Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[janmb]

TV upgrade added kiddies... Coming soon...

https://www.motionrc.com/products/fr...or-upgrade-set

Awesome!

Based on Justin's feedback, the vectoring set has officially been promoted from a nice to have/funny feature to a must-have in my book, so cannot wait.

By all means, was going for VT anyway, but it is important to remember that they also add a fair bit of risk mitigation in all slow phases of flight.

[janmb]

Dan B I balance everything with the gear down, its the first and most critical phase. This includes any of the giant scale warbirds I build, turbines, or foam edf's.

Depends entirely in which direction the gear shifts cg when retracting.

For my part, I don't really ever measure the balance this way at all, expect for initial builds/maiden. After that, cg is just something I adjust in increments based on how the model actually behaves.

Even though I've found the majority of these edf's are way nose heavy per the manual, the wheels retracted adding a little more nose weight isn't going to be a big deal. I would rather deal with a crappy flying nose heavy jet, than holding on to a tail heavy one.

Most are indeed fairly nose heavy if set up per manual.

As for nose heavy vs tail heavy, that depends a bit on the model type. Some models are every bit as nasty when nose heavy as tail heavy - just two different versions of bad.

Not sure if the MiG is troubled by this, but at least the SU-35, which has a fairly similar geometry, has a few really nasty quirks when nose heavy.

[f4u ausie]

Aaawsome pics Mr lamb mrsolt. Looks like the real deal moon and the sun wow

[JLambCWU]

Good info.

Regarding servos, please give up already. We have far from enough data to know how well the marginal stock servos hold up

Your comments are insanity.

Please address the following for the entire crowd from your wealth of knowledge with flying the model.

A. Have you even flown it?

B. How many flights do you have on it?

C. How many flights do you have on other twin 80mm birds?

D. Did you design and or test fly the model?

E. Have you bothered to listen to THE DESIGNERS twitch stream, where he SPECIFICALLY addresses, and then REFUTES what you CONTINUE to repeat in your comments?

https://www.twitch.tv/videos/742367908

Alpha Enos (Who designed and test flew the model mind you) specifically addressing the servo issue here. It starts at the 48 min mark.

[Evan D]

It's just not worth arguing with him...

He even argues your opinion that it flies good is wrong. I agree with you by the way, it is a good flying plane. I think his arguments about how he will fly his Gripen are more laughable like everyone should fly their planes in a scale manner as he does.

[Lcacing]

[Evan D]

I have an alternate theory...

Since it appears that every crash has been with the pushrod on the outer hole and since Motion has cut off the outer hole we can establish without doubt that the issue is not the servo itself but in FACT the servo arm (of course we have to ignore that the instructions say to have it on the middle hole as the opposition is).

It's all physics after all, right?

[GliderGuy]

Howdy,

First, the MiG-29 is a wonderful plane to fly, and congrats to all the Freewing designers and team members for a super nice design.

Second, BEEEEE CAREFUL as has been stated before. Every plane has its quirks.
As we share here (all opinions welcome), we have the opportunity to learn, and THAT'S what's important. Crashed birds should be avoided. ALL your inputs help achieve this important goal (one of many goals for sharing knowledge/ideas).

I want to go back over my falling leaf experience in more detail because this somewhat started the conversation.

Oh yes...My background, for those who might ask from whence I speak:

• RC pilot since late 1960s
• Multi-thousand hour private pilot in both ASEL and gliders / soloed at age 15 in a sailplane
• Two 1000 km straight line distance flights in a sailplane
• Climb to 30,000 ft MSL in a sailplane in a wave over Pike's Peak
• Acrobatic training in a Citabria
• RC planes flown: Ugly Stick with a SuperTiger 60, various sailplanes, Beaver, F-4U Corsair, F-4 Phantom, P-38, AL37, MiG-29
• Well over 1000 R/C flights to date in 2020 (not bragging....just setting the facts)

While my MiG experience was NOT A FLAT SPIN, I have personally been through an inverted flat spin in a sailplane over Colorado at 20,000 ft with an Air Force Academy instructor in the rear seat of the glider. This was an unintentional flat spin as a result of my then 19 year old brazen self wanting to show off my acro skills to the AFA instructor. LOL...a whole other story. But, I can personally state that in such a situation, there is no control authority of any type on any axis. My situation was worse because of the full flying tail design of the sailplane. i had managed to stall the tailplane. It was gone, in terms of effectiveness. Post flight analysis with the instructor showed we were also balanced on the aft CG limit. The recovery (nose drop) was eventually a result of opening the very effective dive brakes. No other control had any effect. The instructor was calling out the altitude and telling me, "You got yourself into this mess, now get us out of this mess." Pucker factor = infinity and, yes, we were wearing chutes....but didn't need them.

