Uncontrolled Loops Elevator failure

[Jonathan St. Cloud]

Just thought I would shift this thread. Not being an aerodynamicist, wouldn't a glider with a jammed elevator run out of energy in short order and end up in a spin within a tight loop and a half or two?

[[email protected]]

I've been mulling this over for years now. We have had 3 similar accidents, Ivens/Egon, Naddler/cadet, Sergio/Jim......all high speed dive, wings bent up into a U shape followed by one or more wing separation!............all in the same basic fuselage (SH 2 place), all with motors. The motors were not in use, so we can eliminate the actual motor, but all fuselages had a large opening in the aft fuselage to allow for the engine. The fuselages were strengthened around the hole, but maybe not enough for a high speed pullout? Let's say these ships got into a high speed dive for whatever reason, maybe as simple as both pilots thought the other guy was flying! Anyway, they realized the problem and pulled hard to get the nose up. Let's say they pulled about 5 G's. What is the aft boom going to do under a 5 G load? It's going to try and bow up a little, but the designed strength prevents any noticeable movement except around the engine hole. What might be going on there? The lower skin is holding in tension, but the upper skin is trying to fail under compression load. Where is it likely to fail? Around the engine hole that buckles slightly inward. This buckling allows the boom to bow upwards, slightly. Now let's look at what this buckling does to the horizontal stabilizer, it digs is slightly and therefore increasing the G load, which increases the bowing in of the engine hole............more G's, more buckling.......you get the picture! I could see this resulting in a 2 second loop
Something to think about,
JJ

[Steve Leonard[_2_]]

On Friday, September 28, 2018 at 10:42:00 AM UTC-5, wrote:
> I've been mulling this over for years now. We have had 3 similar accidents, Ivens/Egon, Naddler/cadet, Sergio/Jim......all high speed dive, wings bent up into a U shape followed by one or more wing separation!............all in the same basic fuselage (SH 2 place), all with motors. The motors were not in use, so we can eliminate the actual motor, but all fuselages had a large opening in the aft fuselage to allow for the engine. The fuselages were strengthened around the hole, but maybe not enough for a high speed pullout? Let's say these ships got into a high speed dive for whatever reason, maybe as simple as both pilots thought the other guy was flying! Anyway, they realized the problem and pulled hard to get the nose up. Let's say they pulled about 5 G's. What is the aft boom going to do under a 5 G load? It's going to try and bow up a little, but the designed strength prevents any noticeable movement except around the engine hole. What might be going on there? The lower skin is holding in tension, but the upper skin is trying to fail under compression load. Where is it likely to fail? Around the engine hole that buckles slightly inward. This buckling allows the boom to bow upwards, slightly. Now let's look at what this buckling does to the horizontal stabilizer, it digs is slightly and therefore increasing the G load, which increases the bowing in of the engine hole............more G's, more buckling.......you get the picture! I could see this resulting in a 2 second loop
> Something to think about,
> JJ

Fuselage will bend down both in front of and behind the wing during high g loading. Tail pushes down to make the nose go up. Top of fuselage should be in tension during high positive g maneuvers. So, I don't think fuselage flexure is a contributor. Could be wrong, but I think that is the wrong tree to bark up.

Steve Leonard

[Bob Kuykendall]

On Friday, September 28, 2018 at 8:42:00 AM UTC-7, wrote:
> I've been mulling this over for years now...

Very interesting, good catch, JJ! I think you're off base about the direction of fuselage bending, but you might be on the right track in general.

* Up elevator tends to bend the tailboom downward.

* Bending the tailboom downward applies compression to the bottom half and tension to the top half.

* In many gliders, the elevator push-pull tube presses aft for up elevator, and pulls forward for down elevator. (Known exceptions are ASW24-29, and the later single-seat Schleicher cockpits based on them)

* In some gliders, the elevator push-pull tube runs along the bottom half of the tailboom

Given a glider with a limber tailboom, the elevator push-pull tube running along the bottom of the tailboom, and the push-pull tube pressing aft for up elevator, the system described will have some measure of positive feedback.

