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Klingberg Wing MkII
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Добавлен 7 май 2017
On this channel I will display and discuss all of the development work related to the Klingberg Wing MkII. Subscribers will be able to follow all the engineering and construction work to complete the first full size prototype aircraft. There will be extensive discussions and demos of composite construction methods used to create very high to strength weight ratio structures. Videos will also include special aerodynamic discussions related to flying wings. All content of this channel is intended for entertainment purposes only. All of the information presented here is experimental in nature and there is no promise, express nor implied, that any of these methods or designs will result in successful aircraft or components. Anyone who becomes a Patron at www.patreon.com/klingbergwing will receive a free set of plans for the 1/4-scale R/C glider.
Fatal Flair 30 Crash - An Engineering Analysis Part 2
Get the initial German crash report here: www.patreon.com/klingbergwing
Link to Part 1: ruclips.net/video/aBImlAiSsek/видео.html
Link to Part 1: ruclips.net/video/aBImlAiSsek/видео.html
Просмотров: 465
Видео
Intro to Lightweighting the Wing Tip Panels - Klingberg Wing MkII Development
Просмотров 247Месяц назад
To access all technical videos, please click the "Join" button! To support the project please visit: www.patreon.com/klingbergwing
Fatal Flair 30 Crash - An Engineering Analysis
Просмотров 17 тыс.Месяц назад
Part 2 is located here: ruclips.net/video/5156GiKsVkc/видео.html Send airfoil coordinates to: rolkling@gmail.com Support my work at:www.patreon.com/klingbergwing Get access to all my videos by clicking on the "Join" button!
Wing Tip 2.0 Build Trades - Klingberg Wing MkII Development
Просмотров 131Месяц назад
Get the full video at: www.patreon.com/klingbergwing Or become a member of this channel by hitting the "Join" button.
Flight Test Results and Glass Cockpit - Klingberg Wing MkII Development
Просмотров 3103 месяца назад
This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Slotted Control Surface Version 2 - Klingberg Wing MkII Development
Просмотров 4914 месяца назад
www.patreon.com/klingbergwing buymeacoffee.com/klingbergwing This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Slotted Flap Test Results - Klingberg Wing MkII Development
Просмотров 2664 месяца назад
www.patreon.com/klingbergwing buymeacoffee.com/klingbergwing This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Flow Separation Primer - Klingberg Wing MkII Development
Просмотров 1,7 тыс.4 месяца назад
buymeacoffee.com/klingbergwing (Goes to gasoline) www.patreon.com/klingbergwing CFD Analysis Video: ruclips.net/video/2mh8szvuD40/видео.html Flap Plate Elevon Testing Video: ruclips.net/video/cIrFkrkYI64/видео.html This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Slotted Flaps, a New Way - Klingberg Wing MkII Development
Просмотров 3,4 тыс.4 месяца назад
Help support the test program: https: buymeacoffee.com/klingbergwing www.patreon.com/klingbergwing Note: Please post in English so the maximum number of people (including me) can benefit from your thoughts.
Making Compound Curved Composite Shapes - Klingberg Wing MkII Development
Просмотров 4205 месяцев назад
This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
KW MkII Development - Composite Sandwich Panel Experiments
Просмотров 3505 месяцев назад
This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Side Quest - Original Klingberg Wing (KW MkI) Structural Design - KW MkII Development
Просмотров 7319 месяцев назад
This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Reynold's Number Issues? - an Analysis Part 1 - Klingberg Wing MkII Development
Просмотров 3219 месяцев назад
This channel presents key activities related to my development of a new, 15m span, ultralight sailplane.
Dihedral Effect Side Quest - Klingberg Wing MkII Development
Просмотров 3129 месяцев назад
This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Re Number Issue Part 5, Final Segment - Extended Elevon - KW MkII Ultralight Sailplane Development
Просмотров 3859 месяцев назад
Xflr Analysis of this control arrangement: ruclips.net/video/sthW7RGetQk/видео.html This channel presents key activities related to my development of a new, 15m span, foot-launchable sailplane.
Re Issues Part 4 Xflr Analysis - KW MkII Development
Просмотров 3709 месяцев назад
Re Issues Part 4 Xflr Analysis - KW MkII Development
Reynold's Number Issues Part 3 - Re Plots -KW MkII Development
Просмотров 2909 месяцев назад
Reynold's Number Issues Part 3 - Re Plots -KW MkII Development
Reynold's Number Issues Part 2- KW MkII Development
Просмотров 6469 месяцев назад
Reynold's Number Issues Part 2- KW MkII Development
Airfoil Tools Walkthrough - Klingberg Wing MkII Development
Просмотров 7889 месяцев назад
Airfoil Tools Walkthrough - Klingberg Wing MkII Development
Wing Skin Repair - KWMkII Ultralight Composite Glider Sailplane Development
Просмотров 484Год назад
Wing Skin Repair - KWMkII Ultralight Composite Glider Sailplane Development
Composite Ultralight Glider - Klingberg Wing MkII Development
Просмотров 1,5 тыс.Год назад
Composite Ultralight Glider - Klingberg Wing MkII Development
Composite Tubing - Sandwich Panel Style
Просмотров 569Год назад
Composite Tubing - Sandwich Panel Style
Klingberg Wing MkII Ultralight Glider - 2nd Flight
Просмотров 2,3 тыс.Год назад
Klingberg Wing MkII Ultralight Glider - 2nd Flight
Tufts of both wings on 2nd flight. Multiple local stall conditions.
