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Nimbus 4DT accident 31 July 2000 in Spain.



 
 
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  #1  
Old June 20th 05, 10:46 PM
W.J. \(Bill\) Dean \(U.K.\).
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Default Nimbus 4DT accident 31 July 2000 in Spain.

The Spanish authorities have now published their report on the accident to
the UK registered Nimbus 4DT which crashed on 31st July 2000 near Toledo,
one of the British crew was killed.

The Spanish report in English translation may be found at
http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB).

The BGA report is at
http://www.gliding.co.uk/accidents/d...dentSummary=67 .
If this will not open, go to http://www.gliding.co.uk/accidents/login.php ,
Username user, Password risingmoon.

The similar accident to a Nimbus 4DM at Minden on 13th July 1999 ref:
LAX99MA251 may be found at http://www.ntsb.gov/publictn/2002/AAB0206.htm
brief report is at
http://www.ntsb.gov/NTSB/brief.asp?e...12X19310&key=1 .

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.



  #2  
Old June 20th 05, 11:28 PM
Stefan
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Default

W.J. (Bill) Dean (U.K.). wrote:

The Spanish report in English translation may be found at
http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB).


Thanks for the link. Very educational, indeed. I think this answers the
question whether spins and spiral dives should be demonstrated and
recovery should be regularly trained.

Stefan
  #3  
Old June 21st 05, 12:30 PM
HL Falbaum
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Default

Yes, indeed. If anything, the spiral dive recovery is more critical from a
structural standpoint. A modern glider is more likely to progress to spiral
dive anyway. The pilot, by his own admission, did the wrong recovery for
either case.

However, since the Spanish report refers heavily to the Minden report, with
many similarities, I wonder if there is something peculiar about the Nimbus
4 DT. Both apparently departed into a stall and incipient spin in a strong
thermal. This pilot had sufficient recent flight experience, and total time,
to have developed good "survival" reflexes, including the "stick forward"
manuver. He had little time in the Nimbus 4, but quite enough in the Nimbus
3 to know how to fly it.

If it was purely the fault of very strong thermals, then the other gliders
in common use at places like Minden would also have similar accidents. This
does not seem to be the case.

Obviously, I have never flown a Nimbus of any kind. I have a few hours in
the Duo-Discus, but nothing larger. The Duo is certainly not malignant in
any way.

So my question is to those with Nimbus D experience. Is there some handling
characteristic that will bite a fairly experinced and competent, but
unsuspecting pilot?

I am thinking that the (biennial USA) Flight Review should include spiral
dive recovery routinely, in addition to the usual other "emergency"
maneuvers.
--
Hartley Falbaum
CFIG USA


"Stefan" wrote in message
...
W.J. (Bill) Dean (U.K.). wrote:

The Spanish report in English translation may be found at
http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB).


Thanks for the link. Very educational, indeed. I think this answers the
question whether spins and spiral dives should be demonstrated and
recovery should be regularly trained.

Stefan



  #4  
Old June 21st 05, 02:13 PM
Bill Daniels
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Default

None of these big gliders are very good at diving. I don't believe there
is anything sinister about the N4DM. They're just not built for diving.
Any time the nose is well below the horizon, they will pick up speed
rapidly. Don't do that.

Large span gliders will fly slowly and that means that there is a large
airspeed difference across their span when circling - my "little" Nimbus 2C
can develop a 15 knot difference. This, plus a thermal gust, can make them
roll into a spiral dive.

Recognizing this and taking prompt action when it happens is actually easy
once you experience it a few times. Just allow the speed to increase a bit
to increase control authority, then stop the turn and then recover normal
airspeed.

If the glider is allowed to progress into a full spiral dive, the options
narrow considerably. Only very gentle and precise control inputs will save
the day. Try not to apply large aileron and elevator inputs
simultaneously - bending and twisting the wing at the same time can break
it.

Reading the Spanish report made it seem that the pilot did not have complete
control of his glider. That's a shame when it's a two seater and there are
a lot of experienced pilots who would have been willing to ride with him and
help him master it.

Bill Daniels


"HL Falbaum" wrote in message
...
Yes, indeed. If anything, the spiral dive recovery is more critical from a
structural standpoint. A modern glider is more likely to progress to

spiral
dive anyway. The pilot, by his own admission, did the wrong recovery for
either case.

However, since the Spanish report refers heavily to the Minden report,

with
many similarities, I wonder if there is something peculiar about the

Nimbus
4 DT. Both apparently departed into a stall and incipient spin in a strong
thermal. This pilot had sufficient recent flight experience, and total

time,
to have developed good "survival" reflexes, including the "stick forward"
manuver. He had little time in the Nimbus 4, but quite enough in the

Nimbus
3 to know how to fly it.

