ACTION:

Final rule; request for comments.

SUMMARY:

The FAA is adopting a new airworthiness directive (AD) for all Schempp-Hirth Flugzeugbau GmbH Model Duo Discus and Duo Discus T gliders. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as cracks in the connecting tube of the elevator U-bracket of the horizontal tail, which could compromise the stiffness of the elevator control system and of the attachment of the horizontal tail. This AD requires repetitively inspecting the elevator U-bracket for cracks and broken weld seams, the rear connection between the horizontal tail and the rear attachment on the fuselage for play and softness, and the foam support for compression between the vertical and horizontal tail, and replacing or repairing damaged parts as applicable. The FAA is issuing this AD to address the unsafe condition on these products.

DATES:

This AD is effective February 24, 2023.

A copy of the AD is located here:
https://www.federalregister.gov/documents/2023/02/09/2023-02773/airworthiness-directives-schempp-hirth-flugzeugbau-gmbh-gliders

On Thursday, February 9, 2023 at 4:44:58 PM UTC-5, soa...@yahoo.com wrote:
> ACTION:
>
> Final rule; request for comments.
>
> SUMMARY:
>
> The FAA is adopting a new airworthiness directive (AD) for all Schempp-Hirth Flugzeugbau GmbH Model Duo Discus and Duo Discus T gliders. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as cracks in the connecting tube of the elevator U-bracket of the horizontal tail, which could compromise the stiffness of the elevator control system and of the attachment of the horizontal tail. This AD requires repetitively inspecting the elevator U-bracket for cracks and broken weld seams, the rear connection between the horizontal tail and the rear attachment on the fuselage for play and softness, and the foam support for compression between the vertical and horizontal tail, and replacing or repairing damaged parts as applicable. The FAA is issuing this AD to address the unsafe condition on these products.
>
> DATES:
>
> This AD is effective February 24, 2023.
>
> A copy of the AD is located here:
> https://www.federalregister.gov/documents/2023/02/09/2023-02773/airworthiness-directives-schempp-hirth-flugzeugbau-gmbh-gliders

If anyone has doubts about the efficiency and governmental proclivity towards make work bureacracy they need to read this "book." Two paragraphs would be plenty outside of Washington!

On Thursday, February 9, 2023 at 1:44:58 PM UTC-8, soa...@yahoo.com wrote:
> ACTION:
>
> Final rule; request for comments.
>
> SUMMARY:
>
> The FAA is adopting a new airworthiness directive (AD) for all Schempp-Hirth Flugzeugbau GmbH Model Duo Discus and Duo Discus T gliders. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as cracks in the connecting tube of the elevator U-bracket of the horizontal tail, which could compromise the stiffness of the elevator control system and of the attachment of the horizontal tail. This AD requires repetitively inspecting the elevator U-bracket for cracks and broken weld seams, the rear connection between the horizontal tail and the rear attachment on the fuselage for play and softness, and the foam support for compression between the vertical and horizontal tail, and replacing or repairing damaged parts as applicable. The FAA is issuing this AD to address the unsafe condition on these products.
>
> DATES:
>
> This AD is effective February 24, 2023.
>
> A copy of the AD is located here:
> https://www.federalregister.gov/documents/2023/02/09/2023-02773/airworthiness-directives-schempp-hirth-flugzeugbau-gmbh-gliders
One wants to speculate on the possibility that this part failed in a couple of recent fatal and non-fatal accidents. At least in one case, it would explain the known facts pretty well.