MiG set up is by the book. Spot on the CG mark, twin Admiral 6000s, one in the middle and one in the rear bay, throws are by the book, all control horn connections by the book.

I will state again...My falling leaf was NOT a flat spin situation. There was no rotation about the yaw axis.

What was I doing?

• Overhead pass at 1/2 throttle (yes conservative....my new servos come today...THANK YOU MRC for these...Awesome Company!)
• Intent was to do a hammer head stall (ok...the maneuver is not truly a stall per se if done correctly)
• Gentle pull up to the vertical, and as the plane slowed...I applied rudder to start the rotation of the nose toward mother earth
• The hammer head was initiated at a high altitude after the pull up from cruise speed...estimating about 300 ft AGL (thank goodness!!!!!)

What happened?

• My timing for the rudder application was too late and I got the MiG too slow
• The MiG departed controlled flight (I cannot recall exactly what she did)
• The MiG quickly settled into a stable falling leaf (gentle wing rocking), no rotation about the yaw axis, positive nose up about 5 degrees...maybe 10 degrees
• Started descending toward Mother Earth

What was I experiencing?

• Absolutely zero response to any control, except throttle. I will stress that there was NONE for the aileron. Not possible to do a roll. I tried.
• The MiG was heading north and away from me and getting smaller and smaller and smaller and lower and lower and lower
• The urge to soil my pants and an elevated heart rate.
• Flashbacks to the sailplane experience
• A MiG going 'THAT A WAY" and getting smaller and smaller lower and lower

What was I thinking?

• Power it Out! Guess what? That didn't work and likely was the reason my nose was staying at a positive up attitude.
• Roll it over to get the nose down. That didn't work.
• Rudder it over to get the nose down. That didn't work.
• Elevator full nose down...no response (probably where I made my mistake...shoulda held full down elevator instead of relaxing it after it didn't respond)
• YOU ARE GONNA CRASH....kill the power to minimize the damage

What happened?

• When I chopped the power (I think this is what did the trick), the nose dropped
• Applied power to climb and GOT RIGHT BACK INTO ANOTHER FALLING LEAF....DAMN! Too aggressive of power application!!!!!
• Somehow got the nose back down and gently applied power until I knew she was flying (now a VERY small plane almost below the trees between me and her)
• Got her back up and headed home to a safe landing. Bless you Futaba for having such good "down low" range
• Completed the "REALLY Far Distance, Down Low" radio range check...and passed

And...now you know the whole story. Guys...be CAUTIONED that until a tried and true recovery method is discovered, you better be HIGH when experimenting with this flight characteristic. Based on my REAL pilot experience/training...an aft CG is only gonna aggravate this characteristic. BEEEEE CAREFUL.

Thanks for your time.

-GG

[Airguardian]

The jet becoming more responsive to flight surfaces when properly balanced is one of the main reasons for doing so in the first place. This is exclusively a Good Thing (tm).

LMAO, yes!

You can use counter-roll tailerons to stop spins though... do that with the Su-35 all the time (Of course you need to neutralize input once the jet stops spinning or risk inverting spin direction) :)

Here's some further thoughts on tailslide recovery:
Yes, as mentioned, cutting throttle off is paramount, but pushing nose down with the stabs isn't.

Yes, it can work out BUT that's not how the fullscale jets perform such maneuvers and there are reasons for it that also apply to our models (have experimented about that extensively with my Su-35 so can pretty much confirm empirically). To exit a tailslide, it's better to hold FULL-PITCH-UP and cut throttle, let the plane fall.

The reason is, as the jet starts falling and gaining negative speed (the wings and stabs have reverse flow over them at the beginning of recovery), the jet can OVERSHOOT the nose down to the point where it makes an inverted cobra. This is pretty usual if you happen to nail the right attitudes for the tailslide. Keeping pitch stick up guarantees that as the nose accelerates down towards the earth, it doesn't over-accelerate and flip the jet over, which is a REAL bad position to get stuck in with this jet. The fullscale aircraft may not even be able to recover from that inverted stall position without vectored thrust. People having experimented with the DCS Su-27 and flight computer assistance disabled will know what I'm talking about, hehehe... :D

Of course, once the jet starts nosing back down, you want to progressively ease on the stick pressure to get back to level flight, but while the plane is falling tail-first, stabs should be kept pitch up or neutral... at least if you are not using vectored nozzles. With vectored nozzles you can do what you please, lol.

My 10 cents ;)

I think every freewing Jet should have an optional tv upgrade like this. Its genius and gives the option for people to buy their jets with of without tv

Agree! :D
(At least on the airframes that are more suited to aerobatic flight)

I have found full throttle passes tend to suck this plane in a down Elevator manner.

That sounds to me like the thrustline may be off and pushing nose down.

Your comments are insanity.

Absolutely disagree.