As the pilot applies up elevator, the increased downward force at the tail bends the tailboom downward. The bending compresses and shortens the lower half of the tailboom structure. The shortening effect reduces the distance between where the elevator push-pull tube starts and where it meets the bellcrank at the bottom of the fin. Since the push-pull tube does not shorten as well, it tends to apply additional up elevator force at the aft bellcrank and consequently the elevator.

The big question is whether the effect is pronounced enough to become divergent at any point within the glider's operational flight envelope. My suspicion is that it's not. In most gliders, the tailboom is so stiff, and the elevator push-pull tube so close to the tailboom neutral axis, that the effect will be so small as to be barely noticeable. However, if perhaps the tailboom is more limber than normal (maybe because of an engine cutout), and the elevator push-pull tube is lower than normal (maybe relocated downward to accommodate an engine installation), the effect might be significant.

However, as B-47 aficionados will recognize, there is one important additional factor: As the tailboom bends downward, the relative incidence between the wing and horizontal stabilizer decreases, reducing the downward force applied by the horizontal stabilizer. This effect will tend to negate the elevator input effect described above, and might in fact completely overpower it.

Overall, this would be a great topic for one of our friends at Akaflieg Cal Poly San Luis Obispo. Some simple FEA on typical glider shapes and structures should be enough to indicate whether further study is warranted.

--Bob K.

[AS]

On Friday, September 28, 2018 at 2:26:57 PM UTC-4, Bob Kuykendall wrote:
> On Friday, September 28, 2018 at 8:42:00 AM UTC-7, wrote:
> > I've been mulling this over for years now...
>
> Very interesting, good catch, JJ! I think you're off base about the direction of fuselage bending, but you might be on the right track in general.
>
> * Up elevator tends to bend the tailboom downward.
>
> * Bending the tailboom downward applies compression to the bottom half and tension to the top half.
>
> * In many gliders, the elevator push-pull tube presses aft for up elevator, and pulls forward for down elevator. (Known exceptions are ASW24-29, and the later single-seat Schleicher cockpits based on them)
>
> * In some gliders, the elevator push-pull tube runs along the bottom half of the tailboom
>
> Given a glider with a limber tailboom, the elevator push-pull tube running along the bottom of the tailboom, and the push-pull tube pressing aft for up elevator, the system described will have some measure of positive feedback.
>
> As the pilot applies up elevator, the increased downward force at the tail bends the tailboom downward. The bending compresses and shortens the lower half of the tailboom structure. The shortening effect reduces the distance between where the elevator push-pull tube starts and where it meets the bellcrank at the bottom of the fin. Since the push-pull tube does not shorten as well, it tends to apply additional up elevator force at the aft bellcrank and consequently the elevator.
>
> The big question is whether the effect is pronounced enough to become divergent at any point within the glider's operational flight envelope. My suspicion is that it's not. In most gliders, the tailboom is so stiff, and the elevator push-pull tube so close to the tailboom neutral axis, that the effect will be so small as to be barely noticeable. However, if perhaps the tailboom is more limber than normal (maybe because of an engine cutout), and the elevator push-pull tube is lower than normal (maybe relocated downward to accommodate an engine installation), the effect might be significant.
>
> However, as B-47 aficionados will recognize, there is one important additional factor: As the tailboom bends downward, the relative incidence between the wing and horizontal stabilizer decreases, reducing the downward force applied by the horizontal stabilizer. This effect will tend to negate the elevator input effect described above, and might in fact completely overpower it.
>
> Overall, this would be a great topic for one of our friends at Akaflieg Cal Poly San Luis Obispo. Some simple FEA on typical glider shapes and structures should be enough to indicate whether further study is warranted.
>
> --Bob K.

