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Official Freewing JAS 39 Gripen 80mm EDF Jet

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  • The actual bird in action!



    Headphones and volume, recommended!
    Live Q&A every Tuesday and Friday at 9pm EST on my Twitch Livestream

    Live chat with me and other RC Nuts on my Discord

    Camp my Instagram @Alpha.Makes

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    • So cool!

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      • dny NATO 2020 Ostrava Click image for larger version

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        • Here is a nice gripen display from F-21 Luleå Sweden. They show a classic dogfight, and a speedcomparison.
          Fun fact, the speaker is not just a gripen pilot, he is also a good rc-gripenpilot. https://youtu.be/BlG6m8w0GcI

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          • That was a very interesting demo. I have seen and filmed russians do this (link below, dogfight starting at 3:55) but it is not really common to see proper 1vs1 dogfight mockups!
            Love these kinds of demonstrations as they add variety to airshows :)



            The speaker also made a great job of explaining to the audience what was going on! :)

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            • 👍😍 Looks unreal how they handle the machines.

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              • Suchoj's dexterity and maneuverability is respectable. And then they are beautiful planes.

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                • Agree!

                  Besides those guys are factory-test-pilots (father and son respectively!), so they do know their business, indeed! :D

                  I recall seeing a Gripen back at Le Bourget 2013 but they had it only in static display... I gotta make it to a show where it pops up in the future and get a proper video!

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                  • Pre-ordered but I don't have a 9ch radio. Is there any way I can use my old DX7 Tx? and still have the canards working the way they should??

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                    • Originally posted by Sapropbuster View Post
                      Pre-ordered but I don't have a 9ch radio. Is there any way I can use my old DX7 Tx? and still have the canards working the way they should??
                      Without thrust vectoring (TV), you only need 7 channels to have the canards operating in both pitch and roll.

                      There's some debate as to how the canards "should" operate. Scale they operate in pitch only. The manual has them operating in pitch and roll.

                      Technically, you only need 6 channels (or even 5) to fly the model, but it would take a reverse servo and a Y-lead to accomplish on 6 channels. Out of the box, without TV, your DX7 will work fine.

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                      • TV coming soon...

                        Gripen Thrust Vector Upgrade Set from Freewing - FJ21811011 This Thrust Vector Upgrade Set is intended for advanced pilots only because it significantly widens the potential agility of the stock Freewing 80mm JAS 39 Gripen. Roll rate, yaw control, and elevator authority are all increased. The aircraft will be able to d
                        My YouTube RC videos:
                        https://www.youtube.com/@toddbreda

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                        • Originally posted by Mizer67 View Post

                          Without thrust vectoring (TV), you only need 7 channels to have the canards operating in both pitch and roll.

                          There's some debate as to how the canards "should" operate. Scale they operate in pitch only. The manual has them operating in pitch and roll.

                          Technically, you only need 6 channels (or even 5) to fly the model, but it would take a reverse servo and a Y-lead to accomplish on 6 channels. Out of the box, without TV, your DX7 will work fine.
                          I note when you watch the MRC videos of the Gripen it is very twitchy on roll. It may be due to the canard mixing to the roll axis?

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                          • Originally posted by Aros View Post
                            🔥 🔥 🔥 can’t wait!!

                            Just a heads up but the description currently shows it’s for the MiG-29.

                            Comment


                            • Originally posted by Reaper911 View Post

                              I note when you watch the MRC videos of the Gripen it is very twitchy on roll. It may be due to the canard mixing to the roll axis?
                              Or twitchy fingers

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                              • Originally posted by Reaper911 View Post

                                I note when you watch the MRC videos of the Gripen it is very twitchy on roll. It may be due to the canard mixing to the roll axis?
                                Narrow deltas are typically extremely roll sensitive and take very little input to achieve a lot of authority. While they certainly don't make things better, I doubt the canards are to blame for this - it is a common theme on all narrow deltas.

                                I will run mine with canards for pitch only, most of all for scaleness sake, but also because it is very much not needed.

                                Moderate rates and a fair share of expo is the answer really.
                                Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

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                                • Originally posted by Reaper911 View Post

                                  I note when you watch the MRC videos of the Gripen it is very twitchy on roll. It may be due to the canard mixing to the roll axis?
                                  They were flying with a lot of turbulent wind, and the jet has low roll inertia, so that's to be expected.

