wings came off

Originally Posted by hinterland

In French Alps last week end..

http://www.ledauphine.com/isere-sud/...e-en-plein-vol

This embarrassing aerial crack up is not a very good advertisement for any glider, but especially not for an UL that sells for $85,000.....(basic glider + fairing for enclosed cockpit) http://www.ruppert-composite.ch/down...sliste2010.pdf

tienshanman wrote:
This embarrassing aerial crack up is not a very good advertisement for
any glider, but especially not for an UL that sells for

You can break *any* aircraft by pulling too many Gs.

On Sep 22, 7:33*pm, John Smith wrote:
tienshanman wrote:
This embarrassing aerial crack up is not a very good advertisement for
any glider, but especially not for an UL that sells for

You can break *any* aircraft by pulling too many Gs.

It's got to be especially tricky when you've only got a 70 knot Vne to
work with.

We think we have to be careful when we're in a glider with only a 108
or 119 knot Vne!

At 07:33 22 September 2010, John Smith wrote:
tienshanman wrote:
This embarrassing aerial crack up is not a very good advertisement for
any glider, but especially not for an UL that sells for

You can break *any* aircraft by pulling too many Gs.

I think you might find that most of the modern gliders we fly are capable
of withstanding more "G" than the human body can take.
Overstressing a modern glider is unlikely to result in a catastrophic
failure unless there is already damage.
Remember the placarded limits have nothing to do with the design limits of
the glider. Most are placarded to +3.5 and -1 which was an arbitary figure
set by the LBA. Most gliders of the type we now fly exceed this level.
That is not to say that people should fly outside the placarded limits.

On Sep 22, 6:05*am, Don Johnstone wrote:
At 07:33 22 September 2010, John Smith wrote:

tienshanman wrote:
This embarrassing aerial crack up is not a very good advertisement for
any glider, but especially not for an UL that sells for

You can break *any* aircraft by pulling too many Gs.

I think you might find that most of the modern gliders we fly are capable
of withstanding more "G" than the human body can take.
Overstressing a modern glider is unlikely to result in a catastrophic
failure unless there is already damage.
Remember the placarded limits have nothing to do with the design limits of
the glider. Most are placarded to +3.5 and -1 which was an arbitary figure
set by the LBA. Most gliders of the type we now fly exceed this level.
That is not to say that people should fly outside the placarded limits.

Curious statement. Cite, please? Humans can take a lot of Gs,
especially when reclined - I've done over 9 g instantaneous in a Swift
and sustained 9 g for 20 some odd seconds in a centrifuge and wouldn't
want to try it in my LS6!

I'm pretty sure a hard pull at VNE in just about any glider (Swift or
Fox excepted, maybe) has a good chance of causing catastrophic
failure.

Kirk

At 12:29 22 September 2010, kirk.stant wrote:
On Sep 22, 6:05=A0am, Don Johnstone wrote:
At 07:33 22 September 2010, John Smith wrote:

tienshanman wrote:
This embarrassing aerial crack up is not a very good advertisement
for
any glider, but especially not for an UL that sells for

You can break *any* aircraft by pulling too many Gs.

I think you might find that most of the modern gliders we fly are
capable
of withstanding more "G" than the human body can take.
Overstressing a modern glider is unlikely to result in a catastrophic
failure unless there is already damage.
Remember the placarded limits have nothing to do with the design
limits
o=
f
the glider. Most are placarded to +3.5 and -1 which was an arbitary
figur=
e
set by the LBA. Most gliders of the type we now fly exceed this level.
That is not to say that people should fly outside the placarded
limits.

Curious statement. Cite, please? Humans can take a lot of Gs,
especially when reclined - I've done over 9 g instantaneous in a Swift
and sustained 9 g for 20 some odd seconds in a centrifuge and wouldn't
want to try it in my LS6!

I'm pretty sure a hard pull at VNE in just about any glider (Swift or
Fox excepted, maybe) has a good chance of causing catastrophic
failure.

Kirk


Prevalence of G-induced loss of consciousness (G-LOC)in the United
Kingdom Royal Air Force (RAF) was found to be 19.3% in 1987. With the
introduction of the Typhoon, a fourth generation aircraft, the prevalence
of G-LOC has been re-assessed to determine the effectiveness of current G
tolerance training. Method: A survey was sent to 4018 RAF aircrew,
irrespective of their current role. Information was requested on G-LOC,
role and aircraft type, experience, and attitudes toward G-LOC prevention.
Results: Responses were received from 2259 (56.2%) individuals, 882 (39%)
of whom were current fast jet aircrew. At least one episode of G-LOC was
reported by 20.1% of all respondents. In front line aircraft, prevalence
of G-LOC among the 882 fast jet aircrew who responded was 6%. In the whole
group, G-LOC was reported most commonly in aircrew under training (70.9%),
and was most prevalent in training aircraft (77.4% of G-LOC events). At
the time of the G-LOC, 64% of aircrew had less than 100 h total flying
time. G-LOC was reported most frequently between +5 to +5.9 Gz, and
“push-pull” maneuvers were associated with 31.3% of G-LOC events.