Interesting thoughts, Bob! One point in JJ's post that caught my eye was the fact that all these accidents happened in SH gliders with a motor. I have to claim ignorance about the way the motor is held in the stowed position but is there a possibility that the engine assembly pushes down onto the elevator control rod when subjected to high g-loads?
Uli
'AS'

[Bob Kuykendall]

On Friday, September 28, 2018 at 12:04:10 PM UTC-7, AS wrote:

> ...is there a possibility that the engine assembly pushes down onto the elevator control rod when subjected to high g-loads?

I am curious about that as well. My worry is that there might be some subtle and unanticipated failure mode that brings the engine support system into conflict with the elevator system. But I am not familiar enough with the gliders of concern to know. Clearly the factory considers them safe.

--Bob K.

[[email protected]]

Very unlikely. The elevator pushrod is mounted to the left side of the engine box, not underneath.

[Tango Whisky]

Le vendredi 28 septembre 2018 21:04:10 UTC+2, AS a écritÂ*:
> On Friday, September 28, 2018 at 2:26:57 PM UTC-4, Bob Kuykendall wrote:
> > On Friday, September 28, 2018 at 8:42:00 AM UTC-7, wrote:
> > > I've been mulling this over for years now...
> >
> > Very interesting, good catch, JJ! I think you're off base about the direction of fuselage bending, but you might be on the right track in general.
> >
> > * Up elevator tends to bend the tailboom downward.
> >
> > * Bending the tailboom downward applies compression to the bottom half and tension to the top half.
> >
> > * In many gliders, the elevator push-pull tube presses aft for up elevator, and pulls forward for down elevator. (Known exceptions are ASW24-29, and the later single-seat Schleicher cockpits based on them)
> >
> > * In some gliders, the elevator push-pull tube runs along the bottom half of the tailboom
> >
> > Given a glider with a limber tailboom, the elevator push-pull tube running along the bottom of the tailboom, and the push-pull tube pressing aft for up elevator, the system described will have some measure of positive feedback.
> >
> > As the pilot applies up elevator, the increased downward force at the tail bends the tailboom downward. The bending compresses and shortens the lower half of the tailboom structure. The shortening effect reduces the distance between where the elevator push-pull tube starts and where it meets the bellcrank at the bottom of the fin. Since the push-pull tube does not shorten as well, it tends to apply additional up elevator force at the aft bellcrank and consequently the elevator.
> >
> > The big question is whether the effect is pronounced enough to become divergent at any point within the glider's operational flight envelope. My suspicion is that it's not. In most gliders, the tailboom is so stiff, and the elevator push-pull tube so close to the tailboom neutral axis, that the effect will be so small as to be barely noticeable. However, if perhaps the tailboom is more limber than normal (maybe because of an engine cutout), and the elevator push-pull tube is lower than normal (maybe relocated downward to accommodate an engine installation), the effect might be significant.
> >
> > However, as B-47 aficionados will recognize, there is one important additional factor: As the tailboom bends downward, the relative incidence between the wing and horizontal stabilizer decreases, reducing the downward force applied by the horizontal stabilizer. This effect will tend to negate the elevator input effect described above, and might in fact completely overpower it.
> >
> > Overall, this would be a great topic for one of our friends at Akaflieg Cal Poly San Luis Obispo. Some simple FEA on typical glider shapes and structures should be enough to indicate whether further study is warranted.
> >
> > --Bob K.
>
> Interesting thoughts, Bob! One point in JJ's post that caught my eye was the fact that all these accidents happened in SH gliders with a motor. I have to claim ignorance about the way the motor is held in the stowed position but is there a possibility that the engine assembly pushes down onto the elevator control rod when subjected to high g-loads?
> Uli
> 'AS'

No. The engine bay's lower enclosure is the shell of the fuselage.

[AS]

> > Interesting thoughts, Bob! One point in JJ's post that caught my eye was the fact that all these accidents happened in SH gliders with a motor. I have to claim ignorance about the way the motor is held in the stowed position but is there a possibility that the engine assembly pushes down onto the elevator control rod when subjected to high g-loads?
> > Uli
> > 'AS'
>
> No. The engine bay's lower enclosure is the shell of the fuselage.