Просмотров 372Год назад
Tufts of both wings on 2nd flight. Multiple local stall conditions.
Klingberg Wing MkII Development - Harness adjustments
Просмотров 137Год назад
Klingberg Wing MkII Development - Harness adjustments
Flight Testing Marina Bch 5-7-22 - Klingberg Wing MkII Development
Просмотров 786Год назад
Flight Testing Marina Bch 5-7-22 - Klingberg Wing MkII Development
Klingberg Wing MkII El Mirage 2nd Flight Cockpit View
Просмотров 416Год назад
Klingberg Wing MkII El Mirage 2nd Flight Cockpit View
Taxi Test - Klingberg Wing MkII Development
Просмотров 354Год назад
Taxi Test - Klingberg Wing MkII Development
Hi! I have read the translated german text. It is too bad a translation (is it from google translate???) but I can extract a rough clue of what the preliminary opinion of Prof. M. Schoenner implies for the accident cause: the Flair pilot coming for landing with a high speed (small angle of attack), deployed suddenly tbe central flap. The large flap, possibly due to the wrong placement of the CoG (more forward than it was advisable) caused a nose heavy moment. This nose heavy moment kept the AoA small. The pilot then tried to flair for landing by pulling the elevon up. However, the large nose heavy moment could not be combated, since the large elevon deflection and the small AoA/ high speed caused a stall in the elevon area in the underside of the wing, therefore ineffectiveness to produce downforce and inability to pitch up. In other words, tbe "tail"was lost. Instead, the wing pitched further down and finally crashed. Seems like a plausible explanation. Possibly, these effects were further exacerbated by the already nose heavy airfoil pitching moment that was used and the quite large washout. However, what I know of the Flair 30 is that it was designed such that the large flap was pitch moment neutral. The fact that it caused irreversible nose heavy moment might have to do with a terribly wrong CoG placement and/or too high speed during deployment. So maybe your further investigation might be able to give us answers. In any case, we thank you very much for the provided info!
Thanks for a very helpful post, it really confirms a lot of my internal thoughts that I was uncertain about. You bring up one very important thought and that is the seemingly key "facts" don't pass basic logical thinking - such as the flaps having a neutral pitching effect. Because this format is limited, I'm posting my full response to you on my Patreon site. It will be available to the Public and I will shortly post a link to that writeup here. And, anyone who visits there can sign up for free - just click the three dots to the right. www.patreon.com/klingbergwing
BTW, would it be possible for you to do a complete and reasonably accurate translation of the original document into English? It would help a me a lot and I'm sure others would be very interested. Let me know, Rol
@@KlingbergWingMkIICertainly! It will be a good chance to cross check the translation and I know of some German guys that can help. Just send me (how?) the original text. Thank you.
Thanks for offering to help translate. Now all we have to do is get the original text - I do not have a copy. I'll check with a couple of my potential sources.
Thanks
Glad to help.
Hi Rol, we would love an update on your project at the Western Workshop of the Experimental Soaring Association In Tehachapi this weekend, sunday is best. Hope you can make it.
Thanks for the offer, but it is a really hard drive for me and cost too much in terms of both time and money. I'm very busy building new outer wing panels and preparing for more testing at Marina Bch and El Mirage. I hope everyone in your group follows my progress on my YT channel. Please pass the link to the group. Fly Safe!
I was a good friend of Gunther Rochelt, and I remember this well. The problem was that the CG was more forward than previous flights, and when the pilot put the large flaps down, the elevons went up so much that the airflow separated on the bottom of the elevons, so they lost the ability to get the nose up. So, it dove it. Bottom line, the flaps were too big, and required an automatic mixer to raise the elevons with flap deployment. Flaps down, elevons up, and back stick let to disaster. RIP.
Hi Eric: Hope all is well with you, your family and aviation projects - they are unparalleled. What you have written is the results of analysis that was done shortly after the crash. I've never seen any math to back it up, but it might be out there somewhere. Apparently the LBA analyzed the crash over a 6 year period and I'm trying to find that report. I'm currently in contact with Gunther's son to see if I can get a copy of the report and a set of airfoil coordinates. Currently, Steve Morris and I have both done some CFD on the design (different codes) and have seen results that do not align with the reported flight characteristics. It is documented that the pitch trim was neutral with flap deflection, but Steve and I don't get that result. Steve is uncertain why. I'm trying to find out more about the crash because I think I've had similar or related issues with my current glider. So, stay tuned and keep posting your work and flights, they are really great.
Ludwig Prandtl Died in 1953. So should have his ideas. They have proved a rabbit hole .. without end.
I would tend to agree, however, they are technically correct and therefore should be retained for reference. The key question is, "Why would you make this post here?" I am looking for airfoil coordinated for the Flair 30 and your comment is not helping in that regard. Post here only if you can help.
It crashed be cause it wasn't a kasperwing no wing can recover from tumble without k wing tech
You don't know what you are talking about. There was no tumble involved.
