Uncontrolled Loops Elevator failure

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

R

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

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

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

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

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.

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.

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.

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.

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.