So how are the control rods/cables routed past the engine bay? On either side of the engine bay? Between the outside shell and the engine compartment?
As I said, I am not familiar with these designs.

Uli
'AS'

[[email protected]]

On Friday, September 28, 2018 at 8:42:00 AM UTC-7, wrote:
> I've been mulling this over for years now. We have had 3 similar accidents, Ivens/Egon, Naddler/cadet, Sergio/Jim......all high speed dive, wings bent up into a U shape followed by one or more wing separation!............all in the same basic fuselage (SH 2 place), all with motors.

It's a bad thing anytime the tail feathers aren't pointing the way you like.. These accidents all ended the same way with the wings coming off from very high G-loads, but the evidence (such as it is) would seem to indicate mostly different starting points.

The Engen/Ivans Nimbus 4DM accident did not seem to involve any control circuit issue but, in the NTSB's judgement and according to witnesses, resulted from excessive Gs associated with recovery from a departure (spin or spiral dive) that started while thermalling.

The Nadler/cadet Arcus M incident apparently started with an uncommanded yaw (I believe flying straight) followed by an unrecoverable spiral dive. Maybe they will find the fuselage and get more information, but that sounds like a different root cause.

We may never know what happened with the Colacevich/Alto DuoDiscus accident, but a series of very high-G loops sounds more like a pitch control problem than a yaw control problem or a departure, though the chain of events up until these final maneuvers is unknown.

Sadly, there are a lot of different ways to end up with the wings coming off. It's important to learn from these tragedies, but for the moment I'd be hard-pressed to go down the path of some common root cause or a single design or construction defect with S-H two-seat gliders. These feel more like isolated incidents to me.

Andy Blackburn
9B

[Retting]

Don’t give up, keep evaluating. Find the answer. This is important.

R

[[email protected]]

On Friday, September 28, 2018 at 6:50:58 PM UTC-4, Retting wrote:
> Don’t give up, keep evaluating. Find the answer. This is important.
>
> R

If the stick was full back(it may not have been), the loop would be tight enough that it would not seem like the second, or third, would have been at a much greater speed.
I've done enough loops in high performance gliders to know that if you don't relieve the pressure a bit at the beginning of the down portion you run out of energy on the following up portion.
I wonder if this was a spiral that looked like loops from the point of observation. In a spiral the speed will increase and loads will rise until failure.
It is very possible nobody was flying due to GLOC.
FWIW
UH

[Andy Blackburn[_3_]]

That seems plausible. An inclined spiral may look like a loop without robbing all the energy at the top. It is hard to imagine a jammed elevator control situation that would result in continuous loops that didn’t end with a stall at the top rather than over-g at the bottom. Worth spending some time to think about the dynamics of a full-aft stick versus witness accounts. They may not line up exactly right.

If the witness accounts are remotely accurate G-LOC would be plausible as well.

An awful mystery.

Andy Blackburn
9B

[Tango Whisky]

You can't get by the engine compartment above or below, so anything that needs to pass goes left or right.

[Morgan[_2_]]

As a Duo owner, the Arcus and now the Duo T crash certainly have my attention. I have very carefully inspected the rudder cables everywhere that I can. Today I did some thorough checking of the elevator circuits and a few checks similar to those called for in the AD for single seaters around the elevator pushrod.

Nothing to indicate I have anything to be concerned about, but it makes you wonder.

I've certainly spent more time thinking about my response to various failure scenarios as a result of these accidents. I don't know that it will help should something go wrong in my glider, but it's better than trying to think of a response under the stress of the moment.

More importantly, my preflight bailout discussions with copilots has become more pointed and serious. Previously I was pretty lax in my bailout briefing with people. Sure, I'd explain the parachute for people that aren't used to wearing one. But it was mostly lip service that we all give the bailout. Canopy, belts, butt...

