Oh no! My favorite design of your's yet, sorry to see it crash. I love how your spirits is still up after all that work. I also appreciate the blow by blow accident footage. Can't wait to see more of this plane.
This is a perfect model to investigate whether or not a stall fence between the flaps and ailerons makes a difference in a model application. In the real world they are fairly common, I've seen very little discussion of them in the RC side.
Rudder inputs when in auto-level mode will just cause slide slip as the ailerons will fight the turn. I think the glide slope of this model will be steeper than what you are used to. Auto-level could have caused this crash as it will not allow the nose to drop when you cut the motor for glide.
@@andrewnielsen3178 It will. It just won't do it well! All the dihedral does is makes it easier for the plane to bank. When you add rudder in one direction, the outer wing speeds up, and creates more lift. The inner wing slows down and creates less lift. This makes it bank. This effect isn't super pronounced on the smaller planes, but is very obvious on the larger models and in full scale airplanes. Rudder will still make an airplane turn, but it won't turn in a coordinated fashion. It'll just skid around the turn.
Well done. Almost. :) Some tips for you if don't mind. 1. The propeller disc efect. The plane will allways selforiented in the wind when you start and push the throtle. You just have seen that. First time it goes to the left, with left wind, and second it goes to the right with the wind from the right. Just remember that. 2. Always make the take of and landing with nose wind. If you don't have this option you may hit the ruder, to compensate, before you push the throtle. After ... does not have effect. 3. The flaps are also breaks. That mix you have - flaperon - does not help you at all. You don't need such surface for flaps. The midle section is enough. 4. You have crashed it because you have stalled it. It have gone to the left with back wind at very low speed and the mix helped you a lot to the crash. I hope you have undersanded my english. It's not my first language. Finally - it happens. Don't warry much. I wish you many rounds with out crashes. Just enjoy it.
A couple of notes after watching the footage back a few times: 1: Its always going to be roll sensitive with every single horizontal control surface inputting roll. - Maybe just the outer two flaperons moving forward? 2: The wing flaperons were deflected opposite (right) of the direction of roll (left) when it went down indicating a complete left wing stall. - maybe build some VG's or slats? 3: Tailwheel aircraft are trash to taxi if the tailwheel isnt connected to a servo. Also, CG in relation to the main gear can have a massive effect on ground handling. The further away the wheels are from the CG, the harder it will be to taxi. I'm sure you have a good idea of what happened vs what the camera showed as you were there in person and I wasn't. I hope the damage wasn't too extensive and we can get a few more videos of the, Farm Hopper. I'd like to see you put FPV on it and go land from hill top to hill top. That's something my buddy Chris and I have been talking about doing got a while now with our bush planes. Anyways, cheers from Canada, eh!
Don't mix the flaps with you're ailerons is my advice, it's not going to benefit you, it's a Cruiser. Ditto those tailerons. Classic Tip stall brought it down, quite nasty and unprovoked...Wing tip fences maybe?
it's just a tip stall..I used to fly in the wind alot. Bet brave ...do aerobatic or try to make it do a sort of hover ( zero ground speed)...it'll tip stall..or sometimes the wing will just stop flying. it's wicked looking..coming out of a snap roll and the model just falls out of the sky.lol....Have me checking my eq over and over again...lol...but it's just a tip stall...guts of cross wind or wind blowing circles...ect. It survived to fly another another day. It's all good.
Put in about 40% expo in ailerons and 30% in elevators. Switch off auto level to land. I don't think your mixing of elevator and ailerons is a viable idea except in extreme 3d aero type model.
Why would you increase the angle of attack the most at the ends of the wings? Shouldn't you increase it the most at the roots of the wings? The way you've got it going, the tip will stall before the root, which means that if you enter a spin it'll be much harder to recover. If you're going to have the wing stall, much better to stall it at the root so that you still have some aileron control at the tip before the spin is fully developed.
Huh. I wrote that before I saw the end of the video, but it looked very much like the left wing stalled. You probably shoved the stick right to compensate, and ended up just stalling the left wing more deeply at the tip and entering the spin. Imagine if the stall had instead been at the root or middle of the wing, with the tip aileron still in good air. Possibly you might have saved it...
One other thing. Some full-sized airplanes are designed so that when you turn the yoke, one aileron goes up further than the other one goes down; that is, the decrease of AOA on one side exceeds the increase of AOA on the other. That's so that most of the work of rolling is done by the downgoing wing, which is to say the wing that has the most margin above the stall. Too much of this means you get a significant pitch-down moment when you roll, which means you have to compensate with the elevator, which may defeat the whole purpose; but a little of it might help, especially if your airplane is intrinsically spinny.
I presume you are talking about the aileron-only behavior, because the flap behavior is clearly increasing AoA more at the root. Well you can't have roll and _not_ increase the angle of attack somewhere (unless you want a purely up-only surface movement on the down-going wing). The most efficient way to achieve roll is by deflecting air out at the wingtips for better leverage. The inboard-most section would require three times the deflection for the same roll effect. Yes, I think the left wing stalled. The autopilot 'shoved the stick' to the right trying to auto-level the plane.
@@iforce2d you say: "The most efficient way to achieve roll is by deflecting air out at the wingtips for better leverage". Please let me add: "as far as you don't stall the wingtips". You are mistakenly asuming increasing angle of attack will always increase lift. I am afraid that if you are already at you maximum angle of attack, i.e. CLmax, deflecting the aileron will inmediately cause stall. What we are trying to tell you is that when you have multiple ailerons in each semi-wing, the outboard aileron shall deflect less than the inboard aileron. This will delay wing tip stall, and the lack of deflection is compensated by the increased leverage. I recommend you read "Mechanics of Flight", from A.C. Kermode. This was a reference book I used in my first year Aerospace Engineering (22 years ago, but this book is still in use!).
@@josemfr I never said increasing angle of attack will always increase lift... I'm saying that aileron deflection is more effective at the tip, obviously in a non-stalled situation otherwise all bets are off :) If what you're telling me is that important, planes with only a single surface for aileron would make sure to put it at the root to avoid tip-stall, but that's almost unheard of. Yes, I noticed you said "when you have multiple ailerons" but a section of wing with no control surface could be considered a control surface that stays neutral, so the overall number of ailerons is not really relevant.
Final comments, the landing gear didn't break! You were weather-vaning, maybe use some soft tension springs to get the tail wheel to follow the rudder, unless you've got room for just one more servo! And excellent design forethought in having the wing carry through spars absorb crash energy to protect the rest of the structure! Great show, as always.
You have put massive amounts of effort into that plane and I have to say you did brilliantly. I love the way you made the ailerons etc. Waiting now for the accident report. Regards Anthony.
Glider pilot here. You experienced a tip stall. Speed too low for 20oz wing loading. And You entered a Dead air pocket. 3 strikes! Wait for a calm day.
@@iforce2d wrong. Torque steer caused by the swirling vortex from the prop causes the reaction you were seeing on the ground. This is a-typical tail dragger behaviour, commonly seen. Build in 5 degrees of right thrust to sort this.
@@iforce2d You get a spiralling slipstream from the prop, which hits the top of the vertical stabiliser, this causes a yaw to the left, especially pronounced on tail draggers. see qph.fs.quoracdn.net/main-qimg-8f3ae66efabcd6cd53d8ad0c8a43a710
It's called 'P Factor' and occurs by the lift created by the left side of the propeller and effects the yaw moment. It's a typical phenomenon in real GA aircraft. It is countered in slow flight by applying right rudder when lifting off the ground. In cruise, it's trimmed out. The crash was caused simply by a stall. That left wing quit flying due to its incidence to the wind and not enough speed. The plane was essentially NOT in coordinated flight at that point. Had you cranked in a bunch of right rudder, it would have floated or 'kited' in the wind.
It was driving around perfectly fine without any of these issues a couple of days earlier, both in and out of the wind (on smoother ground though). Unless I'm mistaken p-factor not an issue until airspeed becomes significant, if I have to answer another comment about that I'll go nuts. Spiralling slipstream.... could be. There is also the possibility that the rocks were just coincidentally causing to to go left every time. Makes me want to try this indoors on a nice smooth surface to really figure it out.
In full scale aircraft you will always apply right rudder to counter torque, p-factor, slipstream. Remember the defending blade gets a better bite at the relative wind which will make it go left.