G-LOC was reported most frequently between +5 to +5.9 Gz.

Studies have shown that prone positioning has little effect, the only
remedy is a G suit and training, not often found in gliders.
The USAF require F16 pilots to demonstrate an ability to withstand a
maximum of 9 Gz and this can only be achieved through training and the
wearing of a G suit.

I am left wondering how sufficient acceleration could be maintained in a
LS6 to load the aircraft, in controlled flight, to sustain 9 G or indeed
more than 6G, ignoring that the pilot is going to become rapidly
unconsious if it were to be achieved. I am at a loss to understand why
anyone would want to do that anyway.

On Sep 22, 8:54*am, Don Johnstone wrote:
At 12:29 22 September 2010, kirk.stant wrote:



On Sep 22, 6:05=A0am, Don Johnstone *wrote:
At 07:33 22 September 2010, John Smith wrote:

tienshanman wrote:
This embarrassing aerial crack up is not a very good advertisement
for
any glider, but especially not for an UL that sells for

You can break *any* aircraft by pulling too many Gs.

I think you might find that most of the modern gliders we fly are
capable
of withstanding more "G" than the human body can take.
Overstressing a modern glider is unlikely to result in a catastrophic
failure unless there is already damage.
Remember the placarded limits have nothing to do with the design
limits
o=
f
the glider. Most are placarded to +3.5 and -1 which was an arbitary
figur=
e
set by the LBA. Most gliders of the type we now fly exceed this level.
That is not to say that people should fly outside the placarded
limits.

Curious statement. *Cite, please? *Humans can take a lot of Gs,
especially when reclined - I've done over 9 g instantaneous in a Swift
and sustained 9 g for 20 some odd seconds in a centrifuge and wouldn't
want to try it in my LS6!

I'm pretty sure a hard pull at VNE in just about any glider (Swift or
Fox excepted, maybe) has a good chance of causing catastrophic
failure.

Kirk

*Prevalence of G-induced loss of consciousness (G-LOC)in the United
Kingdom Royal Air Force (RAF) was found to be 19.3% in 1987. With the
introduction of the Typhoon, a fourth generation aircraft, the prevalence
of G-LOC has been re-assessed to determine the effectiveness of current G
tolerance training. *Method: *A survey was sent to 4018 RAF aircrew,
irrespective of their current role. Information was requested on G-LOC,
role and aircraft type, experience, and attitudes toward G-LOC prevention..
*Results: *Responses were received from 2259 (56.2%) individuals, 882 (39%)
of whom were current fast jet aircrew. At least one episode of G-LOC was
reported by 20.1% of all respondents. In front line aircraft, prevalence
of G-LOC among the 882 fast jet aircrew who responded was 6%. In the whole
group, G-LOC was reported most commonly in aircrew under training (70.9%),
and was most prevalent in training aircraft (77.4% of G-LOC events). At
the time of the G-LOC, 64% of aircrew had less than 100 h total flying
time. G-LOC was reported most frequently between +5 to +5.9 Gz, and
“push-pull” maneuvers were associated with 31.3% of G-LOC events. *

G-LOC was reported most frequently between +5 to +5.9 Gz.

Studies have shown that prone positioning has little effect, the only
remedy is a G suit and training, not often found in gliders.
The USAF require F16 pilots to demonstrate an ability to withstand a
maximum of 9 Gz and this can only be achieved through training and the
wearing of a G suit.

I am left wondering how sufficient acceleration could be maintained in a
LS6 to load the aircraft, in controlled flight, to sustain 9 G or indeed
more than 6G, ignoring that the pilot is going to become rapidly
unconsious if it were to be achieved. I am at a loss to understand why
anyone would want to do that anyway.

G-LOC and structural deformity are two different issues. You can
snatch the stick and pull an instantaneous g-load that will snap the
wings off before your body reacts and you g-loc.

Don Johnstone wrote:
[lots of yadda yadda snipped]
G-LOC was reported most frequently between +5 to +5.9 Gz.

You completely forgot to mention the time factor. G-Loc needs at least 4
seconds to occur. No glider aerobatic maneuvre will give you a high G
load of more than 4 seconds, it's simply not possible, energeticwise.
(Except with a spiral, of course.)

Read for example: http://aeromedical.org/Articles/g-loc.html

On Sep 22, 6:54*am, Don Johnstone wrote:

Studies have shown that prone positioning has little effect...

Prone, as in a Horton? Yes, that would be as expected.

As for the rest, many small aircraft have been shed of their wings in
circumstances where the only possible explanation was deliberate
though injudicious pilot input. So I don't think anybody should doubt
that it is well within the realm of possibility.

Thanks, Bob K.

Max. g is not a structural issue with several modern gliders. Other design
requirements result in a structure that by far surpasses the certification
requirements.

Andor