Nimbus 4DT accident 31 July 2000 in Spain.

"the resulting squatcheloid assymetry"?
What the heck is that?
Anything like the yeti dihedral?

wrote in message
ups.com...
KC, yup.

I wonder at the thread though. Everyone discussing recognition of a
fully developed spin versus spiral dive.

Years ago, Al Blackburn pointed out to me that long span gliders need
to be treated gingerly at speed. His concern had to do with the
application of aileron during dive recovery. While he felt that most
pilots could manage the elevator to avoid structural damage, aileron
asymmetry (and the resulting squatcheloid assymetry) presented a
complicating factor. The longer the span, the more critical its
effects. Add a partial load of water, a yaw moment, and/or spoiler caps
deploying with wing bend and it's not hard to see how things might
quickly get to the breaking point.

Hi Chris-

Thanks for herding the discussion toward more science and less emotion.

I apologize to anyone that may have been offended by my comments above re
"clueless". One person wrote a nice note pointing out that the family is
grieving enough without that type of thing.

The point I was trying to make was that those of us that choose to fly these
very long winged aircraft need to be keenly aware of impending problems and
react to them immediately should they begin to develop. If you decide to
thermal in turbulent conditions at just above stall speed then you should be
on edge every second you are doing so and if a gust begins to push you into
a spin or spiral then you should execute your already planned out and
hopefully second nature, correction. If you haven't thought of this plan or
possibility then you have no business flying at those speeds in that
aircraft.

Will having a plan ALWAYS get you out of trouble? No. But as others have
pointed out, in these birds you only have a very short time before there is
not any amount of skill that will save the aircraft.

Sorry to digress Chris.....I'd still really like to hear more about the
aerodynamic reasons that things go awry.....can only help to formulate the
best plan of action!

Casey

On Wed, 22 Jun 2005 12:54:44 UTC, wrote:

I wonder at the thread though. Everyone discussing recognition of a
fully developed spin versus spiral dive.

Isn't it generally more useful to recognize the difference between a
just-developing spin and a just-developing spiral dive?

Which reminds me of Johnston's Test Question for BGA Instructors
Number Three:

"The offical recovery from a stall with wing drop is different from
the official recovery from a spin. At what point do you, personally,
transition from one to the other?"

Ian

--

Please tell me that this posting is a wind up !

At 09:12 21 June 2005, M B wrote:
Neither this report nor the Minden report it references
mentions anything about the ASI installed.

Were they the wrap-around types which cause
the pilot to not know if the glider is in a spin or
a spiral?

I personally have been in a spiral in a glider, and
not knowing it was a spin or spiral, have done the

spin recovery. Fortunately the glider performance
was low enough this wasn't a problem.

To verify this, I replicated the same situation twice
more
on the same flight. It was surprising how little
onformation I could get through windspeed noise.
I was relying on the ASI, and it was ambiguously
reading either 30kts or 100kts.

Only after landing and seeing the GPS info did I fully
believe that I was spiralling, and not spinning, even
though
I watched the ASI go only from 'fast' to 'really fast.'

Are these gliders regularly installed with
the wrap-around type ASIs? Could 1.8 seconds of confusion
be a contributing factor in these cases?

Of course, assume for the moment that the translation
to
english is awkward and the mention of 'spin' may
be mistranslated...

Has anyone else on this group ever looked at a
wrap-around ASI and wondered what it said?

Have you tried this with students, having them close
their eyes and violently shake their heads and then

try to recover the glider in an unusual attitude?
And have them get confused?

I certainly see the value of the wrap-around ASI and
the added precision it allows during normal flight,
but
I'm not terribly fond of them for spin vs.
spiral recognition. I don't trust my hearing as
an airspeed indicator during stressful situations.

Please tell me that this posting is a wind up !

At 09:12 21 June 2005, M B wrote:
Neither this report nor the Minden report it references
mentions anything about the ASI installed.

Were they the wrap-around types which cause
the pilot to not know if the glider is in a spin or
a spiral?

I personally have been in a spiral in a glider, and
not knowing it was a spin or spiral, have done the

spin recovery. Fortunately the glider performance
was low enough this wasn't a problem.

To verify this, I replicated the same situation twice
more
on the same flight. It was surprising how little
onformation I could get through windspeed noise.
I was relying on the ASI, and it was ambiguously
reading either 30kts or 100kts.

Only after landing and seeing the GPS info did I fully
believe that I was spiralling, and not spinning, even
though
I watched the ASI go only from 'fast' to 'really fast.'

Are these gliders regularly installed with
the wrap-around type ASIs? Could 1.8 seconds of confusion
be a contributing factor in these cases?

Of course, assume for the moment that the translation
to
english is awkward and the mention of 'spin' may
be mistranslated...

Has anyone else on this group ever looked at a
wrap-around ASI and wondered what it said?

Have you tried this with students, having them close
their eyes and violently shake their heads and then

try to recover the glider in an unusual attitude?
And have them get confused?

I certainly see the value of the wrap-around ASI and
the added precision it allows during normal flight,
but
I'm not terribly fond of them for spin vs.
spiral recognition. I don't trust my hearing as
an airspeed indicator during stressful situations.

