Accident in Namibia, SH Ventus 2cxm

Le lundi 1 février 2016 20:01:27 UTC+1, Don Johnstone a écrit*:
At 18:23 01 February 2016, Ramy wrote:
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.

That's not totally true.
- Spain: wrong decision (turn back) after engine failure after take off
- Zapala: hitting the rocks at low altitude in turbulent blue thermal day

Vinon 2009 was actually loss of control in spiral dive, inexperienced crew.
Bitterwasser 2016, the future will tell (the crew is alive and is professional).
The others, I don't know.

These gliders cannot undergo a spin or a spiral dive without an almost certain fatal issue (in particular if they have an engine), unless you are an expert test pilot. I was forced to do that in an ASH25E twenty years ago and although I could stop the spin after less than a turn, the recovery was above Vne and the fuselage was over the vertical position (i.e. slightly negative). I said NEVER again!

In the case of the N4D, it happens that the airbrakes will self-open (photo available) during the pull-up due to both the high lift force and the kinematics of the control rod. No way to avoid loosing the outer wings. Amazingly, I have flown 2 500 hrs in my N4DM, almost at the maximum rear CG, and could never enter a involuntary spin, but twice the beginning of a spiral dive because the inexperienced pilot tried to recover using the opposite aileron and pulling, promptly recovered with stick in the middle and little forward, and full opposite rudder, exit at Vne.

Big ships are like this, if you don't like, don't buy!

All the best,
jmc

On Tuesday, February 2, 2016 at 11:58:17 AM UTC+3, wrote:
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).

"Rigging" is a set of devices for adjusting positions, angles, tensions etc of aerodynamic surfaces -- or as a verb the use of such adjustments. Originally from sailing ships but later applied to aircraft (which were initially made in very similar ways. The "rigging angle", for example, refers to the angle between the chord of the wing and the fuselage.

What we refer to as "rigging" of gliders is merely the use of precision quick-release mechanisms that are expressly designed to not alter the settings!

At 16:34 01 February 2016, Jonathan St. Cloud wrote:
Nimbus 4DM Accident history (loss of control).

- 27/07/1997 Fuentemilanos Spain, 2 fatalities
- 13/07/1999 Minden USA, 2 fatalities
- 13/07/200 Ocana Spain, 1 fatality (4DT)
- 19/11/2006 Zapala Argentina, 2 fatalities
- 22/11/2007 Gariep Dam South Africa, 2 fatalities
- 01/08/2009 Vinon France, 2 fatalities
- 11/01 2016 Bitterwasser Namibia

anyone know the accident history of the ASH-25? I have about 200 hours in
Nimbus 4D and 4DM. Have about 500 hours in a Nimbus 4t that I did spin
and
the single seat nimbus is a beautiful flyer.


Loss of control is a wide category. I know one of the above is a winch
launch gone sour. Not much to do with spinning charachteristics...

At 11:02 02 February 2016, Bruce Hoult wrote:

"Rigging" is a set of devices for adjusting positions, angles, tensions
etc=
of aerodynamic surfaces -- or as a verb the use of such
adjustments.
Origi=
nally from sailing ships but later applied to aircraft (which were
initiall=
y made in very similar ways. The "rigging angle", for example, refers
to
th=
e angle between the chord of the wing and the fuselage.

What we refer to as "rigging" of gliders is merely the use of precision
qui=
ck-release mechanisms that are expressly designed to not alter the
settings=
!
Rigging could be referring to control deflections. These are not
affected by the operation pilots call "rigging" but they can, and do,
change due to wear and to the replacement of parts in the control
linkages. They are adjustable by maintenance personnel. If the
deflections are wrong the glider will not handle as designed and
expected.

Under BGA rules the control deflections on all gliders have to be
checked (and corrected if wrong) at every annual inspection. I expect
other authorities have similar rules.

On Tuesday, February 2, 2016 at 3:41:35 AM UTC-5, BruceGreeff wrote:
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

Bruce Greeff
T59D #1771

"Certification is done dry..." No. Current CS-22 Amendment 1:

"CS 22.221 General
(a) Compliance with the following requirements must be shown in all configurations and, for a powered sailplane, with the engine idling.
For sailplanes equipped to carry water ballast, the demonstrations of sub-paragraphs (b) to (g) must also be made for the most critical water ballast asymmetry that might occur due to any single malfunction or due to lateral accelerations during a spin."

Then, in spin testing (later in CS22 AL1):
"AMC 22.221(b)
Spinning
General
It will normally be sufficient to conduct a number of spins of about two turns in each of the conditions of CS 22.221(b) and subsequently to conduct spins of five turns in the most adverse cases."

You may recall the ETA spin test with one wing full/one empty led to a crash. Both CS-22 AL1 and the ETA test are available by mr. google.