                                  Using the canards in the way they did will likely worsen it too (when flying high alpha). Not so much the fact that they used them for roll but having them deflected pitch up when performing slow high alpha flight. The cure to that is using more rearwards CG and neutral to negative canard deflection on high alpha, achieveable by means of tx mixing or using a gyro (with aft CG setting).

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                                  • Hey paisano! How would you recommend the TX mixing for that, airguardian? Something like mixing 100% elevator up on the wing & canard pitching down like 5-10% ?? Thanksss

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                                    • Hola Petronio!
                                      Mind that for this to work, you want the CoG to be pretty neutrally balanced and ideally with a gyro controlling tha canards in the pitch axis. I did this on all my Freewing Eurofighters and it worked fantastically.

                                      With that adressed, the mixing is a simple pitch-to-canards mix. If you pitch up, canards should pitch up normally (LE-up). The gyro has to be setup to compensate normally (as in, nose up, canard corrects pitch down -> LE-down) and it will automatically do the appropriate compensations in flight and yield a more neutral or slightly negative canard deflection angles that we look for when turning.

                                      You can also disable the pitch to canards mix and leave the gyro working alone, which will have a more radical effect. Of course, better have these configurations on a switch so you can test them safely in flight and go back to normal mode if you don't like them or if there is a problem with the setup.

                                      Otherwise, if you don't want to use a gyro (although that's not what I really reccommend)... I would try something like making a custom curve that doesn't deflect canards at all in the first 20-30% range of stick movement, and then begins to deflect them slowly pitch-down beyond that point, when you apply pitch up. But there are many compromises with this approach so I do not encourage it unless you really know what you are getting into. The gyro way is easier and gets the job done (At the very least, it does on the Eurofighter and I bet it will too on the Gripen).

                                      Salu2! ;)

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                                      • Originally posted by Airguardian View Post
                                        Reminder: 'slight pitch up angle on canards' actually translates to pitch-down deflection when the jet is turning or flying high alpha.

                                        Made this drawing some time ago to try and explain more visually what I was talking about.
                                        The 3rd figure would be the 'ideal' condition you want to achieve.

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                                        Hi Airguardian !

                                        My problem is not the aerodynamics, they are well known to me. What I don't get to grips with is the gyro. I want something like "figure 3.5", like the real aircraft when going slow with high AoA.

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                                        Is it possible to achieve this and still having it to help or stay neutral in "normal" turns? The way I understand the gyro is a rate gyro that reacts to acceleration and tries to dampen it. When using up elevator, signal goes through the gyro, telling it to ignore the positive pitch acceleration and not fight it (the same as the SAS on my helicopters at work). Does that mean that as soon as I go to neutral elevator in the picture above, the gyro will try keep the airframe at that angle? It feels like there is something missing in my model of how it works. How do I get the canards to go from "slightly up" when pitching up, to "very much down" when in correct attitude?

                                        This much of authority might be a problem at higher speed, so if I put the gyro-gain on a slider on the TX then I can have "normal" throws until I decide to go high AoA slow speed passes? Another idea is to have three channels taking care of the pitch axis: ch1 elevons, ch2 TV and ch3 canards, with an opportunity to put a slider on all three surfaces, adding up on elevons and TV and down on canards, getting the machine to tilt up but still with the stick in centre position and fly around like that and letting the gyro work with 20% authority but with another "centre", this is easily doable in openTX. Wonder if it will work though...

                                        This started as a question and ended up somewhere else... Any comments?

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                                        • Originally posted by TangoVector View Post
                                          My problem is not the aerodynamics, they are well known to me. What I don't get to grips with is the gyro. I want something like "figure 3.5", like the real aircraft when going slow with high AoA. Is it possible to achieve this and still having it to help or stay neutral in "normal" turns?
                                          Gotcha!
                                          The answer is yes (kinda).

                                          The next is from my experience flying the Freewing Eurofighter, take it for what it is worth.
                                          The Gripen *should* be very similar. Anyway, always do these things very carefully to avoid surprises!

                                          So, the thing is, if CG is neutrally balanced (that's the key point), the jet does NOT need you to hold pitch stick back for the plane to hold angle of attack. Thus, as the receiver transmits a 'center' input (1500us, remember to detach canards from trim) to the canards' gyro, the canards will remain flat, or slightly pitched down if you set them to hold a slight pitch-down stance when neutral as I do. This slight pitch-down offset will show even throughout a high alpha pass if the CG is neutral enough so you don't have to hold pitch stick back. You can easily trim this out with more rearwards CG and elevons. Remember elevons overpower the canards as they have much more leverage over CG. If you get a bit extreme (not outright reccommending this) you can even go a slight bit tailheavy (yes, I'm talking actual tail heavy, not just 'tail heavier') and this kinda forces the gyro to further pitch down the canards as the jet is constantly trying to pitch up. Of course if you mess this setup by making it too much tailheavy you can crash your plane so do at own risk. I do it with mine without problems. I got to the point I was too tail-heavy for the flight to be comfortable, landed, moved CG forward where the gyro made it perfectly manageable and left it there.