Man, the way the surfaces interact with each other I am completely out of the loop on understanding how it is supposed to work. I got my license in 1970 in a Cessna 150 and I really dislike the flaps moving the aileron and vice versa and then the flaps also move the outer surfaces. Seems weird. The Cessnas have (I know you know this) completely independent surfaces. That I could understand. Obviously you know what you’re doing and I enjoy this build very much. You have the patients of Jobe and I can’t wait for you to find what the creepy movements were caused by not only in the air but during taxi. It’s a fabulous bird though. Keep up the great work. You must have quite an audience by now. //ji John in Oregon
I found myself yelling the phrase my hang-gliding instructor was always yelling at me..."get your speed up!" It seemed like you weren't far from a stall, for a lot of that flight. If you want to explore the stall characteristics, go much, much higher.
That sucks I was hoping to see all those servos work in flight but you can fix I look forward to seeing if the stall was the real cause. Keep up the good work and great videos
You know your cranky when you get upset with the sound of cockatoo's. I like them as they always sound like that are running amok and having fun like people on a bucks or hens night.
Love the optimism with the crash, looks like a pretty solid tip stall from the rear camera footage, probably lost to much speed and the increased aileron deflection on the left wing just stalled it more.
Stopped at 1:20 to say this right away. Putting ailerons into flap configuration is a veeery bad idea. You want the center portion of the wing stalled while the tips are stable and balanced, that is why you ALWAYS PUT AILERONS INTO REFLEX WITH FLAPS DEPLOYED! That is a ticking tipstall timebomb sitting on your desk there. Correct mixing configuration: Flaps up, mixed with ailerons as flaperons (you did this correctly), Flaps deployed with ailerons going slightly into reflex (~5-10° depending on the wing performance) with elevators pushing slightly, no flaperon mix. Elevons... I wouldn't do it, just sync up the two servos to perform as regular elevator, don't let it go up too high or you are risking a violent unrecoverable stall spin. Don't ask how I know... And now back to watching the rest of the video.
I guess nobody told this guy about your rules th-cam.com/video/sk7D2Hvqt8I/w-d-xo.html Seems to me that it's all relative. As long as the center stalls first, do we care what specific angle the 'ailerons' are at?
@@iforce2d That video is of a full size plane. Size matters in models because the air particles (molecules) stay the same while the dimensions are smaller. As you go down in size some ratios have to change to have the performance similar. These configurations simply don't work below a certain size. The problem is your wingtip section is tapered, it will stall first. If you want to make sure the root stalls first no matter what, make a parallel wing or have a fattened section like on a Bird of Time. Also with ailerons you generally want about half the travel down than up, if your aileron down travel is too much that can also induce a tipstall. Of course it is all relative, but there are general rule of thumbs as guidelines, they were developed for a reason.
I'm aware that size matters in various ways, but I've never heard anyone claim that not using reflexed ailerons with flaps deployed will cause a tip stall in a model but not a full size. Perhaps you could explain the reasoning, and at what 'certain size' this reversal happens. Regarding the swept wingtip, not sure why you didn't pause the video to mention that in your original post instead if that was the real problem, but do you really think this 3 degree sweep is that significant? Yes, I'm also aware of using less downward travel for ailerons than upward, which is what's happening in the video if you watch the slow-mo closely at the end, and was one of the motivations for making the mixer. Anyway like I was saying, as long as the center stalls first, do we really care what specific angle the 'ailerons' are at?
And.... We have to get some money together to buy you a hang glider. There are no more powerful lessons learned than the ones received by allowing your kite to get too low on the lee side of a hill on a gusty day.
Great project as always from you, looks like it is easy to repair! Good job on making a strong but fairly flexible aircraft to withstand such an ugly nose crash. I think what happened was the following: The wind is coming from the direction of the sun from what I understand by watching the whole video. Right before the crash, you were on a slow glide with the plane side-into the wind. For some reason (ie input from you, or something else) the plane turned its tail into the wind, which ofcourse dramatically and suddenly made the airspeed over the airfoil drop, which in turn caused a tip stall as you mention. I don't think the plane is as dangerously tailheavy as you mention and it's probably not the main reason of the crash. It's just a wrong move at the wrong time/wrong direction. Anyone care to comment if I my assumptions are wrong or not is more than welcome to, maybe all this I am saying could be bs? For voltage telemetry, you either have to buy the voltage module (its really cheap actually) or do the hack I did www.rcgroups.com/forums/showthread.php?2402288-FlySky-Turnigy-iA6-%28and-iA6B%29-voltage-telemetry-mod/page17 There's info in there for the ia6b that you use, the ia10b and the cheap one that comes with your flysky transmitter. Also a good solution for the voltage telemetry issue with the "older" ia-series receivers, is to just get an x6b receiver. Its amazingly small and light and it ofcourse has on-board voltage telemetry so you just connect the ends of its "batt" connector onto your main voltage pdb pads. Also, I have not noticed worse performance with the x6b as compared to the ia10b or ia6b. I have taken the ia6b and the ia10b out to about 2.5km, and I have taken the x6b out to about 2km with great success other than partial telemetry loss. At the max distance of 2.5km, the screen of my fs-i6 was not displaying anything for voltage and rssi - kind of like how it looks when you have turned on the transmitter without the receiver, yet I still had good and uninterrupted control of the aircraft...
Wow it bounces off the ground really well and took it like a champ! Maybe I need to build with something different than foam board. Mine tend to lawn dart and crush like a crash test dummy was the pilot.
Great to have you share the hits and misses of your ambitious project! I wonder what is the decalage of the plane? It should be from 2 degrees to 3 degrees for your T tail sailplane. You seem to be running out of elevator so that is my surmise. Also, the CG seems forward. The tip stalls are typical of this condition. The design just looks excellent and I’m impressed with the weight of your plane (sans the lead, nuts and bolts).
Nice model and it flew ! ! Just a tip, next time, do the testing of a new plane always 3 mistakes, so you have time to recover some mistakes/mishaps, and don't use any "FC help" on the maiden, always asking for trouble ;o) Fly safe !
The jumpyness you were experiencing was likly due to the airflow around the terrain producing likely alot of turbulence and sink seeing as how the wind was comming from the top of the hills. In calm conditions it probably would have flown very well.
What a hell of an airplane, good job! I am very sorry for your loss. I understand how it goes.. All planes have a shelf life, for some it's shorter than others.
Seems like tip stall, it being tail-heavy made it hard to see the stall approaching, your fly-by-wire controls could have buffed out the pitching moments related to a stall, side slipping and aileron input seemed to have caused a tip stall which then caused a spin. Washout at the wing-tips, airflow fences, and slats would be my first guess to fix it. Slats would be an ideal addition.
nice model - sorry to see the crash. :( rotor (turbulence) behind the buildings maybe? some aileron differential (less down movement than up) might not be a bad idea to reduce adverse yaw.
I know this is a bigger issue with full-scale single prop aircraft, maybe the rotation of the prop is spinning the air in a certain way to put more lift on the right side of the vertical stabilizer? This effect may need a bulky fuselage though, I can't remember exactly
When you are trying to get to know a new airplane it might not be a very good idea to have the auto level on. Maybe you were unconciously expecting it to glide as well as your other builds and the autolevel hid the signs of the airplane not being comfortable at that glide slope. I am not sure what happened but I look forward to seeing the future of this build, thanks for making these videos I enjoy them and they teach me a lot
Sorry for your homemade. Classic tip stall developed into spin. Don't think you would have saved it if it was 'two mistakes high' though. Maybe reduce the throws in flaps and ailerons would be better. At low speeds, you would want minimum throws at the outboard control surfaces. Try reducing throws at the outboard ailerons and always keep throttle when you land. Even the slightest. It will prevent or at least reduce chances of spin.
I actually thought it was flying quite well considering the conditions (wind, no expo, untested mixing). I hope you can get it up and flying again soon and keep developing :)
It's a tail dragger, it needs some right rudder. Very normal. It due to the torque of the motor. Apply throttle gently to get it going with some right rudder. That symptom can be corrected by some right thrust added to the motor.
With all those flaps you should be able to set her low and.slow but I believe all those flaps/flaperons whatever are over kill seems like a great build and flyer without all that overkill why not take off and land on the grass pretty cool though body tail spar might need some reinforcing looked like it was twisting a bit but could have been camera playing tricks on my old eyes I have glow plane made from a price of square pvc down spout foame wings and a peice of aluminum screen door frame that hooks the tail assembly and pvc body together tried to fly it about 20 times crashes and I rebuild it thinks it actually flown about 20 feet gotta love it stay safe
I've been following this build from the beginning. I've been looking forward to seeing your mixing system and fully active trailing edge in action. Especially those HUGE slotted inboard panels. This is certainly not the outcome I expected or hoped for. I'm confident though that you can and will get her airworthy again. If you don't mind, I'm going to offer up of my observations and (experience based) opinions. First - It appeared to me that you have nowhere near the amount of rudder travel that you need. Especially if you intend on using a free castering tail wheel. I would offer that you might start with about 35 to 45 degrees deflection from center for ground handling. Even then, expect some dodgy handling while taxiing in crosswinds . (Dual rates can be used to limit the travel once cruising speeds are obtained. Just don't forget to switch them back up in preparation for landing.) On tailwheel aircraft, the rudder needs to have plenty of authority. (This is true for full size aircraft as well.) Second - Differential Ailerons. During the preflight demonstration of the wing surfaces, I noticed two things almost immediately. (1) No differential aileron, and (2) continued downward movement of the ailerons from the 'drooped' position. When mixed as flaperons, and in the extended position, all aileron movement should only be upwards on the wing you want to roll towards. Increasing the downward input on the opposite side serves only to increase an already considerable amount of adverse yaw and invite tip stalls. An example of what I mean, while not exactly the same, can be seen in action on most jet airliners. When the flaps are lowered on an airliner, it involves the majority of the wings trailing edge. When the wing is configured thusly, roll control spoilers become active on the wings upper surface in order apply authoritative roll control during reduced speed, without inducing adverse yaw. (Adverse yaw is especially dangerous for swept wing aircraft during low speed, low altitude operations.) I would suggest, as a place to start, that when the trailing edge is retracted, downward aileron travel be limited to 50% of the upward aileron movement. As the trailing edge is extended, the downward movement of aileron be further limited so that once the 'Full Flap' position is reached, there is only upward aileron movement on the wing that you want to roll towards. I would further offer that you may wish to mix it so that only after the outboard aileron has reached its upper limit, the central panel should become 'upwardly mobile'. I would also suggest that once the inboard panels have been extended to 20-25 degrees, they cease any roll input movements. [I also want to say that as the airspeed starts dropping down near stall, the use of the rudder becomes more important.] Third - During the stall event that led up to the crash. I saw that as the stall and subsiqent roll [to the left] began, the trailing edge of the left wing began moving downwards. This increased the angle of attack on the already stalled wing, deepening the stall and increasing the rate of roll, initiating the spin. This unfortunately prompted the ground to jump up and smack the plane out of the sky. Neutralizing the roll input and generous use of opposite rudder MAY have stopped the roll and allow you to recover from the stall. However, the ground may have already been too close to avoid. (Shifty like that, the ground can be.) I've got to tell you though, your workmanship continues to impress me. Cutting and hinging those wing panels to the tolerances you've achieved is quite the task. I do hope that the bent flap can be restored to its former glory without too much trouble. I'll leave you with this little bit of wisdom that was shared with me by an old flight instructor during my spin training years ago. Perhaps shared isn't the right word. He pretty much hammered it into my psyche; "If you're stalling or spinning, shove that stick to the front and CENTER. Then pick that low wing up with the rudder." I happy to say that it has worked every time. I just remembered something else that he said during my first spin training flight. It's pertinent here because of something you said. Upon reaching 3,000 feet, Ray (the instructor and owner of the plane we were flying, an Aronca Champ), went over the procedure we were about to perform. When he was done, he asked if I was ready. I suggested that we climb up to 4,000 feet as I really wanted to be two mistakes high. He assured me that we already had more than enough altitude to satisfy that requirement. He reduced the throttle and began easing back on the stick. As the airspeed was falling off, he off handedly quipped, "You must be pretty impressed with yourself if you think you're only about to make two mistakes." I looked up in the mirror to get a look at his face trying to judge how serious he was being. He looked up and our eyes met in the mirror and I could see that he was grinning. He suddenly pointed forward and shouted, "Your plane!" I looked away from the mirror and out the windscreen just in time to see the world turn upside down as he started laughing behind me. I must humbly admit that I made quite a few more than two mistakes over the course of the next hour or so. He let me make exactly as many as I needed to. Before that flight I was terrified of spins, after, I actually enjoyed them. He was probably the best flight instructor I had the honor to fly with. Cheers
The downward aileron travel is already limited to 50% of the upward aileron movement, although watching the video again it doesn't look much like it, so I'll double check on that. But yes, that was one of the motivations for making the mixer. It was the autopilot that commanded the right roll to autolevel, but at that altitude even if I was doing everything manually it was already too late. With enough altitude if the plane is set up correctly the autolevel can recover anyway, so manual or not doesn't matter too much overall, but I think it was tail-heavy so there were mistakes all over the place :]
Do you think it was a bit Light, for the wing area? super interested to see how this turns out ! I am living vicariously through these plane builds. I would love to have the time and resources to build planes like this. Thanks for all your work.
Once in the air it was getting along ok at around half throttle so I think the wing loading is probably not too bad. On the other hand getting off the ground took all the strength it could muster... not sure what to make of it.
Geez those flaps... you trying to stop the bloody thing ?!?! :) That is a lot of mixing for that kind of plane. I wonder if you are using FRSKY or what as a Radio. Sbus mixer?!? I gotta look into this. I like the FCB. Omnibus is nice.
What is the weight of the craft? It almost appeared to be a bit heavy. It appeared the left wing stalled. Loved the variable Flaperons. Interesting concept!
Biggest issue is the rearward cg. Fix that and the rest will fall into place without nearly as much stress. Great looking model. Get some weight forward and it will be a great flier.
Yeah I was way too lax with the CG placement. I just placed it kinda roughly and as I left my house I was actually thinking it might cause problems, then somehow with the taxiing issues I completely forgot about it, even while flying and feeling the terrible handling. I moved CG much further forward and will try again.
I'm not entirely convinced this was an accident, since you tend to immediately get back to building planes when one is done! Shame it doesn't (didn't) fly as well as you wanted to. Can't wait for the next one.
Always make a stearable nose wheel connected to the rudder servo. Classic stall. Your airspeed dropped too low. Plane looks a little on the heavy side.
After looking at the slow mo a bunch of times it looks like you get some buffeting just before the tip stalls. Of course there is no way for you to feel that on the ground but aircraft shake for lack of another word other than buffet just before a stall. If you had a sensor that could detect one then you would always no a couple seconds before a stall and if you couldn't prevent it you could at least start your recovery at the earliest possible moment.
Turning left because of p factor...... tail dragger to prevent ground loops toe in the wheels slightly (you will need to experiment to find the right amount for your setup) (the easy this helps is if the plane turns left then toe causes left wheel to roll easier and the right wheel to scrub sideways acting like a break on the right wheel pulling that side back which causes the airplane to point straight ahead naturally.....also you need to lift the tail so the rudder will be effective....(raising the limit eliminates p factor ....(p factor the tail down puts the bottom of the propeller forward the top backwards this causes side forces.... the slipstream from the prop also corkscrews around the fuselage and strikes the side of the vertical tail pushing the tail around .... when leaving the tail in the ground the wing is in stall or near stall which creates drag .... the length of the wing makes this drag more effective at the tip of wing which is leverage over the cg.... lifting the tail gets rid of bear stall drag and makes the rudder effective.....40 years experience in rc and also experience in the real thing
Looked like a stall and started to enter a spin. If you had been higher up and pulled up elevator at that attitude you would have entered a spiral dive. It doesn't look like you have any dihedral, was that on purpose? Even a little would make it a lot more stable I think.
It came into the turbulence of the hill you are on .... looked like you hit a rotator .... caused by the hill and buildings....seemed you have cg to far back which causes instability which makes errors compound instead of returning to stable flight... this trail heavy also causes ground loops to increase...
What a Amazing Effort........it looks Soooo cool in the Air and I love the rear camera view..... I guess you will add tail wheel control ......Mmmm that did looked like a stall at the end......wonder what your speed was about...... maybe some winglets will help until its sorted......or VG's Brett
maybe a sort of adverse yaw feedback loop at the end there? You have the same issue with takeoff I mentioned before, the Ranger always wants to turn under power on the ground
Since the plane is pitched up while it's on the ground, you will have left turning tendencies no matter what because of p-factor. Don't know how much that will affect a model aircraft of this side though, it should easily be offset with rudder though. Just my ,02
@@iforce2d It's about the angle of attack of the blades, and then of the whole prop itself. If you're producing maximum thrust from 0 airspeed, it would actually be the highest then. Depends on the prop design
3:40 planes with bycicle landing gear configuration are very susceptible to crosswinds . crosswind corrections must be applied . Ailerons into the crosswind and rudder towards the opposite side
Unfortunately, it didn't look like a tip stall. (from what I can tell from the video, so don't take this as gospel) It was begining to get into a gentle stall, and was gradually rolling to the left due to the left rudder, but to counteract the left roll you used right aileron. Normally this would be okay, but once the plane is already partly stalled, this just adds more left rudder due to the adverse yaw, and stalls the left wing more due to the increased angle of attack having the ailerons down on that side. If it was a tip stall it probably would have had a more agressive initiation. It does still ask the question though of why it got into a stall in the first place, it seemed like you still had enough speed? And like you say, always stay a few mistakes high when testing ;) It looked like it was only a couple more meters away from pulling out
I think it was just tail-heavy, that would explain the appalling handling characteristics too. There would have been no rudder involved because I don't recall doing that and the autopilot doesn't do it either. The counteracting aileron was done by the autopilot though.