I was told by a local glider expert that the part in question is the
same (or at least very similar) to a part in my Stemme. Last summer I
abandoned a flight on a terrific soaring day because the glider just
didn't feel right. Upon inspection, the horizontal tail could be moved
up and down at the tips by about 14 mm (+/- 7 mm). I ordered the part
in question and had it installed.
Flies great again! Do your self a favor and take are of that.
Dan
5J
On 2/10/23 10:10, jfitch wrote:
> On Thursday, February 9, 2023 at 1:44:58 PM UTC-8, soa...@yahoo.com wrote:
>> ACTION:
>>
>> Final rule; request for comments.
>>
>> SUMMARY:
>>
>> The FAA is adopting a new airworthiness directive (AD) for all Schempp-Hirth Flugzeugbau GmbH Model Duo Discus and Duo Discus T gliders. This AD was prompted by mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI identifies the unsafe condition as cracks in the connecting tube of the elevator U-bracket of the horizontal tail, which could compromise the stiffness of the elevator control system and of the attachment of the horizontal tail. This AD requires repetitively inspecting the elevator U-bracket for cracks and broken weld seams, the rear connection between the horizontal tail and the rear attachment on the fuselage for play and softness, and the foam support for compression between the vertical and horizontal tail, and replacing or repairing damaged parts as applicable. The FAA is issuing this AD to address the unsafe condition on these products.
>>
>> DATES:
>>
>> This AD is effective February 24, 2023.
>>
>> A copy of the AD is located here:
>> https://www.federalregister.gov/documents/2023/02/09/2023-02773/airworthiness-directives-schempp-hirth-flugzeugbau-gmbh-gliders
> One wants to speculate on the possibility that this part failed in a couple of recent fatal and non-fatal accidents. At least in one case, it would explain the known facts pretty well.

The Summary only mentions the Duo Discus and Duo Discus T. It also applies to all variants of the Arcus and Nimbus 4. It should also serve as notice to stop lifting the tail of the glider by putting your shoulder under the horizontal and picking it up. When you do that, you are loading these fittings that have the proposed AD applied to them.

Steve Leonard

On Friday, February 10, 2023 at 2:56:45 PM UTC-5, Steve Leonard wrote:
> The Summary only mentions the Duo Discus and Duo Discus T. It also applies to all variants of the Arcus and Nimbus 4. It should also serve as notice to stop lifting the tail of the glider by putting your shoulder under the horizontal and picking it up. When you do that, you are loading these fittings that have the proposed AD applied to them.
>
> Steve Leonard
Thanks for that Steve. Spot on!
I can't think of an aerodynamic or trailer storage condition that would cause the damage. Motor gliders may be at higher risk due to heavier tail weights.

KS

On Friday, February 10, 2023 at 5:55:12 PM UTC-8, Karl Striedieck wrote:
> On Friday, February 10, 2023 at 2:56:45 PM UTC-5, Steve Leonard wrote:
> > The Summary only mentions the Duo Discus and Duo Discus T. It also applies to all variants of the Arcus and Nimbus 4. It should also serve as notice to stop lifting the tail of the glider by putting your shoulder under the horizontal and picking it up. When you do that, you are loading these fittings that have the proposed AD applied to them.
> >
> > Steve Leonard
> Thanks for that Steve. Spot on!
> I can't think of an aerodynamic or trailer storage condition that would cause the damage. Motor gliders may be at higher risk due to heavier tail weights.
>
> KS

I have always felt that SH method of attaching the horizontal stab is on the flimsy side. Oh, it’s strong enough for vertical loads, but give it a good side load and…………not so much! I must have half a dozen of those U members in my junk box, all from ground loop accidents. They’re all bent with one elevator up and the other bent down about 15 degrees! The load path goes from the U member on the vertical fin into the elevator receiver, then through 2 little elevator bearings with 6mm bolts, then into the horizontal stab spar . The forward sliding attachment also uses a 6mm rod in most models.
After Surgio’s accident at Truckee, I made a quick mock-up that showed a large load on one side of the horizontal stab ( like a big bird strike) would twist the U member leaving one elevator up and the other one down! This scenario also resulted in the whole horizontal stabilizer tilted to one side and digging in (leading edge down). Would this explain the high G loops seen by some whitnesses?
So, armed with this information, what should we do? I recommend you closely inspect the U member before every assembly and inspect the bearings on both sides of the elevator and look at the bearing mounts, too. They stand off about an inch behind the spar.
Something to consider,
JJ

