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Official Freewing MiG-29 Fulcrum Twin 80mm Thread

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  • Originally posted by Airguardian View Post
    The more I read about these dive crashes the more confused I am... there seems to be a common problem yet unidentified.

    What I know so far is I am NOT going to maiden with factory reccommended CG.
    That will give some more margin (less stress required on elevators to pull nose up) but the root cause seems yet to elude us all.
    I bet I will be bypassing the blue box for mostly everything too.
    Same for me. Seems like a common denominator here, but hard to tell exactly what.

    The user experience clearly sounds like too nose heavy / too little elevator authority. And while stock elevator throws are fairly moderate, they ought to be plenty.

    I doubt blue box issues. Any signal bleed ought to produce very visible jerks in the model.

    Aerodynamic blanking of tailerons is a good candidate.

    Flutter makes no sense to me in these cases. We see or hear nothing of the sort in any of the vids we've seen. And the surfaces were still working, and had been doing as commanded...


    Falcon, any possibility that you either somehow did a mistake when measuring cg, or a battery managed to shift forward during flight?

    This thing doesn't sound like loss of control at all, but simply having a cg you didn't have authority to handle.

    Sorry for your loss
    Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

    Comment


    • Adding to my prior post and the thoughts presented here about a possible wing/elevator interaction due to being in the same airflow plane, here’s a thought....

      In full scale sailplanes, we use self-adhesive turbulator tape to control airflow on the wing and reduce drag...counter intuitive, but you can do the research. All super ships use this tape to reduce drag.

      Two types: Zig Zag and Dimple

      Why couldn’t we use it on the MiG to forestall any possible negative wing/elevator interaction...if it even exists? In full-scale sailplanes, placement of the tape typically is.... span wise, along the bottom of the wing about 6 inches ahead of the trailing edge ( need to scale this).

      Basically using the tape not what it was designed for (reduce drag), but as a easy to apply vortex generator.

      Might consider placing it parallel to the leading edge of the elevator along the full length of the elevator. Distance from the leading edge is TBD. Top? Bottom? Both? I haven’t a clue.

      This is readily available at sailplane parts stores such as Wings and Wheels. Search TURBULATOR TAPE.

      -GG

      An example of both types shown below. I couldn’t find a good image of the dimple type, but you get the idea.

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      Click image for larger version  Name:	48CB560A-C4B6-4F87-9904-7D370509325E.jpeg Views:	0 Size:	58.7 KB ID:	278713

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      • Here is an uncut video of yesterday’s 12th flight and first time without armament. My set up.

        Tailerons mixed with small amount of ailerons
        Statically balances vertical stabs( @1oz of weight on each)
        RT5500 45c
        CC BEC Pro set at 5.6v
        Hitec servos on elevators (HS 5085)
        CG @ 15mm behind book CG ( I think could be moved back a few more mm) Elevator trim is about 1mm above bottom of fuse. Rx mounted in center bay
        BB moved to rear battery compartment.








        Attached Files
         

        Comment


        • Originally posted by janmb View Post

          <snip>

          Falcon, any possibility that you either somehow did a mistake when measuring cg, or a battery managed to shift forward during flight?

          This thing doesn't sound like loss of control at all, but simply having a cg you didn't have authority to handle.

          Sorry for your loss <snip>
          Hello Janmb,

          I guess that's always a possibility, but I'm pretty careful when it comes to marking CG (even though FW put the marks on the wings, I still verified it with exact measurements) and I have a jig to put the model on where I can balance it exactly right, using those marks. Since the front end of the aircraft was destroyed, it's very tough to determine if there was any battery shift; although I wouldn't rule that out as a possibility, it's highly improbable. All I can tell you is that I secured them pretty well for the flight and the entire flight went pretty well, right up to the point where I started a descent.

          What is compelling to me is that the same nose-down attitude that you saw in that video, mirrors my experience, which mirrors the experience of the two other models in that video. That can't be a coincidence. Aerodynamic anomalies are very tricky to deal with because they won't always yield the same results in two comparative events. Things such as wind vector, model velocity, flap position (and even throw) could mean the difference from a model that recovers to a model that won't recover.

          In my situation, the stabilator blanking makes the most sense. The aircraft did not at any time fly like it was nose heavy - there was ZERO pitch trim set on my transmitter. A shallow nose-down attitude should not have shifted the batteries at all (impossible? No. Improbable? Yes.). The aircraft did not fly like it was out of CG, or I would have noticed it right away (back to the absence of nose up or down trim required). The only thing that gives me pause is the fact that it seems that people here are flying with a slightly aft CG and the aircraft seems to respond well to that.