@@iforce2d Oh, sorry, I misunderstood what was happening, when you were saying that it was side slipping, I assumed that you were doing it intentionally. That makes it even more strange that it was side slipping so much. Being tail heavy might explain the lack of yaw stability a bit, but wouldn't normally be enough on its own, I await to hear if you find anything more.
@@iforce2d Also, to counteract the adverse yaw, I would get rid of the mixing from ail to flaps, and then have the ailerons that are in use moving only in the up direction (or at leats much more in the up direction), it won't be as good for roll, but atleast you wont get loads of adverse yaw. This is very common on 6 servo wing gliders
I think I should have said 'crabbing' instead of side slipping, might have got the terminology wrong there. Yeah since I have that mixing available to do whatever I want, I think I'll set the ailerons to only go up.
Could b e'P-factor' that is casuing your plane to go left. As the prop rotates with the nose high, the starboard side of the prop bites more air and rotates the nose left, especially as you gain ground speed.
Also, maybe try using a 'landing flap setting' when landing or making a slow apprach without power. You could try having a tad of relfex on your ailerons and a tad more of the inboard flap cambered downwards (alsow called 'crow'). That way you load up the inboard section of the wing more so that the tips of the wings are less prone to stalling. My two cents :-)
Noooo i was waiting for this flight video 😢 , didn’t expect it to end up with a crash ! did you soft-mount the flight controller ? all the vibrations from the motors could make the gyro goes crazy and therefore the flight controller sends wrong outputs to the servos .. i really enjoyed watching the whole building videos :) .. thanks a lot and fly safe 👍🏽👍🏽
Nothing wrong with the design, it was the x-wind giving the illusion that it was in a sideslip when in fact it was only crabbing from the wind. When aileron and rudder controls were crossed at the low speed and high angle of attack, it entered a cross-control stall into a spin. Opposite rudder and neutral aileron would've saved it.
Applying opposite aileron is instinctive but all it does is increase the angle of attack of the stalled wing, deepening the spin. It's important to use lots of rudder at low speeds with aileron only to balance it out.
There was no rudder input anywhere. The autopilot was doing the 'instinctive' roll response (although if it was in manual mode I probably would have anyway :) but it doesn't do any rudder.
I would look at shimming the left side of the motor when looking from behind out a hair. Due to torque roll it’s said that the motor should be angled a little to the the right. I’ve never had to really worry about it much because I haven’t had a build try to ground loop like yours is. I looked up your bird really hoping the real wiki article was written the way you have it and was disappointed to see it’s not.........
It looks like classic stall. Then using ailerons can situation go worse due to lift loss... You should try to rescue with throttle and rudder only. I suppose the reason is zero leading edge angle and lack of engine deviation... The last one causes take off problems we saw...
Because it's not free stability. It often makes the plane weaker, induces dutch rolls at higher speeds, makes the plane more suseptible to wind and reduces stability when inverted. And ontop of that, depending on your definition, it doesn't actually add stability, it only adds self centering, e.g. the plane can still rock around, it will just stop it from rocking too far, which a competent pilot (or flight stabiliser) is very good at doing anyway.
In this case it is a high wing and so it gets free stability. Many high wing aircraft need anhedral because its too stable Now some washout or vortex generators to prevent tip stalls and ensure it is always a root stall would be a good idea.
@@lukeattubato By stability, I was referring to inherent stability, like in no autopilot, hands off the controls stability. True, stability doesn't help win 20mm cannon duels, or do much for a pilot performing aerobatics at the edge of the envelop, but is twitching agility really of major importance in a STOL aircraft?
@@Reach41 Yes, true, in this case instability inverted probably won't affect the plane too much, but did you not see the other 3 negatives? and you say you were refering to without an autopilot, but he does have an autopilot (and he's a competent pilot), so that seems irrelavent. And I'm not really sure where you got agility from, since dihedral doesn't affect agility, but yes, agility is very important for a STOL aircraft, its needed to quickly change pitch/roll while on aproach when you have low airspeed, and little height. You need to very quickly be able to make small corrections.
Too slow , too low-stabilization has nothing to do , when pane flies too slow , but apart form everything you shouldn't have flown in such place - you have no space to make good approach , no margin for mistake. From one side fence , from another building , against fence is abyss - request for disaster. One thing I can suggest: add GPS , return to home works perfect. Are you using INAV , Betaflight or Mission control? I can see that you are pushing SBUS signal form F4 onto this distribution PWM board -> very smart solution. Good luck.
As for loss of control right there toward the end, that looked for all the world like a stall/spin. Might have initiated it with aileron input, or maybe it was something completely different -- didn't seem to be going that slow. Wind shear?
If the prop is spinning to the right , motor torque can sometimes cause the plane to pull to the left . Also , unless you enjoy the challenge .... all those dual elevator & multiple aileron/flaperon configurations are unnecessary and only add potential points of failure . KISS .... Keep It Simple Sir !
Fix the aileron differential, balance point, remember wind shadowing effects and it will be fine. I think you have WAY too much control throw on the ailerons though unless you plan to 3D fly it.
I guess tail heavy would explain it. Looked quite wafty as if the vertical stab wasn't doing enough. Any way it survived the crash well, but I feel your disappointment.
Oh no! My favorite design of your's yet, sorry to see it crash. I love how your spirits is still up after all that work. I also appreciate the blow by blow accident footage. Can't wait to see more of this plane.
Also looked like a lot of adverse yaw as well. Once you deploy those flaps you'll find out *ALL* about adverse yaw :-)
Hey! Haven't seen a video in a while, hope everything is okay!
And then he almost immediately releases a video
Tip stall
This is a perfect model to investigate whether or not a stall fence between the flaps and ailerons makes a difference in a model application. In the real world they are fairly common, I've seen very little discussion of them in the RC side.
I was just thinking the same thing. The same material that all the control horns were made of would work well to build the stall fences.
Are wing fences still used in modern planes?
Mate I loved the build. I’m learning heaps from your videos. Keep at it. We all crash sometimes. That’s how we learn.
Rudder inputs when in auto-level mode will just cause slide slip as the ailerons will fight the turn. I think the glide slope of this model will be steeper than what you are used to. Auto-level could have caused this crash as it will not allow the nose to drop when you cut the motor for glide.
I think he is right been practicing that in realflight and it is a hard skill for me
Rudder will not create turn without dihedral in wing.
@@andrewnielsen3178 It will. It just won't do it well! All the dihedral does is makes it easier for the plane to bank. When you add rudder in one direction, the outer wing speeds up, and creates more lift. The inner wing slows down and creates less lift. This makes it bank. This effect isn't super pronounced on the smaller planes, but is very obvious on the larger models and in full scale airplanes.
Rudder will still make an airplane turn, but it won't turn in a coordinated fashion. It'll just skid around the turn.
@@andrewnielsen3178 you're right with symmetrical airfoils only.
Effect of yaw is rolling. So becareful if you used to much rudder. My RC get into spiral dive because of it....
Well done. Almost. :)
Some tips for you if don't mind.
1. The propeller disc efect. The plane will allways selforiented in the wind when you start and push the throtle. You just have seen that. First time it goes to the left, with left wind, and second it goes to the right with the wind from the right. Just remember that.
2. Always make the take of and landing with nose wind. If you don't have this option you may hit the ruder, to compensate, before you push the throtle. After ... does not have effect.
3. The flaps are also breaks. That mix you have - flaperon - does not help you at all. You don't need such surface for flaps. The midle section is enough.
4. You have crashed it because you have stalled it. It have gone to the left with back wind at very low speed and the mix helped you a lot to the crash.
I hope you have undersanded my english. It's not my first language.
Finally - it happens. Don't warry much.
I wish you many rounds with out crashes. Just enjoy it.
