Accident in Namibia, SH Ventus 2cxm

It would be interesting to know the CG location for all of these.

Le lundi 1 février 2016 20:01:27 UTC+1, Don Johnstone a écrit*:
At 18:23 01 February 2016, Ramy wrote:
Scary! And I don't think there are that many nimbus 4DM out there.
Will be
interesting to compare this number to number of 4DM made. I
wouldn't want
to fly one myself.

Ramy

It would appear that 100 Nimbus 4D were built, of those 11 were 4DT
and 12 were 4D leaving a total of 87 DM of all types.

There is a list of 7 accidents in the previous post due to loss of control.

Just over 8% of the total built have been lost to loss of control
accidents.

I wonder how many other people have to die or parachute to safety
before someone asks the question, should this glider be flying at all.

As the N4DM is certified, it had to be demonstrated that it will exit a spin after 3 turn at most.
Loosing 1800 m in any certified glider while trying to stop the spin is hilarious. This corresponds to something like 12-15 turns. Something has gone wrong very seriously.

Bert
Ventus cM TW

I would rather fly an L-13...

Boggs

Thanks for the detail on your accident in Namibia, Francois. It's fantastic that you are here to help us learn from it.
Quite different to intentionally spinning a training glider like ASK21.
Jim

At 20:13 01 February 2016, Tango Whisky wrote:
Le lundi 1 f=E9vrier 2016 20:01:27 UTC+1, Don Johnstone a
=E9crit=A0:
At 18:23 01 February 2016, Ramy wrote:
Scary! And I don't think there are that many nimbus 4DM out
there.=20
Will be
interesting to compare this number to number of 4DM made.
I=20
wouldn't want
to fly one myself.=20

Ramy=20
=20
It would appear that 100 Nimbus 4D were built, of those 11
were 4DT=20
and 12 were 4D leaving a total of 87 DM of all types.
=20
There is a list of 7 accidents in the previous post due to loss of
contro=
l.
=20
Just over 8% of the total built have been lost to loss of
control=20
accidents.
=20
I wonder how many other people have to die or parachute to
safety=20
before someone asks the question, should this glider be flying
at all.

As the N4DM is certified, it had to be demonstrated that it will exit
a
spi=
n after 3 turn at most.=20
Loosing 1800 m in any certified glider while trying to stop the
spin is
hil=
arious. This corresponds to something like 12-15 turns.
Something has gone
=
wrong very seriously.

Bert
Ventus cM TW

Not sure that spinning is the issue per se, it is what happens after
it stops spinning that seems to be the main issue. For whatever
reason it seems that some pilots have had difficulty stopping VNE
being exceeded in the recovery.
A test pilot might be able to demonstrate a successful recovery but
what about mere mortals?

On Monday, February 1, 2016 at 4:30:20 PM UTC-5, Don Johnstone wrote:
At 20:13 01 February 2016, Tango Whisky wrote:
Le lundi 1 f=E9vrier 2016 20:01:27 UTC+1, Don Johnstone a
=E9crit=A0:
At 18:23 01 February 2016, Ramy wrote:
Scary! And I don't think there are that many nimbus 4DM out
there.=20
Will be
interesting to compare this number to number of 4DM made.
I=20
wouldn't want
to fly one myself.=20

Ramy=20
=20
It would appear that 100 Nimbus 4D were built, of those 11
were 4DT=20
and 12 were 4D leaving a total of 87 DM of all types.
=20
There is a list of 7 accidents in the previous post due to loss of
contro=
l.
=20
Just over 8% of the total built have been lost to loss of
control=20
accidents.
=20
I wonder how many other people have to die or parachute to
safety=20
before someone asks the question, should this glider be flying
at all.

As the N4DM is certified, it had to be demonstrated that it will exit
a
spi=
n after 3 turn at most.=20
Loosing 1800 m in any certified glider while trying to stop the
spin is
hil=
arious. This corresponds to something like 12-15 turns.
Something has gone
=
wrong very seriously.