          Comment


          • Originally posted by Lcacing View Post
            Here is an uncut video of yesterday’s 12th flight and first time without armament. My set up.

            Tailerons mixed with small amount of ailerons
            Statically balances vertical stabs( @1oz of weight on each)
            RT5500 45c
            CC BEC Pro set at 5.6v
            Hitec servos on elevators (HS 5085)
            CG @ 15mm behind book CG ( I think could be moved back a few more mm) Elevator trim is about 1mm above bottom of fuse. Rx mounted in center bay
            BB moved to rear battery compartment.
            Awesome video man. Terrific flying!

            Comment


            • The batteries really can't shift if using the center and rear locations. Look under the canopy and it's really locked in unless the canopy was lost. The rear can't shift forward if forward to the wall already and even if it did the change in balance caused by the rear battery is minimal because it's so lose to the CG.

              Someone mentioned the MCBe. There have been many reported issues with the MCBe's, not as many as with the older cube but still quite a few. The MCBe is in a lot more planes than just this, the F-18 and F-22.

              Comment


              • Originally posted by leithalweapon View Post
                Has anyone had a crash that bypassed the MCB-e? Chinese made electronics sound more likely than an intermittent aerodynamic problem. I think we will see more crashes if it is a flaw with the design.
                That's a great question for debugging.
                I would also ask if all crashes so far have been with factory recommended nose-heavy CG at 145mm or if any happened with more rearwards CG?
                That could be quite telling too.

                Originally posted by RCjetdude View Post
                The same MCB-e is used in the F-22. To my knowledge they have not had a rash of unexplained elevator failures and they came out even before the F-18. If the blue box was the issue wouldn't we be seeing more reports of similar problems with the F-22?
                The F-18/22 have just a couple of 17g servos, where on the MiG, ALL are 17g servos (+2x 23g now).
                And the forces the servos see will be higher due to bigger aero loads and bigger plane inertia.
                Expect the MiG to be much more power hungry than the Raptor.

                Originally posted by GliderGuy View Post
                Keep all possibilities under consideration and settle on NONE without justification. CG to blame? Why am I not seeing issues, and I am flying right on factory CG? Right now, we are only guessing. And that’s good to have the dialogue. Eventually, it will be figured out. At this point, it is anybody’s guess.
                Absolutely!
                Agree.

                Are you also using factory recommended rates?

                Originally posted by GliderGuy View Post
                All super ships use this tape to reduce drag.

                Why couldn’t we use it on the MiG to forestall any possible negative wing/elevator interaction...if it even exists? In full-scale sailplanes, placement of the tape typically is.... span wise, along the bottom of the wing about 6 inches ahead of the trailing edge ( need to scale this).
                This may or may not work... first we would have to make sure that blanking is the problem at all. As I said, so far it's just a theory.

                Then, these tapes are designed for gliders that will be flying slightly faster than the MiG-29 so the effect may not be the exact same but if we indeed have a boundary layer problem, then yes, use of such a tape or other means of vortice generators could improve something. But the placement of vortex generators has to be very specific, usually in the 'still laminar' portion of the wing to induce the vortices right ahead of where the boundary layer would detach. We do not know where that is on the MiG-29 (or whether it is a problem at all).

                A way to find out (to some degree) would be to place short threads over one wing and use an action camera to film it while flying in different conditions... ideally in elevator blanking conditions which may be hard to replicate, and dangerous at that. :/

                Originally posted by GliderGuy View Post
                Might consider placing it parallel to the leading edge of the elevator along the full length of the elevator. Distance from the leading edge is TBD. Top? Bottom? Both? I haven’t a clue.
                Placing it on the elevator would make little sense IMO. You would want it on the wing's top OR bottom at a very precise chord length which, as I said, should be determined by some experimentation or trial and error.

                We'd be trying to prevent boundary layer separation on the WING, causing the elevator to live in a wake of turbulent, de-energized flow.
                In that condition, adding turbulator tape on the stabs themselves would pretty much do nothing.

                Comment


                • Originally posted by Lcacing View Post
                  Here is an uncut video of yesterday’s 12th flight and first time without armament. My set up.
                  Congrats, well done!
                  So far the most interesting flight video to surface yet!

                  And just as forseen, the jet seems to fly much better with a more balanced CG.
                  There definitely didn't seem to be much of a problem with 'falling leaf' scenarios, at least with this more-rearwards CG setting and proper handling.

