed would not likely change,
since it is carried by the wing (a lifting part), not the fuselage.

A glider designed to carry a motor will have a higher "non-lifting
parts" limit (perhaps from more structure, stronger lift pins, etc) than
a similar non-motorized one, in order to preserve the cockpit load.

Not really. For allmost every turbo equipped glider the max.
total weight is the same as the one for the pure glider, and in some
cases the turbo has one even lower. The discus 1 for example has a
MTOW of 525 kg without the engine, but with the turbo it reduced to
450 kg.

An increased "non-lifting parts" limit would not necessarily increase
the total allowed weight, which depends on several factors (landing gear
strength and tow hook mounting come to mind as possibilities).

I don't know why the Discus 1 turbo has such a lower MTOW, but I'd guess
the major effect is you would fly it with a lot less water ballast -
about 100 liters less! I don't think this reduction has anything to do
with the "non-lifting parts" limit, but might be related to required
climb rates or other regulation.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA