Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[GliderGuy]

Very long elevator wire, thin wire, but no loss of voltage in the system, maybe induction from the power wires, temporary voltage drop in wire, servo goes to failsafe?

All conditions the same, a wire with less surface area (smaller diameter) will pick up less noise from a radiating noise source according to my HAM radio guru. Radiated noise will decrease with an inverse square of the distance, so it’s a good thing to route wires farther away from noise sources. But...that practice is common knowledge.

Post 2318 by Firebird is based upon sound principles.

-GG

[viper1gj]

Here it is, posted by Rudy:

Thanks Rudy, I got it today and it's a perfect match. Will help cover up my chopping for turbine conversion and 3D printed CL tank.
Gary

[Airguardian]

Here some calculations, inspired by an post from skyfox60 from rc-network.de comparing the effect of LV and HV servos in general:

• Assume a standard low voltage setup with 5 Volts at the receiver
• Assume the tail servo wants 15 Watts, which means it pulls 3 Amperes

Your calcs look fine (for a more powerful mini servo) but I'm afraid they don't quite apply to the MiG-29 stock servos, as someone in the thread already measured their stall current at around 0.7A. The servos will just give-up before ever reaching 1A each.

Those calcs would still apply to a more powerful servo of course, but the crashes so far have been all with stock servos I think, so that's not it. ;)

[HaroldAnderson]

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.

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.

[Dan B]

I am probably one of many with an unexplained non-responsive elevator leading to a crash. My Mig 29 had around 10 flights on it with the MRC upgrade servo's installed from day one as per MRC instructions.
A diving then low height 3 feet pass along the runway at full power, gave no elevator response. She would not pull up. Ended up going for about a 120mph slide down the runway.
.

Sorry Molly914. I had one of the earlier crashes (see Post#1665) that was initially blamed on my RX setup. Can you tell us what RX you used? Satellites? Location, etc? It would be interesting to compare our receiver installation to see if there was anything in common, or if you had the ideal setup as many here say they use and therefore shouldn't be the cause of your crash.
Dan B.

[Wefinance01]

Let me start by saying, I have been out of this hobby for 3 years bc I've gotten into boating. Boy, I see the same folks from the Rcgroups and the same pride. I got this plane still in the box ready to be built after in finish installing a 383 stroker in one of my boats. I have read all the pages of this thread and have watched all the videos of the crashes. My take is that this plane is fine with the supplied servos and linkages. The box maybe questionable in quality but it is what it is made in China. The problem i observed is like what I have experienced in past that resulted in similar loss of one or more controll surfaces. Vibration from the motor causing the pin at the extension connection or at the blue box to temp disconnect or fail. Sometimes, the crimp with these thin wires maybe too tight causing a break at the connector. Check those and be happy.

[fredmdbud]

In any of these cases of elevator non-responsiveness, has anyone tried letting the plane slow down (reducing or cutting the throttle) and seeing if elevators recover?

[Firebird]

We will find out soon what is actually really going on with the signal strength and voltage at the elevator servos. I just ordered Hacker telemetrie servos which are sending telemetrie data about signal strength, voltage at the servo, torque load, temperatur, blockade and overload live to the TX where the data gets recorded.

[CristianMarin]

Maiden report

Made 3 flights yesterday and all went well.
My configuration:

1. Changed elevators servos with Corona DS-238 MG. Stock pushrods.
2. Changed flaps servo with upgraded servos sent by MRC
3. Eliminated the blue box...., well not entirely, is still used for front landing light 🤣. Still needed a 5v Spektrum 2 channels voltage regualtor for the BB.
4. Every servo has it's own channel. Using a Spektrum power receiver on 2 LiFe 2200 mAh, so no UBEC needed. The receiver goes under the wood rear battery tray.
5. Chokes all around.
6. RC-Castle afterburner installed. The ones with the led strip.
7. CG 10 mm back from stock location.

Everybody here reported that the plane does not need elevator compensation when flaps are down, but mine needed. It had a violent pitch down when flaps were fully deployed. A 7% mix calm that down. Elevator worked very well even when flaps were at full deflection.
Unfortunately, the next flight will be when spring comes. Time for build here.

[Simjet67]

Has anyone got details on reinforcement of the ordnance? a club mate took this photo of my Mig about to start a knife edge pass and you can clearly see the larger missiles bending.

