Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[GliderGuy]

From web calculator....not much gained:

24 AWG shown below for a 3 foot distance / voltage drop assuming 5 volts at the source:

0.5 A = 0.08 V drop
1 A = 0.15 V drop
1.5 A = 0.23 V drop
2 A = 0.31 V drop

Larger wire = less of a drop.

Consider the small wires coming off the 8 A UBEC.

-GG

[robertbulko]

Watching youtube videos and reading the thread, I can clearly see she has not enough power, and I believe the Blue box is not able to handle the current needed for the Elevators or control surfaces in general. When it was just introduced, I was disappointed with the fact she has no thrust vectoring (TV) but after seeng many videos, I see why she does not have them. It looks like, the motors are not able to deliver enough power and with TV it will be even worse. Also, I think the Blue box can be the cause of crashes, I would bypass it and test it without. Of course, strong servos for the Elevators is the "must have" condition. GOOD LUCK ;)

[Nickc2023]

Given all the recent talk about adding ferrite rings/rf chokes as well as my own speculation as to if they are really nessary , I thought this would be worth mentioning. Yesterday I purchased the eflight 1.5m p51 from my local hobby shop. It runs on 6s power with a 100 amp esc and has the same AR637t smart rx that I put in my mig 29. When I opened the canopy I was quite surprised to see that there were not 1 but 2 rf chokes installed by the factory! 1 rather large square one on the power and esc wires and another barrel clamp on type on ALL of the wires plugged into the rx (same as the Amazon ones I installed in the mig... thanks GG!) I'll admit I was skeptical at first but figured, why not and put them on anyway. Seeing them pre-installed by Horizon kinda made me feel that there is something to this. For the 10 bucks the whole set of chokes (from the Amazon link a few posts back) cost its definitely worthwhile to throw em in the higher amp draw aircraft IMO.

[janmb]

Careful....no confirmation that “only” the elevator control was lost. That’s just the most critical to keep one from diving into the ground.

That elevator only loss assumption is not supported, I don’t believe.

True. The immediate panic will naturally focus on the lack of elevator response anyway, especially when already being in a wing level attitude and roll input not being immediately necessary at all.

What makes me doubt brownout/radio loss or glitching though, is the total lack of fail-safe kicking in, cutting the throttle. We have seen soooo many of these crashes now, where there is an apparent total loss of control, yet the model stays at whatever throttle setting it had at the time.

Sure, some pilots mess up/forget fail-safe, but not that many. Especially considering most use spektrum anyway, where messing up failsafe is something you actively have to work really hard to do, vs other brands where it is rather easy to forget. Heck, a lot of pilots on spektrum probably fly with properly configured failsafe settings without even knowing it lol

So if radio trouble was the predominant issue with these crashes I would have expected to hear a lot more fans being cut on the way down.

[janmb]

When ELE was lost, seemed like throttle still responded. What can be said from this?

Stayed at whatever level it was at least.

[Raydar]

One thing I noted on my plane when I got it and it may have absolutely nothing to do with all the failures is the bec placement. It is directly in line of being interfered with by the canopy magnet. I have never mentioned this before as doubt it is the cause of these issues but having worked on a lot of electrical issues in the past having it there to me is not best practice. I KNOW I will be shot down with it does not matter but I have seen enough weird stuff in my time to make me think twice.

There was one guy on here or regroup that posted good telemetry on rx voltage but apparently experienced the issue so it's probably not likely the cause but it's something I personally would reposition as it does no harm.

[xviper]

Given all the recent talk about adding ferrite rings/rf chokes as well as my own speculation as to if they are really nessary , I thought this would be worth mentioning. Yesterday I purchased the eflight 1.5m p51 from my local hobby shop. It runs on 6s power with a 100 amp esc and has the same AR637t smart rx that I put in my mig 29. When I opened the canopy I was quite surprised to see that there were not 1 but 2 rf chokes installed by the factory! 1 rather large square one on the power and esc wires and another barrel clamp on type on ALL of the wires plugged into the rx (same as the Amazon ones I installed in the mig... thanks GG!) I'll admit I was skeptical at first but figured, why not and put them on anyway. Seeing them pre-installed by Horizon kinda made me feel that there is something to this. For the 10 bucks the whole set of chokes (from the Amazon link a few posts back) cost its definitely worthwhile to throw em in the higher amp draw aircraft IMO.