Please address the following for the entire crowd from your wealth of knowledge with flying the model.

Absolutely irrelevant questions.

E. Have you bothered to listen to THE DESIGNERS twitch stream, where he SPECIFICALLY addresses, and then REFUTES what you CONTINUE to repeat in your comments?

He has, and so have I. I made the question myself if I recall correctly.
What Alpha replied and what Jan argues are not incompatible.

We have already made our points clear with this respect, I don't think there's much to gain by keeping to stir the pot. Let everyone form their opinions based on their own common sense from what has already been debated on both sides of the argument. ;)

[Airguardian]

I will state again...My falling leaf was NOT a flat spin situation. There was no rotation about the yaw axis.
[...]
The MiG quickly settled into a stable falling leaf (gentle wing rocking), no rotation about the yaw axis, positive nose up about 5 degrees...maybe 10 degrees

Started descending toward Mother Earth

At that point, keeping throttle on will make it worse as you already noticed.
In this scenario, and in opposition to what I previously said about tail-slide exit, I would leave neutral stabs rather than pitch-up or down, to force maximum 'area' on the tail end to force the nose down (as the jet is almost falling flat). The difference being that as the plane has already settled in terms of attitude, it has already bled the 'rotation energy' that could make it overshoot and enter a negative, belly-up stall.

Absolutely zero response to any control, except throttle. I will stress that there was NONE for the aileron. Not possible to do a roll. I tried.
[...]
Roll it over to get the nose down. That didn't work.[*]Rudder it over to get the nose down. That didn't work.

Elevator full nose down...no response (probably where I made my mistake...shoulda held full down elevator instead of relaxing it after it didn't respond)

There's another good reason to use tailerons. You could have used them (roll deflection) to induce yaw and force the jet into a nose-down attitude.

When I chopped the power (I think this is what did the trick), the nose dropped

Applied power to climb and GOT RIGHT BACK INTO ANOTHER FALLING LEAF....DAMN! Too aggressive of power application!!!!!

This actually talks good things about the jet's inherent stability and good high alpha handling IMO.
You also kind of want to have full-rates for this type of scenario (and why I usually reccommend to use full throws and more expo on jets, instead of limiting throws).
Limited throws may leave you helpless where otherwise recovering from the stalled maneuver may have been a no-brainer.

Will do experiment with this once I get mine! ;)

[leithalweapon]

We're not training for Top Gun. It's a model. Cheese and Rice.

[Jdcrow]

First off, glad you were able to recover the jet.
This was one of my cautions from my maiden flight report on Motion’s Mig-29, and Alpha later spoke to this on a live Twitch stream as well.

When exploited, this makes for some BEAUTIFUL power tail slides on the model, but invariably terra’firma will claim some as well for people that don’t give themselves a lot of altitude when performing them.

It is why I also cautioned people to fly the model at a more forward CG when trying this. (Yes that can mean on the marked CG markings) Keep working the CG further and further back until you find the limit. The limit happens to be around 3/4 of an inch aft of the marked CG for those who are wondering when flying light batteries. When you get aft of that, she will generally flip over on her back, usually dramatically, and then have elevator authority again from the increased airflow.

I said generally, not always. I got mine to almost an inch aft of the marked CG with light 4400mah RTs while doing some testing, and out of a nose high power stall she proceeded to do a rapid double back flip before settling back into her tail slide. Power to idle and a hard roll to the wing, and she dropped the nose and flew away. Power to idle alone would not recover the jet this far aft, you have to roll off on a wing. The pitch which was fine before when closer to being on the CG marks, was obviously hyper sensitive at this aft CG and required mid elevator rates (usually flying the jet on high) from take off to touchdown, and a very gentle thumb even on 30% expo to fly her back down in one piece. The double backflip and recovery took close to 200ft of altitude, so user beware.

I might also mention that mine has almost 30 flights on it now, and the stock 17g elevator servos have performed great when set up per the manual. This includes unscale rapid G onsets, negative and positive, from low to high speed. It also includes power dives with intentional pull outs 10-20ft over the runway, as well as falling leaf full deflection slams.

For those wondering. You can get her to CG 1/2” aft of the CG markings with 4400mah Roaring Tops right here, using the middle and aft bays. My jet has a sound system just slightly forward of the CG and RC Geek centerburners well aft of it. Moving the middle position battery aft allowed me to fly it with a CG around 1” aft of the markings.

okay....i keep seeing various batteries on the middle position. i just cant seem to get the aircraft to cg there.

Spektrum Smart 5000mAh 50c, which are spec'd at 660g each. I have to move the rear battery forward, and the front bay battery against the rear most wall to balance out.

in that configuration, gear down, it will just teeter nose down when lifted at CG marks, then gently settle level. (indoors, not wind impacted)

Anyone video their cg configuration and balancing?