If it was purely the fault of very strong thermals, then the other gliders
in common use at places like Minden would also have similar accidents.

This
does not seem to be the case.

Obviously, I have never flown a Nimbus of any kind. I have a few hours in
the Duo-Discus, but nothing larger. The Duo is certainly not malignant in
any way.

So my question is to those with Nimbus D experience. Is there some

handling
characteristic that will bite a fairly experinced and competent, but
unsuspecting pilot?

I am thinking that the (biennial USA) Flight Review should include spiral
dive recovery routinely, in addition to the usual other "emergency"
maneuvers.
--
Hartley Falbaum
CFIG USA


"Stefan" wrote in message
...
W.J. (Bill) Dean (U.K.). wrote:

The Spanish report in English translation may be found at
http://www.gliding.co.uk/accidents/r...s4dtreport.pdf (3MB).


Thanks for the link. Very educational, indeed. I think this answers the
question whether spins and spiral dives should be demonstrated and
recovery should be regularly trained.

Stefan




  #5  
Old June 21st 05, 09:55 AM
M B
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Posts: n/a
Default

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.

At 22:42 20 June 2005, Stefan wrote:
W.J. (Bill) Dean (U.K.). wrote:

The Spanish report in English translation may be found
at
http://www.gliding.co.uk/accidents/r...s4dtreport.pdf
(3MB).


Thanks for the link. Very educational, indeed. I think
this answers the
question whether spins and spiral dives should be demonstrated
and
recovery should be regularly trained.

Stefan

Mark J. Boyd


  #6  
Old June 21st 05, 10:01 AM
Stefan
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Posts: n/a
Default

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 understand you're an instructor? I shudder at the thought that a
licensed pilot, let alone an instructor would rely on the ASI to tell
whether he's in a spin or a spiral.

Stefan
  #7  
Old June 21st 05, 06:08 PM
Eric Greenwell
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Posts: n/a
Default

M B wrote:

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.


Don't the controls feel differently at 30 knots and 100 knots? That
should be a good clue as you begin the spin recovery.


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

Eric Greenwell
Washington State
USA
  #8  
Old June 22nd 05, 05:30 AM
Kilo Charlie
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Default


"Eric Greenwell" wrote in message
...
M B wrote:


Don't the controls feel differently at 30 knots and 100 knots? That should
be a good clue as you begin the spin recovery.


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

Eric Greenwell
Washington State


I am a partner in a Nimbus 3D. I have not had a lot of time in it but have
flown aircraft of all kinds for 36 years including hundreds of glider and
powered aerobatic hours. In order to get the Nimbus to go beyond the green
arc it takes a very large amount of forward stick even with the trim all the
way to the forward stop.....with flaps in -2. I absolutely disagree that it
would be easy to let it get away from you and end up in a spiral with the
exception of possibly entering it from a spin. The spin enty on the other
hand is docile and easy to recover from. As has been pointed out, if one is
clueless re incipient spins then the scenario in these 2 accidents might
easily unfold. Only education, planning and practice will prevent similar
accidents.

Casey Lenox
KC
Phoenix


  #9  
Old June 22nd 05, 01:54 PM
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Default

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.

  #10  
Old June 22nd 05, 02:33 PM
Bert Willing
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Default

As long as a 26m glider is certified under JAR22, there is no issue of
control inputs versus speed other than for a 15m glider.

What changes drastically with a long wing is the entry into a spin or a
spiral dive. The long wing makes that you can have large discrepancies of
effective angle of attack along the wingspan (which can make the spin entry
under g-load quite interesting). Long wings also have much more angular
momentum once the spin/spiral dive is developped - it can be as much as 5
times the angular momentum of a 15m glider, and that makes that recovery
will take a certain time even if correct counter procedures are undertaken.
And during that time, the glider will accelerate like hell so that you are
likely to operate you final recovery well beyond what's written in the
flight manual.

I think that training of instant recovery of a spin entry (or spiral dive
entry) is mandatory if you want to fly a 25+m ship safely. But in contrary
to short wings, it would be plain stupid to train the recovery of a fully
developed spin/spiral dive in these ships (beyond fligh testing for
certification) and that's the reason that a flight manual will usually call
it illegal.

Been there, done it, and don't feel that I want to get there again.
--
Bert Willing

ASW20 "TW"


a écrit dans le message de news:
...
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.



 




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