Admittedly, your section out near the tip is getting close to symmetrical, but all this attention to the top of the wing at the elevon is really for a very small part of the envelope. Unless you are running a seriously rearward CofG, the part of the wingtip (on a swept flying wing) that is doing the most work is the underside. Problems generated by the top of the tip are in the realm of adverse yaw, and this can be handled with use of differential movement in the control system. While this sounds like a way of limiting your down elevator movement, reality is that you use up elevator about 90% more than you use down. From a practical point of view, your 'coander' sticks and film are adding unbalancing weight to your surface, which could prove prone to flutter. You would do better to hotwire a thin foam shape, and I'm thinking a 2% thick, (something like 6" wide by 1/8" thick) smooth bulge which you can solar film onto both sides of the surface, creating a biconvex shape at the hinge line, followed by a reflex section (to help reattach the flow) at about 50% chord of the control surface. Just some ideas to avoid going the vortex generator path.
Where did you get your aero eng degree?
Suggestion- contact Michel Colomban (CM) in France. He is still living and may have a direction for your search.
Wouldn't the center of lift tend towards the rear while slow?
You have asked the wrong question. The center of lift does not move with changes in speed. The correct question is, What happens to the pitching moment when the controls are deflected - especially the flap? I and another aero eng are still in the process of analyzing the design to answer this critical question.
@@KlingbergWingMkII Yes...control deflection. One model of that pitch behavior is C-150 full flap deflection forcing a strong down pitch adjustment when still well above stall.
You seem confused over this concept. From the Aviation Stack Exchange, "The aerodynamic center does not move when plain or camber flaps are used." The change in pitching moment is due to the increase in camber and hence the amount of circulation around the airfoil. This is standard aerodynamic theory. I only post this correction so my viewers do not become mis-informed.
I just posted this video of a recent flight in a production SWIFT3 where benign stall characteristics at maximum elevon deflection are demonstrated while thermaling. The SWIFT3 avoids the problems you mention regarding control surface stall by using an airfoil that is thin in the chordwise region of the control surface. The airflow does separate at max deflection but there are no adverse effects on handling: ruclips.net/video/Q2AuMTkoyB8/видео.html
Thanks Steve. Don't know if you/ve seen the following video, but my xflr analysis of an airfoil similar to the Swift (BTW, do you have the coords for the Swift airfoil and may I have a copy?) shows exactly what you are talking about. It is clear that at low Re it is important to keep the control hinge line outside of the adverse pressure gradient. I discuss the topic in detail in the video. I mention this as I bet most folks have not seen the video or don't really understand my pts. I suspect that the hinge line of the Flair flap at 40% is the root cause of flow separation and hence a full-on stall (at AoA less than normal stall) and caused the Flair to pitch down rapidly with no room for recovery. I will be posting a full analysis of this issue in the near future. Fly Safe, Rol. Video on the topic: ruclips.net/video/2mh8szvuD40/видео.html
Hey. Long time ago I worked for Rochelt at the Solair 2 projekt 1997,years after the Flair crash .I have seen the remains of Flair 30 . Rochelt told later the pilot was too far forward ,so was the center of gravity. I could imagine the wigtips that have to produce downforce may have stalled on their lower surface. I will see if I can find out something about the profile. Stay alive!
Having the airfoil coordinates would be a huge help. Let me know if you get them or can give me a lead on where to get them - thanks!
Do you happen to know whether or not Gunter was a licensed engineer? If yes, what type of degree did he have?
@@KlingbergWingMkII First of all Günther was a visionary and manager. He was well known in germany for his many airplanes . A team of engineers did the structural and aerodynamic calculations for his projekts so he was well based from a scintific point of view.The real problem was how to finance? He him self was professor for industiedesign in Hamburg- where I met him.
@@KlingbergWingMkII I will try to get, but I can not promise,
@@KlingbergWingMkII I had a call with Holger Rochelt , son of Günther Rochelt ,5 min. ago. He flew the Flair30. I may send you his telephone number so you could get in contact with him. But not here in public. Do have a E-mail adress or something where I could send you the number privatly?
I am living in germany and I met Günter Rochelr three times. And I have seen how the model of the flair 30 crashed at winch towing. But what I know about the final crash of the full scale flair is the following issus. The wing was overloaded. and the CG was too much in front of limimit. Here in germany we beive tha a air flo seperation at the lower furface of the airfoil was the reason oft the fatal lethal crash. In comnination of maximum set of flap defection and over limit CG the seperation of the lower surface of the wing tip overcame the ability to pitch up the whole wing ad the wing crashed nose dowt at the final approach into the ground.
Thanks for the input. I have read the original accident report (poorly translated) and your comments align with that report. However, regarding classic aerodynamics, that analysis appears to be flawed. Having a CG forward of the limit will not cause an aircraft to dive into the ground, especially after 45 minutes of flying time on the fatal flight. A forward CG would require a lot of up elevon to take off or not take off at all depending on how far out of range it is. This would be apparent at the start of flight. A good pilot (seems the accident pilot was very good) would not continue a flight with this issue. But, if the CG were at or near the aft limit, then a good pilot might be able to fly the aircraft for an extended period of time and then either a gust, or different flap setting causes the aircraft to diverge from it's stable config and either pitch up rapidly or dive into the ground. An unstable aircraft can go either way. What most people seem to be missing is that this was, of course, a dynamic event and most of the analysis I've seen is from a static point of view. This approach can lead to incorrect conclusions.
