Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[nuts-n-volts]

I apologize for posting this again, but imho... I still see this as less than stellar engineering of the voltage used to power the system, including inadequate wiring in long runs. The retracts are the root cause as they can only be operated at less than 6V (5.1V optimal). These limit what the blue box can handle and any connected servos as well. I separated and run all flight controls from an 8.4V LiPo with heavier extentions, better servos. I isolated the bec and the blue box on 5.1V only running retracts and lights. I can load up the system with full flaps, full throttle, gear, and lights with no sign of low servo power. Balanced tailerons, carbon pushrods, better ball links round it all out. Stiffen foam if you feel it needs it. There's also the issue of non-scale taileron pivot points that increase aerodynamic loads back there dramatically. Angled back and aerodynamically centered pivots as on the full-size reduce the loading to the servos had they chose to incorporate. AND, the misaligned thrust angle, which I'm currently trying to get back to work on and correct. (Sometimes life gets in the way!) Can't wait to get back to it.

To correct all these issues at the factory would increase the price as it is now. Most of these don't need to be addressed and can be flown with pilot care, knowing the different idiosyncrasies. I say this as many 29s are still flying basically stock. More power to ya! I put it to each owner that "it is what it is" and to solve the problems in his own way (not necessarily mine). For the most part, the jet is certainly flyable and looks great.

As these foam jets have gotten bigger, heavier, and faster, the loads increase. It's a no brainer. You won't catch many turbine guys running low power stuff or inadequate set-ups... at least not for long!

[xviper]

If you're a veterans r.c. modeler. All these changes are obvious.

Also to an intermediate modeler. I'm not sure that a novice or beginner should be getting this plane. It even says so in the web page.

Wow,

I guess you learn something new every day (if you allow yourself to)! Slow flap deployment as a cause for failure/crashes/bad juju? That's definitely a new one on me! Frankly, I'm having a hard time reconciling that. In my simpleton mind, it seems something else is the root issue if slowing flap deployment does something bad. Side-note, has anyone had or reported issues with missed approaches (full throttle with full flaps already deployed)? I think the fact that my engine has a spool-up delay will probably help a bit since my airframe doesn't see instant strain from the thrust.

Do I understand that the new kits include 30gr servos and all these hardware upgrades? Am I reading that right?

I think you may have missed a critical piece of information. It's not the slow flap deployment that is the cause of these "few" crashes. Slow flap deployment can tax the digital servos that run them, although many have slow flaps with this plane and not had an issue. It's already been said that a 2 second deployment isn't going to be a problem. It's when guys set their flap deployment time to over 7 seconds that could create issues with the servos. It's using full flaps at a high airspeed that has been suspect. When you are coming in for a landing with flaps and need to do a go around, your airspeed is not very high (or at least, it shouldn't be). You pour on the coals and still have time to pull the flaps up before airspeed increases to a point where it might interfere with elevator function.
I think it's the misunderstanding of, or the overlooking of some of the posted information that can lead to rumours (incorrect ones) running rampant.

[Evan D]

Slowed servo issues have been noted on the forums for a long time, back when the Avanti was introduced a lot of people noted flaps, usually just one, wouldn't retract after extending or one wouldn't extend... The reason was determined to be the slow function in our radios though I still think a lot of people didn't have their ATVs adjusted right and the flaps when up were straining the servos. Later a few had flap issue on the 90mm F-18 but I think most agreed that it was due to too weak a servo.

I don't think many reports of flap issues with the MiG have been reported, it's been assumed it's the elevator servos that have been the issue but there has been a lot of speculation as to why and most agree it's the design of the stab, aerodynamic and mass balance points, and that using stronger servos along with linkage, horns, etc are the way to correct for it.


Yes, Tom is saying there will be a kit included inside the box on MiGs sold, at least from Motion. You will need to remove the stock servos and put in the upgraded ones as well as remove the stab control horns and install those.

[Airguardian]

Side-note, has anyone had or reported issues with missed approaches (full throttle with full flaps already deployed)? I think the fact that my engine has a spool-up delay will probably help a bit since my airframe doesn't see instant strain from the thrust.

