P-38 - The Ultimate EPO Lightning

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Official Freewing MiG-29 Fulcrum Twin 80mm Thread

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  • Originally posted by janmb View Post

    This is indeed a highly interesting finding, and may very well be 100% spot on. It does indeed fit the observed failure mode pretty damn perfectly.

    Not necessarily very easy to mitigate either, but now that we know to deal with it, at least some effort can be made to alleviate that risk.

    Thanks for the analysis, sounds highly plausible and will definitely take it into account.



    What kinda bothers me though, is that we hear all this talk about how every model is put through several hundred test flights during the development phase. Well, if that is indeed the case, then I find it quite peculiar that any conceptual problems like this one doesn't rear its ugly head enough for the developers to catch it. Sure, it may happen just once every 50 or 100 flights, or even less, but still, with multiple prototypes being flown for hundreds of flights, the chances of such a failure manifesting itself should be fairly high.

    This does at first seem to explain those few crashes and the strange loss of elevator control as discussed by Firebird . However, if this is indeed something extremely intermittent, I can't image what the odds would be of BOTH elevator signal wires experiencing it at the same time, one maybe but both would be at a greater odds than the lottery. And if only one experienced it, the jet would have rolled over from one elevator working and the other having lost signal. Just my 2 cents from someone with extremely limited electrical/RF experience.
    Hugh "Wildman" Wiedman
    Hangar: FL/FW: Mig 29 "Cobra", A-10 Arctic, F18 Canadian & Tiger Meet, F16 Wild Weasel, F4 Phantom & Blue Angel, 1600 Corsair & Spitfire, Olive B-24, Stinger 90, Red Avanti. Extreme Flight-FW-190 Red Tulip, Slick 60, 60" Extra 300 V2, 62" MXS Heavy Metal, MXS Green, & Demonstrator. FMS-1700mm P-51, Red Bull Corsair. E-Flite-70mm twin SU-30, Beast Bi-Plane 60", P2 Bi-Plane, P-51.

    Comment


    • I visited with my HAM radio guru who put me on to the RF choke idea. Passing along his comments:

      The shielding (copper tape, etc.) will be most effective when it is grounded (like to the PCB ground trace). But, regardless it will have some effect when placed between the ESC and servo wires.

      To help minimize the potential noise on the servo wires back in that area...

      Use the copper (etc.) tape between the ESC and servo wires AND place a clip-on ferrite RF choke on the servo wire back near each servo. (LOL - Saw that one coming.)

      The Re-routing room isn’t much back there. May not be enough room to make much difference.

      I’m gonna do mine this afternoon.

      -GG

      Comment


      • GG,
        Do you have stock in the Ferrite ring companies?

        Comment


        • Originally posted by Waconut View Post
          GG,
          Do you have stock in the Ferrite ring companies?
          LOL - I knew you’d appreciate his comments. I have room for just a few more on the plane. And there are more inside!

          Helps with moving the CG rearward, as an added benefit! And the higher wing loading pushes out the speed where max L/D in the glide is achieved.

          -GG

          Just kidding!

          Click image for larger version  Name:	D16ECC9E-45D9-42ED-AE48-0C3ED1374E43.jpeg Views:	0 Size:	251.4 KB ID:	281930

          Comment


          • Having servo wires cohabitating with speed controllers in the ducting isn't exactly a unique trait to this bird is it?

            Comment


            • Hello,

              Originally posted by Firebird View Post
              When i opened the compartment holding the fan and the motor controller, i found both - elevator and rudder servolines - passing freely, directly underneath the controller. I‘m not a electronic expert but i do suspect the motor controller to create a certain electromagnetic noise at midrange powersetting. (...)
              That is an obvious suspicion, and I guess many had it already, too, including myself. However, there are other airplanes, such as the Freewing Su-35 and the Freewing / SebArt MiG-29, where there is a very long central channel between the ducts which contains *every wire* that goes to the back: 2x3 highly AC powered lines going to the fans, plus servo leads for 2 elevators, 2 rudders, and for the TV nozzles. The ESCs sit at the beginning of the channel on top of all these wires, and the elevator and rudder wires go right below the fans, from the central channel to the outside of the fuselage. But neither the Su-35 nor the SebArt ever had the problem that we suspect with the Freewing MiG.