> I have always felt that SH method of attaching the horizontal stab is on the flimsy side. Oh, it’s strong enough for vertical loads, but give it a good side load and…………not so much! I must have half a dozen of those U members in my junk box, all from ground loop accidents. They’re all bent with one elevator up and the other bent down about 15 degrees! The load path goes from the U member on the vertical fin into the elevator receiver, then through 2 little elevator bearings with 6mm bolts, then into the horizontal stab spar . The forward sliding attachment also uses a 6mm rod in most models.
> After Surgio’s accident at Truckee, I made a quick mock-up that showed a large load on one side of the horizontal stab ( like a big bird strike) would twist the U member leaving one elevator up and the other one down! This scenario also resulted in the whole horizontal stabilizer tilted to one side and digging in (leading edge down). Would this explain the high G loops seen by some whitnesses?
> So, armed with this information, what should we do? I recommend you closely inspect the U member before every assembly and inspect the bearings on both sides of the elevator and look at the bearing mounts, too. They stand off about an inch behind the spar.
> Something to consider,
> JJ

I suspect SH will beef up the design slightly and call it good. Slim chance that they will re-configure the part to be more robust (like AS?). Glider mfgs certainly can't admit the "other" guy has a better design.

lørdag den 11. februar 2023 kl. 20.51.56 UTC+1 skrev Craig Reinholt:
> > I have always felt that SH method of attaching the horizontal stab is on the flimsy side. Oh, it’s strong enough for vertical loads, but give it a good side load and…………not so much! I must have half a dozen of those U members in my junk box, all from ground loop accidents. They’re all bent with one elevator up and the other bent down about 15 degrees! The load path goes from the U member on the vertical fin into the elevator receiver, then through 2 little elevator bearings with 6mm bolts, then into the horizontal stab spar . The forward sliding attachment also uses a 6mm rod in most models.
> > After Surgio’s accident at Truckee, I made a quick mock-up that showed a large load on one side of the horizontal stab ( like a big bird strike) would twist the U member leaving one elevator up and the other one down! This scenario also resulted in the whole horizontal stabilizer tilted to one side and digging in (leading edge down). Would this explain the high G loops seen by some whitnesses?
> > So, armed with this information, what should we do? I recommend you closely inspect the U member before every assembly and inspect the bearings on both sides of the elevator and look at the bearing mounts, too. They stand off about an inch behind the spar.
> > Something to consider,
> > JJ
> I suspect SH will beef up the design slightly and call it good. Slim chance that they will re-configure the part to be more robust (like AS?). Glider mfgs certainly can't admit the "other" guy has a better design.

These models presents such a discomforting number of cases of poor design and poor manufacturing quality. Yet, it doesn't seem to affect the number of buying customers.
In our country there's reason to believe, that identified faults reported to our authority won't systematically find it's way to the manufacturer.
Look out for yourself out there.

A good design is resilient towards foreseeable unintended (ab)use.
Who would ever consider lifting up a 40 kg plus tail by lifting under the tailplane? Apparently foreseeable.

On Sunday, February 12, 2023 at 5:54:29 AM UTC-5, Per Givskov wrote:
> lørdag den 11. februar 2023 kl. 20.51.56 UTC+1 skrev Craig Reinholt:
> > > I have always felt that SH method of attaching the horizontal stab is on the flimsy side. Oh, it’s strong enough for vertical loads, but give it a good side load and…………not so much! I must have half a dozen of those U members in my junk box, all from ground loop accidents. They’re all bent with one elevator up and the other bent down about 15 degrees! The load path goes from the U member on the vertical fin into the elevator receiver, then through 2 little elevator bearings with 6mm bolts, then into the horizontal stab spar . The forward sliding attachment also uses a 6mm rod in most models.
> > > After Surgio’s accident at Truckee, I made a quick mock-up that showed a large load on one side of the horizontal stab ( like a big bird strike) would twist the U member leaving one elevator up and the other one down! This scenario also resulted in the whole horizontal stabilizer tilted to one side and digging in (leading edge down). Would this explain the high G loops seen by some whitnesses?
> > > So, armed with this information, what should we do? I recommend you closely inspect the U member before every assembly and inspect the bearings on both sides of the elevator and look at the bearing mounts, too. They stand off about an inch behind the spar.
> > > Something to consider,
> > > JJ
> > I suspect SH will beef up the design slightly and call it good. Slim chance that they will re-configure the part to be more robust (like AS?). Glider mfgs certainly can't admit the "other" guy has a better design.
> These models presents such a discomforting number of cases of poor design and poor manufacturing quality. Yet, it doesn't seem to affect the number of buying customers.
> In our country there's reason to believe, that identified faults reported to our authority won't systematically find it's way to the manufacturer.
> Look out for yourself out there.
>
> A good design is resilient towards foreseeable unintended (ab)use.
> Who would ever consider lifting up a 40 kg plus tail by lifting under the tailplane? Apparently foreseeable.