                  Keep it up! :D

                  PS: I just uploaded a video of a Jetlegend MiG-29... FWIW, here it goes!
                  I dig this scheme BTW, may consider it for mine in due time, who knows? :D

                  Comment


                  • Lcacing - Well done indeed. More confidence that the falling leaf is recoverable by working the throttle (I assume you chopped the power...was kinda hard to tell in the video). If you have time, please post your procedure for the recovery from the falling leaf.

                    Another data point to present
                    ========================

                    I measured my flap movement. My flaps sit at 1 mm negative when retracted and 30 mm positive when extended. During the build, I decided to leave the flap's positive travel alone and not mess with them (reasoning that 22 mm vs 30 mm was "close enough"). One flap push rod was a bit long (beyond ball link adjustment capability). I didn't want to take the time to modify that push rod. Besides...negative flap is used in sailplanes for cruising between thermals, so I just left it as a "benefit" for speed flying. I adjusted the other flap to match. I did not adjust the ailerons to be negative and match the flaps.

                    I am using factory rates on all other controls...and mostly fly on low rate. In the pattern on low rate.

                    I like to mentally practice emergency procedures. This practice is what allowed me to save the P-38 when the elevator control horn came unglued from the elevator. From flying the P-38, I knew that it would pitch up when the flaps are lowered and before elevator/flap mixing was implemented. When she failed to respond to the elevator, without much thinking...i switched to flaps for pitch control and got her down safely. I had a concern that the elevator servo might fail...and what to do? The actual happenstance was about as bad when the horn came unglued.

                    So, I have been thinking about the dreaded nose dive. Here is what I am mentally practicing. May not work...but as least I have a "go to" to try if/when it occurs.

                    As fast as possible, i will do the following with quickly moving fingers:
                    1. Full up elevator
                    2. Switch to high rate...if not already in high rate
                    3. Bring the flaps up
                    4. Go to full power (counter intuitive) so the thrust line will help raise the nose.

                    If the above doesn't work, the damage (from what I've seen) won't be much worse.

                    TURBULATOR TAPE (counter intuitive)
                    ==============================
                    More info on this stuff to add to my prior post. This stuff impacts the drag at ALL speeds. Most high performance sailplanes achieve their max L/D (best glide ratio) at around 55 to 60 mph. Much slower than the MiG is flying. Glide rations of 75:1 have been achieved (75 miles forward for every mile lost in still air). High speeds L/D at 100+ mph are still north of 35:1. We also carry several hundred pounds of water in the wings to increase the achieved L/D at high speeds (also counter intuitive). Heavier gliders go better.

                    Genius aeronautical engineers at sailplane factories figured out that the air molecules don't want to let go of the trailing edge of the wing/tail. So turbulator tape is place about 6 inches ahead of the trailing edge (typically on the bottom surface of the wing running parallel to the trailing edge) to generate turbulence that causes the air molecules to more easily "let go" of the trailing edge. It's purpose is not to generate any effect on the boundary layer ahead of the turbulator tape. It generates turbulence downwind of itself to help break up the boundary layer so the air molecules will detach from the trailing edge more easily and decrease drag.

                    Thinking about the function of the turbulator tape, I came to an "assumption" (correct or not) that maybe it could solve the MiG issue (if indeed there is an aerodynamic issue at all). I wanted to post the information in case it might just work. Who knows? It sure is an easy experiment. It might just possibly have a good effect on the MiG.

                    -GG

                    P.S. I made several flights this morning beginning at sunrise. As time passed, the winds eventually got up to 12 mph with gusts to 14 mph. The later flights took some concentration on final approach to correct gust upsets. Elevator response was always there. One "might" conclude that gusts could possibly be an opportunity for flow separation to rear its ugly head, if indeed there is an aerodynamic issue at all. It never did.

                    Comment


                    • Originally posted by Jdcrow View Post

                      ordered mine today. I didnt see a place on the order to tell them which sound file to load. I emailed them as their customer service hours were Mon-Thurs.

                      I assume they will ask once they see the order.?

                      Also,
                      What did you do to stage the Doors/Nose Gear Light to operate after your startup routine.
                      As long as you can use a SD card reader in a PC it is very simple to edit the text file for which sound files that you want to use. All instructions are included.

                      For the start up with the light simply plug it in with the gear down, but the transmitter switch in the gear up position. When you put the switch down the light turns on.

                      I mounted my exciter/speakers on each side of the battery against the bottom of the upper surface. Make sure you scuff the foam and exciter surface for maximum adhesion.



