Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[janmb]

I was waiting for someone to say it first, it looks like a stall to me as well, maybe its not and you find a problem, but I have seen that too many times from jet guys and myself included, it just looked to slow to me.

Yeah looks like a classic tip stall. Was widely discussed on FB too, with similar opinions.

[janmb]

Should never have doubted myself, studied the K45g3 video once again and got a screenshot of the tank installed clearly showing the tank size markings on the top and it is the same 1000ml tank I have and for the space available looks to be a optimal use of the space right infront of CG. So its decided the original 1000ml for me plus a 2 oz UAT right up front.

I promise not to harp on anymore about this untill I actually have a model to tinker with lol.

Harp on imo!

Do you have a link to that particular tank? Need to get one myself :D

[Nickc2023]

Thanks GG!

[DCORSAIR]

Cool video from the hill-top!
Could do with a bit of post-processing stabilization though but it was amazing nonetheless! :D



A 'nose-heavy' stall.
That's how excessively-nose-heavy planes stall when pulling too much on the elevator when flying slow (another reason I loathe nose heavy CGs).
But from the video alone I can't quite determine if it's just a stall or something else.

An asymmetric flap deflection could pretty much cause the same reaction, and an EDF stopping and causing assymmetric thrust would do it too.



From the info available, it looks like either a nose-heavy stall or one of the flap servos lacking juice, possibly because of the use of a Blue Box but that's pure speculation on my part.
I can't say anything for certain here, other than the proper use of tailerons and better CG placement would have likely helped avoid the crash.

Oh I'm sure you will have the right answer...

[Airguardian]

It must have been the aliens.
I see no other possible explanation.

[Raydar]

Harp on imo!

Do you have a link to that particular tank? Need to get one myself :D

https://uk.banggood.com/350CC380CC45...r_warehouse=CN

I got the last 1000cc one from Banggood sitting here but they look to have more stock coming shortly, I also ordered a tank from Aliexpress that I think is the same one but it has barely moved in weeks, if it is also the same when it comes I will update you but the Aliexpress option was twice the price for what appears to be the same tank.

[Raydar]

Aliexpress link to what I believe to be the same tank, please don't buy this untill I get this second tank and verify it's the same though if i was a betting man as it looks exactly like it in 1000cc size. If it is the same it is far more expensive and much slower shipping than banggood. If your googlefoo is strong I am sure it will be available from many places.

https://www.aliexpress.com/item/3297...4fb24c4da2h7M9

[Sky Wolf]

JLamb flying his Mig in St George yesterday from a unique perspective. I was standing at the top of a hill while filming (1300" away and 600' above). See the attached pic for a view of where I was standing in relation to the runway. The red X was my position on the hill. Be sure to watch in HD!

Pat, that was an incredible vantage point you were able to capture. Almost looked like the real military canyon flights.

[crxmanpat]

Pat, that was an incredible vantage point you were able to capture. Almost looked like the real military canyon flights.

Thanks. Every year we go to this event, someone climbs the hill and gets video. This year it was me. Although I wish they would have waited a little while before flying as I was pretty winded after climbing up! Gave me the shakes and heavy breathing. I need to get in shape.

[xviper]

Hello all, just wanted to throw this out there. There has been a lot of talk about adding ferrite rings as an added security measure. Some have pointed out that the plane comes from the factory with the green ferrite ring on the "throttle" line. Mine has one but it is on the power supply line from the bec just like in my f22 from the factory. Is my setup messed up or am I just reading it wrong? I never had any issues with my f22 (stock original setup) but for a few cents I figure why not add a few. Thanks!

That's what they all look like. Those green rings are always on the throttle line from the ESC to the RX. What GliderGuy is talking about is putting RF chokes on the main power lines from the battery to the ESC. Those are an aftermarket option that an owner may or may not choose to do.

[GliderGuy]

Actually on ALL the lines circled. You can group some together and run through a single RF choke and placed as close to the ESC as possible.

On the MiG....right by the aft end of the rear battery on each side of the battery. Catch all the lines coming from each ESC.

Sample ESC shown - not MiG ESC.

-GG

[janmb]

https://uk.banggood.com/350CC380CC45...r_warehouse=CN

I got the last 1000cc one from Banggood sitting here but they look to have more stock coming shortly, I also ordered a tank from Aliexpress that I think is the same one but it has barely moved in weeks, if it is also the same when it comes I will update you but the Aliexpress option was twice the price for what appears to be the same tank.

Thanks

[Gringotuerto]

The most IMPORTANT thing is that the wires coming from the ESCs act as antenna and splay out RF noise....