I've lost three friends this summer to bailouts that didn't happen or didn't happen soon enough. So my new briefing approach is still to cover canopy, belts, butt. But more about what I'll say "bail out, bail out, bail out" and the fact that it's very likely everyone for themselves. The chaos of a bailout situation won't afford a nice cordial, "no, you first, I insist, please do." There may only be one chance to get out.

Will I try to get my copilot out first, you bet. Can I guarantee in the moment that I'll know if they did or not, very unlikely.

I'm also very clear that if we have altitude and have any questions about controllability of the glider, we will get out. We aren't going to "see how this works out" if it seems unlikely to remain in control. Bailing out while still under semi-control seems a lot more viable than when something snaps and goes really wrong. I'd rather take my chances parachuting into inhospitable terrain than having a glider depart even semi-controlled flight.

One last thing I've decided I should start doing. Briefing the removal of the pin and the canopy latch on the right side. It's not intended for emergency use, but in the case of a right slip due to a rudder cable failure, I realize it might be very difficult to get rid of the break-away canopy if the wind is forcing it closed. A pre-briefed situation about the use of that latch might make a difference.

All things I hope to never test.

Morgan
5H

[Jonathan St. Cloud]

Not that is adds to the discussion, but by my count there have been 7 Nimbus 4D’s that have suffered spin/spiral wings break off.
The owner of a local N4D replace a metal bracket thingy in the elevator assembly on his 18 year old glider, it was the same part number for a
Dou discus and Arcus. Lots of common parts in the tail feathers of all twin place S-H gliders. Sure would be nice to know failure mode.

[[email protected]]

To add to the possibilities. In Denmark we've had a couple of cases of poor welding joints.
One Arcus had the air brake triangle coupling to the fuselage horn fail due to poor welding quality on top of the triangle being poorly designed. The pilot got in control of the plane by pulling the other brake and landed safely. After this it turned out SH didn't know whether the right triangles were installed in our Duo. They'd been mixed up between Duo's and Arcus's and apparently they're different.
Another Duo Xlt had the airbrake pushrod separate in the fuselage due to poor welding. This didn't result in an AD.
To a worrying extent the the learning feedback in European aviation is malfunctioning. The authorities are the ones supposed to address this.

[Nick Kennedy[_3_]]

A couple of observations from the cheap seats:
It sure looks like to me over the years there have been way too many Shempp Hirth Open class gliders going in; now with a latest rash of two seat motor equipped ships losing control and coming apart in the air for no obvious reason.
I have NO faith in the NTSB getting to the bottom of any of this. AFAIK the Nephi Arcus fuselage is still in the forest up by Monroe Peak Ut. I thought a loss of control surfaces was a major red flag and cause for a real investigation. Kinda hard to do a investigation when the fuselage after 3 months is still in the woods.
Concerning the Glider Bob Saunders Stemme NTSB investigation and final report,I found to be shallow and half assed at best. I never went to the crash sight, I wish I had now, to look at it with my own eyes to see what really happened. See where the engine switch's were and the engine controls etc etc.
Jonathan stated he knows of 7,7!! Nimbus 4's that have had the wings come off in flight, Holy S*%#t that's a lot!
These gliders we fly are built and stressed tested to take huge loads and most of the time do quite well; why are some coming apart? Design defects? FOD? Poor Maintenance, incorrect assembly, poor piloting skills? All of the above?
Or are all these accidents just the actual statistical odds catching up to us?
I wonder as several of these ships have obviously had control failures. And that is a tough nut to swallow. If I thought there was any history of my LS3a failing me I would not fly it, period. But people continue to fly those 2 place Shempp Hirth ships with and without motors, god bless them, they are braver than me! But this point I would not climb in one, but that's just me, there I said it. Something is obviously screwed up in those planes.
Keep the rubber side down and the shiny side up.

[Steve Koerner]

All of this horribleness points to one particular conclusion in my mind. Personal parachutes are not a satisfactory solution in way too many situations. We need to have whole aircraft chutes -- period. I think in most of these cases, actual and speculated, there would have been opportunity to activate a whole aircraft system.