[Evan D]

We have to remember that there are people who post in these threads that don’t have or haven’t flown the specific model. In some cases they never intend to buy it...

On the flip side there are those that are on here just to discuss the model and don’t care about the full scale plane or physics.

[xviper]

okay....i keep seeing various batteries on the middle position. i just cant seem to get the aircraft to cg there.

Spektrum Smart 5000mAh 50c, which are spec'd at 660g each. I have to move the rear battery forward, and the front bay battery against the rear most wall to balance out.

in that configuration, gear down, it will just teeter nose down when lifted at CG marks, then gently settle level. (indoors, not wind impacted)

Anyone video their cg configuration and balancing?

Spektrum smart batteries tend to be on the light side. I've always felt that with these smart batteries, we aren't getting a true mah and "C" rating as stamped on the label. The typical 5000mah, 6s batteries in my collection each weight between 750g to well over 800g - Gens Ace, ChinaHobbyLine, Turnigy HD, Admiral, Revolectrix.

[janmb]

It's just not worth arguing with him...

He even argues your opinion that it flies good is wrong. I agree with you by the way, it is a good flying plane. I think his arguments about how he will fly his Gripen are more laughable like everyone should fly their planes in a scale manner as he does.

1. I have never ever commented on how the mig flies or disputed anyone elses ideas about how well it flies. I despute Justin's ideas about the servos being proven to be fine. That is a completely different discussion and has nothing to do with how the model performs.

2. I wasn't aware I had commented on how neither myself nor anyone else will or should fly the Gripen.

[janmb]

Your comments are insanity.

Please address the following for the entire crowd from your wealth of knowledge with flying the model.

A. Have you even flown it?

B. How many flights do you have on it?

C. How many flights do you have on other twin 80mm birds?

D. Did you design and or test fly the model?

E. Have you bothered to listen to THE DESIGNERS twitch stream, where he SPECIFICALLY addresses, and then REFUTES what you CONTINUE to repeat in your comments?

https://www.twitch.tv/videos/742367908

Alpha Enos (Who designed and test flew the model mind you) specifically addressing the servo issue here. It starts at the 48 min mark.

A: No, and explained to you earlier from both me and others (Kallend etc I believe), nor is that relevant what so ever in terms of discussing what boils down to basic physics. The debate on whether or not servos are fine has nothing what so ever to do with your (or anyone else's) experiences when flying the model. On the flipside, if I have received my own model already and put 100 flights on it, that would NOT have given me any more or any less basis for an opinion on this particular issue.

B: See A

C: About 300. See A for relevance.

D: No, nor is that relevant, and nor did you.

E: Yes, as I told you before, I have listened to every minute of Alpha's stream.


Since I am insane, lets do a little follow up questionnaire shall we...


A: Do you agree that we know for a fact that the servos fail when configured with the wrong geometry?

B: Do you agree that the load difference the servo sees when comparing the third vs the second hole is approx 30%? (basic math, feel free to do your own measurements)

C: Do you understand the concept of Mean Time Between Failure?

D: Do you understand the relation between marginal performance vs MTBF?


What we know, for a fact at this point and well admitted by MRC and Alpha too, is that the servo is prone to immediate failure when configured with approx 30% more loads than what they experience with manual recommended linkage geometry. That means that the practical margin between the loads the servo sees and the loads it can handle at its maximum performance is somewhere between 0% and best case 30%. Which means that even with manual geometry, the servo sees loads very close to its maximum tolerance on a very frequent basis. Which is a nice recipe for a low MTBF.

[GliderGuy]

OOPS!

Called support on this. We went through all aspects. My new upgrade reverse servo is wired backwards. Hope this isn’t a batch error.

Factory is working this.

Just be aware.

-GG

[janmb]

we can establish without doubt that the issue is not the servo itself but in FACT the servo arm

Nope.

Since he worded it much better than I ever can, let me quote what Kallend wrote on rcgroups:

"I agree with janmb: a safety margin that can be overcome my moving a pushrod by one hole is an insufficient safety margin on a 4kg 150kph model."



This is simply all there is to it. Servos that fail with a slightly worse geometry than intended are too marginal.

[janmb]

He has, and so have I. I made the question myself if I recall correctly.
What Alpha replied and what Jan argues are not incompatible.

Thanks. I doubt that will ever sink in though.

[Bushong572]

Just maidened mine......upgraded servos installed. Overall, I'm pretty happy with it. It flies well and is easy to land.
2 things though: I was hoping to get a little longer run time (4 minutes MAX on RT 5500 mah....I'm pretty hard on EDFs though) and my CG is 5mm aft of the marks and I still needed 5mm of up elevator. The plane does not fly nose heavy to me, but that seems like a lot of up trim (and alot of drag)