Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[mshagg]

While there are several factors in play for sure, I dare say Fred's video and the previous pics we've seen of the same effect, is pretty darn definite.

For sure, the root cause appears to be extreme force in certain situations. I guess it's the mode of failure which is the question. Servo overloaded? Mechanical binding? Surface effectiveness when it takes on the shape of a bannana? Regardless, efforts to support this area of the fuse should head most of them off.

I wont be flying mine without a camera pointed at the h. stab that's for sure. If she goes in, she'll at least get us some data in the process!

[leithalweapon]

Best advice I can give is to have someone stand next to you and make sure the flaps are only deployrd at slow speeds. If you do feel a loss of control in a dive go for the flap switch first. This way you will learn to not use the flaps improperly and never experience this problem on this plane or any other.
Seems like too many people are discouraged from flying theirs.

[fredmdbud]

Nope, and anyone who tells you otherwise is being disingenuous.

Plenty of good ideas but no definitive explanation for the crashes and thus, no sure fire way to avoid them. Xviper may be on to something in seeking solace in the occult.

Knife Liddle's video seems to say otherwise - upgraded to 8S, CG set back 10mm, upgraded (HS-5245MG) servos and elevator rods, and 3mm reflex on flaps (basically some supplemental up-pitch):

[GliderGuy]

Impressive - His flaps tore off in the first 30 seconds thus avoiding the realm of high speed w/flaps down.

LOL


-GG

[HellHathNoFury]

I don't not read any definitive solutions or reasons why some MiGs are doing the dirt dive. So far, I see only theories and visualizations as to what solutions may be for unknown problems. I'm going to start flying this thing with a bible in one pocket, a horseshoe in another and my lucky rabbit's foot hanging from my neck.

Don’t forget..A Wing & a Prayer

[RCjetdude]

Knife Liddle's video seems to say otherwise - upgraded to 8S, CG set back 10mm, upgraded (HS-5245MG) servos and elevator rods, and 3mm reflex on flaps (basically some supplemental up-pitch):

What the heck?!?

[xviper]

Knife Liddle's video seems to say otherwise - upgraded to 8S, CG set back 10mm, upgraded (HS-5245MG) servos and elevator rods, and 3mm reflex on flaps (basically some supplemental up-pitch):

From the looks of the video, his MiG was going under full power as fast, if not faster than some of those "crash dives". I'm starting to think that high speed, coupled with flaps, is something we should be concerned about. High speed alone doesn't seem to be it. He was able to pull up with ease when flying really fast. Still doesn't explain the low/medium speed crashes.

[GliderGuy]

From the looks of the video, his MiG was going under full power as fast, if not faster than some of those "crash dives". I'm starting to think that high speed, coupled with flaps, is something we should be concerned about. High speed alone doesn't seem to be it.

That’s what I am seeing in the non-crash part of Fred’s video. Looks pretty normal.

Case in point...I blast around at full power for a time on each flight and never had even a hint of non response. Now with the CG back 15 mm and 80% less FFS trim and on the inner servo arm hole, I feel even better. This includes an occasional full power coming down from on high, too. Luck? I doubt it.

The speed bear, if it exists, has had plenty of opportunity to bite me with the number of flights on this MiG.

-GG

PS - I avoid putting flaps down until setting up for a landing at less than 1/2 power. After Fred’s video, I am putting the gear down first now. Then flaps!

Disclaimer: Historic results are not an indicator of future performance.

[mshagg]

They all fly well until they stop flying lol.

But I concur, I've pulled full up elevator at 215km/hr with these big hitec servos and it changed direction so abruptly the tail was skidding just like the full scale ones. Not a hint of hesitation, flex or mushiness.

Which is the puzzling bit, when some have gone in just setting up for a flat pass along the flight line.

[HaroldAnderson]

What the heck?!?

The landing sounded like a good one but we'll never know. 🙄
Adjust that hatcam!

[fredmdbud]

From the looks of the video, his MiG was going under full power as fast, if not faster than some of those "crash dives". I'm starting to think that high speed, coupled with flaps, is something we should be concerned about. High speed alone doesn't seem to be it. He was able to pull up with ease when flying really fast. Still doesn't explain the low/medium speed crashes.

The crashes with no flaps (RCPlaneReviewer, Flight6677) indicate that the 23g upgrade servos are marginal - my flaps-down flight basically pushed the load on the elevator servos over the top.

Yes, flying with flaps outside their normal use (take-off, landing, slow/dirty passes) is ill-advised, but upgrading to higher than the 23g (3.4kg-cm -> HS-5245MG 4.4kg-cm) gives more margin in flaps-up high-speed flight. Flaps-down dives with the upgrades, I'd say, would still be a risky proposition. The number of crashes has seemed to diminish, along with increased business for higher-torque servos (e.g. HS-DL100/150, etc - I spoke with the guy who sells these).

[RCjetdude]

After reviewing all the Mig crash videos and reading through all the comments concerning possible causes, I have come to a conclusion...

[xviper]

If I could find servos that are much higher torque and still have them fit in the same hole, I'd consider it. Flying at my altitude, my MiG doesn't seem to be that fast, so I'm less worried about power dives, nor am I too worried that I forget to lift the flaps up before doing so. Looking at those servos, after about 23g, they seem to jump into the next size category. I guess I'm just not looking in the right places. I don't want to be reaming out the servo holes.