Danke! Hello and greetings to you! Great videos, especially the ones about airflow dynamics over aerofoil- and control-surfaces. Maybe, you could include some more information in separate videos, if possible and if you have time, about GA wing design and development, including the theory and technical challenges in wing design, too, as you have done with your 'Klingberg Wing'. I do not fly myself, but have a big passion for aviation, am looking to learn more about aircraft design theory, practices and conversion into aircraft, full scale or model. Carry on with your great videos; have learnt a great deal about airflow characteristics over and under aerofoil sections just from your videos alone. Keep up the great work! With best greetings from UK Andy
Thank you very, very much for your generous donation. That will cover the cost of some gas so I can get out for more testing!
Was this aircraft a one off prototype? The idea of aeroelasticity is very interesting and certainly plausible but indeed without the original there is no proof..
Yes, one of a kind so difficult to reach conclusions without specific design data.
I have a theory but would help to see the video of the crash.... Is there a link or do I need to go hunting for it?
The crash was indeed filmed/recorded, which was new info for me. The location of that recording is currently unknown, but I'm in contact with a fellow in AU who knows some of the folks involved, but generally does not speak of the event. He may be a possible source. Stay tuned.
I've recently had some surgery and typing is really difficult. My experience may not be very valuable or interesting to you as it's all based on self gained knowledge designing my own rc models over the last 40+ years. I know that aeronautical properties change a lot at scale. With that said, it is true, especially with wings, that there are things done within the designs in any scale that will create huge swings in performance and especially stability. In my humble opinion, these large light "rigid" wings aren't very rigid because of weight concerns. Two things. COG of course is everything. Nose heavy gets away with a lack of correct position. But tail heavy on an aircraft with no tail is a HUGE catastrophic problem. Put a pin in that for the moment. Wing twist is used in nearly every design I've ever seen. Especially in rc models without a fly by wire controller using 10 dof IMU's.... Basically your wing design isn't perfect so we are going to pretwist the wing, to give the wing a little extra up elevon to correct any bad handling tendencies. I know this is basic stuff and very abbreviated I'm trying to demonstrate a basic understanding not trying to tell you anything you don't know. Bare with me, I'm getting there. Other things I've had to work through... Wing sweep. Winglets. Size and locations of control surfaces. All these things I've have added to my early designs because they were bad and I had to according to everyone I didn't ask for advice from... You may be experiencing yourself currently. But as my designs got more complicated I went from an aircraft that wouldn't fly to something that could but not great but then would become a better flyer but began to start eroding the performance to the point of becoming unfliable. And programmable flight controllers became necessary to stay in the air like modern fighters. That's when I changed the goal to making an efficient wing that tracked and steered correctly WITHOUT winglets. That remained stable WITHOUT twist or washout. I reduced the size of the flight surfaces and increased the sweep to bring everything back to a more stable platform and a wider chord at the wing tips. What I found was that the combination of all these things were flexing and twisting the wing to the point where the center of gravity was shifting aft. And in a really strange still not quite understood phenomenon was resulting in a nose down condition. If I'm right, you have a worse problem than I did because you have a PILOT. A pilot moves around. A pilot wants to be comfortable and we all fly full scale aircraft with at least some body English. My wife drives with her tongue hanging out of her mouth. Literally. What I noticed one time was when the car did something unexpected her tongue English was going the wrong way. That got me thinking about the battery in my wing. It was not only moving but it too wanted to be comfortable and was moving in the wrong direction under these weird loads because I used a rubber band (old school) to help secure it. It was pulling on the heavy side by using the wires as a fulcrum. I still don't understand everything that was going wrong there. But what I did was secure the battery, dialed in the correct cog and removed washout. Took advantage of adverse yaw in the elections and flattened the wing. I had good results with 2° anhedral for more aerobatic maneuvers. Thin longer and stronger control surfaces at the root of the wing instead of thick large but short length surfaces at the tip. I'm also blending two airfoils. I have the root airfoil and the tip airfoil and through the magic of CNC hotwire foam cutting I get a PERFECT blended wing with 50/50 throughout the length of the wing. Taking advantage of two airfoils at different areas of the wing means less compromise in choosing one for two very different parts of a wing plan. Just don't get them backwards and spend a year trying to fly something that is literally fighting the air and itself and literally negating every single benefit you thought you were taking advantage of.
Airfoil numbers: I'm going to assume you may have reached out to John Roncz before his passing last year. If not, another source could be Jim Marske. Jim"s expertise is flying wings almost exclusively. Also, Matt Kollman who has been making rigid wing hang gliders for some time. Good luck!!
Good idea. Do you have any contact info for those still living?
Jim Marske also recently died. Contact info for Matt Kollman, who worked with Jim, can be found over at KollmanWings. Jim's website is still up and still nice to look over. There may be clues about the Flair 30 in Marske's stuff (which Matt Kollman may have insights on).
Stay with free flight models and you can stay safe and learn about aerodynamics more economically.
Only partially true. Models have much lower Re numbers so they do not always behave the same. Just ask the Wright Bros. The Flair had extensive model testing which did not show any problems. I make these comments so that viewers do not get mis-directed by incorrect technical comments.
