Accident in Namibia, SH Ventus 2cxm

Just like any other certified glider according to the European CS-22 norm, a 25+ m glider has to undergo successful spin tests, including tests with asymmetrical water ballast. That's how the Eta glider used for certification broke up some years ago: when getting out of a spin with full ballast in one wing, the other empty, the fuselage couldn't resist the torsional load and failed.

Excerpt from the CS-22 rules:

Spinning

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.

(b) The sailplane must be able to recover from spins of at least five turns or such lesser number at which the spin changes into a spiral dive, by applying the controls in a manner normal for recovery and without exceeding either the limiting air-speed nor the limiting positive manoeuvring load factor for the sailplane. Tests must be conducted with wing-flaps and airbrakes neutral (see AMC 22.335) and with:
(1) controls held in the position normal for spins;
(2) ailerons and rudder used in opposite directions;
(3) ailerons applied in the direction of rotation.
In addition and where applicable, tests must be conducted in critical combinations of airbrake extension, wing-flap deflection, waterballast including trim water-ballast and with the powerplant extended or retracted. For wing-flap positions for which a VFE limitation is established, the flap position may be adjusted during recovery after the auto-rotation has stopped. (See AMC 22.221 (b))

(c) A sailplane, in the configurations certificated for intentional spinning, must be able to recover from any point in a spin as defined in CS 22.221(b) in not more than one additional turn. In those configurations not approved for intentional spinning, sub-paragraph (d) must be applied. (See AMC 22.221 (c), (d), (e) and (f))

(d) A sailplane in the configurations not certificated for intentional spinning, must still be able to recover from a spin as defined in CS 22.221(b) in not more than one and a half additional turns. (See AMC 22.221 (c), (d), (e) and (f))

(e) In addition, any sailplane must be able to recover from a one turn spin in any configuration in not more than one additional turn. (See AMC 22.221 (c), (d), (e) and (f))

(f) The loss of altitude from the point at which recovery is initiated to the point at which horizontal flight is first regained must be determined in all of the above mentioned cases. (See AMC 22.221 (c), (d), (e) and (f))

(g) It must be impossible to obtain uncontrollable spins with any use of the controls.

CS 22.223 Spiral dive characteristics
If there is any tendency for the spin to turn into a spiral dive the stage at which this tendency occurs, must be determined. It must be possible to recover from the condition without exceeding either the limiting air speed or the limiting positive maneuvering factor for the sailplane. Compliance with this requirement must be shown without the use of air brakes.

Curiously enough the ASH-26E is not certified for spins.


On Friday, January 15, 2016 at 1:51:30 PM UTC-8, wrote:
Just like any other certified glider according to the European CS-22 norm, a 25+ m glider has to undergo successful spin tests, including tests with asymmetrical water ballast. That's how the Eta glider used for certification broke up some years ago: when getting out of a spin with full ballast in one wing, the other empty, the fuselage couldn't resist the torsional load and failed.

Excerpt from the CS-22 rules:

Spinning

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.

(b) The sailplane must be able to recover from spins of at least five turns or such lesser number at which the spin changes into a spiral dive, by applying the controls in a manner normal for recovery and without exceeding either the limiting air-speed nor the limiting positive manoeuvring load factor for the sailplane. Tests must be conducted with wing-flaps and airbrakes neutral (see AMC 22.335) and with:
(1) controls held in the position normal for spins;
(2) ailerons and rudder used in opposite directions;
(3) ailerons applied in the direction of rotation.
In addition and where applicable, tests must be conducted in critical combinations of airbrake extension, wing-flap deflection, waterballast including trim water-ballast and with the powerplant extended or retracted. For wing-flap positions for which a VFE limitation is established, the flap position may be adjusted during recovery after the auto-rotation has stopped. (See AMC 22.221 (b))

(c) A sailplane, in the configurations certificated for intentional spinning, must be able to recover from any point in a spin as defined in CS 22.221(b) in not more than one additional turn. In those configurations not approved for intentional spinning, sub-paragraph (d) must be applied. (See AMC 22.221 (c), (d), (e) and (f))

(d) A sailplane in the configurations not certificated for intentional spinning, must still be able to recover from a spin as defined in CS 22.221(b) in not more than one and a half additional turns. (See AMC 22.221 (c), (d), (e) and (f))

(e) In addition, any sailplane must be able to recover from a one turn spin in any configuration in not more than one additional turn. (See AMC 22.221 (c), (d), (e) and (f))

(f) The loss of altitude from the point at which recovery is initiated to the point at which horizontal flight is first regained must be determined in all of the above mentioned cases. (See AMC 22.221 (c), (d), (e) and (f))

(g) It must be impossible to obtain uncontrollable spins with any use of the controls.

CS 22.223 Spiral dive characteristics
If there is any tendency for the spin to turn into a spiral dive the stage at which this tendency occurs, must be determined. It must be possible to recover from the condition without exceeding either the limiting air speed or the limiting positive maneuvering factor for the sailplane. Compliance with this requirement must be shown without the use of air brakes.

On Friday, January 15, 2016 at 1:58:38 PM UTC-8, Jonathan St. Cloud wrote:
Curiously enough the ASH-26E is not certified for spins.

And the reason for that would be, what in Aviation is known as common sense. You want engine oil spilling over a possibly warm/hot exhaust? An engine bay fire?

The ASH-26E handles beautifully, I expect it to recover from a spin very well. Certainly all pushing I have done both with and without an engine installed, it was just great.

On Friday, January 15, 2016 at 2:09:14 PM UTC-8, Darryl Ramm wrote:
On Friday, January 15, 2016 at 1:58:38 PM UTC-8, Jonathan St. Cloud wrote:
Curiously enough the ASH-26E is not certified for spins.

And the reason for that would be, what in Aviation is known as common sense. You want engine oil spilling over a possibly warm/hot exhaust? An engine bay fire?

The ASH-26E handles beautifully, I expect it to recover from a spin very well. Certainly all pushing I have done both with and without an engine installed, it was just great.

I suspect that Schleicher just doesn't want you to do spins, not that it can't. In addition to oil, I wonder if there's a concern that wing mounted water or fuel tanks could expand with the centrifugal force and damage the wing skins?

-tom

On Friday, January 15, 2016 at 4:51:30 PM UTC-5, wrote:
...how the Eta glider used for certification broke up some years ago:
when getting out of a spin with full ballast in one wing, the other empty,
the fuselage couldn't resist the torsional load and failed.

I was briefed that the Eta accident was caused by not recognizing
that the spin had degenerated to spiral dive, followed by incorrect
recovery from spiral dive. Was I briefed incorrectly (by a factory
test pilot, briefing me on spin recovery in another make/model)?

Thanks,
Best Regards, Dave

Dave,

your version is correct.

By my count there have been four Nimbus 4D spin/spiral non-recoverable accidents. Two accidents both flight crew were killed and two accidents both flight crew bailed out.

Dave is indeed right, but that was not my point, just that the Eta did break up during spin tests.

If you want the whole story, here is the final investigation report:

http://www.bfu-web.de/EN/Publication...ublicationFile

On Monday, January 18, 2016 at 12:37:39 PM UTC-8, wrote:
Dave is indeed right, but that was not my point, just that the Eta did break up during spin tests.

If you want the whole story, here is the final investigation report:

http://www.bfu-web.de/EN/Publication...ublicationFile

Interesting read. What structural load factors do the sailplane designers use?

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.