Carbon leading edge failure

[Ward Odenwald]

Flew twice from the Smithsburg training hill today. Conditions were ideal, albeit cold - light snow, mid 30s, 10 to 15 mph straight in at launch. Decided to land on my wheels on the second flight due to the textured air during the flight. My approach was like any other wheel landing that I’ve had, dragging my feet to reduce speed before my wheels (aka skids) scraped along the ground. Soon after touching down, my wheels sunk into the wet field and my forward momentum was enough to bring the nose down on the field but not enough to suggest that I had just done significant damage to the glider. No damage to the control frame or me and no apparent damage to both leading edges and the nose fairing after inspecting the sail and running my hands along the leading edges. During the walk back to the setup area there was also no indication that anything was damaged even when the glider was parked tail into the wind with the wings load with moderate air pressure. Breaking down/packing up the glider was also normal even when removing the tip wands. The surprise came after I folded the leading edges in toward the keel. While I was rolling the sail up, Charley broke the news to me as he was standing at the nose. The right leading edge brake was 2.5 to 3 inches from the nose plate. I’ve included the nose plate and nose fairing in the photos which, based on their “like new” appearance, indicate that the nose did not suffer greatly during this less than graceful return to earth. Last night, before packing the glider, I visually inspected the leading edge and cross tube - nothing detected. Not being an engineer, I have more questions than answers as to why the leading edge experienced an almost 90-degree clean break instead of just cracking. Was the break triggered by just this event or was it the result of combined/cumulative insults? Given the break on the right side, what’s up with the left leading edge as it must have also been stressed? Also surprised/pissed-at-myself that the break went unnoticed until packing up the glider.

Take home message: Had I unzipped the under surface of the wing and stuck my head inside after the landing, I may have detected the break. However, if the broken halves were reunited and pressed together by the sail tension, which would explain why the glider behaved normal during ground handling and break down, I would have most likely only detected the break by running my hands along the leading edge from inside the wing as poor visibility (heavy/dark overcast) was all that I had. So for now, the only message(s) that I’m confident of are that: 1) I’m lucky that I didn’t take another flight and, 2) the fewer assumptions you make about your glider after a seemingly minor incident will help avoid flying with a significantly comprised wing. Any insights will be greatly appreciated! Ward

[sailin]

Ward, I am very sorry to hear about the leading edge break. Thank you very much for posting about this incident in such a detailed way. This is the type of stuff that benefits the whole community and keeps us all diligent and informed. Thanks man !!!

Hoping for a speedy repair and a soon to be soaring flight for you. Look forward to flying with you soon.

Jon

[rlweber]

Sorry to hear about the break. On the positive side a fellow named Bill stopped by as I was breaking down my glider in the bridge Liz at Woodstock ( had an hr long flight in moderate, but cold conditions with snow flurries)and asked about you. He really appreciated the pics u took of his house. Way to build good will for the sport!

[rlweber]

Sorry to hear about the break. On the positive side a fellow named Bill stopped by as I was breaking down my glider in the bridge Liz at Woodstock ( had an hr long flight in moderate, but cold conditions with snow flurries)and asked about you. He really appreciated the pics u took of his house. Way to build good will for the sport!

[Pete Schumann]

Wow! Scary stuff. Thanks for posting Ward. It will have us all looking closer at our gliders and CF tubes.

Pete

[Danny Brotto]

I saw Ward’s beak on his LiteSpeed yesterday. It was in soft soil, headwind, and not at all dramatic. I was really surprised to see the damage that was seemingly caused by the light whack. I’ve got to wonder if that damage was created previously or occurred progressively with that minor impact exposing it?

From my experience, carbon does not break cleanly rather it splinters with sections of the laminate layers still connected. That LE break was rather clean. I’m wondering if something else was going on here? Does an inner sleeve end there at the break?

Definitely should get some pictures out to the manufacturer for comment.

Danny Brotto

[mcgowantk]

Ward - Thanks so much for posting about your leading edge and including some good pictures of the break. I also fly a Moyes Litespeed so I have a new chore for today.