A couple of notes after watching the footage back a few times:
1: Its always going to be roll sensitive with every single horizontal control surface inputting roll. - Maybe just the outer two flaperons moving forward?
2: The wing flaperons were deflected opposite (right) of the direction of roll (left) when it went down indicating a complete left wing stall. - maybe build some VG's or slats?
3: Tailwheel aircraft are trash to taxi if the tailwheel isnt connected to a servo. Also, CG in relation to the main gear can have a massive effect on ground handling. The further away the wheels are from the CG, the harder it will be to taxi.
I'm sure you have a good idea of what happened vs what the camera showed as you were there in person and I wasn't. I hope the damage wasn't too extensive and we can get a few more videos of the, Farm Hopper. I'd like to see you put FPV on it and go land from hill top to hill top. That's something my buddy Chris and I have been talking about doing got a while now with our bush planes. Anyways, cheers from Canada, eh!
Don't mix the flaps with you're ailerons is my advice, it's not going to benefit you, it's a Cruiser. Ditto those tailerons.
Classic Tip stall brought it down, quite nasty and unprovoked...Wing tip fences maybe?
it's just a tip stall..I used to fly in the wind alot. Bet brave ...do aerobatic or try to make it do a sort of hover ( zero ground speed)...it'll tip stall..or sometimes the wing will just stop flying. it's wicked looking..coming out of a snap roll and the model just falls out of the sky.lol....Have me checking my eq over and over again...lol...but it's just a tip stall...guts of cross wind or wind blowing circles...ect.
It survived to fly another another day. It's all good.
@@oneeyemonster3262 It's not that kind of model, it's an FPV Cruiser. The exact opposite of what you are describing...🤔🤔😒😒
Put in about 40% expo in ailerons and 30% in elevators. Switch off auto level to land. I don't think your mixing of elevator and ailerons is a viable idea except in extreme 3d aero type model.
Why would you increase the angle of attack the most at the ends of the wings? Shouldn't you increase it the most at the roots of the wings? The way you've got it going, the tip will stall before the root, which means that if you enter a spin it'll be much harder to recover. If you're going to have the wing stall, much better to stall it at the root so that you still have some aileron control at the tip before the spin is fully developed.
Huh. I wrote that before I saw the end of the video, but it looked very much like the left wing stalled. You probably shoved the stick right to compensate, and ended up just stalling the left wing more deeply at the tip and entering the spin. Imagine if the stall had instead been at the root or middle of the wing, with the tip aileron still in good air. Possibly you might have saved it...
One other thing. Some full-sized airplanes are designed so that when you turn the yoke, one aileron goes up further than the other one goes down; that is, the decrease of AOA on one side exceeds the increase of AOA on the other. That's so that most of the work of rolling is done by the downgoing wing, which is to say the wing that has the most margin above the stall. Too much of this means you get a significant pitch-down moment when you roll, which means you have to compensate with the elevator, which may defeat the whole purpose; but a little of it might help, especially if your airplane is intrinsically spinny.
I presume you are talking about the aileron-only behavior, because the flap behavior is clearly increasing AoA more at the root. Well you can't have roll and _not_ increase the angle of attack somewhere (unless you want a purely up-only surface movement on the down-going wing). The most efficient way to achieve roll is by deflecting air out at the wingtips for better leverage. The inboard-most section would require three times the deflection for the same roll effect.
Yes, I think the left wing stalled. The autopilot 'shoved the stick' to the right trying to auto-level the plane.
@@iforce2d you say: "The most efficient way to achieve roll is by deflecting air out at the wingtips for better leverage". Please let me add: "as far as you don't stall the wingtips". You are mistakenly asuming increasing angle of attack will always increase lift. I am afraid that if you are already at you maximum angle of attack, i.e. CLmax, deflecting the aileron will inmediately cause stall. What we are trying to tell you is that when you have multiple ailerons in each semi-wing, the outboard aileron shall deflect less than the inboard aileron. This will delay wing tip stall, and the lack of deflection is compensated by the increased leverage. I recommend you read "Mechanics of Flight", from A.C. Kermode. This was a reference book I used in my first year Aerospace Engineering (22 years ago, but this book is still in use!).
@@josemfr I never said increasing angle of attack will always increase lift... I'm saying that aileron deflection is more effective at the tip, obviously in a non-stalled situation otherwise all bets are off :) If what you're telling me is that important, planes with only a single surface for aileron would make sure to put it at the root to avoid tip-stall, but that's almost unheard of. Yes, I noticed you said "when you have multiple ailerons" but a section of wing with no control surface could be considered a control surface that stays neutral, so the overall number of ailerons is not really relevant.
Final comments, the landing gear didn't break! You were weather-vaning, maybe use some soft tension springs to get the tail wheel to follow the rudder, unless you've got room for just one more servo! And excellent design forethought in having the wing carry through spars absorb crash energy to protect the rest of the structure! Great show, as always.
You have put massive amounts of effort into that plane and I have to say you did brilliantly. I love the way you made the ailerons etc. Waiting now for the accident report. Regards Anthony.
Glider pilot here. You experienced a tip stall. Speed too low for 20oz wing loading. And You entered a Dead air pocket. 3 strikes! Wait for a calm day.
It wants to go to the left due to the torque of the motor.
You might want to check the thrust angle
Torque of the motor would induce a roll, not a yaw. More likely it was simply weather-vaning.
@@iforce2d wrong. Torque steer caused by the swirling vortex from the prop causes the reaction you were seeing on the ground. This is a-typical tail dragger behaviour, commonly seen. Build in 5 degrees of right thrust to sort this.
@@iforce2d You get a spiralling slipstream from the prop, which hits the top of the vertical stabiliser, this causes a yaw to the left, especially pronounced on tail draggers. see qph.fs.quoracdn.net/main-qimg-8f3ae66efabcd6cd53d8ad0c8a43a710
It's called 'P Factor' and occurs by the lift created by the left side of the propeller and effects the yaw moment. It's a typical phenomenon in real GA aircraft. It is countered in slow flight by applying right rudder when lifting off the ground. In cruise, it's trimmed out.
The crash was caused simply by a stall. That left wing quit flying due to its incidence to the wind and not enough speed. The plane was essentially NOT in coordinated flight at that point. Had you cranked in a bunch of right rudder, it would have floated or 'kited' in the wind.
It was driving around perfectly fine without any of these issues a couple of days earlier, both in and out of the wind (on smoother ground though). Unless I'm mistaken p-factor not an issue until airspeed becomes significant, if I have to answer another comment about that I'll go nuts. Spiralling slipstream.... could be. There is also the possibility that the rocks were just coincidentally causing to to go left every time. Makes me want to try this indoors on a nice smooth surface to really figure it out.
In full scale aircraft you will always apply right rudder to counter torque, p-factor, slipstream. Remember the defending blade gets a better bite at the relative wind which will make it go left.
Man, the way the surfaces interact with each other I am completely out of the loop on understanding how it is supposed to work.
I got my license in 1970 in a Cessna 150 and I really dislike the flaps moving the aileron and vice versa and then the flaps also move the outer surfaces. Seems weird. The Cessnas have (I know you know this) completely independent surfaces.
That I could understand.
Obviously you know what you’re doing and I enjoy this build very much. You have the patients of Jobe and I can’t wait for you to find what the creepy movements were caused by not only in the air but during taxi. It’s a fabulous bird though. Keep up the great work. You must have quite an audience by now. //ji John in Oregon
I saw the thumbnail and almost cried😭😭😭
Love the view from the back! That landing gear looks really effective to me. Hell of alot better than the STOL plane lol!!!!!
Just listening to the narration makes it sound like about half of my projects. "WTF...why...that's impossible...there is no reason for that, etc"
"now why the bloody hell is that happening? Oh, you little bastard.... Where's my bloody screwdriver?"
Yep. Me too. 😂
I found myself yelling the phrase my hang-gliding instructor was always yelling at me..."get your speed up!" It seemed like you weren't far from a stall, for a lot of that flight.
If you want to explore the stall characteristics, go much, much higher.
Secondary effects of controls #FTW Wonderful build, well done
For a completely built from scratch plane, that was awesome! A little repair and fine tuning, it will be great
That sucks I was hoping to see all those servos work in flight but you can fix I look forward to seeing if the stall was the real cause. Keep up the good work and great videos
You know your cranky when you get upset with the sound of cockatoo's. I like them as they always sound like that are running amok and having fun like people on a bucks or hens night.
Seriously? They annoy me even when they're 1km away and I'm inside the house and not already cranky.
