Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[GliderGuy]

https://youtu.be/yiEtDOK8Wls

Not sure why there isn’t a preview attached…

Something is WRONG! I would not fly again until you sort it out. Please post photos of your radio set-up and antenna placement.

Does your radio gear report frame holds or frame losses? There is nothing about the bird that would make it behave like that. The MiG-29 just doesn’t do that (unless you fly fast with flaps down with weak servos).

Nothing in your set-up is out of the ordinary. Lots of folks are set up like yours is. The reflex ailerons and flaps will actually tend to hold the nose up. Take it from a full scale high performance glider pilot who uses reflex flaps all the time (but NOT for landing…it increases the stall speed too much).

Have someone take the MiG away and hold it up. Manipulate the controls through a predetermined pattern with the EDFs on. Try different attitudes in relationship to the transmitter (won’t be easy to do). Does the control movement violate the predetermined pattern? You gotta sort out the radio issue. It will cause a crash….most probably.

Are you using RF chokes? Search the forum and read/learn about them. I had a few uncommanded loss of control events (crashes) on other EDF birds before I started using them. I have had NONE since.

Solve the RADIO PROBLEM before you fly again. Know that the MiG airframe normally doesn’t do the stuff your video is showing.

Consider yourself VERY lucky! You might not get away with it again.

-GG

PS - A final thought…are you using heavy duty hardware to drive the full flying stabilizers? If not….pushrods might be bending under load.

[Birdseed]

Xviper,
Thanks for your comments. You’re absolutely right, it did seem to happen when just levelling the wings. Ill double check there isn’t any odd coupling going on.
I don’t have thrust vectoring so thats not a factor.
What i will do is take the “ reflex” out of the flaps, and see how it performs. I’m certainly not discounting your suggestion that the flaps/ailerons being raised doesn’t cause a dive until its banked over.

[Birdseed]

Gliderguy,
Ill get some pics of my radio install tomorrow. However I’m using the powerbox core and i didn’t get any low signal warnings. I’ve also got the elevator set to “hold” in the event of a failsafe. I had a total of 16 frame losses during the 3rd flight so I don’t think that’s the issue. Having said all that, the receiver is in the pocket beside the rearmost battery and one of the two aerials is parallel and attached to the lower plywood battery plate. That is sub optimal, so after this experience, I’m going to make some changes regardless.
Ill take your suggestion and do additional range checks at different angles.
I’m not using RF chokes. Have to admit in 20 yrs of RC flying I’ve never used them, and have no knowledge of them.
It doesn’t give me a warm rosy feeling that the elevator servo leads ( and rudder) run parallel to the power cables to the ESC. However, if there was interference from the ESC, having it affect both elevators at the same time seems unlikely.

I’ve the latest mig 29 kit version, so with larger more outboard set servos, with a metal servo horn and heavy duty hardware. There’s a bit more vertical play in the Clevis than normal-eg the servo arm isn’t as thick as the clevis is, but I don’t think this is giving any play.

My plan therefore is to
1) Do the suggested range checks, then
2) move the receiver to the forward most battery compartment.
3) Bypass the blue box and have a channel for each flap and aileron to allow easier adjustment.
4) Adjust my CC BEC from 5.1V to 6V
5) re install the original BEC and use that to feed the blue box to control the retracts and lights.( I undertand they take up to 5.5V whereas the servos can take 6V)
6) adjust the wingtips to give them the 3mm reflex discussed in other threads.
7) set flaps to normal up position
8) Have aileron reflex set as an option on another switch.
9) Have much more elevator expo than I had before
10) Next time I fly it, fly it in much smoother conditions!

[Evan D]

Sounds like you have a good plan.

You probably have used chokes before. The ferrous rings (usually green) on the lead from many ESCs to the receiver.