I also had the same experience as you when I got my Eflite P-51 some months ago. I had no idea what those things were at the time. It wasn't till GG brought it up that I was educated. I now have a choke on my Mig. Can't say if it does anything but this is a very expensive foamie - one that I'd like to do what I can to keep from crashing. Next up, a horseshoe in one pocket and a rabbit's foot in the other.

[Waconut]

Just an observation and I have no idea if it means anything but all of the crashes on video that I have seen the MiG had just come out of a turn and leveled out when elevator control was lost. Like a said just an observation.

[xviper]

Just an observation and I have no idea if it means anything but all of the crashes on video that I have seen the MiG had just come out of a turn and leveled out when elevator control was lost. Like a said just an observation.

That's a GOOD observation and one that should be added to mix for future guessing games.

I've only had the chance to fly mine 4 flights before the bad weather hit, so maybe my turn will come next spring. Hoping all the guessing will lead to a final definitive conclusion by then.

[Skosh25]

One thing I noted on my plane when I got it and it may have absolutely nothing to do with all the failures is the bec placement. It is directly in line of being interfered with by the canopy magnet. I have never mentioned this before as doubt it is the cause of these issues but having worked on a lot of electrical issues in the past having it there to me is not best practice. I KNOW I will be shot down with it does not matter but I have seen enough weird stuff in my time to make me think twice.

There was one guy on here or regroup that posted good telemetry on rx voltage but apparently experienced the issue so it's probably not likely the cause but it's something I personally would reposition as it does no harm.

My receiver is in the front bay. I intend to add an extension to the bec and tuck it back under the wing next to the rear battery.

[GliderGuy]

My receiver is in the front bay. I intend to add an extension to the bec and tuck it back under the wing next to the rear battery.

That aligns with what I did. No issues.

-GG

[leithalweapon]

Man...! I feel for ya! That just isn't right! It seemed pretty good up to that point. And, I don't think it stalled in the turn. The down, or lack of up elevator, seemed to happen just before it leveled out from that turn. ...in the last roll input. I see a little up applied as it reacts with a small climb correction half way thru the turn, then more left aileron and it seems to be failing as it levels out for the run.

And I believe from what was said on the video that the controls bypassed the box? Double check the ubec for sure and, of course, the servos. I just have a feeling the ubec is letting go after a good load. I would load it up and watch to see if it heats up while checking V/A.

That is not me in the video. I just found it on Youtube.

[mshagg]

Hi everyone my first posting to this great site.
I have just received my Mig29 here in uk and will shortly start the assembly. I have been taking note of the blogs regarding the possibility of the elevator causing planes to crash or lack of response. I shall be upgrading both the servos to D85mgs and elevator push rods to the suggested F14 swing wing rods. Also will bypass bb and use two channels for elevators. I do wonder if a possible cause or certainly may add to the problem is the very light weight servo extension leads used for the elevators considering the length of the run. Surely when the servos are under heavy load they will demand more power the lightweight leads will create a resistance to the demand required by the servos under stress and heavy load. I shall be upgrading these servo leads to a heavier higher quality leads I would have thought that this has got to help and certainly can’t do any harm.
any thoughts?

I dont want to discourage what is probably a sensible mod, but the D85s are comparable on paper to the upgraded high torque freewing servo. If you want a substantial increase in available torque you're looking at a different form factor servo. That is the path I went down, but appreciate it's a somewhat extreme modification.

FWIW Hitec indicates the D85MG is suited to planes up to 50oz (1.4kg). The 645MW is, according to Hitec, suited for planes up to 15lb (6.8kg).

I can say from experience going from the micro form factor to the physically larger servo was like dialling all of the expo out of the model. My sense, just based on the responsiveness of the plane now, is that the micro form factor is at or approaching its limit under the load of these surfaces.