Bert
Ventus cM TW

Not sure that spinning is the issue per se, it is what happens after
it stops spinning that seems to be the main issue. For whatever
reason it seems that some pilots have had difficulty stopping VNE
being exceeded in the recovery.
A test pilot might be able to demonstrate a successful recovery but
what about mere mortals?

Hmmm.... maybe some of these pilots were taught, "Stick fully forward" in the spin recovery vs., "Get the nose below the horizon" instead. In a draggy trainer, they're slow to accelerate so not as much of an issue, in a "clean ship" speed happens very fast comparatively.
Some of this comes to, "Muscle memory" and whether or not good ideas were trained earlier.

I also agree, some ships do markedly different things depending on CG. Curious if there is a common CG (forward, aft?) on the accident ships.

PS, I know none of the involved pilots nor their experience, so I'm sorta guessing here.

On Monday, February 1, 2016 at 11:01:27 AM UTC-8, Don Johnstone wrote:
At 18:23 01 February 2016, Ramy wrote:
Scary! And I don't think there are that many nimbus 4DM out there.
Will be
interesting to compare this number to number of 4DM made. I
wouldn't want
to fly one myself.

Ramy

It would appear that 100 Nimbus 4D were built, of those 11 were 4DT
and 12 were 4D leaving a total of 87 DM of all types.

There is a list of 7 accidents in the previous post due to loss of control.

Just over 8% of the total built have been lost to loss of control
accidents.

I wonder how many other people have to die or parachute to safety
before someone asks the question, should this glider be flying at all.

The statistic is probably much worse giving that not all gliders are airworthy and flying from one reason or another.

Ramy

As the N4DM is certified, it had to be demonstrated that it will exit a spin after 3 turn at most.
Loosing 1800 m in any certified glider while trying to stop the spin is hilarious.

Maybe not if you in it. But I do see your point, was a spiral mistaken for a spin?

Cheers

Paul


This corresponds to something like 12-15 turns. Something has gone wrong very seriously.

Bert
Ventus cM TW

The very long wing open class gliders have a bad record on spin recovery.
They will generally transition to a spiral dive quite early in a spin,
but will accelerate very rapidly on the exit.
If they do get into a stable spin, the momentum in the wings is a problem.

If you have water in the wings, or fuel, then you are a test pilot.
Certification is done dry.

There are at least five Nimbus 4D accidents I am aware of where recovery
was past Vne and the glider broke up on recovery. Ash25 - same story.

Bruce

On 2016-02-02 08:12, Paul B wrote:

As the N4DM is certified, it had to be demonstrated that it will exit a spin after 3 turn at most.
Loosing 1800 m in any certified glider while trying to stop the spin is hilarious.

Maybe not if you in it. But I do see your point, was a spiral mistaken for a spin?

Cheers

Paul


This corresponds to something like 12-15 turns. Something has gone wrong very seriously.

Bert
Ventus cM TW


--
Bruce Greeff
T59D #1771

Le vendredi 15 janvier 2016 22:07:57 UTC+1, Jonathan St. Cloud a écrit :
The rigging is very important on a Nimbus and when I first got mine is was rigged horribly and flew horribly. Fixed the rigging and it was a beauty to fly.


Hi Jonathan,
Very interesting. I have a N4DM since 17 years and 2.500 hours and see no possibility at all to change any setting during rigging. I can't understand how I may "rig horribly"... Thanks for explaining to me and others.
Instead, I can change the setting of the flap angle and the force of airbrake locking by changing the extension of the controls between the fuselage and the inner wing, but this is something that takes time and attention, not simply a rigging. BTW, I actually change the airbrake locking force twice a year, for cold flights in Patagonia and warm ones in Europe. See my book "Dancing with the Wind" page 194 and following (on sale at Cumulus Soaring)..
All the best
jm