Shaun, the problem is not throttle but speed. Flaps couldn't care less about your throttle setting. You can go slow with full thrust and nothing bad should happen. It's the act of deploying flaps at speed that causes stab problems on the MiG, as the flaps change the angle of incidence of the airflow over the stabs. The more you deflect them, the bigger the aerodynamical load that the stabs need to cope with (and in turn, the servos).

Of course, one may point to a relation between throttle and speed but that it's not a direct relation.
Think of high alpha flight, throttle may be at 100% and the jet would still be flying very slow.
I am pretty sure that Tom meant 'throttle' as a 'simplification' of speed.

I'm talking about a matter of fact as-is, not redesign. Would an aerodynamic fix work in post-stall when the surfaces aren't effective?

You are wording this a bit cryptically and I don't think I really get your point. Thrustline is totally off in post-stall too.
You angle the jet nose up, bring it to 0 speed, add full throttle and the jet backflips. Current angle is neither working in post-stall, nor in forward flight.

Maybe an intelligent way of dealing with the pitch-up it is offering 3D STLs with a variety of angles to suit different CGs? Hmmmmm.

Thrustline should NOT be changed with CG unless you are shifting CG vertically.
I guess you are asuming that you partially compensate for for wing/airframe pitching moment with thrust and that is a terrible solution for a number of reasons.
Mainly because it's highly speed dependant. Wing/airframe pitching moment increases with speed while thrustline pitching moment decreases with it, so any adjustment to that with thrustline is bound to cause erratic behavior of the aircraft with speed changes.

And the correct answer is to use stab trim (and/or airfoil reflex) instead. It is also depending with speed but the behavior is much less erratic as both wing and stab pitching moment change accordingly with speed (albeit with different distances with respect to CG, thus having different degrees of leverage). This is also one of the reasons why neutral CGs are interesting because the trim required diminishes and aircraft behave more linearly with speed.

Or just buy the TV units and set the TV pitch trim for the desired angle at neutral.

Of course, that's a solution but I was thinking about those that don't want to use TV units, they may want to benefit from a proper thrustline too, don't you think?

Here's an idea - why not set your plane on a plane balance stand at one CG point, and see how much pitch induced at a certain throttle setting. Then change CG, rebalance on the stand, and see if there's a difference in pitch at the same throttle setting?

Thrustline induced pitching moment cares about 'vertical distance' to CG, not horizontal, which virtually doesn't change when moving CG forward/aft (It does by an infinitessimal amount to be precise, and can pretty much be ignored). And if thrustline is actually aligned with CG (not always possible or ideal), then shifting CG forward/aft actually has 0 contribution to how thrustline affects aircraft pitching... because it's always neutral (zero).

Then do the same with another plane, like the F/A-18, where the thrustline aligns with the centerline of the fuselage?

No it doesn't. Freewing's Hornet has a terrible thrustline, pushing the nose of the jet down when adding throttle. It's been acknowledged by a number of pilots and you can test it out yourself if you still have your jet around.

[fredmdbud]

Wow,

I guess you learn something new every day (if you allow yourself to)! Slow flap deployment as a cause for failure/crashes/bad juju? That's definitely a new one on me! Frankly, I'm having a hard time reconciling that. In my simpleton mind, it seems something else is the root issue if slowing flap deployment does something bad. Side-note, has anyone had or reported issues with missed approaches (full throttle with full flaps already deployed)? I think the fact that my engine has a spool-up delay will probably help a bit since my airframe doesn't see instant strain from the thrust.

Do I understand that the new kits include 30gr servos and all these hardware upgrades? Am I reading that right?

It's not the thrust setting but the airspeed that determines when the flaps start affecting the stabilators - you can maintain full thrust from a missed approach until you reach the desired approach altitude in an expedited climb.

[Dirty Dee]

Flew my MiG today and had some scary signal lockouts that almost gave the plane a permanent dirt nap. First flight I was ~20' flying level when the plane suddenly had full down elevator and bounced off the grass. Broke the pitot tube and scuffed the bottom a fair bit, but it could have been worse.

