Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[Bushong572]

Electric Brakes.....

Can you use the stock UBEC to power the brakes....or are you tapping into 1 of the 6s batteries? If so, are you using the full 6s?

[Evan D]

I messed up the poll and started a new one...

https://www.rcgroups.com/forums/showthread.php?3742755-If-you-have-crashed-a-FW-Big-Mig

[leithalweapon]

I don't guess anyone is listening but this is a very good point. Why both elevators non-responsive at the same time. Two tunnels and two sets of servo leads. We should be seeing planes doing uncommanded rolls, etc when one servo loses signal and the other is still responding. The odds of both servos simultaneously losing signal seems pretty remote to me.

Both tunnels, speed controllers and wire routings are identical. Maybe rudder control is also lost, but nobody has noticed it.
the receiver and both servos share a common signal, ground and power connection. Think of the Y cable as one single cable not two.

[janmb]

I messed up the poll and started a new one...


https://www.rcgroups.com/forums/show...d-a-FW-Big-Mig

Great work, hopefully something good comes out of this.

[themudduck]

I haven't heard a peep from the experts telling us for sure about the servos (I've seen much guessing here) - do these digital servos even have a fail-safe mode, in other words are they designed to simply stop working when they see interference or a signal drop out? What do these servos do when they see interference? What do they do when they are overloaded? We don't know if the servos are quitting due to flight loads or low voltage or interference or if its a loss of radio signal at the RX due to interference from batteries, bad antenna placement, etc. Without knowing these technical points we're all just staggering around in the dark.

[themudduck]

I messed up the poll and started a new one...


https://www.rcgroups.com/forums/show...d-a-FW-Big-Mig

I didn't crash but I did experience the elevator failure in a slight dive, so I contributed to the poll. Looks like only one other person has done it, so far. Evan D - I hope that you get a number of responses so we can get a better idea of what's happening!

If I can make a suggestions, a couple more questions to consider:
(a) were chokes used on the power wires (b) what receiver was used (c) was a satellite used (d) was the plane in a dive (steep or not) (e) was the plane flying at high speed, medium speed, low speed

not sure if you can add these to the poll...

[Evan D]

I can’t change it... they can add text to the thread... I hope it helps us.

[Hugh Wiedman]

Forgive me for posting on this thread and you can say my opinion doesn't matter since I've not flow this Mig, but I definitely have a huge interest in discovering the cause of these crashes as my Mig is coming soon and I desperately want, like all of you, to find out the cause. I won't be upset if you say my opinion doesn't hold water, but here it is anyway. So with that said, I still believe the number 1 culprit has got to be signal loss of the RX. The RX is the main variable out there, what RX's are used, it's location, the location of the antennae, the use of any satellite remote receivers, chokes, shielding, y-connectors, blue boxes, etc. There's a lot of wires and potential RF interference potential in this bird considering the hundreds of potential RX issues that make this very difficult to pinpoint. I don't think it is an aerodynamic issue or even a servo torque issue otherwise the thousands of successful flights would also be affected. IMO, a signal loss would be consistent with all crashes. Both elevators "stuck" in the same position (which to me negates a single servo issue-trace it to the source). Some crashes people have "felt" they still had throttle control, but when the elevators seemed to not be working, did they reduce throttle and it was just a coincidence that the failsafe mode on the RX was also to cut throttle? Then when the throttle was off, and the signal came back, so did the throttle response? I also saw some did have the EDF's running full throttle at crash? Is it possible that the RX failsafe position on that receiver was to remain at "last command" position, being at or near full throttle? The one thing Freewing has no control over is the RX we use and how we install it. Virtually everything else regarding this aircraft is somewhat consistent to the hundreds out there so if it were any of those, I believe we'd be seeing a lot more crashes.

[HaroldAnderson]

A follow up on an earlier post for two stage doors. Here are the pins to move from the wing wiring harness connectors at the blue box. Remove the 3rd wire (next to the red wire) and solder those together and install a connector to connect directly to the blue box two stage door output. Works great and as others pointed out, is not scale but looks cleaner and is cool!! I don't remember who posted the first note about the blue box having two stage door output but credit to them.

Here is the post with the pics again for dual stage or double stage doors.