@@iforce2d thousands here and I love them. Not as much as the giant black & red ones
Love the optimism with the crash, looks like a pretty solid tip stall from the rear camera footage, probably lost to much speed and the increased aileron deflection on the left wing just stalled it more.
I agree with your summary at the end. The entire flight I was saying it is acting tail heavy. You probably noticed that from the take off as well.
At least the landing gear didn't break!
Stopped at 1:20 to say this right away. Putting ailerons into flap configuration is a veeery bad idea. You want the center portion of the wing stalled while the tips are stable and balanced, that is why you ALWAYS PUT AILERONS INTO REFLEX WITH FLAPS DEPLOYED! That is a ticking tipstall timebomb sitting on your desk there.
Correct mixing configuration: Flaps up, mixed with ailerons as flaperons (you did this correctly), Flaps deployed with ailerons going slightly into reflex (~5-10° depending on the wing performance) with elevators pushing slightly, no flaperon mix. Elevons... I wouldn't do it, just sync up the two servos to perform as regular elevator, don't let it go up too high or you are risking a violent unrecoverable stall spin. Don't ask how I know...
And now back to watching the rest of the video.
I guess nobody told this guy about your rules th-cam.com/video/sk7D2Hvqt8I/w-d-xo.html
Seems to me that it's all relative. As long as the center stalls first, do we care what specific angle the 'ailerons' are at?
@@iforce2d That video is of a full size plane. Size matters in models because the air particles (molecules) stay the same while the dimensions are smaller. As you go down in size some ratios have to change to have the performance similar. These configurations simply don't work below a certain size.
The problem is your wingtip section is tapered, it will stall first. If you want to make sure the root stalls first no matter what, make a parallel wing or have a fattened section like on a Bird of Time. Also with ailerons you generally want about half the travel down than up, if your aileron down travel is too much that can also induce a tipstall.
Of course it is all relative, but there are general rule of thumbs as guidelines, they were developed for a reason.
I'm aware that size matters in various ways, but I've never heard anyone claim that not using reflexed ailerons with flaps deployed will cause a tip stall in a model but not a full size. Perhaps you could explain the reasoning, and at what 'certain size' this reversal happens.
Regarding the swept wingtip, not sure why you didn't pause the video to mention that in your original post instead if that was the real problem, but do you really think this 3 degree sweep is that significant?
Yes, I'm also aware of using less downward travel for ailerons than upward, which is what's happening in the video if you watch the slow-mo closely at the end, and was one of the motivations for making the mixer.
Anyway like I was saying, as long as the center stalls first, do we really care what specific angle the 'ailerons' are at?
And.... We have to get some money together to buy you a hang glider. There are no more powerful lessons learned than the ones received by allowing your kite to get too low on the lee side of a hill on a gusty day.
Great project as always from you, looks like it is easy to repair! Good job on making a strong but fairly flexible aircraft to withstand such an ugly nose crash.
I think what happened was the following: The wind is coming from the direction of the sun from what I understand by watching the whole video. Right before the crash, you were on a slow glide with the plane side-into the wind. For some reason (ie input from you, or something else) the plane turned its tail into the wind, which ofcourse dramatically and suddenly made the airspeed over the airfoil drop, which in turn caused a tip stall as you mention. I don't think the plane is as dangerously tailheavy as you mention and it's probably not the main reason of the crash. It's just a wrong move at the wrong time/wrong direction. Anyone care to comment if I my assumptions are wrong or not is more than welcome to, maybe all this I am saying could be bs?
For voltage telemetry, you either have to buy the voltage module (its really cheap actually) or do the hack I did www.rcgroups.com/forums/showthread.php?2402288-FlySky-Turnigy-iA6-%28and-iA6B%29-voltage-telemetry-mod/page17
There's info in there for the ia6b that you use, the ia10b and the cheap one that comes with your flysky transmitter.
Also a good solution for the voltage telemetry issue with the "older" ia-series receivers, is to just get an x6b receiver. Its amazingly small and light and it ofcourse has on-board voltage telemetry so you just connect the ends of its "batt" connector onto your main voltage pdb pads. Also, I have not noticed worse performance with the x6b as compared to the ia10b or ia6b. I have taken the ia6b and the ia10b out to about 2.5km, and I have taken the x6b out to about 2km with great success other than partial telemetry loss. At the max distance of 2.5km, the screen of my fs-i6 was not displaying anything for voltage and rssi - kind of like how it looks when you have turned on the transmitter without the receiver, yet I still had good and uninterrupted control of the aircraft...
Wow it bounces off the ground really well and took it like a champ! Maybe I need to build with something different than foam board. Mine tend to lawn dart and crush like a crash test dummy was the pilot.
Great to have you share the hits and misses of your ambitious project! I wonder what is the decalage of the plane? It should be from 2 degrees to 3 degrees for your T tail sailplane. You seem to be running out of elevator so that is my surmise. Also, the CG seems forward. The tip stalls are typical of this condition. The design just looks excellent and I’m impressed with the weight of your plane (sans the lead, nuts and bolts).
Nice model and it flew ! ! Just a tip, next time, do the testing of a new plane always 3 mistakes, so you have time to recover some mistakes/mishaps, and don't use any "FC help" on the maiden, always asking for trouble ;o) Fly safe !
The jumpyness you were experiencing was likly due to the airflow around the terrain producing likely alot of turbulence and sink seeing as how the wind was comming from the top of the hills. In calm conditions it probably would have flown very well.
What a hell of an airplane, good job! I am very sorry for your loss. I understand how it goes.. All planes have a shelf life, for some it's shorter than others.
Seems like tip stall, it being tail-heavy made it hard to see the stall approaching, your fly-by-wire controls could have buffed out the pitching moments related to a stall, side slipping and aileron input seemed to have caused a tip stall which then caused a spin.
Washout at the wing-tips, airflow fences, and slats would be my first guess to fix it.
Slats would be an ideal addition.
nice model - sorry to see the crash. :( rotor (turbulence) behind the buildings maybe?
some aileron differential (less down movement than up) might not be a bad idea to reduce adverse yaw.
A maiden crash?
No problem! You've got great video footage. Yay!
It flew nicely and looks fairly resilient, as it should be. Good luck on the remaiden.
👍
I know this is a bigger issue with full-scale single prop aircraft, maybe the rotation of the prop is spinning the air in a certain way to put more lift on the right side of the vertical stabilizer? This effect may need a bulky fuselage though, I can't remember exactly
When you are trying to get to know a new airplane it might not be a very good idea to have the auto level on. Maybe you were unconciously expecting it to glide as well as your other builds and the autolevel hid the signs of the airplane not being comfortable at that glide slope.
I am not sure what happened but I look forward to seeing the future of this build, thanks for making these videos I enjoy them and they teach me a lot
Sorry for your homemade. Classic tip stall developed into spin. Don't think you would have saved it if it was 'two mistakes high' though. Maybe reduce the throws in flaps and ailerons would be better. At low speeds, you would want minimum throws at the outboard control surfaces. Try reducing throws at the outboard ailerons and always keep throttle when you land. Even the slightest. It will prevent or at least reduce chances of spin.
I actually thought it was flying quite well considering the conditions (wind, no expo, untested mixing). I hope you can get it up and flying again soon and keep developing :)
It's a tail dragger, it needs some right rudder. Very normal. It due to the torque of the motor. Apply throttle gently to get it going with some right rudder. That symptom can be corrected by some right thrust added to the motor.
Good old propwash. You need to offset the motor axis, with a slight down angle as well.
With all those flaps you should be able to set her low and.slow but I believe all those flaps/flaperons whatever are over kill seems like a great build and flyer without all that overkill why not take off and land on the grass pretty cool though body tail spar might need some reinforcing looked like it was twisting a bit but could have been camera playing tricks on my old eyes I have glow plane made from a price of square pvc down spout foame wings and a peice of aluminum screen door frame that hooks the tail assembly and pvc body together tried to fly it about 20 times crashes and I rebuild it thinks it actually flown about 20 feet gotta love it stay safe
The grass is much worse than the gravel, it has bumps and ruts you could hide a coke can inside, and there are no flat areas anyway.
I've been following this build from the beginning. I've been looking forward to seeing your mixing system and fully active trailing edge in action. Especially those HUGE slotted inboard panels. This is certainly not the outcome I expected or hoped for. I'm confident though that you can and will get her airworthy again.
If you don't mind, I'm going to offer up of my observations and (experience based) opinions.