All of the manufacturers need to get on the ball. GP gliders is now doing it. I have a whole aircraft system in my Lambada. I feel safer because of it. There have been at least two saves in Lambadas alone.

[Nick Kennedy[_3_]]

Oh
One more accident comes to mind
The ASH31m glider that went in just east of Ely last year.
Very experienced pilot climbing through 15,000' lost control and even though very high could not get it back together and had to bail, very lucky to live through that one. I'm not clear if the wings departed in that one.

[Tango Whisky]

Le samedi 29 septembre 2018 17:45:07 UTC+2, Nick Kennedy a écritÂ*:
> A couple of observations from the cheap seats:
> It sure looks like to me over the years there have been way too many Shempp Hirth Open class gliders going in; now with a latest rash of two seat motor equipped ships losing control and coming apart in the air for no obvious reason.
> I have NO faith in the NTSB getting to the bottom of any of this. AFAIK the Nephi Arcus fuselage is still in the forest up by Monroe Peak Ut. I thought a loss of control surfaces was a major red flag and cause for a real investigation. Kinda hard to do a investigation when the fuselage after 3 months is still in the woods.
> Concerning the Glider Bob Saunders Stemme NTSB investigation and final report,I found to be shallow and half assed at best. I never went to the crash sight, I wish I had now, to look at it with my own eyes to see what really happened. See where the engine switch's were and the engine controls etc etc.
> Jonathan stated he knows of 7,7!! Nimbus 4's that have had the wings come off in flight, Holy S*%#t that's a lot!
> These gliders we fly are built and stressed tested to take huge loads and most of the time do quite well; why are some coming apart? Design defects? FOD? Poor Maintenance, incorrect assembly, poor piloting skills? All of the above?
> Or are all these accidents just the actual statistical odds catching up to us?
> I wonder as several of these ships have obviously had control failures. And that is a tough nut to swallow. If I thought there was any history of my LS3a failing me I would not fly it, period. But people continue to fly those 2 place Shempp Hirth ships with and without motors, god bless them, they are braver than me! But this point I would not climb in one, but that's just me, there I said it. Something is obviously screwed up in those planes..
> Keep the rubber side down and the shiny side up.

In any open class two-seater, once you've done a full turn in a spin, you are very likely to lose your wings.
The angular momentum of these wings plus the fuselage is about 4 times higher than that of a 15 m ship, but the rudder is only twice as large - so it will take more twice the time to stop the rotation, all the while accelerating vertically. Little chance *not* to exceed vne.

[[email protected]]

If the fuselage bows down under positive G's, that would reduce the declanage and therefore reduce the up elevator requested. If the pilot is looking at rocks and trees where the blue sky should be on his canopy, he's going to pull even harder to make the rocks go away. More bowing down reduces the angle of the horizontal stab even more and reduces the requested up elevator. Is this the reason these big ships end up going so fast? He's pulling back, but the ships going faster and faster and soon the wings start bowing up. I remember flying with the Chase 101 (no composite structure, solid foam wings with glass covering) the pilot got into a spiral dive and the wings bowed up in a big U...........sound familiar? Anyway, the pilot bailed out and later reported that the ailerons wouldn't roll him out of the spiral. Think about it, they're little more tip rudders when in the vertical position. Our composite toys are quite flexible structures, I watched a Discus land in a barley field, he touched down about 40 knots, caught his left wing in the barley and spun around. The fuselage bowed like a banana and the T tail laid over about 45 degrees. The ship came to an abrupt stop at about 180 degrees and the T tail snapped back up to vertical and just sat there and quivered for second or two! I don't have to worry too much about all this because my Genesis doesn't have a boom, but it does have a ballistic parachute! If I were still flying a big ship, I'd make damned sure one of us had his head out of the cockpit AT ALL TIMES!
My, how I have rambled on, sorry.
JJ

[kinsell]