[GliderGuy]

xviper- These have been discussed as drop in upgrades:

https://www.promodeler.com/DS150CLHV

I have a 6 ch, so the below is based on that. If you have an 8 ch rig, then these might be your path.

However, I see they draw more current at stall which may lower the voltage back there unless you upgrade the wiring. Also, a reverse servo option is not offered, and the internal potting precludes a hand re-wiring. Thus, an external server reverser circuit must be used....introducing another layer of potential failure. Prior posts do not recommend using add-on reverse circuits.

Thus, I backed away. Must wait for a TX/RX upgrade. Also...not a huge increase in torque, but better than the MRC upgrades at 4.8V. Read the spec sheet carefully.

-GG

[mshagg]

Promodelers strike me as the most superior option on paper, although to get the most out of them (and to get your money's worth coz they aint cheap) you'd want to run them at high voltage which, given the constraints of the BB, means running a second (and isolated) HV BEC for the elevators.

But yes, there's a decent jump in torque when you go to the next servo size up. Thankfully not a decent jump in price, either.

[xviper]

xviper- These have been discussed as drop in upgrades:

https://www.promodeler.com/DS150CLHV

I have a 6 ch, so the below is based on that. If you have an 8 ch rig, then these might be your path.

However, I see they draw more current at stall which may lower the voltage back there unless you upgrade the wiring. Also, a reverse servo option is not offered, and the internal potting precludes a hand re-wiring. Thus, an external server reverser circuit must be used....introducing another layer of potential failure. Prior posts do not recommend using add-on reverse circuits.

Thus, I backed away. Must wait for a TX/RX upgrade. Also...not a huge increase in torque, but better than the MRC upgrades at 4.8V. Read the spec sheet carefully.

-GG

Thanks for the link. Those would add $110.00 US to the plane. I have no problem with servo reversers. I've been using them quite liberally for many years without a single incident. Plus, I've been using the cheap HobbyKing reversers and none have glitched. At this point, I'm flying on what mods that have been presented. None have cost any money. I really don't want to start making this plane more expensive than what it already is. If I was into that ball park pricing, I would have gone to the next level, that being one of the HSD models, but I'll bet even there, people will still find deficiencies. For the time being, the lucky rabbit's foot will have to do, until the real cause of these failures is found. I guess I'll just keep flying it till it won't anymore for whatever reason.

[paulrkytek]

I am not buying this plane mainly because I dont like hauling 6kg around and about 4kg is my comfort limit and I am happy enough with my other Freewing jets but I have read with great interest all the posts since it came out and have yet to reach a conclusion and probably never will . Reading all the posts and watching countless videos has been a good, thought stimulating way to kill time in retirement and although I have learned a lot reading all the posts the only thing I am certain about is that things can get overcomplicated and overthought. I enjoy the hobby, people fly for different reasons so good luck them all. I like to scratch build, build from kits, assemble and fly and watch planes fly and I doubt I will ever tire of it but I just accept the following
1. If I design and build and it looks good to me and flies as I intended, great, if it does not that`s ok, try again , modify or build something else.
2. If I buy a plug and play plane and I fly it and crash it my first assumption is that somewhere along the line I had brain failure either when I assembled it or set it up to fly or the way I flew it, though much less so nowadays as I spend a lot of time on the flight sim and watching videos before I fly. Going down the line I Iook at servo and radio failure, electrical systems failure.
Many years ago you could buy a kit, assemble a plane as per instruction and watch the wings fold into 2 the first time you flew it, boy have things moved on since then and we expect a great deal more from our models each year and 90% of the time the main manufacturers get it right but I still look at everything I buy and if the hairs stand up on the back of by neck when I look at how the plane is made, designed, assembled and especially how and where it is strengthened and I will modify it so that I am happy and I accept that if I do that then be it on my own head. I dont expect every plane to be all things to all man.
Philosophically speaking my thought are this :
1. if you think you cannot fly it dont buy it
2. I you cannot afford to bin it dont buy it
3. If you alter it and bin it, thats the way it goes.
4. If a manufacturer sends you a free upgraded part do the hairs on the back of your neck stand up, if not fly it, if they do then fly something else until you are truly happy .
5 . Its a hobby, relax enjoy it. whilst you can.

[Yellowbird911]

It may be in here somewhere but can't find it. Has anyone had an uncontrolled dive that have upgraded to higher torque servos. Not the Freewing higher torque but something with 2 to 3 times the torque. The fellow on Youtube that put a K55 in his has got to be doing over 125mph but has larger servos.

[Yellowbird911]

Here is the link to the STL files for the Centerline tank if anyone is interested. Is on Thingiverse also but they haven't processed the files yet. It hold 41oz of fuel in the forward section. PM me if you have any questions.

https://drive.google.com/folderview?id=1RD3kLa4ameRxlmXFmEPeQoCYHNVN7Eu7

[GliderGuy]

It may be in here somewhere but can't find it. Has anyone had an uncontrolled dive that have upgraded to higher torque servos. Not the Freewing higher torque but something with 2 to 3 times the torque. The fellow on Youtube that put a K55 in his has got to be doing over 125mph but has larger servos.

Careful....The answer to the question may be too limited in scope. Guys upgrading are likely also not going to fly in the realm that has been shown to cause problems.

The solution may end up being a “this and that” in combination. Not just a one item solution.

-GG