OK, so I'm watching these in somewhat random order, but feel I should comment here. Right from the beginning here, you are chasing a problem (obvious in the video), but I feel chasing it from the wrong direction. You are having to pitch forward to stabilise your towing climb, and running into problems with the elevon airflow separating. The problem is not the elevon, but your tow position. Move your tow hooks further up. As for the aerodynamic/Reynolds numbers/flow separation problems, to start with, these won't be a problem in gliding flight (or if the tow hooks are moved), except in stall recovery, and more pointedly, rolling out of steep turns (when the elevon is in aileron mode). The flat plate, hung off the trailing edge, will work, but for three different reasons. Yes, the upper (or lower) surface flow discontinuity can be cured by using a flat plate (which [#1] in effect means you've created a reflexed surface), but you have also [#2] increased your wing area, and thus lowered your wing loading, and you have [#3] extended your elevon moment arm aft, giving it better leverage and thus less requirement for deflection. A possible cure I see (as well as the tow hook), is to go to a bi-convex section at the elevon, or in other words, make the elevon thicker (2~3%?) than the section of wing it is attached to, have a look at the P51 Mustang elevators. You could also try extending the chord of the elevon (gaining #2 and #3 benefit), and utilising a reflexed surface (Mustang ailerons), but I'm not sure of how these changes work at the Re you are using...? Keep at it.
Yes, tow position was part of the problem. I know have it towing through the vertical CG position. However, even with the tow position off somewhat, there should have been enough elevator control to overcome the moments and there was not. The root cause was separated flow on the elevons. This is due to a Re issue and is discussed at length in other videos. To the best of knowledge, I have since solved that Re issue. Finally, the most recent results and data are available only to members of my channel. You can access them by clicking the join button - only $0.99 per month. Hope to see you there!
Not much of a description on the crash (leading up to pitching down) as you read the statement. Was he at high speeds leading up to the pitching down or was he at slow speeds? Almost sounds like tuck under if it was at higher speeds as I have not only heard about tuck under it happened to me with an RC sailplane. I was told there is nothing that can be done when getting into this bad situation except watch it go down. Luckily enough I had plenty of altitude and slowly pushed out of it. I believe if I were a test pilot on something with a high aspect ratio wing I would have camera's on the tips pointing inward down the wing with a reference point as well as a camera pointing down to the tip of the wing to look for this. Torsional strength when weak the wing tips tend to oscillate violently and either explode or slow down the craft. A stiffer wing tends to lift the tips trailing edges. I met the gentleman that perished in 1995 at lookout mountain as I was looking forward to watching him fly his Swift and went out for dinner then when I came back it was at the landing zone in pieces. I was told from a friend of his he was doing loops as he normally had done in the past then went to strafe the field and it went into a bad oscillation and he could see him bouncing in the cockpit and I am not sure if the wing folded before it hit the ground. That was a bummer of an evening. Would be very interesting to see what happened. Take care
I'm not asking for help in analyzing the problem. I'm asking folks if they have any info/source for the airfoil coordinates..
Hello Rol! I think I have seen you showing us the book "Tailless Aircraft in Theory and Practice" from K. Nickel. Please look in pages 469, 470, 471 and 472 where it discusses about Flair 30. It has also a view of the airfoil, so maybe you can copy it for analysis. That said, pls be advised that G. Rochelt, the designer of Flair 30, has also passed away (I think he died in an aicraft related accident), since many years now. But Nickel, the author of the book was also German and I am sure they had discussed a lot about Flair 30.
Thanks! I had totally forgotten about that. The info in the book will not solve the whole problem, but will be very helpful. For one item, it confirmed my analysis that the flaps were set up to be neutral in pitch trim when deflected. The pic are not sufficient for getting good coordinates, but they give me some clues that will be useful in future analysis.
Günther Rochelt died from cancer. RIP
I remember this accident well. Here in Europe we follow with illusion the development of the various versions of the Flair. His design make us dream about a flying wing with the pilot integrated and flying prono on the wing, with a magnificent performance due to optimization of the aerodynamics, designed by a team of aeronautical engineers from a german university (if my memory doesn’t fail). The accident, as you said, was never completely explained as long as I know; but I remember articles in hang gliding magazines (Drachenflieger and others) suspecting a problem with aeroelasticity (not a flaw in the aerodinamic design) naming possible not enough rigidity (materials. construction?) of the wing following a recover of a steep dive previous to landing
An interesting note about the aeroelasticity, but probably not something where there is enough info available on the construction methods to be useful.
The three-view reminds me of the Horten "Piernífero". 😄
Other than that you said the Fatal Flair Crash was the wing ‘falling out of the air,’ and you said you spun in at Torry Pines, I know nothing of these accidents. However, I am a Glider pilot and did witness a hang glider wing with elevons fatality, cerca 1980 at Salt Creek beach. Incidentally, saw two others involving hang gliders at Torrey Pines before the parasails took over. Washout or an airfoil transition from root to tip will help prevent the sudden tip stall and subsequent spin, however depending on the torsional rigidity of the wing; higher speeds can create enough lift on the upper surface to twist the wing tips downward eventually overwhelming the ability to pull out and pitch downward. The pitching down from wing twist increases with higher lift, lower Reynolds number airfoils, and decreases with symmetrical type airfoils. Not aware of any elevator or elevon reversal other than over speeding the design limitations or torsional integrity of a wing. Obviously a stalled wing can be fatal if not enough altitude to recover. I’ve encountered wind shear and wind reversals on the ridges where the free fall can occur, very sudden and unpredictable. Airspeed and altitude are essential in these cases.
If you look at my old videos, can will see that I believe I have solved the stall/spin problem (inboard winglets, control that do not run out to the tip, and special elevon shapes). I believe the Flair crash did not involve a spin as turning or rotation was not reported in any of the 1st person reports.
@@KlingbergWingMkII what’s your conclusion; summing it up in one concise sentence if possible, serious mistakes can be avoided. Thanks for sharing.