                      Comment


                      • Originally posted by GliderGuy View Post
                        So, I have been thinking about the dreaded nose dive. Here is what I am mentally practicing. May not work...but as least I have a "go to" to try if/when it occurs.

                        As fast as possible, i will do the following with quickly moving fingers:
                        1. Full up elevator
                        2. Switch to high rate...if not already in high rate
                        3. Bring the flaps up
                        4. Go to full power (counter intuitive) so the thrust line will help raise the nose.
                        Not sure I'd advocate for step 4.
                        The jet will likely be going fast enough on a dive, and full throttle may have a pitch-down component at speed instead of up due to pressure distribution changes in the intake area. This is at least an issue with the Su-35 and F-18, and by design similarity, I bet it will be a factor too on the MiG-29.

                        Comment


                        • I was thinking, if the elevator is getting blanked out on the mig wouldn't we have seen a rash of the same issues on many other aircraft where the elevator is in the same plane as the wing? My eflight f16, FW f16, FW f22 and hanger 9 f22 all come to mind. I know the 70mm f16's don't have flaps but the 90's do as do both f22's and that eflight f16 can hold one hell of a high alpha for about as long as you want it to.

                          Comment


                          • Click image for larger version

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                            Originally posted by GliderGuy View Post
                            MiG Speed
                            =========

                            S25....126 mph is VERY respectable in my books. Is that adjusted for natural wind effects? Missiles on or off? Thanks.

                            -GG
                            Clean jet (no weapons/pylons) 5500mah, 70C Roaring Tops, CG on the CG marks. Calm winds.

                            I did the flight LIVE on FB, otherwise people jump in with all kinds of speculation. (Especially people who haven’t flown it)
                            Video intentionally shows battery placement, and the windsock being dead calm. Temperature was 82° and the density altitude was over 7,000ft.

                            They were also my oldest pair of Roaring Tops. Still faster than the latest top Spektrum 4000-5000, HRBs, Admiral HDs, CNHL 70C, Pulse, Zeee, etc. I have 52 6S lipos, my Mig-29 now has almost 100 flights, the Roaring Tops even after 100s of cycles are still the best. I’ve literally tried everything that is out there and commercially available. Every battery besides the Roaring Tops was a minimum 5-6mph slower, no joke. I don’t work for Roaring Top or any other vendor, and I pay for my batteries.

                            That said, I said multiple times during the flight that we were trying to achieve maximum AIRFRAME speed. NOT level course or timed speed. That it was GPS over the ground max speed.

                            I turned around pretty high after the first two speed passes from mostly level. Because it was around 300ft up, I left it at idle after pulling over the top until I started pulling to level off over the runway, then punched it. Because she is so big, she doesn’t look as fast as she’s actually moving.

                            The T-33 and L-39 are both faster with the inrunners.

                            Look forward to seeing everyone else’s speed mods on it.
                            Subsequently, we also radar’d the birds down at St George and had 4 fliers there. Pat can speak to it, but I think they radar’d around 120mph.


                            Comment


                            • Originally posted by Nickc2023 View Post
                              I was thinking, if the elevator is getting blanked out on the mig wouldn't we have seen a rash of the same issues on many other aircraft where the elevator is in the same plane as the wing? My eflight f16, FW f16, FW f22 and hanger 9 f22 all come to mind. I know the 70mm f16's don't have flaps but the 90's do as do both f22's and that eflight f16 can hold one hell of a high alpha for about as long as you want it to.
                              Interesting, for sure. But, there are a lot of variables between these birds. My old RC sailplane sure was subject to elevator blanking, and its wing/horizontal tail were in the same plane.

                              Airguardian...good feedback on #4. I would try #4 as a last resort if she didn't respond to #1 thru #3. Pucker factor = huge at that point.

                              Comment


                              • Originally posted by Lcacing View Post
                                Here is an uncut video of yesterday’s 12th flight and first time without armament.
                                Impressive flying indeed! Glad to see someone being successful too - it seems we have had so many crash videos and so little awesomeness lately.

                                Also glad to see someone being successful with (imo) better setups! Class crosswind landing too! Glad I wasn't the pilot though, poor brain :D



                                Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                                Comment


                                • Originally posted by Nickc2023 View Post
                                  I was thinking, if the elevator is getting blanked out on the mig wouldn't we have seen a rash of the same issues on many other aircraft where the elevator is in the same plane as the wing? My eflight f16, FW f16, FW f22 and hanger 9 f22 all come to mind. I know the 70mm f16's don't have flaps but the 90's do as do both f22's and that eflight f16 can hold one hell of a high alpha for about as long as you want it to.
                                  Good point.