              So just having the elevator wires near the ESCs is not explaining it. There would need to be other reasons, such as ESC-specific emissions, veryvery long wires, induction from the current in the battery leads that go to the ESCs before it hits the extra capacitors, power loss, ...

              Cheers,
              Henrik

              Comment


              • Originally posted by GliderGuy View Post
                I visited with my HAM radio guru who put me on to the RF choke idea. Passing along his comments:

                The shielding (copper tape, etc.) will be most effective when it is grounded (like to the PCB ground trace). But, regardless it will have some effect when placed between the ESC and servo wires.

                To help minimize the potential noise on the servo wires back in that area...

                Use the copper (etc.) tape between the ESC and servo wires AND place a clip-on ferrite RF choke on the servo wire back near each servo. (LOL - Saw that one coming.)

                The Re-routing room isn’t much back there. May not be enough room to make much difference.

                I’m gonna do mine this afternoon.

                -GG
                There ya go! My idea of wrapping an ESC with a foil, was at least a step forward! "But, regardless it will have some effect when placed between the ESC and servo wires to help minimize the potential noise on the servo wires back in that area..." Of course, shielding needs to be grounded to have the right effect, but the bigger claim was the EMF from the battery cables that add to the problems...

                Comment


                • Hello,

                  this may be redundant, but as the elevator issue is still not resolved (Does it exist or is it all bad luck and misinterpretation? If it exists, then what is the cause?), I am crossposting this post from me from RCG:

                  Under the most rearward battery compartment, there is a "snake pit" of wires that go
                  • towards the blue box
                  • but also directly to the receiver, such as the throttle.
                  These wires are routed below the wooden panel that serves as a battery holder. Fine so far.

                  In my case, at least one servo wire was emerging from below the wooden panel improperly, namely it was sandwiched (by the factory) between the frontal end of the wooden panel and the foam. I had to manually pull it out, and it showed stress marks: You can see the effect of the relatively "sharp" edges of the wooden panel onto the servo wire. All three leads of the servo lead have little horizontal cuts, the lower cut being more pronounced than the upper. You can also see the indentation of the foam from the wire on the pictures. The little cuts as seen here look harmless.

                  However, suppose that the plane flies, the fans emit vibrations, and the edge of the wooden panel actually would saw through the shielding of the servo lead. With bad luck, you could have a short, possibly only temporary while the engines are running and vibrations are strong. This short is on the "active end" of the blue box, i.e. the end from which the control leads go to the control surfaces. Maybe having a short there does cripple / disable the blue box, even temporarily?

                  This would explain why the telemetry from one of the crash reporters showed good readouts from the receiver (including voltage), because the receiver is "on the other side" of the blue box. It would also explain why throttle response was still there, as the throttle is not routed via the blue box.

                  Opinions?
                  Attached Files

                  Comment


                  • Still no news about the thrust vectoring units? They are the reason I bought this plane in the first place...

                    Cheers,
                    Henrik

                    Comment


                    • I only placed the “shielding” (aluminum self-adhesive pipe tape I had handy) between the ESC and the servo wire run area. The smallest of the barrel-type clip-on RF chokes fits perfect in the area ahead of the elevator servo. Photo below is prior to tucking it in.

                      Will it decrease the probability of an incident occurring? Who knows....but it is easy work to accomplish.

                      -GG

                      Click image for larger version  Name:	B8D93263-7792-4AFC-B345-9C152F7723E7.jpeg Views:	0 Size:	73.2 KB ID:	281953Click image for larger version  Name:	41355C9F-566E-4620-82D0-05B950733B39.jpeg Views:	0 Size:	59.0 KB ID:	281954

                      Comment


                      • I cut my battery to ESC wires by about 7". There was no reason for the length especially since I don't use the forward bay.