[Bajora]

Finally got to see one of these in person ... Michael Troy's Freewing Mig 29 :cool:

[PaulZ]

Looks much better. where did you get the brakes (what HSD plane are they for)?

Thanks

These are the 65mm wheels+brakes sold for the HSD F-16

[Waconut]

https://youtu.be/cLwenDNqdQ0

Another crash. Kinda appears to stall in the turn, but it could just be the angle the video was shot.

I went back and watched this video for probably a 5th time and noticed something else. During the post crash inspection the stabilator control rod broke loose on the right side( assuming from crash impact) the servo arm broke at the last hole.
I thought there was an advisory not to use the last hole on the servo arm? Maybe it was the 2nd hole and the end hole had been cut off?

Now mind you I do not have this bird (yet) and I am just making observations based off of videos and previous post.

I would really like to see this issue resolved so I can order one with confidence it isn’t going to be a $1,000 lawn dart.

[mshagg]

Pretty sure that was the replacement servo horn which comes with the last hole removed.

[Airguardian]

With more and more new videos showing up on this plane, what can we deduce from all the successful examples and all the crashes?

I think the only common denominator to them all so far is that they featured factory recommended CG or nose heavier than that, no ferrite rings/clips on the ESC wires and all were using stock pushrods... plus most of them manifested towards the end of the flight. This suggests to me (speculation, not fact) that the servos may be struggling a lot due to trim drag (possibly overheating) and stopping to respond at some point.
If anyone else crashes in this fashion, please check your stab servos temperature straight away!

Taking only the crashes into account ................................................
Original servos for elevators - crash.
New upgraded servos for ELE - crash.
BB left in play - crash.
BB taken out of the equation - crash.
Book CG - crash.
CG back 10mm to 15mm - crash.

I think there has not been a single crash report (with jets nose-diving like that) with CG shifted back, but I may have missed it. Please help me on that!

When ELE was lost, seemed like throttle still responded. What can be said from this?

Not a brownout, but failure on the stab control at some point (servo, linkage, lack of current supply...)

Still no examples of crashes when the elevator rods have been beefed up.

I think there has been one at least, but it was possibly a brownout (the guy who commented he had one satellite antenna unplugged used beefed up pushrods if I recall correctly?)

Loss of ELE was momentary (~2 seconds), then came back after altering throttle. What could this mean?

Throttle-pitch coupling inducing pitch-down at speed due to intake pressure change, servos lacking authority (for whatever reason, including reduced throws, nose heaviness, pushrod bending, possible aerodynamic wake condition on the stabs...)

As mentioned, we still don't have an answer to the riddle.
It may be one of these things, many of them, or none at all.

Personally I am inclined to think we may have seen some brownouts and the rest are for different reasons.
I think many factors are accumulating on some of the jets, leading to the bad pitch scenarios we've seen.
I'd start digging with power supply, servos not coping after prolonged use under nose-heavy conditions (even the new beefier ones), CG itself, programmed throws being insuficient on some of the jets, weak pushrod linkages worsening it all...

But again, hard to point the finger at a specific single thing from the info available. That is not a good scenario sadly for us... but we'll work it out together! :)

[themudduck]

Yeah in the video you can see that the end of the servo arm is cut off. So he was using the middle hole.

I don't think this is a mechanical issue, I think the elevators are not working due to some kind of radio issue. Its just flying along and all of a sudden - no elevator control. It doesn't make a lot of sense because we're all using different receivers. BTW I installed the chokes, but it happened to me on Saturday and as I reported, I managed to regain control just in time.

Here's a pic of me doing a knife-edge pass. It will hold this all the way down the line.

[xviper]

I think there has not been a single crash report (with jets nose-diving like that) with CG shifted back, but I may have missed it. Please help me on that!

I wish I could find that evidence but I can't. I just seem to recall that one crash was with the CG set aft but that's just my bad memory or I dreamt it. If I come across it, I'll post it up. I'm not concerned about "jets", just this one but I'm sure that's what you meant.