On 09/29/2018 09:45 AM, Nick Kennedy wrote:
> A couple of observations from the cheap seats:
> It sure looks like to me over the years there have been way too many Shempp Hirth Open class gliders going in; now with a latest rash of two seat motor equipped ships losing control and coming apart in the air for no obvious reason.
> I have NO faith in the NTSB getting to the bottom of any of this. AFAIK the Nephi Arcus fuselage is still in the forest up by Monroe Peak Ut. I thought a loss of control surfaces was a major red flag and cause for a real investigation. Kinda hard to do a investigation when the fuselage after 3 months is still in the woods.
> Concerning the Glider Bob Saunders Stemme NTSB investigation and final report,I found to be shallow and half assed at best. I never went to the crash sight, I wish I had now, to look at it with my own eyes to see what really happened. See where the engine switch's were and the engine controls etc etc.
> Jonathan stated he knows of 7,7!! Nimbus 4's that have had the wings come off in flight, Holy S*%#t that's a lot!
> These gliders we fly are built and stressed tested to take huge loads and most of the time do quite well; why are some coming apart? Design defects? FOD? Poor Maintenance, incorrect assembly, poor piloting skills? All of the above?
> Or are all these accidents just the actual statistical odds catching up to us?
> I wonder as several of these ships have obviously had control failures. And that is a tough nut to swallow. If I thought there was any history of my LS3a failing me I would not fly it, period. But people continue to fly those 2 place Shempp Hirth ships with and without motors, god bless them, they are braver than me! But this point I would not climb in one, but that's just me, there I said it. Something is obviously screwed up in those planes.
> Keep the rubber side down and the shiny side up.
>

The NTSB prelim said the wreckage debris field from Nephi was about a
mile long and taken to a secure facility for analysis. I assume this
includes the fuselage?

[Jonathan St. Cloud]

On Saturday, September 29, 2018 at 8:45:07 AM UTC-7, Nick Kennedy wrote:
> A couple of observations from the cheap seats:
> It sure looks like to me over the years there have been way too many Shempp Hirth Open class gliders going in; now with a latest rash of two seat motor equipped ships losing control and coming apart in the air for no obvious reason.
> I have NO faith in the NTSB getting to the bottom of any of this. AFAIK the Nephi Arcus fuselage is still in the forest up by Monroe Peak Ut. I thought a loss of control surfaces was a major red flag and cause for a real investigation. Kinda hard to do a investigation when the fuselage after 3 months is still in the woods.
> Concerning the Glider Bob Saunders Stemme NTSB investigation and final report,I found to be shallow and half assed at best. I never went to the crash sight, I wish I had now, to look at it with my own eyes to see what really happened. See where the engine switch's were and the engine controls etc etc.
> Jonathan stated he knows of 7,7!! Nimbus 4's that have had the wings come off in flight, Holy S*%#t that's a lot!
> These gliders we fly are built and stressed tested to take huge loads and most of the time do quite well; why are some coming apart? Design defects? FOD? Poor Maintenance, incorrect assembly, poor piloting skills? All of the above?
> Or are all these accidents just the actual statistical odds catching up to us?
> I wonder as several of these ships have obviously had control failures. And that is a tough nut to swallow. If I thought there was any history of my LS3a failing me I would not fly it, period. But people continue to fly those 2 place Shempp Hirth ships with and without motors, god bless them, they are braver than me! But this point I would not climb in one, but that's just me, there I said it. Something is obviously screwed up in those planes..
> Keep the rubber side down and the shiny side up.

Just wanted to say, in almost 1700 hours of glider time, I have about 400 hours in s single seat N4 and about 100 in two different N4D's, one motor one pure sailplane. The hours in these long wingers are the most pleasant of my soaring career, especially the two place nimbus 4D. These aircraft are not easy to fly, but they fly magnificently! Have never flown 21 or 23 meters, but the 26.5 meter birds can efficiently dolphin fly for hundreds of kilometers, something you just can't do in a std, 15m or 18m bird. Plus they are graceful and beautiful, but a bit of inattention can leave dwindling options. They are like dating a super model, I imagine.