                        Originally posted by HK111 View Post
                        Hello,


                        That is an obvious suspicion, and I guess many had it already, too, including myself. However, there are other airplanes, such as the Freewing Su-35 and the Freewing / SebArt MiG-29, where there is a very long central channel between the ducts which contains *every wire* that goes to the back: 2x3 highly AC powered lines going to the fans, plus servo leads for 2 elevators, 2 rudders, and for the TV nozzles. The ESCs sit at the beginning of the channel on top of all these wires, and the elevator and rudder wires go right below the fans, from the central channel to the outside of the fuselage. But neither the Su-35 nor the SebArt ever had the problem that we suspect with the Freewing MiG.

                        So just having the elevator wires near the ESCs is not explaining it. There would need to be other reasons, such as ESC-specific emissions, veryvery long wires, induction from the current in the battery leads that go to the ESCs before it hits the extra capacitors, power loss, ...

                        Cheers,
                        Henrik

                        Comment


                        • Originally posted by HK111 View Post
                          Hello,

                          this may be redundant, but as the elevator issue is still not resolved (Does it exist or is it all bad luck and misinterpretation? If it exists, then what is the cause?), I am crossposting this post from me from RCG:

                          Under the most rearward battery compartment, there is a "snake pit" of wires that go
                          • towards the blue box
                          • but also directly to the receiver, such as the throttle.
                          These wires are routed below the wooden panel that serves as a battery holder. Fine so far.

                          In my case, at least one servo wire was emerging from below the wooden panel improperly, namely it was sandwiched (by the factory) between the frontal end of the wooden panel and the foam. I had to manually pull it out, and it showed stress marks: You can see the effect of the relatively "sharp" edges of the wooden panel onto the servo wire. All three leads of the servo lead have little horizontal cuts, the lower cut being more pronounced than the upper. You can also see the indentation of the foam from the wire on the pictures. The little cuts as seen here look harmless.

                          However, suppose that the plane flies, the fans emit vibrations, and the edge of the wooden panel actually would saw through the shielding of the servo lead. With bad luck, you could have a short, possibly only temporary while the engines are running and vibrations are strong. This short is on the "active end" of the blue box, i.e. the end from which the control leads go to the control surfaces. Maybe having a short there does cripple / disable the blue box, even temporarily?

                          This would explain why the telemetry from one of the crash reporters showed good readouts from the receiver (including voltage), because the receiver is "on the other side" of the blue box. It would also explain why throttle response was still there, as the throttle is not routed via the blue box.

                          Opinions?
                          Those cuts aren't deep enough. The enamel on the wire is pretty tough and hasn't been sliced. Would take a lot more abuse to slice that jacket. I've seen wires that were completely flattened; pinched; twisted; sliced and stretched and they still worked. However, if there are "quality control issues", and the reviews start piling up with defectives, then bring out General Patton with his riding crop and see who jumps!...

                          Comment


                          • Originally posted by mshagg View Post
                            Having servo wires cohabitating with speed controllers in the ducting isn't exactly a unique trait to this bird is it?
                            No it's not. FW Su-35 is a good example as Henrik pointed out but there are many others.

                            Then again, most of those are probably not running setups as powerful as the MiG-29... and at least on the Su-35, there were ferrite rings on the ESC leads as a stock feature... so there's that. Nothing conclussive of course, but another thing to have in check until further notice I guess :)

                            Comment


                            • Originally posted by HK111 View Post
                              Hello,


                              That is an obvious suspicion, and I guess many had it already, too, including myself. However, there are other airplanes, such as the Freewing Su-35 and the Freewing / SebArt MiG-29, where there is a very long central channel between the ducts which contains *every wire* that goes to the back: 2x3 highly AC powered lines going to the fans, plus servo leads for 2 elevators, 2 rudders, and for the TV nozzles. The ESCs sit at the beginning of the channel on top of all these wires, and the elevator and rudder wires go right below the fans, from the central channel to the outside of the fuselage. But neither the Su-35 nor the SebArt ever had the problem that we suspect with the Freewing MiG.