I don't think it is.

from the accident report
The pilot realized that they had started to spin and
that, in order to come out of the spin, he pulled back
hard on the control stick and applied full flaps, without
regaining control (no surprise there then)..........the
glider quickly gathered speed (?)....and the flaps
got heavier and heavier.
....the flap position was 2 deg positive.

I fly an ASW17 and in my conversion brief I was told
that the first action is spin recovery was flaps to
neutral. If this action was not carried out then recovery
was not certain. It would appear from the exerpt from
the Nimbus manual that the same applied. It is to be
hoped that some of the above passage is the result
of iffy translation, if not it is a very strange sequence
of events.

The report conclusions do not help. I am no expert
on the 4DM but is it possible to exceed VNe in a spin?

At 11:54 21 June 2005, Mark Wright wrote:
Please tell me that this posting is a wind up !

At 09:12 21 June 2005, M B wrote:
Neither this report nor the Minden report it references
mentions anything about the ASI installed.

Were they the wrap-around types which cause
the pilot to not know if the glider is in a spin or
a spiral?

I personally have been in a spiral in a glider, and
not knowing it was a spin or spiral, have done the

spin recovery. Fortunately the glider performance
was low enough this wasn't a problem.

To verify this, I replicated the same situation twice
more
on the same flight. It was surprising how little
onformation I could get through windspeed noise.
I was relying on the ASI, and it was ambiguously
reading either 30kts or 100kts.

Only after landing and seeing the GPS info did I fully
believe that I was spiralling, and not spinning, even
though
I watched the ASI go only from 'fast' to 'really fast.'

Are these gliders regularly installed with
the wrap-around type ASIs? Could 1.8 seconds of confusion
be a contributing factor in these cases?

Of course, assume for the moment that the translation
to
english is awkward and the mention of 'spin' may
be mistranslated...

Has anyone else on this group ever looked at a
wrap-around ASI and wondered what it said?

Have you tried this with students, having them close
their eyes and violently shake their heads and then

try to recover the glider in an unusual attitude?
And have them get confused?

I certainly see the value of the wrap-around ASI and
the added precision it allows during normal flight,
but
I'm not terribly fond of them for spin vs.
spiral recognition. I don't trust my hearing as
an airspeed indicator during stressful situations.

Don Johnstone wrote:

It is to be
hoped that some of the above passage is the result
of iffy translation, if not it is a very strange sequence
of events.

Perfectly correct translation. No strange sequence at all.

The report conclusions do not help. I am no expert

Yes, they do. Know your airplane, know the emergency procedures and
particlarly know its behaviour in regading to spins. Practice spin
recoveries, practice spiral dive recoveries. And any pilot who is even
tempted to pull back the stick in a spin is not airworthy.

on the 4DM but is it possible to exceed VNe in a spin?

Certainly not. But many gliders will not stay in the spin but go into a
spiral dive. Which was obviously the case here.

Stefan

Don Johnstone wrote:

It is to be
hoped that some of the above passage is the result
of iffy translation, if not it is a very strange sequence
of events.

Perfectly correct translation. No strange sequence at all.

The report conclusions do not help. I am no expert

Yes, they do. Know your airplane, know the emergency procedures and
particlarly know its behaviour in regading to spins. Practice spin
recoveries, practice spiral dive recoveries. And any pilot who is even
remotely tempted to pull back the stick in a spin is not airworthy.

on the 4DM but is it possible to exceed VNe in a spin?

Certainly not. But many gliders will not stay in the spin but go into a
spiral dive. Which was obviously the case here.

Stefan

On Tue, 21 Jun 2005 13:11:53 UTC, Stefan
wrote:

And any pilot who is even
remotely tempted to pull back the stick in a spin is not airworthy.

I suspect that many or all of us are to some extent tempted to do just
that. That's why we need training and practice in the right thing ...

Ian


--

At 13:24 21 June 2005, Stefan wrote:
Don Johnstone wrote:

It is to be
hoped that some of the above passage is the result
of iffy translation, if not it is a very strange sequence
of events.

Perfectly correct translation. No strange sequence
at all.

The report conclusions do not help. I am no expert

Yes, they do. Know your airplane, know the emergency
procedures and
particlarly know its behaviour in regading to spins.
Practice spin
recoveries, practice spiral dive recoveries. And any
pilot who is even
tempted to pull back the stick in a spin is not airworthy.

I agree entirely. But was this glider ever spinning?
The report does make the point that intentional spinning
of the 4DM is prohibited.

on the 4DM but is it possible to exceed VNe in a spin?

Certainly not. But many gliders will not stay in the
spin but go into a
spiral dive. Which was obviously the case here.

I don't see that as obvious. How did it get from spin
to spiral dive. The action taken by the pilot would
not have prevented the auto-rotation, in fact it should
have ensured that it continued and that the glider
remained stalled. Stall plus autorotation =spin.

The question is was the glider ever in a spin. Reading
Bill's post that is a pertinent question? My point
about the conclusions not helping is that they say
that the structural failure was from a 'spiral dive
OR spin'. I have to accept that the recovery action
taken by the pilot was incorrect but what was he trying
to recover from?

Stefan