[Hugh Wiedman]

Birdseed definitely something wonky going on there, agree with the others that you'll need to do some investigation. I understand that it did this with the gyro off, correct?, so you can obviously rule that issue out. Not sure that it had anything to do with the elevator control rods, but I will say that I got my Mig just as they came out with the upgrade package. Servos looked good, but I had already bought the ProModeler DS150's so I used those instead, however, I used the excellent aluminum servo control horn and their upgraded control rods. Before I even got a chance to maiden it, some idiot (wonder who that was ) knocked something off a higher shelf in my hangar which impacted one of the horizontal stabilizers. Wasn't all that heavy and did zero marks on the foam & paint of the elevator, but the control rod bent severely. The DS150's can not be moved like cheaper servos when not on and the impact was born completely by the control rod. Bent it back, but felt it actually bent way too easily, so swapped it out for the Hangar 9 4 1/2" Titanium 4-40 rods I had purchased before seeing the upgrade package. Now they're rock solid with absolutely no play. Doesn't take much elevator at a reasonable speed to change orientation on this bird so I'm wondering if the control rods are bending or if there is too much play in the linkage. I know that even the original rods inserted inside a carbon fiber tube are stiffer than the upgraded rods but that titanium rod ain't bending no way no how. Probably out in left field here, but just a thought. Haven't heard of anyone with issues on the Mig with the upgrade package so most likely something else.

[Shaun Evans]

Hi,

I know the book CG is too far forward, but I'm curious how far aft you guys have flown yours?

Thanks!

[GliderGuy]

Hi,

I know the book CG is too far forward, but I'm curious how far aft you guys have flown yours?

Thanks!

10 to 15 mm easy….maybe 20 mm aft of mark max unless you have VT installed. It gets to be a matter of deep stall/high alpha lock recovery as the CG moves aft.

-GG

[Airguardian]

15-20mm here too.

Like GG says, better not venture further aft until you install VT to prevent nasty high alpha lock surprises.

Excellent flights as usual Airguardian!

Thanks!
Great FPV flying on your end too! :)

Some of us are slow on the sticks by nature, no playback slowdown required.

Unfortunately, there are some things that just can't be 'faked' with just being 'slow on the sticks', particularly when you get in the realm of post-stall maneuvers... wish they were, though! ;)

So the question is, is the models diving behaviour a result of a fwd CG, or am I experiencing the mig’s dreaded nose diving tendency-despite elevator servos being vastly over torqued?

That's weird indeed. Maybe a gyro issue?
Another thing that comes to mind: Defective wiring somewhere, causing intermittent shorts.
I'd replace the stab wiring by some better, higher gauge leads, and take the opportunity to take the servos out and inspect them up close. The wires in particular. It is a known issue with Freewing that they sometimes clip the wires during factory installation which can lead to problems like this.

What i will do is take the “ reflex” out of the flaps, and see how it performs.

I wouldn't do that... You will load the stabs further, the opposite of what you want.

4) Adjust my CC BEC from 5.1V to 6V
5) re install the original BEC and use that to feed the blue box to control the retracts and lights.( I undertand they take up to 5.5V whereas the servos can take 6V)

Remember to 'decouple' the circuits, there shouldn't be any red wires running between the receiver and the bluebox if both are powered separately at different voltages!

[GliderGuy]

Birdseed….here is a link to the heavier duty wire to run to the full flying stab servos from up front. Get the 80 cm length.

https://www.hacker-motor-shop.com/Se...0025080&p=8312

The webpage says 0.5qmm which is 20AWG.

This will help reduce any IR <voltage> drop going to the tail servos

I agree….leave the aileron and flap reflex in.

-GG

[Tigerman]

What the verdict on remote receiver.. I have thie.Mig 29 and to me it is an expensive model (worth every penny) I have a Spektrum AR8020T receiver in the Mig 29 but was wondering if it is worth spashiing out on a remote receiver for piece of mind just in case :. Are the satellite receivers a good idea or a waist of money. The satalite receiver I want is £50 (not sure what that us in dollars). But if it is going to save my Mig 29 it would worth every penny. What the opinion on these satalite receiver. Good or a waist of money?

[Evan D]

I almost always use them. On my Mig I have two. One in the nose and one under the right vertical stab. Good insurance.

[kallend]

What the verdict on remote receiver.. I have thie.Mig 29 and to me it is an expensive model (worth every penny) I have a Spektrum AR8020T receiver in the Mig 29 but was wondering if it is worth spashiing out on a remote receiver for piece of mind just in case :. Are the satellite receivers a good idea or a waist of money. The satalite receiver I want is £50 (not sure what that us in dollars). But if it is going to save my Mig 29 it would worth every penny. What the opinion on these satalite receiver. Good or a waist of money?

The MiG has two batteries and two motors, each of which can block the 2.4GHz signal. A remote, properly placed, can ensure a clear signal path regardless of the attitude of the model. Good insurance.