                                          At the point where the jet is slightly tail heavy, the gyro will actively pitch the canards slightly down but over time plane will drift nose up and you will manually have to force the nose down too in addition to the gyro correction but it is not too bad if done properly. Actually I find my Euro, when set up this way, is the easiest jet to fly of all my fleet.

                                          Originally posted by TangoVector View Post
                                          The way I understand the gyro is a rate gyro that reacts to acceleration and tries to dampen it.
                                          Yes. Gyro will try to make angular turn rate equal 0º/s when rx input is centered.
                                          It is not perfect so there will be drift, but the drift is so slow (if done properly) that the 'response time' of the whole system is such that a skilled pilot can manage it no problem.

                                          Originally posted by TangoVector View Post
                                          When using up elevator, signal goes through the gyro, telling it to ignore the positive pitch acceleration and not fight it (the same as the SAS on my helicopters at work). Does that mean that as soon as I go to neutral elevator in the picture above, the gyro will try keep the airframe at that angle? It feels like there is something missing in my model of how it works. How do I get the canards to go from "slightly up" when pitching up, to "very much down" when in correct attitude?
                                          The rate gyro will not hunt for an 'angle' (º) but for an 'angular rate' (º/s). A heading hold gyro would hunt for angle but that's a different story.
                                          In the case of *most* rate gyros... let me make an example so it is easier to understand.

                                          Plane starts in level flight (0º/s pitch rate), then the pilot pitches up rather agressively, gyro sees this input as pilot asking for 'pitch up at Xº/s'.
                                          Initially, briefly, the canards pitch up normally, quite as if the gyro wasn't there. Plane starts increasing pitch rate according to control surface throws, aerodynamic forces and inertia.
                                          As the jet nears 'Xº/s' in pitch the gyro makes the canards quickly reduce 'pitch up' input. When jet achieves 'Xº/s' the gyro commands canards to be neutral. At this point, the inertia and/or the extra authority of elevons over canards will likely force the jet to overshoot and pitch up 'faster than Xº/s' (you are still holding stick pitch-up), so the gyro deflects canards pitch down to sustain the desired/commanded 'Xº/s' turn rate. At some point an equilibrium is reached and that yields your 'slightly pitched down canards' during a turn. Deflecting more or less the pitch stick changes the pitch angular rate setpoint to increase or decrease accordingly.

                                          That's the easy part, of course, you will likely achieve that even with rather nose heavy CGs. Achieveing the same on a sustained high-alpha level flight is more difficult (requires further aft CG and/or, negative canards offset at center stick).

                                          In practice, you don't really get to see the canards pitching up at any point because it happens so fast you don't notice... unless you pitch up VERY aggressively, then you will see canards flip pitch-up, then down on their own.

                                          Does that make sense?

                                          Hope I managed to make it comprehensible. :p

                                          Originally posted by TangoVector View Post
                                          This much of authority might be a problem at higher speed, so if I put the gyro-gain on a slider on the TX then I can have "normal" throws until I decide to go high AoA slow speed passes?
                                          From my experience with the Eurofighter, gyro gain can be set pretty high without experiencing oscillations, but as always, gain must be worked up very slowly through several flights and if at any point oscillations appear, reduce speed, land and lower the gain.

                                          I don't even wanted to max out canards' gain because it looked much less realistic both on the ground and in the air, so there's some trial and error and personal preference in there too.

                                          Here are two videos of my Eurofighter flying pretty much neutral or slightly tail heavy with a gyro on canards (only pitch) and a separate 3 axis gyro on nozzles to improve post-stall handling and predictability.

                                          First video is super-slow motion so you can see in all detail how my canards are reacting. Second video is real time.

                                          Of course, when you command full pitch up, if the jet runs out of authority (e.g. 0 speed and throttle off) the canards will deflect fully up because they lack the authority to move the nose around. You can see this happening in the flat spins as I hold full back-pressure on the pitch stick.





                                          Hope that helped! :)

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