[AirHead]

Forgive me for posting on this thread and you can say my opinion doesn't matter since I've not flow this Mig, but I definitely have a huge interest in discovering the cause of these crashes as my Mig is coming soon and I desperately want, like all of you, to find out the cause. I won't be upset if you say my opinion doesn't hold water, but here it is anyway. So with that said, I still believe the number 1 culprit has got to be signal loss of the RX. The RX is the main variable out there, what RX's are used, it's location, the location of the antennae, the use of any satellite remote receivers, chokes, shielding, y-connectors, blue boxes, etc. There's a lot of wires and potential RF interference potential in this bird considering the hundreds of potential RX issues that make this very difficult to pinpoint. I don't think it is an aerodynamic issue or even a servo torque issue otherwise the thousands of successful flights would also be affected. IMO, a signal loss would be consistent with all crashes. Both elevators "stuck" in the same position (which to me negates a single servo issue-trace it to the source). Some crashes people have "felt" they still had throttle control, but when the elevators seemed to not be working, did they reduce throttle and it was just a coincidence that the failsafe mode on the RX was also to cut throttle? Then when the throttle was off, and the signal came back, so did the throttle response? I also saw some did have the EDF's running full throttle at crash? Is it possible that the RX failsafe position on that receiver was to remain at "last command" position, being at or near full throttle? The one thing Freewing has no control over is the RX we use and how we install it. Virtually everything else regarding this aircraft is somewhat consistent to the hundreds out there so if it were any of those, I believe we'd be seeing a lot more crashes.

There's no need to ask for forgiveness for posting Hugh. You are totally in the right mind to be speaking out about a possible catastrophe when RC pilots are experiencing this "sinister electronic voodoo" that begs an answer. I couldn't imagine watching in desperation as the "big bird goes down" savaged by an electronic demon! I don't know if "Firebird" has had any luck with installing new servos, but you would think that would be a resolution! As for receivers; if all other channels are working, why would mostly only elevators be the culprit?. Some real voodoo going on there. Has anyone taken apart one of the servos to see if they have funky wiring or some other anomaly? I can't buy this jet right now, but I do love the MiG 29.....

[HaroldAnderson]

I few my Mig yesterday and did a few passes with the throttle at between 75 and 100 percent and with half flaps. I definitely noticed a tendency for the nose to drop and had to pull quite a bit more on the elevator to keep the nose level. It was more pronounced when I came out of a turn and coming towards me. As soon as I got rid of flaps or reduced throttle the tendency was gone. I did not rigorously test this, but I certainly was aware of it. A less experienced or nervous pilot could certainly interpret this as an aerodynamic issue or loss of a control surface. I certainly think part of this is pilot error. I'm flying with the upgrades servos, chokes, CG back, etc and it flies fine. It certainly makes an impression at the field with pilots that have not seen it before. Even the turbine guys think it's a cool EDF.

I've noticed the same tendencies. Once with half flaps and a full throttle dive while testing the elevator blanking theory I too had the sensation of lack of elevator control. It is a very bad feeling. I killed the throttle as soon as I noticed the plane might be becoming unresponsive. It responded but was probably already responding to my increased elevator pull. It all happened very fast and was over. It only happened once during a lot of high speed dives with half and full flaps. I was flying in a lot of wind that day and there was some turbulence too. Flying directly into the wind when it happened or seemed to happen at least.

[Hugh Wiedman]

[/U]As for receivers; if all other channels are working, why would mostly only elevators be the culprit?. ...

Are we sure the other channels are working when there is apparently no elevator control in a dive? I can see a pilot, now in a somewhat panic mode, move the elevator stick and/or the throttle, but in a high speed dive with no response, who is going to use aileron/rudder/flaps/gear?

[leithalweapon]

Are we sure the other channels are working when there is apparently no elevator control in a dive? I can see a pilot, now in a somewhat panic mode, move the elevator stick and/or the throttle, but in a high speed dive with no response, who is going to use aileron/rudder/flaps/gear?

I was able to roll left and right when I lost elevator authority. When the plane pitched nose down when up elevator was given I assumed I somehow got inverted. My insticnt was to roll upright, but when I started the roll I saw the verticle stabs where pointing up. At that moment I saw dollar signs and a tounge lashing from my wife and cut the throttle, but don't remember hearing anything. It happens instantly with no odd behavior to warn you. Comes out of it, if your lucky, the same way. You just get control back suddenly.

[Nickc2023]

I wanted to test the bec output under load so I put a y connector (same gage as stock wiring) in the ar637t, plugged the bec into one end and connected a meter to the power and ground of the other end. Voltage was 5.02 powered up but not moving any control surfaces. I flipped the gear switch started moving all control surfaces and about half way through the retract cycle hit the flap switch as well. Lowest it sagged to was 4.85v. Thats not too bad for every single thing powered by the bec drawing all at once. Even if you drop a little more for loaded servos it shouldn't be too much for the bec to handle I wouldn't think. 🤔 I took a video but I guess the resolution is too high since I keep getting error messages when I try to upload it.