First - It appeared to me that you have nowhere near the amount of rudder travel that you need. Especially if you intend on using a free castering tail wheel. I would offer that you might start with about 35 to 45 degrees deflection from center for ground handling. Even then, expect some dodgy handling while taxiing in crosswinds . (Dual rates can be used to limit the travel once cruising speeds are obtained. Just don't forget to switch them back up in preparation for landing.) On tailwheel aircraft, the rudder needs to have plenty of authority. (This is true for full size aircraft as well.)
Second - Differential Ailerons. During the preflight demonstration of the wing surfaces, I noticed two things almost immediately. (1) No differential aileron, and (2) continued downward movement of the ailerons from the 'drooped' position.
When mixed as flaperons, and in the extended position, all aileron movement should only be upwards on the wing you want to roll towards. Increasing the downward input on the opposite side serves only to increase an already considerable amount of adverse yaw and invite tip stalls.
An example of what I mean, while not exactly the same, can be seen in action on most jet airliners. When the flaps are lowered on an airliner, it involves the majority of the wings trailing edge. When the wing is configured thusly, roll control spoilers become active on the wings upper surface in order apply authoritative roll control during reduced speed, without inducing adverse yaw. (Adverse yaw is especially dangerous for swept wing aircraft during low speed, low altitude operations.)
I would suggest, as a place to start, that when the trailing edge is retracted, downward aileron travel be limited to 50% of the upward aileron movement. As the trailing edge is extended, the downward movement of aileron be further limited so that once the 'Full Flap' position is reached, there is only upward aileron movement on the wing that you want to roll towards.
I would further offer that you may wish to mix it so that only after the outboard aileron has reached its upper limit, the central panel should become 'upwardly mobile'.
I would also suggest that once the inboard panels have been extended to 20-25 degrees, they cease any roll input movements.
[I also want to say that as the airspeed starts dropping down near stall, the use of the rudder becomes more important.]
Third - During the stall event that led up to the crash. I saw that as the stall and subsiqent roll [to the left] began, the trailing edge of the left wing began moving downwards. This increased the angle of attack on the already stalled wing, deepening the stall and increasing the rate of roll, initiating the spin. This unfortunately prompted the ground to jump up and smack the plane out of the sky.
Neutralizing the roll input and generous use of opposite rudder MAY have stopped the roll and allow you to recover from the stall. However, the ground may have already been too close to avoid. (Shifty like that, the ground can be.)
I've got to tell you though, your workmanship continues to impress me. Cutting and hinging those wing panels to the tolerances you've achieved is quite the task. I do hope that the bent flap can be restored to its former glory without too much trouble.
I'll leave you with this little bit of wisdom that was shared with me by an old flight instructor during my spin training years ago. Perhaps shared isn't the right word. He pretty much hammered it into my psyche; "If you're stalling or spinning, shove that stick to the front and CENTER. Then pick that low wing up with the rudder." I happy to say that it has worked every time.
I just remembered something else that he said during my first spin training flight. It's pertinent here because of something you said.
Upon reaching 3,000 feet, Ray (the instructor and owner of the plane we were flying, an Aronca Champ), went over the procedure we were about to perform. When he was done, he asked if I was ready. I suggested that we climb up to 4,000 feet as I really wanted to be two mistakes high. He assured me that we already had more than enough altitude to satisfy that requirement.
He reduced the throttle and began easing back on the stick. As the airspeed was falling off, he off handedly quipped, "You must be pretty impressed with yourself if you think you're only about to make two mistakes."
I looked up in the mirror to get a look at his face trying to judge how serious he was being. He looked up and our eyes met in the mirror and I could see that he was grinning. He suddenly pointed forward and shouted, "Your plane!"
I looked away from the mirror and out the windscreen just in time to see the world turn upside down as he started laughing behind me. I must humbly admit that I made quite a few more than two mistakes over the course of the next hour or so. He let me make exactly as many as I needed to. Before that flight I was terrified of spins, after, I actually enjoyed them. He was probably the best flight instructor I had the honor to fly with.
Cheers
The downward aileron travel is already limited to 50% of the upward aileron movement, although watching the video again it doesn't look much like it, so I'll double check on that. But yes, that was one of the motivations for making the mixer.
It was the autopilot that commanded the right roll to autolevel, but at that altitude even if I was doing everything manually it was already too late. With enough altitude if the plane is set up correctly the autolevel can recover anyway, so manual or not doesn't matter too much overall, but I think it was tail-heavy so there were mistakes all over the place :]
Do you think it was a bit Light, for the wing area? super interested to see how this turns out ! I am living vicariously through these plane builds. I would love to have the time and resources to build planes like this. Thanks for all your work.
Once in the air it was getting along ok at around half throttle so I think the wing loading is probably not too bad. On the other hand getting off the ground took all the strength it could muster... not sure what to make of it.
Geez those flaps... you trying to stop the bloody thing ?!?! :) That is a lot of mixing for that kind of plane. I wonder if you are using FRSKY or what as a Radio. Sbus mixer?!? I gotta look into this. I like the FCB. Omnibus is nice.
What is the weight of the craft? It almost appeared to be a bit heavy. It appeared the left wing stalled. Loved the variable Flaperons. Interesting concept!
Forget the tip stall crap.It may have been in the final moment but the adverse yaw action was happening for quite some time on the fatal approach.
Biggest issue is the rearward cg. Fix that and the rest will fall into place without nearly as much stress. Great looking model. Get some weight forward and it will be a great flier.
Yeah I was way too lax with the CG placement. I just placed it kinda roughly and as I left my house I was actually thinking it might cause problems, then somehow with the taxiing issues I completely forgot about it, even while flying and feeling the terrible handling. I moved CG much further forward and will try again.
Idk, don't fly yet but if I did, I love this plane! Selling kits yet? Lol
Normal People : maiden flight
He : maiden crash
The propeller will try to swing the nose to the left. Try offsetting the motor to the right.
I'm not entirely convinced this was an accident, since you tend to immediately get back to building planes when one is done! Shame it doesn't (didn't) fly as well as you wanted to. Can't wait for the next one.
Funny. And true!
Always make a stearable nose wheel connected to the rudder servo. Classic stall. Your airspeed dropped too low. Plane looks a little on the heavy side.
Wheels can never be ''Too big''
After looking at the slow mo a bunch of times it looks like you get some buffeting just before the tip stalls. Of course there is no way for you to feel that on the ground but aircraft shake for lack of another word other than buffet just before a stall.
If you had a sensor that could detect one then you would always no a couple seconds before a stall and if you couldn't prevent it you could at least start your recovery at the earliest possible moment.
Turning left because of p factor...... tail dragger to prevent ground loops toe in the wheels slightly (you will need to experiment to find the right amount for your setup) (the easy this helps is if the plane turns left then toe causes left wheel to roll easier and the right wheel to scrub sideways acting like a break on the right wheel pulling that side back which causes the airplane to point straight ahead naturally.....also you need to lift the tail so the rudder will be effective....(raising the limit eliminates p factor ....(p factor the tail down puts the bottom of the propeller forward the top backwards this causes side forces.... the slipstream from the prop also corkscrews around the fuselage and strikes the side of the vertical tail pushing the tail around .... when leaving the tail in the ground the wing is in stall or near stall which creates drag .... the length of the wing makes this drag more effective at the tip of wing which is leverage over the cg.... lifting the tail gets rid of bear stall drag and makes the rudder effective.....40 years experience in rc and also experience in the real thing
My heart started beating so fast when I got the notification
Looked like a stall and started to enter a spin. If you had been higher up and pulled up elevator at that attitude you would have entered a spiral dive.
It doesn't look like you have any dihedral, was that on purpose? Even a little would make it a lot more stable I think.
Nice cant wait for Part 5. Time you built a runway maybe ?
Consider mixing in a bit of up elevator with the flaps, as they add a nose down moment to the system when activated.
auto-level takes care of that
iforce2d Ah ok. Didn’t consider the FC
It came into the turbulence of the hill you are on .... looked like you hit a rotator .... caused by the hill and buildings....seemed you have cg to far back which causes instability which makes errors compound instead of returning to stable flight... this trail heavy also causes ground loops to increase...
Ron's on the money with the Auto-level, shame to see her go down so hard but it took it well for how violent it was. Bixler always gets the last say.
What a Amazing Effort........it looks Soooo cool in the Air and I love the rear camera view.....