I don't have one yet because I don't have all the data I need to do a proper analysis. I have info coming in from multiple sources that will help, but I really need the airfoil coordinates.
Talking as a complete amateur, but having flown hang gliders, including a couple of EF-5's, and being somewhat of a Horten fan, I'm looking at the 3-view and thinking the flaps go a long way out to a point fairly aft of the CofG. Then hearing your comment about flow separation just aft of the hinge line, leaves a bit of a dilemma... Did the machine stall and fall flat to the ground (signs of the leading edge at least trying to maintain flow), or did it pitch down into the ground (as you mentioned), suggesting the outer part of the flap (being a little more washed out than the centre, and being further aft), maintained lift and overpowered the small elevons? Beyond that, there is the pilots experience with the craft as well as his overall experience as a glider pilot. How well would he recognise the onset of stall, did he at least try to pitch (stick forward) down to break the stall? As an aside, I'd watched most of your Mk1 wing video's and was impressed, and noticed a few things; you could have made a lightweight self inflating streamliner behind you, and looking at the elevon positions during most flights, you either needed to be a bit braver and dive in a little more speed (yes, I know you only had a few feet here and there), or maybe the wing needed just a little more washout? Intriguing to hear you are still at it. Bravo.
We will never know for sure what caused the Flair crash, but it is looking like it was a flow separation and very rapid stall onset that is the root cause.
Just a note to say thanks for your review of the incident, as I hadn’t heard about it prior to your site. In Australia we had two great ultralight aircraft designers pass away in a short period whilst flying low hour prototypes. From that a lot of the local groups put pressure on other pilots exploring new design to incorporate ballistic recovery systems or spring deployment parachutes until the aircraft is proven. I admit I was not interested in doing that until the designer of my first ultralight was killed by aileron flutter and I had been asked to attend the crash site to do an investigation how it happened. I flew an earlier design and was the only person current on them. Is there any reason why this is not recommended on prototypes elsewhere?
Testing any new aircraft at altitude with out a parachute is unthinkable! I'm looking at having two of them.
The book 'Schwanzlose Flugzeuge by Nickel Wohlfahrt' lists in chapter 12.5 for the ROCHELT FLAIR 30 the following data Spannweite 12 m Flügelfläche 11m² Flügelstreckung 13.1 Profil CM-140-K47 mit einem c mo = - 0.048 Schränkung 5° linear Packmaß 35 cm x 60 cm x 660 cm beste Gleitzahl 30 bester Sinken ca. 0.5 m/s Gleitzahl im Bremsflug 5 (Klappen auf 45°) Klappenstellungen Schnellflug -4° Normalflug 0° Start und Thermikflug 15° Sinkflug 30° Bremsflug 45° Transport 180°
Thanks for the reference. Several folks have pointed it out and it will help my analysis.
Thank you for making this video Rol..... I've always been interested in what happened to the Flair. Nickel's 'Tailless Aircraft in Theory and Practice' has a drawing of the wing section. Reverse engineering the co-ordinates from that might end being the way to go. IIRC, the deep chord flaps folded over against the upper surface of the wing to allow for easier transportation and storage of the glider. My theory on the crash (complete conjecture on my part... I'm no aerodynamicist) was that the sailplane pilot weighed a little less than the (usual) test pilot. With flaps deployed, and the glider effectively operating at a higher AOA, I've read that the lift moves inboard (and thus forward) on a swept wing, putting the glider into a tail heavy state, thus causing the sudden nose dive. I've experienced this on several of the model wings I've built. They fly great with no nasty habits, but then on landing approach with flaps deployed, the model losing speed and descending to slower air nearer the ground, it very suddenly dives in. No warning and no chance of recovery. It took very little nose weight to resolve the issue. As you mentioned, 50hrs is a reasonable amount of air time, and I would have thought that this issue would have come to light within that period. If the only thing that had changed on this fatal flight was the pilot, then that's a factor worth looking in to. As mentioned though, take all this with a pinch of salt.... I'm just an armchair critic!!
Thanks! See my full reply in the other comments.
@@KlingbergWingMkII Lots of interesting info..... good to see this getting plenty of interest!
Also followed the same path to find out what happened and came up with nothing. So I hope someone comes forward. It was a terrible tradegy. My speculation : Crash appears to have happened at speed, so Re likely > 10^6 ruling out low speed separation. My bet would be separation of flow underside the elevons making them ineffective, hence your need for co ordinates to model the airfoil and whole wing at the appropriate AoAs and Re. The 40% chord flap I'm sure would have been self trimming for moment. Is it possible that rapid deployment at speed probably set off the couple of high drag falling sufficienly below the cg which, in turn was unable to be resisted by full up-elevon with separated flow or not. I also wonder if spanwise flow from fully deploying flaps may have rendered the elevons less effective. Nickel and Wohlfahrt refer to sudden camber flap deployment needing to be gradual. It's a beautiful design by a brilliant designer, the large flap and elevon chord made for improved portability of a rigid wing togeter with exceptionally high Cl possibilities.
Yes, the speed that the pilot was flying at the time will be important. At higher speeds, Re would not be an issue as you stated. My current guessing is that the pilot felt he was going to overshoot the landing site and dumped a bunch of flap and unknowingly, and unexpectedly stalled the entire wing, even though he probably had plenty of speed (well above stall speed).