                                  A bit on the side, but I must admit I'm surprised the F-22 doesn't have major problems with this. At first glance, it certainly should. I have had TONS of flights with that model, at crawling pace, ridiculous amount of flaps, and still extremely good elevator authority. But it certainly boggles me WHY lol. I bet Jandro has opinions :P
                                  Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                                  Comment


                                  • Originally posted by GliderGuy View Post
                                    I would try #4 as a last resort if she didn't respond to #1 thru #3. Pucker factor = huge at that point.
                                    Good thinking!
                                    It is always a great idea to have a preplanned course of action for when something goes wrong. If suspecting an aerodynamic cause (blanking in this case) my number one would be 180deg roll and number two "push" on the elevator. Or a 90deg roll and knife-edge rudder. Any of those would change the airflow over wing and elevator and if the cause is aerodynamic get back to having the nose pointing upwards or turning tight and take it from there. Maybe it will never have to be used, since guessing the problem has not shown during extensive testing or for most of the other -29s flying. But that's just my .02 and I don't own a Mig-29 (yet).

                                    Comment


                                    • Originally posted by janmb View Post
                                      A bit on the side, but I must admit I'm surprised the F-22 doesn't have major problems with this. At first glance, it certainly should. I have had TONS of flights with that model, at crawling pace, ridiculous amount of flaps, and still extremely good elevator authority. But it certainly boggles me WHY lol. I bet Jandro has opinions :P
                                      This goes a bit off topic so will keep it short.

                                      The different wing planforms and airfoils will of course produce varying results.

                                      Then again this may be happening (if at all) on the MiG-29 in very particular conditions, high speed dive, probably slightly negative AoA, nose-heavy CG and reduced elevator throws (for whatever reason). Anything that deviates from those conditions may make it a non-issue. After all, we have many people flying the jet for hundreds of flights now (such as Justin here), even using nose-heavy CGs and they have not reported any similar problems. So it's either a super-specific phenomena or the issue is something else altogether.

                                      The F-22 in particular also has higher sweep built on the wing, and lower 'relative thickness', which means that it will probably behave very differently from the MiG-29 wing.

                                      Comment


                                      • Thanks for the positive comments on my last video!!!

                                        The loss of elevator response during a dive issue is quite interesting, not sure if CG (fwd/aft) has anything to do with it. The only flight video I've seen that I can, with all certainty, say that it was an extremely nose heavy CG was Pilot Ryans maiden flight, I even think he still had the stock servos. No issues from what I could tell, he did do a few dives and if CG had something to do with it, that flight would have showed some evidence related to CG.

                                        Going back to my flight, on maiden flights, after trim, pitch and roll, and CG check, I always, always check stall charactersitics regardless of plane type. The MiG behaved quite differently and recovery was even more interesting. Once I reached about 3-4 mistakes high, I slowed the MiG, reducing throttle and adding elevator, as the AOA increased, lets say past 50 degrees, there was no elevator response, the only way the nose would move was by throttle, the more throttle I added the nose kept going up, adding down elevator did noting. I maxed the throttle and the plane "flipped" and once the nose pointed down and speed increased, I regained elevator control. I did the same maneuver a few more times and it reacted the same way.
                                        If during the "flip" you keep adding up elevator and reduce throttle, the MiG will enter another stall and the dreaded falling leave, at this point there are two viable options, elevator to neutral and zero throttle and allow the plane to drop the nose on its own. Once the nose drops, add a little throttle to increase speed and gently add elevator. The second option that I like is to reduce elevator input but max throttle, the nose will go up and it will "flip" again and once the nose points down add throttle/elevator and fly away. I think the safest way, with less altitude loss, is zero throttle/neutral elevator. One thing to keep in mind is that my MiG is set up with tailerons and ailerons so I do have more roll control than standard configuration.

                                        If you watch the video of the F22, it sort does the same inputs, also note how it uses up flaps to help get out of it. Maybe a mix to explore
                                         

                                        Comment


                                        • I got in two flights on the new mig 29 this weekend. Using HRB 5000’s and a 1 1/2 ounce of nose weight. Both flights went very well although I will remove a half an ounce of weight for the next flight. I did not notice any negative tendencies but I have not really rung it out hard yet.
                                          I do like the size and large wheels. Very happy with it.

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