I agree that your nose cone and nose plate look in good condition - no damage that I could see. So I don't see why a break could have existed for some time.

I also agree with Danny about the way the leading edge broke damage. Do you have any more thoughts now that you have slept on it? Can you see if the break was parallel to the fibers? I just find it a very interesting break. Was there any history of damage or crashes on the glider when you bought it?

Last and most important, I am glad that you are ok. As I am sure you will, I would be interested in seeing what response you might ultimately get from Moyes, etc. on the break.

Take care and thanks again for sharing this.

Tom McGowan

[Ward Odenwald]

Here are two additional views. There is some minor fraying but most of the brake is remarkably clean with little or no detectable damage to the surfaces flanking the brake. Why this occurred is still a mystery. I’ve had landings like this in the past with no issues. I bought the RS4 from Filippo Oppici in the fall of 2010 with only ~15 to 18 hrs on it. Filippo took delivery in April of that year and used it to compete around the world. His reason for selling was that his hook in weight was at the low end of the optimal weight for the glider. Except for the leading edge, the glider is/was in excellent condition including the original down tubes. My plan is to forward Moyes the link to this thread and ask them for their insights and suggestions. Ward

[markc]

Very disconcerting.... Ward, when you took delivery, did you have a chance to examine the noseplate junction in detail? I have to admit I'm kinda/sorta hoping that there was some undisclosed history for the glider..... A single noseover and *snap* ? That is just damn freaky!

Very glad that you did not fly again, and I hope the repairs aren't astronomical....

MarkC

[Ward Odenwald]

When not flying, the glider was parked in the basement set up with the wings fully extended (no VG tension or batons) and the leading edges were supported with lines from the ceiling. Given the easy accesses to every part of the glider, I’ve had a close look at most if not every square centimeter of it after each flying day. No stress related damage was ever detected along the leading edges or at their attachment points to the nose plate. Part of my routine is to slide my hands along the leading edges near the nose from inside the wing feeling for frayed fibers – none detected. My best guess is that when the glider nosed in, the forward momentum induced a compression stress that combined with other undetected earlier induced small or internal stress fractures/cracks was enough to trigger the leading edge failure. If just a single event caused the brake, I would have expected to see evidence of the impact force either on the nose plate, the keel, the other leading edge or on the nose cone fairing. If the break was the end result of multiple events, close inspection of the other leading edge may reveal stress related changes in the tube. Another possibility is a defect in the tube during its construction. As for the repair(s) being astronomical, someone once told me “that when a carbon composite part breaks its sounds just like money.” Ward

[RichH]

Just a guess on my part Ward but I wonder with the glider coming from a comp pilot and all the packing and shipments that occur with competing whether some damage could have occurred then..There has been plenty of damage to leading edges during shipments..A carbon fiber leading edge I would think could sustain damage from compression and would leave little evidence on the surface of the leading edge..possibly leaving deep cracks that would eventually fail during another event..(your nose over)

[Rich E]

Carbon composites can suffer from Barely Visible Impact Damage (BVID) where following an impact, which can be relatively minor, there is internal delamination or stress raiser formed internally which can usually only be detected by a non-destructive testing (NDT) technique such as x-ray, ultrasound or dye penetration techniques. Repeated stress cycles (aka flights) then cause further fatigue until catastrophic failure occurs as in your case. My guess is that at some point in the last, perhaps during transit as suggested earlier, some damage occurred in that area that wasn't detectable through sight or touch and that your nose over was just enough to causes the failure (fatigue having consumed the residual structural integrity between initial damage and failure).

To prevent this manufacturers obviously overbuild their structures to build in a healthy safety margin but clearly this can be exceeded.

I wonder if annual inspections for carbon gliders should include a NDT technique to check for BVID/voids/delamination etc and similarly after any significant impact (e.g. After any crash, carbon bike frames, forks, handlebars etc are supposed to be sent back to the manufacturer for testing. A cycling team mate had his forks fail, luckily while going uphill but still at 20mph and face planted - a few minutes later and it would have been on a descent at up to 50mph). Finally, given that carbon can only fail catastrophically, (no bending, buckling etc as per metals) maybe its suitability as a material for hang gliding needs rethinking unless there is an easy and affordable testing option for owners.