P.S. I did this pattern 3x and got the same results and the bec was just barely warm to the touch.

[Hugh Wiedman]

I was able to roll left and right when I lost elevator authority. When the plane pitched nose down when up elevator was given I assumed I somehow got inverted. My insticnt was to roll upright, but when I started the roll I saw the verticle stabs where pointing up. At that moment I saw dollar signs and a tounge lashing from my wife and cut the throttle, but don't remember hearing anything. It happens instantly with no odd behavior to warn you. Comes out of it, if your lucky, the same way. You just get control back suddenly.

leithalweapon I stand corrected, something that is not an unusual occurrence. Thanks for setting me straight about the other surfaces, you definitely have some nibble fingers and a super quick brain to react that fast. I'd still be working on making sure I had the gear up after take-off as it was auguring into the ground if that happened to me! A day late and a dollar short for sure. I guess I'm back to the drawing board. Where is the NTSB when you need them. We need to call the Smithsonian channel and "Air Disasters" to help us out.

[RC30Flyer]

I haven't heard a peep from the experts telling us for sure about the servos (I've seen much guessing here) - do these digital servos even have a fail-safe mode, in other words are they designed to simply stop working when they see interference or a signal drop out? What do these servos do when they see interference? What do they do when they are overloaded? We don't know if the servos are quitting due to flight loads or low voltage or interference or if its a loss of radio signal at the RX due to interference from batteries, bad antenna placement, etc. Without knowing these technical points we're all just staggering around in the dark.

Mudduck... coming from giant scale and large high voltage/high torque digital servos, I can tell you that when I did testing on a few servos for RedwingRC back in the day that the servos when overloaded, just stall out and give up. Also takes a couple milliseconds to recover when the overload is gone. Its logic built into the chip. It's kinda the same way our electric retracts will just stall out if they become bound up in any way and forces an unwanted voltage spike or overheat condition. That logic that is built into the chip is what will save the motor/PCB/and gears in it, in the event there is an overload or stoppage before the limit switch is hit. I'm currently modding my rudder and elevator leads away from the high voltage lines and ESCs for my new MiG. This may not be the issue at all, but I'm not taking the chance, given what I've seen in the past with my 30 and 40 percenters using a main control box. Just my 2 cents tho...

[Firebird]

That looks much better. Where did you order them?
What do you have on the mains?

Thanks

I ordered the nose tires at turbine-rc.com

On the mains I installed the FMS F7-F tires.

[Firebird]

Are they the same wheels I’m seeing on fanjetsusa.com?

I think the the tires you found are from the same brand - it‘s just the 57mm version. Mine are 45mm. I choose 45mm because we have 100m paved runway at the field - i don’t necessarily need them bigger. (Trying not to add to much weight shifting the CG when retracting).

[kallend]

Mudduck... coming from giant scale and large high voltage/high torque digital servos, I can tell you that when I did testing on a few servos for RedwingRC back in the day that the servos when overloaded, just stall out and give up....

Did you measure the maximum current drawn by the stalled servos?

[janmb]

Forgive me for posting on this thread and you can say my opinion doesn't matter since I've not flow this Mig, but I definitely have a huge interest in discovering the cause of these crashes as my Mig is coming soon and I desperately want, like all of you, to find out the cause. I won't be upset if you say my opinion doesn't hold water, but here it is anyway. So with that said, I still believe the number 1 culprit has got to be signal loss of the RX. The RX is the main variable out there, what RX's are used, it's location, the location of the antennae, the use of any satellite remote receivers, chokes, shielding, y-connectors, blue boxes, etc.

First of all, don't let anyone tell you to shut up just because you don't have the model yet. You can easily have a better basis for an opinion than many of those who do.

Second, I would normally agree that radio glitches would be the most likely culprit. But in this case we're seeing a lot crashes at relatively short ranges, very similar attitudes. Most pilots fly on Spektrum. And while that is certainly not the most solid radio system in the world, it does have one really strong point: You have to deliberately sabotage your setup to avoid having a good failsafe setting. So you can safely assume that 95% of the spektrum guys cut throttle when having a failsafe situation. And most of the crashes we've seen have lost elevator control without losing throttle apparently.

If rx was indeed the most common factor, I would expect to see a lot more 0 throttle by the time the model hits the dirt