[Hugh Wiedman]

What the verdict on remote receiver.. I have thie.Mig 29 and to me it is an expensive model (worth every penny) I have a Spektrum AR8020T receiver in the Mig 29 but was wondering if it is worth spashiing out on a remote receiver for piece of mind just in case :. Are the satellite receivers a good idea or a waist of money. The satalite receiver I want is £50 (not sure what that us in dollars). But if it is going to save my Mig 29 it would worth every penny. What the opinion on these satalite receiver. Good or a waist of money?

I concur with Evan D and kallend I have the AR10360T receiver in my Mig 29 with the 2 main antennae going off to each side under the back battery tray and the SRXL2 remote all the way in the nose with it's 2 antennae going on a different plane and have gotten a very consistent signal with minimal frame losses. Is it absolutely necessary ??, maybe not but for about $45 US, well worth the insurance. Ferrite chokes wherever possible as well. I now always use a remote in almost every one of my EDF's. My SU-30 started out with just the AR8360T, no remotes and used to have 500 to 600 frame losses per 3:30 flight times (not acceptable-about 50 per is minute good, 100 per minute means it needs to be addressed) and occasionally several Holds (definitely heading for disaster there-must be 0) before installing a remote. With the remote, no holds and frame losses in the acceptable range. Same issues with my 2 F-18's and A-10, all with the AR637T's, initially way to may frame losses no matter where the receiver and antennae were placed, but after adding the remote it's back in line. I even added the DSMX remotes on my earlier EDF's with the now discontinued AR636 receivers in my 2 F-4's and Stinger 90 that cut the frame losses by more than half after putting them in.

Bottom line is that after installing the remote (no matter how I positioned the main receiver and it's antennae), I cut frame losses dramatically and eliminated any holds. The only EDF's I do not have a remote in is the Avanti and my F-16, only because the receiver and antennae are up front in the nose about as far from the ESC, EDF's and battery as you can get and have always had a good signal on those. The remote would only be positioned back where the interference originates from so left them out. I say add at least 1, if not 2 remotes to your Mig!

[Tigerman]

It is a no brainer then remote receiver all order
Thanks guys

[t33jetman]

Looking back

[Birdseed]

15-20mm here too.




That's weird indeed. Maybe a gyro issue?
Another thing that comes to mind: Defective wiring somewhere, causing intermittent shorts.
I'd replace the stab wiring by some better, higher gauge leads, and take the opportunity to take the servos out and inspect them up close. The wires in particular. It is a known issue with Freewing that they sometimes clip the wires during factory installation which can lead to problems like this.



I wouldn't do that... You will load the stabs further, the opposite of what you want.



Remember to 'decouple' the circuits, there shouldn't be any red wires running between the receiver and the bluebox if both are powered separately at different voltages!

Thanks for the suggestion.
I actually changed the wiring to powerbox cable before the maiden. I’m also using savox servos which on 7.4V put out 15kg of torque. (To be fair as they’re only running at 5.1V it will be much less, but far more than the stock, even upgraded stock ones which are rated at 4.5kg)

Curious that both servos would do anything odd at exactly the same time.

[Turbinefancy]

Looking back

Beautiful scheme, excellent work!

[kallend]

Curious that both servos would do anything odd at exactly the same time.

Indeed! Suggests some kind of power anomaly or radio glitch that affected both.

[Evan D]

We had a pilot lose control of his over the weekend (he also lost his F-22 so it was a very bad day for him). During flight he lost pitch control with the plane having and holding a full up pitch attitude. At the crash scene he found both elevator servos locked full up. Not to second guess anything else but I assume he had both servos going to the MCBe as he typically built things by the book. Sounds similar?

Thanks for the suggestion.
I actually changed the wiring to powerbox cable before the maiden. I’m also using savox servos which on 7.4V put out 15kg of torque. (To be fair as they’re only running at 5.1V it will be much less, but far more than the stock, even upgraded stock ones which are rated at 4.5kg)

Curious that both servos would do anything odd at exactly the same time.

[Ironside]

Anyone have the ability to draw and print a couple of these "exhaust skids" for me? Looking to install a couple on my Mig. PM me if you willing to help me out.


Another option would be if someone has a set of the vectored thrust skids that they aren't using because of a crash or some other reason.