Clearly not much help to you at this point but hopefully Moyes will be able to do you a deal on a replacement leading edge. Failing that there are an increasing number of specialist carbon repairers out there that may be able to help. Again another team mate has had 2 frames repaired and has been both very happy with the result and to race on both. While scale is a factor, it is just a tube and much less complex in shape compared to a bike frame so it may be an option. As for cost in the hundreds of dollars range for a snapped frame rather than thousands.

[lbunner]

Could a previous whack have been the initiating event?

[Ward Odenwald]

Rich E, thanks for your input. Your experience and insight with cycling composites and the possibility that BVIDs are cumulative events leading to failure - fits with my non-expert impression/guess. I don’t have the resources to examine the other leading edge with non-destructive testing techniques but I believe that if this failure was triggered by multiple events there should be evidence of those events within the intact leading edge. Moyes has asked for additional photos of the break and the surrounding sail that I will send tomorrow and post here. I spent this evening looking for additional stress along both leading edges (visually and sliding my hands along the tubes) and nothing was detected. The only barely visible defects were confined to the break and immediate flanking sides but beyond several millimeters of the break, the surface of the tubes looked normal with no touch snags. Ward

[Roger]

Does anyone know the cause of Wolfi's LE failure?

[Ward Odenwald]

Here are better views of the inner surface on both sides of the break. To the untrained eye, it looks like there are many small fractures that are both adjacent to and farther away from the break. For reference, the last image is of the left leading edge. Ward

[Dunegoon]

Hi Ward,

I should have posted some information earlier about your glider, but this is what I saw. The glider looked "unusual" that the airfoil was flat and had little camber. The leading edges were not loaded and curved properly. I tried to diplomatically mention this to you a few times. When I first looked at it I thought the leading edge was broken at the crossbar. I am not familiar with ultra modern gliders, so at first I was not even sure what I was looking at. I noticed this on the ground and as you were moving it to the breakdown area. Of course this was the first time I was introduced to you and didn't want to immediately say, oh hello, and by the way your glider is BROKEN. I would not have let you attempt to fly without voicing my concerns. That is why I followed you to the break down area and stuck around as you took it apart. Of course I immediately saw the problem as expected when you disassembled the glider and brought it to your attention.

With a carbon fiber airframe I would say that this is a typical failure path. Even with a mild wack a shock impulse is sent down the very ridged leading edge basically snapping the leading edge exactly where expected. This is not due to impact of the nose but the transmission of a very high energy impulse from the wingtip. A lot of energy is stored in the curved LE and sail. I did some work in the early 80s with hang glider design and engineering research at ERAU, so take my observations and conclusions for what they are worth (probably nothing LOL). Problems like this are why carbon airframes are very tricky to work with. How do you tell when they are bad, other than destructive testing? I would expect you to find out from Moyes that this is a common failure. The entire airframe should be removed and examined as a system, not just parts.

Hope I have provided some information and insight as to why failures like this can occur.

Charley F.

[Ward Odenwald]

Thanks Charley, I'm hoping to learn more from Moyes soon. I'm left with the same impression - how do you tell when a carbon component is close to failure? My concern is not being able to determine if the other carbon components are airworthy. If this is a common failure, as you suggest, I'm worried about other less than new carbon gliders. Ward

[mcelrah]

Ward,

Sorry for your financial set-back WRT the LE and glad you caught this before attempting to fly again.

For what it's worth, I was at Smithsburg when you whacked and the noise was loud and sharp, like a rifle shot.

- Hugh

[RichH]

One of the risks with buying a used carbon fiber framed aircraft is you can not tell what stress the cf members of your airframe have received. I think it would be a good practice to periodically replace major cf frame components. I do believe most manufacturers recommend this after a period of time as a matter of their inspection process. When packaging a cf framed glider for shipment it might be wise to wrap your gilder in a material where any compression damage could be seen visually..I have seen damage occur to a leading edge of a glider unpacked from a cardboard box where no visable damage occurred to the box itself..