I'm not sure I agree. There are two possibilities: (1) radiated noise; (2) conducted noise. Also, there are two sources here: (a) ESC; (b) switching converter (BEC). I have experience in designing both switching converts and radios, but I'm not going to tell you I know the answer 100% here. I can just say, I grew a lot of grey hairs chasing conducted problems between the switcher and the radio, or various radio components, and I don't recall many radiated problems. So I would tend to suspect conducted first. But our setup and application was a bit different (cell phones).

In this case, my plane came with a choke on the BEC. The switcher is thus named because it switches between connecting and disconnecting the battery to a network of passive components. Long story, but for reasons I won't go into, the switching frequency is high. This is always a huge problem for radios. There is effectively a tiny ripple on the power supply. It doesn't have to be at 2.4GHz to cause problems. There is a tiny bit a power at every harmonic of the switcher frequency. The radio is being powered by that BEC. Every amplifier, oscillator, mixer....has a tiny bit of noise in its supply. In non-technical terms, this is like "a tiny bit of feces in the water supply"; it is connected to everything, and only takes a small impurity to cause problems.

So I'm going to guess that the choke I see is for this purpose. Conducted ripple on the power supply. Putting one on the throttle wire could help for a similar reason. It is not supplying power, but it is a load on the power supply and can transmit noise back to the Rx on the power or ground wires. Once it gets into the power supply....same problem.

But if I have time to look into this more, I'll let you know what I learn.

[GliderGuy]

That would be awesome! The more we can learn about these high current ESCs the better.

Much appreciated,
Thanks.

-GG

[Sky Wolf]

Thanks. Every year we go to this event, someone climbs the hill and gets video. This year it was me. Although I wish they would have waited a little while before flying as I was pretty winded after climbing up! Gave me the shakes and heavy breathing. I need to get in shape.

OMG...You had to walk all the way to the top?? I assumed you drove around to it, but after looking at the pic again I only see one roads. And it looks like the long way around. I can’t imagine if someone gets all the way to the top, only to realize “Doh...I forgot to bring...”

[Sekhet]

I'm not sure I agree. There are two possibilities: (1) radiated noise; (2) conducted noise. Also, there are two sources here: (a) ESC; (b) switching converter (BEC). I have experience in designing both switching converts and radios, but I'm not going to tell you I know the answer 100% here. I can just say, I grew a lot of grey hairs chasing conducted problems between the switcher and the radio, or various radio components, and I don't recall many radiated problems. So I would tend to suspect conducted first. But our setup and application was a bit different (cell phones).

In this case, my plane came with a choke on the BEC. The switcher is thus named because it switches between connecting and disconnecting the battery to a network of passive components. Long story, but for reasons I won't go into, the switching frequency is high. This is always a huge problem for radios. There is effectively a tiny ripple on the power supply. It doesn't have to be at 2.4GHz to cause problems. There is a tiny bit a power at every harmonic of the switcher frequency. The radio is being powered by that BEC. Every amplifier, oscillator, mixer....has a tiny bit of noise in its supply. In non-technical terms, this is like "a tiny bit of feces in the water supply"; it is connected to everything, and only takes a small impurity to cause problems.

So I'm going to guess that the choke I see is for this purpose. Conducted ripple on the power supply. Putting one on the throttle wire could help for a similar reason. It is not supplying power, but it is a load on the power supply and can transmit noise back to the Rx on the power or ground wires. Once it gets into the power supply....same problem.

But if I have time to look into this more, I'll let you know what I learn.

Many millennia ago, a professor in electronic engineering at the USAF Academy, when discussing RF interference, would always utter the phrase, "When in doubt, choke it out!"
I've never forgotten that saying and to this day if I think there is even the slightest chance of RF interference I use a choke or some kind of RF shield.

[Airguardian]

It's a good advice.

I wonder if any of my past brownouts on jets happened because of this.
I think I mostly use ESCs that have the ferrite rings on the Rx lead but can't swear it for all my previous models...

[Tony Hung]

https://youtu.be/7STGWWFuKCc enjoy~

[GliderGuy]

It's a good advice.

I wonder if any of my past brownouts on jets happened because of this.
I think I mostly use ESCs that have the ferrite rings on the Rx lead but can't swear it for all my previous models...

Based on my experience, the one green ferrite ring is not sufficient. As evidenced in my previous posts...

-GG

[Gringotuerto]

Many millennia ago, a professor in electronic engineering at the USAF Academy, when discussing RF interference, would always utter the phrase, "When in doubt, choke it out!"

That is often true, but if you get particularly unlucky a ferrite bead can actually create a resonant peak, especially when placed near a decoupling cap. Article below.

https://www.analog.com/en/analog-dialogue/articles/ferrite-beads-demystified.html#

I guess we've ratholed on this topic for a while here...if I find out more I'll post it over on the Electronics->Radios and Receivers forum on HS.

Theory aside, a good range check is probably the best way to catch all noise issues pre-flight.