I wonder if the airfoil note there is a description of the design pitching moment coefficient and hinge position, rather than a specific name. Rochelt was involved in human powered and solar powered flight - maybe someone in those circles would be able to help out. I could pull an airfoil from the PDF, but it won't be very convincing I would be extracting the as-built airfoil.
That's an excellent point that I had not considered as I didn't not know he was involved with the HPA world. Now that you mention it, I see some similarities with the Gossamer Condor and Albatross airfoils - low speed stuff. From Nickel's book it also appears the airfoil as similar to was on the early Swift designs. You are right, extracting coordinates from the available pics and drawings would be useless for engineering analysis. However, more info will help guide my speculations.
As you have said it might have been a safer design with 8 degrees of twist rather than 6. I don't see any leading-edge slots ahead of the elevons, are they in the photos and perhaps left out of the drawing? They have been known to prevent tip stalls, and spins which can be unrecoverable in some cases. A big flow fence between the elevon and flap might help to minimize spanwise flow. I wasn't aware of this accident; I have no information on the airfoil. Interesting analysis, thanks.
Fences are for boundary layer problems. Spanwise flow is a potential flow field problem - something completely different
I remember Steve Morris flying a proto-type at Ed Levin Park in Milpitas, CA in 1990 or thereabouts. It seemed to fly nice. A couple years later they were flying the SWIFT (Swept Wing In-board Flaps for Trim) which I hope is still being made.
That prototype was the Odyssey - not related to the Flair in any way.
SWIFT is still made by Aériane in Belgium.
Might be worth asking patrons if they would be ok with releasing the videos to the regular RUclips channel in a delayed manner. Could acknowledge them in your videos and they would still be getting the technical drawings as a bonus
The project is to the point where I'm providing highly technical information and education. All the new knowledge is hard won and at significant cost. Access to that knowledge should entail at least a token payment.
Thanks Sir for your share!!
Nice to have found your channel. A aircraft design that always interested in me was the CFM Shadow, designed and built by Cook. I now see where his wing D spar design has inspired others, was well as he was inspired VJensen.
D-tube construction has been around since the '30's
I've been interested in designing and building my own hang glider for some time and have done nothing like this before. Being new to this, it would never have occurred to me to watch out for aerodynamic control effectiveness problems when the local Reynolds Number is around 400,000. Much less would I have thought that - until you came along - that there has never even been any research into this problem, posed by local Reynolds Numbers around 400,000. Anybody blundering into control effectiveness problems - without being aware of what you've found - would likely have found themselves in trouble and not be able to solve the problem. Thank you for drawing everyone's attention to this - valuable work, on your part!
Thanks, I'm glad to hear how you have found so much value in the work that I do. I look forward to seeing you as a new member on my Patreon site. Given all the value you have received, I'm sure your pledge will be most generous. Pledge at: www.patreon.com/klingbergwing
@@KlingbergWingMkII Not right now - simply because I can't see my way clear to getting any project of my own started, for financial reasons among others. If my financial situation in particular improves sufficiently, then I'll have no difficulty joining your Patreon site. Meanwhile, best wishes!
Beautiful idea. All the best engineering is, of course, beautiful. Elegant solution.
Thank you very much!
So you're increasing the AOA of roughly 100% of your MAC-aft chordline in order to .. lower the AOA? Doesn't that mean there's an inevitable bottom portion of the speed envelope where you're guaranteed to tip-stall and consequently experience an uncontrollable nose-up moment, as your center-of-lift moves forward?
Well those are terms I know, but what you are trying to say with me I haven't a clue.
I flew my hang glider at Dillon Beach around 1982.
It was a great spot! I wish it was up to us today, it would be the best spot for me to do my testing. But hey, we're still kickin; and flyin
Have you approached any composites manufacturers to be sponsors at least with material donations?
Nope, it's a tad difficult to get a sponsor for an aircraft whose flight qualities are still open to question.
Dear Mr. Klingberg, Iam a Glieder constructor from Germany and I love your ideas. Best greetings and much love and success I send you from germany. Gerd Greifenstein
Many thanks
Out of curiosity, what effect would small stall fences mounted to the control surfaces have?
Been there, done that: ruclips.net/video/eH4HDLJVp4E/видео.html Fences are for boundary layer problems. This is a Reynold's Number problem. You may wish to review: ruclips.net/video/2mh8szvuD40/видео.html
Thank you. I have a better idea of what you mean. I’ll be honest, I barely have a hobbyist understanding of aerodynamics. I’m a towboat captain on the Lower Mississippi River. I guess I could brag about practical experience in flow dynamics but honestly I have no formal training. After watching several of your videos I keep thinking about the morphing wing profiles that several universities are studying. The problem there is obviously weight. But in that vein, would a two piece control surface be feasible? Shipbuilders had a similar issue with low speed maneuverability and came up with a two piece rudder that increased handling capability and improved fuel efficiency while having a very simple mechanism. The Becker is interesting nonetheless. ruclips.net/video/UDBeCqzYO5k/видео.htmlsi=T2oV7V1xDziQWore
Morphing wing - really cool concept. However one would have to solve the weight/complexity issue to make them effective on a ultralight glider. What one might gain in aero efficiency would most likely be lost in weight gain, not to mention the big increase in build cost. I can't comment on the multi-part boat rudder concept as I've never seen one and I'd have to study it carefully. I can safely say that boats are not airplanes and water is not air - not all concepts transfer well between the two worlds. Overall, I'd say that designing aircraft is like making a fine wine - it is all about compromise across many, many factors and it takes about 50 years to learn how to make a good one....and then you die. (Old wine makers joke!)