[Flying Lobster]

Boy that is scary--though I remember ages ago Mike Chevalier's carbon RLE snapped on his TRX after he landed once. I think that this is a highly unusual break given that the area it happened in is generally a low -load area when the wing is set up properly. I would suspect the only way a break like that could happen would be a very sharp impact/compression, and would be even more unusual lacking any evidence on the sail inside/outside of such a force. My wild guess is that the former owner being a comp dude may have disassembled the glider and somehow the tube got crushed/impacted in an odd way during his wanderlust adventures.

[Flying Lobster]

Just looked more closely at your left LE comparison shot--it looks like there is some kind of reinforcement and abrasion pad around the tube--is that the area where your break occurred on the failure tube? I wonder if that area rides up against something rigid when folded--another way that a sharp force may have compromised it.

[Ward Odenwald]

The abrasion pad is to protect the LE from close contact with the crossbar when folded and the brake is approx.5 inches from the pad closer to the nose.

This afternoon, Moyes (via Kraig Coomber) emailed their impression of what may have triggered the break. As you can see from Kraig’s comments and my response, I’m satisfied with their efforts. Given that the past history of the glider is not fully known and subtle cumulative dings may have gone unappreciated and undetected, I believe that the most heuristic aspect of the LE break (and this discussion or “cautionary tale”) is that everyone should reinforce their efforts to pay close attention to the parts of their glider that take the most abuse - especially if they are carbon composites!
------------
Hi Ward,

I have discussed this in detail with the Moyes factory and our carbon manufacturer and we keep coming back to prior damage being the ultimate cause of the failure. I understand that your pre-flight process is thorough and that you are confident that you would have identified a fracture, but we are unable to come up with an alternate cause. We have also investigated the serial number and have found no record of abnormal failures for that generation of leading edge. Although we are 100% confident in the product, we do agree these are unusual circumstance and would like to do our best to get you back in the air as soon as possible. Your options are to go with a replacement carbon leading edge (special order - 4 weeks ) or to replace both with aluminum front sections (in stock ready to ship). . .

Let me know what you think. Thanks,

Kraig

Dear Kraig,

Thank you and the rest of Moyes for your help and “best guess” as to what may have triggered the brake. Not knowing the complete history of the glider, one can only speculate as to what type of stress(s) compromised the leading edge. As I described earlier, prior to flying that day there were no signs of damage to the surface of both leading edge tubes near the nose. The night before flying, part of my “pre-pack” routine was to check if the carbon inserts in the leading edge pockets are symmetrical and not shifted within the pocket. To accomplish this, from inside the sail, I grasp the leading edge and push with my free hand on the carbon wafers. During this process, if there was any visible or touch evidence of a significant fracture along the outer surface of the tube, I believe that I would have detected it. My guess is that I’ll never really know if the break was due to a combination of multiple/cumulative stress insults that created undetected cracks along the tube’s inner surface or my wheel landing/nose-in triggered enough focused energy on the leading edge to snap it.

As for repairs, my first thought is to replace the forward leading edges with aluminum sections keeping the aft carbon edges. If this aluminum/carbon leading edge combination does not significantly alter the glider’s flying characteristics, I believe that it’s my best option.

Thanks again,

Ward

[Flying Lobster]

Hmmmm...I would be interested to know what kind of force(s) it would take to actually produce such a failure (and at a variety of conditions/temperatures). I would personally have trouble gauging what is a damaging whack or ding otherwise.

[huddlec]

Mike Chevalier's LE on his TRX did not break from a landing. It was damaged by a loading-on-the-truck incident. It wasn't until the glider was being set up by another pilot at Spruce Knob launch that the broken LE was discovered. The pilot lifted the wing to install the big tip fairing (or whatever those tips were called) and the LE snapped a couple of feet from the end. Very disturbing for the pilot since he was about to fly the glider.