                              So just having the elevator wires near the ESCs is not explaining it. There would need to be other reasons, such as ESC-specific emissions, veryvery long wires, induction from the current in the battery leads that go to the ESCs before it hits the extra capacitors, power loss, ...

                              Cheers,
                              Henrik
                              Given that all of this is speculation, I'll add mine:

                              I'd be inclined to look at the leads from the batteries to the ESCs. These have the highest currents and will be generating large, varying magnetic fields capable of inducing currents in nearby signal level wiring. The three-phase wires from ESC to motors will be largely canceling each other out. IMO, of course.

                              I'm still more inclined to think there's some aerodynamic explanation, such as elevator blanking, that's only triggered under some, maybe unusual, conditions. There have certainly been instances in full-size aviation where such things happened.

                              Comment


                              • Originally posted by RudyD54 View Post
                                For anyone who does what I did and accidentally snaps off the pitot tube in front and needs a new one, the part is the following:



                                The MiG-29 parts pictures aren't up yet and when I called support they said it came with the nose cone (it does not) and had no idea what "Plastic Nose Cone Part" referred to. I placed an order for both parts which are luckily priced reasonably. The nose cone comes with ONLY the nose cone and the wood piece you glue into it. Plastic nose cone part includes everything attached for 4.49.
                                That's a pretty easy 3D print part. I don't have one for this MiG but I already posted the equivalent part for the ArrowsRC MiG on Thingiverse. Those pitots are easy to snap off especially if you operate from grass.

                                Comment


                                • After about a dozen flights with no issues I decided anyway to do my elevator upgrades today. Overall very pleased with how it turned out. Used the F-14 wing swing pushrods with 4-40 safety lock kwik links. Test flights tomorrow. (and yes, I have RF chokes, cap packs, crow in ailerons/flaps, and elevator Y to receiver).
                                  Click image for larger version

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                                  Comment


                                  • Would be nice in this modern world to run fiber optic cable to all electronic components in an airplane. No electromagnetic interference. Unfortunately, it would require nano sized fiber to copper conversion to run servos and ESC signal plus receiver wiring. It would solve a lot of issues for sure. Someday....

                                    Comment


                                    • Thanks for your feedback!

                                      I just wanted to share the status of rerouting the elevator and rudder servo cables on my mig 29. In order to get as far away as possible from the controller and the long main power and esc control cable i chose to use the way following the maingear control cable. From there i pushed a hole through the foam to lead the cables under the plastic cover of the gearmotor bay. I opened the rear fuselage area behind the maingear mounting with just 4 clean cuts using a sharp cutter. I found plenty of space there for the cables and also ferrite rings. From there i just pushed one more hole into the foam to reach the servo mount area.
                                      To finalize the work you just glue the cut foam part back in place.

                                      Here are some pics of my work:



                                      Comment


                                      • The cone shaped washer/ spacer should go between the ball and horn if you use it. Allows the ball link to be used at greater angles.


                                        Originally posted by Skosh25 View Post
                                        After about a dozen flights with no issues I decided anyway to do my elevator upgrades today. Overall very pleased with how it turned out. Used the F-14 wing swing pushrods with 4-40 safety lock kwik links. Test flights tomorrow. (and yes, I have RF chokes, cap packs, crow in ailerons/flaps, and elevator Y to receiver).
                                        Click image for larger version

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Views:	708
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ID:	281968

                                        Comment


                                        • For those of you who want to install the elevator and rudder servo cables the same way i did - find attached some pics of the angle of the holes you need to drill or push in the foam and maximum distance you can push in order to not damage other areas. For the hole at the maingear don‘t push deeper than 6,5cm. For the hole in the tailsection don’t push deeper then 7,5cm.
                                          Here the angle you need:

                                          Comment

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