4th flight, I had sudden signal loss and it was nosediving into the field. but thankfully I regain control last second and I was able to pull back out into almost a hover, and bring it around for a landing. Some guys at the field noticed a plume of dust from the plowed field, so I must have been very close!

It was a field boundary orientation day, so a bunch of people were using radios to let flyers know if you were getting too close to the restricted boundaries, so I wonder if that could have contributed to the lockouts? I'm going to relocate my receiver and satellite a bit further from the packs and blue box, and install some RF chokes.

Besides that, was a good flying day, and the new livery is nice and visible

[fredmdbud]

Flew my MiG today and had some scary signal lockouts that almost gave the plane a permanent dirt nap. First flight I was ~20" flying level when the plan suddenly had full down elevator and bounced off the grass. Broke the pitot tube and scuffed the bottom a fair bit, but it could have been worse.

4th flight, I had sudden signal loss and it was nosediving into the field. but thankfully I regain control last second and I was able to pull back out into almost a hover, and bring it around for a landing. Some guys at the field noticed a plume of dust from the plowed field, so I must have been very close!

It was a field boundary orientation day, so a bunch of people were using radios to let flyers know if you were getting too close to the restricted boundaries, so I wonder if that could have contributed to the lockouts? I'm going to relocate my receiver and satellite a bit further from the packs and blue box, and install some RF chokes.

Besides that, was a good flying day, and the new livery is nice and visible

If there are significantly more fliers than usual, not a bad idea to rebind TX & RX so a better set of channels are selected in the noisier environment.

And yup, RX spatial and orientation diversity certainly helps. Pick locations where there is minimal chance all receiver antenna get shadowed by ESCs, PCBs, etc, at any plane orientation.

[fredmdbud]

No it doesn't. Freewing's Hornet has a terrible thrustline, pushing the nose of the jet down when adding throttle. It's been acknowledged by a number of pilots and you can test it out yourself if you still have your jet around.

A pitch-down moment is better than a pitch-up one. And yes, I still have mine around, probably for that reason when I played around with aft-CG.

[Airguardian]

I didn't compare up vs down. Both are bad.

[Hugh Wiedman]

Flew my MiG today and had some scary signal lockouts that almost gave the plane a permanent dirt nap. First flight I was ~20" flying level when the plan suddenly had full down elevator and bounced off the grass. Broke the pitot tube and scuffed the bottom a fair bit, but it could have been worse.

4th flight, I had sudden signal loss and it was nosediving into the field. but thankfully I regain control last second and I was able to pull back out into almost a hover, and bring it around for a landing. Some guys at the field noticed a plume of dust from the plowed field, so I must have been very close!

It was a field boundary orientation day, so a bunch of people were using radios to let flyers know if you were getting too close to the restricted boundaries, so I wonder if that could have contributed to the lockouts? I'm going to relocate my receiver and satellite a bit further from the packs and blue box, and install some RF chokes.

Besides that, was a good flying day, and the new livery is nice and visible

In an effort to beat GliderGuy to the punch, have you put any ferrite chokes in as he has so often mentioned? I've become a disciple of his teachings and must say since then, plus adding satellites and keeping the main active portion of the antennae away from any electronics, I've noticed my signal has become much better, with very few frame losses and no signal holds (yes I check every plane after every flight). At least it was only minor damage!

[Dirty Dee]

Hugh Wiedman no chokes, yet, but I have a box of them from when I installed them on my SU-35 so the MiG will be getting that treatment.

[fredmdbud]

An interesting read: ADB165245.pdf (dtic.mil)

• "Evidently the aircraft does not automatically trim to 1-g flight as does the F-15/16/18 class of fighters, since I recall having had to trim during airspeed transients both during the loop and at other times during the flight."
• "I needed to apply continual pitch trim inputs to keep the stick forces zeroed out during airspeed transitions."

Different speeds, different throttle settings, trimming required.