>>A good design is resilient towards foreseeable unintended (ab)use.<<
Correct, but in aviation, there are limits to that, unless you are designing a flying tank.

>>Who would ever consider lifting up a 40 kg plus tail by lifting under the tailplane? Apparently foreseeable.<<
Have seen it time and again! Same with turning the glider on the main wheel w/o a tail dolly installed by just yanking on the wing tip. Just because you have the dough to own a nice, shiny toy doesn't mean you have the brain power to understand the mechanics of things!
I am sure these sort of things are covered in the 'Feeding & Care' manual, as in 'Do not ....'

Uli
'AS'

On Sunday, February 12, 2023 at 7:05:28 AM UTC-8, AS wrote:
> On Sunday, February 12, 2023 at 5:54:29 AM UTC-5, Per Givskov wrote:
> > lørdag den 11. februar 2023 kl. 20.51.56 UTC+1 skrev Craig Reinholt:
> > > > I have always felt that SH method of attaching the horizontal stab is on the flimsy side. Oh, it’s strong enough for vertical loads, but give it a good side load and…………not so much! I must have half a dozen of those U members in my junk box, all from ground loop accidents. They’re all bent with one elevator up and the other bent down about 15 degrees! The load path goes from the U member on the vertical fin into the elevator receiver, then through 2 little elevator bearings with 6mm bolts, then into the horizontal stab spar . The forward sliding attachment also uses a 6mm rod in most models.
> > > > After Surgio’s accident at Truckee, I made a quick mock-up that showed a large load on one side of the horizontal stab ( like a big bird strike) would twist the U member leaving one elevator up and the other one down! This scenario also resulted in the whole horizontal stabilizer tilted to one side and digging in (leading edge down). Would this explain the high G loops seen by some whitnesses?
> > > > So, armed with this information, what should we do? I recommend you closely inspect the U member before every assembly and inspect the bearings on both sides of the elevator and look at the bearing mounts, too. They stand off about an inch behind the spar.
> > > > Something to consider,
> > > > JJ
> > > I suspect SH will beef up the design slightly and call it good. Slim chance that they will re-configure the part to be more robust (like AS?). Glider mfgs certainly can't admit the "other" guy has a better design.
> > These models presents such a discomforting number of cases of poor design and poor manufacturing quality. Yet, it doesn't seem to affect the number of buying customers.
> > In our country there's reason to believe, that identified faults reported to our authority won't systematically find it's way to the manufacturer.
> > Look out for yourself out there.
> >
> > A good design is resilient towards foreseeable unintended (ab)use.
> > Who would ever consider lifting up a 40 kg plus tail by lifting under the tailplane? Apparently foreseeable.
>
> >>A good design is resilient towards foreseeable unintended (ab)use.<<
> Correct, but in aviation, there are limits to that, unless you are designing a flying tank.
> >>Who would ever consider lifting up a 40 kg plus tail by lifting under the tailplane? Apparently foreseeable.<<
> Have seen it time and again! Same with turning the glider on the main wheel w/o a tail dolly installed by just yanking on the wing tip. Just because you have the dough to own a nice, shiny toy doesn't mean you have the brain power to understand the mechanics of things!
> I am sure these sort of things are covered in the 'Feeding & Care' manual, as in 'Do not ....'
>
> Uli
> 'AS'

What I don't understand (after reading the tech note) is why the FAA thinks that it will take 7 hours to do this inspection (15-30 min should do). No holes have to be cut to access the U-bracket, it is visible with the tailplane removed.

Tom

Same conditions applies to S-H ventus 2a-There is an AD for that model as well
Dan