I guess you will add tail wheel control ......Mmmm that did looked like a stall at the end......wonder what your speed was about......
maybe some winglets will help until its sorted......or VG's
Brett
maybe a sort of adverse yaw feedback loop at the end there? You have the same issue with takeoff I mentioned before, the Ranger always wants to turn under power on the ground
Since the plane is pitched up while it's on the ground, you will have left turning tendencies no matter what because of p-factor. Don't know how much that will affect a model aircraft of this side though, it should easily be offset with rudder though. Just my ,02
p-factor is hardly an issue at that speed I would think
@@iforce2d It's about the angle of attack of the blades, and then of the whole prop itself. If you're producing maximum thrust from 0 airspeed, it would actually be the highest then. Depends on the prop design
It's about the angle of the blades relative to the airflow, not the ground.
@@iforce2d which, when you're rolling on the ground, is equal to the pitch of the aircraft, creating p-factor
lol the plane was going much slower than even the wind coming at it from the side, give it up man :)
P-factor. Radical on the ground.
3:40 planes with bycicle landing gear configuration are very susceptible to crosswinds . crosswind corrections must be applied . Ailerons into the crosswind and rudder towards the opposite side
ooops never mind
Well. I guess I wasn't the only one whos maiden didn't go well. Lost my Ryan STA after the elevator servo crapped out in full Up
Unfortunately, it didn't look like a tip stall.
(from what I can tell from the video, so don't take this as gospel)
It was begining to get into a gentle stall, and was gradually rolling to the left due to the left rudder, but to counteract the left roll you used right aileron. Normally this would be okay, but once the plane is already partly stalled, this just adds more left rudder due to the adverse yaw, and stalls the left wing more due to the increased angle of attack having the ailerons down on that side.
If it was a tip stall it probably would have had a more agressive initiation.
It does still ask the question though of why it got into a stall in the first place, it seemed like you still had enough speed?
And like you say, always stay a few mistakes high when testing ;) It looked like it was only a couple more meters away from pulling out
I think it was just tail-heavy, that would explain the appalling handling characteristics too. There would have been no rudder involved because I don't recall doing that and the autopilot doesn't do it either. The counteracting aileron was done by the autopilot though.
@@iforce2d Oh, sorry, I misunderstood what was happening, when you were saying that it was side slipping, I assumed that you were doing it intentionally. That makes it even more strange that it was side slipping so much.
Being tail heavy might explain the lack of yaw stability a bit, but wouldn't normally be enough on its own, I await to hear if you find anything more.
@@iforce2d Also, to counteract the adverse yaw, I would get rid of the mixing from ail to flaps, and then have the ailerons that are in use moving only in the up direction (or at leats much more in the up direction), it won't be as good for roll, but atleast you wont get loads of adverse yaw.
This is very common on 6 servo wing gliders
I think I should have said 'crabbing' instead of side slipping, might have got the terminology wrong there. Yeah since I have that mixing available to do whatever I want, I think I'll set the ailerons to only go up.
OOOOOOhhhhh !!a pond I see floats on a future plane
Cool shame it crashed on the maiden hope you iron out all the problems 😀🏴👍
Very cool, can’t wait for the post fix vid
Did you offset the motor? Great build though, was waiting for the maiden... look forward to the next try...
the twitching corpse on the ground ... so sad, sniff.
flew into the wind lee shadow from the building and tree. result loss of headwind component and airspeed followed by stall
P-factor is making it turn left.
Runcam saw the ground and panicked
Could b e'P-factor' that is casuing your plane to go left. As the prop rotates with the nose high, the starboard side of the prop bites more air and rotates the nose left, especially as you gain ground speed.
Also, maybe try using a 'landing flap setting' when landing or making a slow apprach without power. You could try having a tad of relfex on your ailerons and a tad more of the inboard flap cambered downwards (alsow called 'crow'). That way you load up the inboard section of the wing more so that the tips of the wings are less prone to stalling. My two cents :-)
That`s not a crash, that`s a hard landing !
Hi I found it. A pity that happened that accident charmed me as it flies. I'd leave him alone the ailerons on the tips.
Noooo i was waiting for this flight video 😢 , didn’t expect it to end up with a crash !
did you soft-mount the flight controller ? all the vibrations from the motors could make the gyro goes crazy and therefore the flight controller sends wrong outputs to the servos .. i really enjoyed watching the whole building videos :) .. thanks a lot and fly safe 👍🏽👍🏽
Nothing wrong with the design, it was the x-wind giving the illusion that it was in a sideslip when in fact it was only crabbing from the wind. When aileron and rudder controls were crossed at the low speed and high angle of attack, it entered a cross-control stall into a spin. Opposite rudder and neutral aileron would've saved it.
Applying opposite aileron is instinctive but all it does is increase the angle of attack of the stalled wing, deepening the spin. It's important to use lots of rudder at low speeds with aileron only to balance it out.
There was no rudder input anywhere. The autopilot was doing the 'instinctive' roll response (although if it was in manual mode I probably would have anyway :) but it doesn't do any rudder.
I would look at shimming the left side of the motor when looking from behind out a hair. Due to torque roll it’s said that the motor should be angled a little to the the right. I’ve never had to really worry about it much because I haven’t had a build try to ground loop like yours is. I looked up your bird really hoping the real wiki article was written the way you have it and was disappointed to see it’s not.........
It is amazing that left wheel did not broke off :)
It looks like classic stall. Then using ailerons can situation go worse due to lift loss... You should try to rescue with throttle and rudder only.
I suppose the reason is zero leading edge angle and lack of engine deviation...
The last one causes take off problems we saw...
One of these days you'll have to explain to us why you don't do dihedral for the free stability.
Because it's not free stability.
It often makes the plane weaker, induces dutch rolls at higher speeds, makes the plane more suseptible to wind and reduces stability when inverted.
And ontop of that, depending on your definition, it doesn't actually add stability, it only adds self centering, e.g. the plane can still rock around, it will just stop it from rocking too far, which a competent pilot (or flight stabiliser) is very good at doing anyway.
In this case it is a high wing and so it gets free stability. Many high wing aircraft need anhedral because its too stable
Now some washout or vortex generators to prevent tip stalls and ensure it is always a root stall would be a good idea.
@@lukeattubato By stability, I was referring to inherent stability, like in no autopilot, hands off the controls stability. True, stability doesn't help win 20mm cannon duels, or do much for a pilot performing aerobatics at the edge of the envelop, but is twitching agility really of major importance in a STOL aircraft?
@@nocare This also isn't true, look up the 'Pendulum Fallacy' it applies to rockets aswell. washout would likely have helped in this case though.
@@Reach41 Yes, true, in this case instability inverted probably won't affect the plane too much, but did you not see the other 3 negatives? and you say you were refering to without an autopilot, but he does have an autopilot (and he's a competent pilot), so that seems irrelavent.
And I'm not really sure where you got agility from, since dihedral doesn't affect agility, but yes, agility is very important for a STOL aircraft, its needed to quickly change pitch/roll while on aproach when you have low airspeed, and little height. You need to very quickly be able to make small corrections.
I like your design. Not the best weather for a first flight.
As a pilot I'm wondering why you made the flaps and ailerons so complex?
Nice........at least you didn't crash it on takeoff, which could happen with the CG further to the nose and the same runway.
Too slow , too low-stabilization has nothing to do , when pane flies too slow , but apart form everything you shouldn't have flown in such place - you have no space to make good approach , no margin for mistake. From one side fence , from another building , against fence is abyss - request for disaster.
One thing I can suggest: add GPS , return to home works perfect.
Are you using INAV , Betaflight or Mission control? I can see that you are pushing SBUS signal form F4 onto this distribution PWM board -> very smart solution.
Good luck.
This is what happens when you paint planes. 🤔
Great work nether-the-less.
As for loss of control right there toward the end, that looked for all the world like a stall/spin. Might have initiated it with aileron input, or maybe it was something completely different -- didn't seem to be going that slow. Wind shear?
I'm suspecting tail-heavy, would also explain the appalling handling characteristics.
4:20 that's probably because of counterforce that's applied because of motor spin
If the prop is spinning to the right , motor torque can sometimes cause the plane to pull to the left . Also , unless you enjoy the challenge .... all those dual elevator & multiple aileron/flaperon configurations are unnecessary and only add potential points of failure . KISS .... Keep It Simple Sir !
Fix the aileron differential, balance point, remember wind shadowing effects and it will be fine. I think you have WAY too much control throw on the ailerons though unless you plan to 3D fly it.
Hey, at least the landing gear works!
lol yeah now I just need to get them both working at the same time :)
@@TheKodakmanthat entire plane is a lot of drag. By design, he wants it to fly slowly.
The landing gear really took the crash well. You probably wont have to fix them in the event of another crash :P
I guess tail heavy would explain it. Looked quite wafty as if the vertical stab wasn't doing enough. Any way it survived the crash well, but I feel your disappointment.