Wonder what the challenges are to a flat component like that - making it stiff enough, flutter issues, etc.
Yes, flutter can be a big issue with flat plates and has to be studiously avoided. Spanwise flutter is not an issue because they are directly attached to the wing TE. However, torsion can be a big issue. Most of the "flat plate" controls I've used or seen are actually thin wedges so they form a torsion box to make them stiffer. One also has to be careful of what impact the placement of the control connection point might have. All that said, there are many powered ultralights that use flat, fabric covered, controls and I have not heard of any flutter problems. However, those controls are usually much shorter in terms of span.
Didn´t the Aeros Phanton use the flat plane?
From what I can see in the online photos, the answer to your question is, "Yes" It is nearly identical to what I used on my original Klingberg Wing back in the '80s. I should mention that the Phantom appears to have a much larger wing chord than my wing at the elevon. Maybe as much as 30% larger. This means they would not have had the same Re problems I'm dealing with.
Oh, BTW, have you flown a Phantom? I'd love to get first hand comments about its handling. If you don't do you know of someone who has flown one? Please let me know.
I found the original owners manual for the Phantom online! It states that the pilot must stay aware for spins. It says the glider will enter a full-blown spin in just a 1/4 turn! I'm not surprised to read this as the glider has strip ailerons which can really aggravate spanwise flow and promote spins. So, flat plate good, strip ailerons bad. In my early videos I explain why an elevon with "reverse" taper (smaller chord at the root and bigger at the tip) prevents this problem. In fact, I have a spreadsheet for calculating the planform of the elevon required to prevent spins. The results are based on the taper and washout parameters of the main wing.
@@KlingbergWingMkII Some of my glider-club-buddies flew the Phantom. Newer heared anything about spinning. Most of them went back to traditional gliders because the thing was mutch to heavy and quite difficult to land. In alpin CX-competions it is a big disadvantage, if you have to care too much about finding a siutable landing field with the perfect wind. After rought landings the pilots were traped under the havy glider some times in a position that did not allow them to free themselfes from glider or harness.
Rather than the reverse duct sticking up, why not reprofile so the duct follows the same profile as the wing and make the leading edge of the flap dive inside the duct?
Of course as that would be lower drag. However, this is an initial experiment and before I spend a lot of time do a bunch of fancy building, let's see if it even works.
On an aircraft design I worked on we gave the ailerons a small increase in thickness. This, combined with hinge placement, kept the top surface of the aileron protruding into the boundary layer as it sips off the wing surface.
Yep, that would be standard design procedure. You can see me test that option in my earlier videos. It proved ineffective, probably because of the low Re. Near stall speed my wing operates at an Re range that is largely unexplored. See this vid for my CFD analysis of the issue: ruclips.net/video/2mh8szvuD40/видео.html
Looks like you are creating a slotted panel surface with the intent of keeping the flow from separating. The ME-163 has a similar slot detail near the leading edge of each wing to minimize flow separation. The Cessna 177 uses a short reverse (upside down) slot on the stabilator for better control response. You could also try VGs as a quick way to energize airflow over the flap. I would curve the internal channel for a smooth transition from bottom to top and eliminate the big flat piece. Interesting concept.
All good pts. There are many aircraft that have employed leading edge slats. I think the most interesting is the Tiger Moth (or was it the Gypsy?) which had LE slats that deployed automatically when it hit a predetermined AoA. If you check out my earlier videos you will see I've tried dozens of different VG options. Problem is, at 20 mph and a very low Re (under 500K) it is very difficult to energize the flow. VGs bring high energy flow from the freestream into the boundary layer but if there isn't much energy in the freestream, then they are useless. What I'm doing here is a simple first rough cut (my common approach to problem solving). Optimizing the solution comes later if the method proves to be effective.
To differentiate the effect of trip strip, you could also just close the air intake with a tape.
No, the cover on the upper surface could still act as a trip strip even if the bottom slot is closed. Good engineering dictates that the configuration for the upper cover be as close to identical as possible.
I have a prediction, the flow will be interrupted by the deflector and act as a spoiler in the flap up position. Flap down it will act as a choke point and cause undesirable characteristics. better design may be to design a slotted flap that has a smooth airfoil leading edge and eliminate the excess hardware. Notice on the illustrations you've used from the laminar air flow style wing that very much attention was paid to SMOOTH airflow.
Interesting thoughts. Given the format we are working in, I'm not sure I'm correctly visualizing what you describe. That said, the best I can do is to note that I'm not doing this test to use on my flaps. I use the word "flap" as a generic term for a control surface. The elevons for my wing are flaps that must travel up and down, so I'm not sure what you are describing would work. The test I'm going to do is set up for down only to represent what happens on my wing. On my wing I'm having problems with the flow over the elevons only when they are deflected down. Does this make sense?
Thank you for sharing. Interesting concept and I'm looking forward to seeing the results.
Be sure to sign up at my Patreon site to get the results
Hi Rol, Tehachapi, Labor Day Weekend?
Will they let me test my wing there?
@@KlingbergWingMkII I'll check. in the past we demoed the Carbon Dragon on auto tow after the sailplanes were down. We'll call it demo flights not test flights due to fatal at airport with powered homebuilt. There are hang glider sites near by. Airport runway is about 5000'.