S-3 pilots I've spoken with often mention the need to constantly re-adjust trim with changes in throttle.

So it does not appear probable that there is such a thing in real practice as an ideal thrust line that does not require some trim with power. Perfect balance in the static case is not identical to non-stall conditions, with contributions by aerodynamics and the control surfaces.

Looks like the only thing that can ensure a post-stall recovery (without TV) is altitude - cut back throttle and let the plane regain speed and get out of the stall envelope.

[GliderGuy]

In an effort to beat GliderGuy to the punch, have you put any ferrite chokes in as he has so often mentioned? I've become a disciple of his teachings.....

Hugh is not a paid spokesperson....

DD....glad it was not worse.

Seriously, if the RF chokes save even one ship....it has been all worth the effort.

-GG

[Hugh Wiedman]

Hugh is not a paid spokesperson....

-GG

We need to revisit that! "Will Work Cheap for RC Products"
My Mig is coming on Monday and the majority of upgraded items RudyD54 recommended that he's using are being shipped as well. Just got some custom graphics delivered from Callie for this one and a 2nd Hornet. Guess I'll be busy for the next couple months.

[Airguardian]

In an effort to beat GliderGuy to the punch, have you put any ferrite chokes in as he has so often mentioned?

I have. Two on the horizontal stab leads, two on the ESC leads to rx. Four in total.

An interesting read: ADB165245.pdf (dtic.mil)[LIST]

Thanks for that link!

Different speeds, different throttle settings, trimming required.

Of course, I have not disputed that at any point. I think you didn't read well my comments. But you want to limit the amount of trim you need to use for the plane to fly level, and the speed ranges of full scale aircraft are an order of magnitude bigger than on our model aircraft, yet still the deviation is typically not so crazy. I am used to flying the Su-27 on DCS and I know perfectly well one has to be retrimming the aircraft constantly, that's besides the point.

S-3 pilots I've spoken with often mention the need to constantly re-adjust trim with changes in throttle.

Throttle... or speed?
Then again, an S-3 has underwing nacelle mounted engines, it's not quite the same as what we have on MiG, Su, Hornet... different limitations apply and it's not an aircraft meant to be super-maneuverable either.

So it does not appear probable that there is such a thing in real practice as an ideal thrust line that does not require some trim with power. Perfect balance in the static case is not identical to non-stall conditions, with contributions by aerodynamics and the control surfaces.

This I agree with, it's not the same scenario.
We know from the Su-35 experience in particular that the thrustline for level flight and hover are pretty different.

You are still missing the point:
- If anything, by design thrustline has to compensate for asymmetries in vertical drag profile, not forward/aft shifting of CG.
- Most of the trimming required on the aircraft through different speed envelops are to do with imbalance in pitching moment between wings/airframe and stabs, that's the major driving point for required trim. Again, little to do with thrustline.
- The degree to which the FW MiG-29 and F-18 thrustline are off is huge and very far off what should be expected from a scale perspective.

Looks like the only thing that can ensure a post-stall recovery (without TV) is altitude - cut back throttle and let the plane regain speed and get out of the stall envelope.

With this I also agree.

[kallend]

To those putting RF chokes in the servo leads. . .

Are you trying to prevent noise entering the receiver, noise entering the servo, noise on the signal line, noise on the power line, or something else. And what is the source of this noise, EM from the EDF/ESC?

Has anyone put a 'scope on any of the wires to see what's really going on?

[GliderGuy]

To those putting RF chokes in the servo leads. . .

Are you trying to prevent noise entering the receiver, noise entering the servo, noise on the signal line, noise on the power line, or something else. And what is the source of this noise, EM from the EDF/ESC?

Has anyone put a 'scope on any of the wires to see what's really going on?