[GliderGuy]

We will find out soon what is actually really going on with the signal strength and voltage at the elevator servos. I just ordered Hacker telemetrie servos which are sending telemetrie data about signal strength, voltage at the servo, torque load, temperatur, blockade and overload live to the TX where the data gets recorded.

That’ll be interesting. But, you have also replaced and re-routed all your elevator wiring to non-stock. Right?

-GG

[GliderGuy]

Has anyone got details on reinforcement of the ordnance? a club mate took this photo of my Mig about to start a knife edge pass and you can clearly see the larger missiles bending.

I took a left-over wire puller from another FW build. Cut 8 lengths long enough to form a loop around the perimeter of each fin (followed the outer fin shape). Glued these on to the bottom side of each fin and painted them. You cannot see them. Each large fin is extremely stiff now.

Originally posted by mshagg in post #1058. You can see the fin action very well if they are not braced. I was concerned that the flexing would eventually lead to cracking of the plastic and a subsequent loss of fins.

-GG

[GliderGuy]

Maiden report


Everybody here reported that the plane does not need elevator compensation when flaps are down, but mine needed. It had a violent pitch down when flaps were fully deployed. A 7% mix calm that down. Elevator worked very well even when flaps were at full deflection.

Congrats! What is your measured flap deflection when down?

-GG

[CristianMarin]

Congrats! What is your measured flap deflection when down?

-GG

Done by the book. I don't remember the exact number.

[Firebird]

That’ll be interesting. But, you have also replaced and re-routed all your wiring to non-stock. Right?

-GG

Right, I installed new, upgraded servo cables for elevator and rudder as shown in my previous posts as far away from the rest of the cables (powerlines and esc) as possible.

But - i left the stock elevator servo cables in for now. So we will get direct telemetrie comparison of the stock elevator cable impulse signal quality (and voltage at the servo) compared to the impulse quality and voltage of rerouted / upgraded elevator servo cable.

We will see this servo signal quality comparison with the impellers running and without load. I hope after this we can see the problem more clearly and avoid more losses.

[Radar-Guy]

Installed two more landing lights and changed to the “double stage door” setup, all by tapping the appropriate ribbon wires at the MCB.

[bandetx]

So anyone figured out the elevator thing yet?

Is it just all started as propaganda by someone who crashed and wouldn't admit it, or is it real?

[Evan D]

Well, it is real. Many seem to have crashed, especially early on for simply not reading the instructions especially the elevator push rod location and balance. But there have been others and many have not been able to come to a singular reason. While many are saying the sky is falling and running around like chicken little I think many are for more normal reasons like piloting error. I really think at the end of the day there have been no higher a percentage than other planes. I think the cost of this plane really brings it to a higher awareness.

All my opinion though...

[janmb]

So anyone figured out the elevator thing yet?

Is it just all started as propaganda by someone who crashed and wouldn't admit it, or is it real?

No real conclusion on that yet - nor sure there ever will be. A number of potential culprits and amendments have been discussed, but nothing conclusive yet.

As for what started it was a string of different, yet very similar crashes. It is the similarity between them that is worrying. Pilots crashing new releases is perfectly normal and expected - for a multitude of various reasons. Build mistakes, setup mistakes, piloting mistakes, and the occasional hardware failure. But in those cases, the crashes are very varied in nature. In the case of the mig, almost every single crash has been very similar and without any obvious explanations.

Fair enough, the number we've seen is still less than 10, from probably a good few thousand flights world wide. The real numbers we clearly don't know, neither crashes nor successes (nor does anyone else, including motion/fw), so kinda boils down to speculation and derivation at this point.

The jet being released with marginal elevator servos is the only hard fact we have here.

[DCORSAIR]

So anyone figured out the elevator thing yet?

Is it just all started as propaganda by someone who crashed and wouldn't admit it, or is it real?

All I know is, I'm glad I didn't buy this mystery Mig, because flying around wondering when will my Mig expire cannot be to relaxing, and I just love the fact that if you don't read the instructions and install the linkage in the wrong hole on the servo horn, you will crash, sorry but that's just stupid, you should be able to move the linkage to any hole to your liking and not have to worry about stalling out the servos....