On Tuesday, February 2, 2016 at 3:47:08 PM UTC+3, James Thomson wrote:
At 11:02 02 February 2016, Bruce Hoult wrote:

"Rigging" is a set of devices for adjusting positions, angles, tensions
etc=
of aerodynamic surfaces -- or as a verb the use of such
adjustments.
Origi=
nally from sailing ships but later applied to aircraft (which were
initiall=
y made in very similar ways. The "rigging angle", for example, refers
to
th=
e angle between the chord of the wing and the fuselage.

What we refer to as "rigging" of gliders is merely the use of precision
qui=
ck-release mechanisms that are expressly designed to not alter the
settings=
!
Rigging could be referring to control deflections. These are not
affected by the operation pilots call "rigging" but they can, and do,
change due to wear and to the replacement of parts in the control
linkages. They are adjustable by maintenance personnel. If the
deflections are wrong the glider will not handle as designed and
expected.

My point, precisely.

Le mardi 2 février 2016 13:41:43 UTC+1, Dan Daly a écrit*:

You may recall the ETA spin test with one wing full/one empty led to a crash. Both CS-22 AL1 and the ETA test are available by mr. google.

No. The Eta crashed when trying to recover from a spiral dive (dry). The load on the rudder simply snapped the tail boom.

The ASH25 did crash during flight testing when spinning with water in only one wing. The centrifugal force of the water made the wing skin pop, and Martin Heide had to parachute down. He had been suspicious about this outcome beforehand and had tried to talk authorities into dropping this part of the test, but to no avail. So he did the test starting at 10'000 ft.

On Tuesday, February 2, 2016 at 8:48:43 AM UTC-5, Tango Whisky wrote:
Le mardi 2 février 2016 13:41:43 UTC+1, Dan Daly a écrit*:

You may recall the ETA spin test with one wing full/one empty led to a crash. Both CS-22 AL1 and the ETA test are available by mr. google.

No. The Eta crashed when trying to recover from a spiral dive (dry). The load on the rudder simply snapped the tail boom.

The ASH25 did crash during flight testing when spinning with water in only one wing. The centrifugal force of the water made the wing skin pop, and Martin Heide had to parachute down. He had been suspicious about this outcome beforehand and had tried to talk authorities into dropping this part of the test, but to no avail. So he did the test starting at 10'000 ft.

******
According to the Oct 2009 BFU Investigative report 3x221-0/05, the test was a spinning trial with asymmetric fuel (not water as I said - you are correct on that) - page 1 (History of the flight). According to the conclusions, the spin changed to a spiral dive and the use of rudder for recovery broke the tail (page 5). I guess we are both right, and both wrong in some parts! The asymmetric condition was not noted in conclusions, so probably not critical in comparison to the engineering conclusions.

I didn't say anything about ASH25 but it sounds interesting... I did a brief search but couldn't find it online. When did it happen?

Thank you for the correction.

Le mardi 2 février 2016 15:59:41 UTC+1, Dan Daly a écrit*:
On Tuesday, February 2, 2016 at 8:48:43 AM UTC-5, Tango Whisky wrote:
Le mardi 2 février 2016 13:41:43 UTC+1, Dan Daly a écrit*:

You may recall the ETA spin test with one wing full/one empty led to a crash. Both CS-22 AL1 and the ETA test are available by mr. google.

No. The Eta crashed when trying to recover from a spiral dive (dry). The load on the rudder simply snapped the tail boom.

The ASH25 did crash during flight testing when spinning with water in only one wing. The centrifugal force of the water made the wing skin pop, and Martin Heide had to parachute down. He had been suspicious about this outcome beforehand and had tried to talk authorities into dropping this part of the test, but to no avail. So he did the test starting at 10'000 ft.

******
According to the Oct 2009 BFU Investigative report 3x221-0/05, the test was a spinning trial with asymmetric fuel (not water as I said - you are correct on that) - page 1 (History of the flight). According to the conclusions, the spin changed to a spiral dive and the use of rudder for recovery broke the tail (page 5). I guess we are both right, and both wrong in some parts! The asymmetric condition was not noted in conclusions, so probably not critical in comparison to the engineering conclusions.

I didn't say anything about ASH25 but it sounds interesting... I did a brief search but couldn't find it online. When did it happen?

Thank you for the correction.

I think that the ASH25 happened in 1985 or 1986. Martin Heide told me about it a week or two later.

Ailerons, flaps and mixing was rigged wrong. Once that was corrected she was a beauty. Recovered from spin entry within quarter turn of control inputs, dry. Single place Nimbus 4. I still miss that bird!

On Tuesday, February 2, 2016 at 12:58:17 AM UTC-8, wrote:
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