Weeellllll.....Some key considerations are:

- My HAM radio friend who put me on to these said the these high current ESCs generate RF noise which is then radiated by the wires coming from the ESC. He suggested my F-4 and A-10 crashes “might” be due to this noise....especially since I never had issues with the low current ESC planes. He also said keep the chokes as close to the ESC as possible for those chokes.
- Other HAMs in this thread have also agreed with my HAM friend’s assessment.
- I have had no radio related crashes since I installed them....thousands of flights (F-4, MiG-29, AL37).
- The RF chokes are cheap, easy to install.
- Prior to installing them, lost an F-4 and an A-10 twice (once repaired) due to no response to control inputs
- All this with the same radio TX/RX type.

To your question, I am unaware of any measurements made. But Hugh’s “checking” showing improved signal with no frame drops (I defer to Hugh for details) and my personal results of “radio related crashes before RF chokes” and “none-zero-zip crashes since I began installing them” Is all the “reason” I need....sans any RF scope measurements.

F-4 = 3 chokes / two on the ESC forward side and an extra (probably overkill) near the green ferrite ring on the throttle line
AL37 = 7 chokes (probably overkill...but can’t hurt) / 4 on the ESC (both sides because it was easy to do....the motor side of the ESC is 3-phase and low noise). So, probably not needed on motor side, one near the green ferrite ring on the throttle line, and one near each elevator servo....did not worry about the rudder.
MiG-29 = 8 chokes / two on each ESC, one near the green ferrite ring, one near each elevator servo, and the one supplied by Futaba on the SR-10 servo reverser which drives the MKS HV69 servos

Food for thought.....no radio related crashes with RF chokes!!!

Cheap, light weight, easy to install, good results with them...measurements (beyond experimental results) may be unnecessary.

-GG

[Epsilon83]

For those who like tinkering and have Arduino knowledge, I have a channel expander design that will add 6 channels to an AR630, AR631, AR637T (or an AR8360T) and I am willing to share my version of the code (a modified version of the code posted on Github by kambalunga from RCG). It uses an Arduino Pro Mini + one Schottky diode, so the cost is minimal, around US$6

For those willing to wait, the FCC has details of a new Spektrum 10 channel stabilized receiver, https://fccid.io/BRWSPMAR10360T/User...Manual-4950535

Is there a build log or anything? Very interested in building one!

[kallend]

Weeellllll.....Some key considerations are:

- My HAM radio friend who put me on to these said the these high current ESCs generate RF noise which is then radiated by the wires coming from the ESC. He suggested my F-4 and A-10 crashes “might” be due to this noise....especially since I never had issues with the low current ESC planes. He also said keep the chokes as close to the ESC as possible for those chokes.
- Other HAMs in this thread have also agreed with my HAM friend’s assessment.
- I have had no radio related crashes since I installed them....thousands of flights (F-4, MiG-29, AL37).
- The RF chokes are cheap, easy to install.
- Prior to installing them, lost an F-4 and an A-10 twice (once repaired) due to no response to control inputs
- All this with the same radio TX/RX type.

To your question, I am unaware of any measurements made. But Hugh’s “checking” showing improved signal with no frame drops (I defer to Hugh for details) and my personal results of “radio related crashes before RF chokes” and “none-zero-zip crashes since I began installing them” Is all the “reason” I need....sans any RF scope measurements.

F-4 = 3 chokes / two on the ESC forward side and an extra (probably overkill) near the green ferrite ring on the throttle line
AL37 = 7 chokes (probably overkill...but can’t hurt) / 4 on the ESC (both sides because it was easy to do....the motor side of the ESC is 3-phase and low noise). So, probably not needed on motor side, one near the green ferrite ring on the throttle line, and one near each elevator servo....did not worry about the rudder.
MiG-29 = 8 chokes / two on each ESC, one near the green ferrite ring, one near each elevator servo, and the one supplied by Futaba on the SR-10 servo reverser which drives the MKS HV69 servos

Food for thought.....no radio related crashes with RF chokes!!!

Cheap, light weight, easy to install, good results with them...measurements (beyond experimental results) may be unnecessary.

-GG

Thanks, but I wasn't asking about chokes in the ESC leads (which seem like a good idea). Some people are putting them in the elevator servo leads, and that is what I was wondering about.

[kallend]

Is there a build log or anything? Very interested in building one!

Here