Official Freewing MiG-29 Fulcrum Twin 80mm Thread

[janmb]

I’ll play your game, ensuring surfaces are going to correct way is far , far more important than tight linkages and tight servos.
We can do this all day, bottom line, balancing the stabs does help.

Against flutter - potentially yes. A little bit. In whatever degree flutter has been a problem on any full flying stab foamie what so ever this far, let alone this particular model.

Against the servo load problems we have seen with the mig this far - not one little bit.

Making sure people don't get the wrong idea about a certain measure solving their problems when it does in fact not is important - and not a game.

[JLambCWU]

I suggest you try to actually read the post you are responding to next time.

I had read your post. That was my point.

[Lcacing]

Against flutter - potentially yes. A little bit. In whatever degree flutter has been a problem on any full flying stab foamie what so ever this far, let alone this particular model.

Against the servo load problems we have seen with the mig this far - not one little bit.

Making sure people don't get the wrong idea about a certain measure solving their problems when it does in fact not is important - and not a game.

My post was before the servo issue, it was not a suggestion to solve an issue that most of us didn’t know existed with the MiG. No matter how you spin your response based in your vast experience, balancing the stab has some benefit, even if it’s a very small advantage.

So you are telling me there’s a chance!!!!

[janmb]

I had read your post. That was my point.

If you had, you wouldn't have tried making that point since I proactively addressed it in my original post on the topic.

"Obviously have no experience with this particular model yet,"

I know you have flown the model and I haven't. That does not mean that you cannot give poor advice, nor does it mean I cannot give good advice.

The mig abides by the same laws of physics as any other model. Recommending people to make sure they are nose heavy if trying slow flight is, based on simple physics, poor advice prone to leading some into serious problems. It is a lot more risky to try flying high alpha while nose heavy compared to a balanced model. Even slightly tail heavy is safer in that particular aspect.

I recommend watching Ryan's video on the mig btw - a brilliant demonstration of the negative impacts of nose heaviness. No slow flight going on there, but he makes the model stoop and toss a wing even in situations where that should be next to impossible.

[MikeT]

I love it when we overthink stuff.

Mike

[Skosh25]

"aged" years" "days" "time" "sleep" What are these terms of which you speak?

More proof Alpha is some sort of cybernetic organism. 😂

[xviper]

I love it when we overthink stuff.

Mike

I suggest having a few stiff shots to kill off those brain cells - no more overthinking anything. Overthinking stuff in this hobby tends to be an anti-social activity that causes egos to be stomped on.

[Evan D]

Maiden done. First I have elevators on the innermost hole and ailerons in one hole and then radio ATVs adjusted to proper throw.

Balanced per the marks is slightly nose heavy for me. I needed 12 clicks of up which has the tips at 4mm to the fuse. No other trim. Other than that it flies similar to my Arrows.

Tailerons makes the roll good for me. I flew on mid rates the whole flight except aileron was where I used high plus tailerons most of the flight.

Take off and landings are very smooth, a lot of that is the size.

[Airguardian]

If you’re going to slow flight the jet, your probably better off with the CG a bit further forward until you’re comfortable with how the jet enters and recovers from it.

I didn’t realize you had flown the model, and or slow flight’d it yet!

Just as Jan already did, I would highly encourage NOT TO go with a nose heavy setup for high alpha. And just as Jan says, experience on the model is NOT required to make a few reasonable predictions of what is going to happen. Of course, experience with the model is welcome but doesn't outright give you reason on anything you have to say about it.

Some F-18 pilots were also eager to jump on me for saying certain things with regards to that bird before I got to fly mine and... well, turns out I knew better than them despite having not flown it yet at that point. Arguments must either stand on their own merit or fall apart regardless of who tells them, otherwise we are talking fallacies of authority here, I like to be rigorous on this stuff.

On that regard, and following your own logic, you have experience with slow-flying the MiG but I would ask... have you actually shifted CG back and tried again?
Otherwise how did you reach the conclussion that nose-heavier is better?

Probably the same way that Jan did... only I am more inclined to back Jan's approach to this particular issue rather than yours.

Look, I see where you stand and there is some merit to it. WITHOUT thrust vectoring, if the jet enters a state of 'too much angle of attack' where you lack stab authority to pull back to level, you kinda want to be slightly nose heavy so that the jet will be able to nose down and realign with airflow on its own, and not just brick out of the sky. BUT that will pretty much happen just as well with a more neutral CG as long as you stay on the 'stable' margin. That said, having to fight a nose-heavy balance means loading more both the stabs and the wings, which results in the aircraft having less margin between a controlled and stalled condition. And nose-heavy CG induces many negative behaviors to the airplane's dynamics, both in normal flight and high alpha. Wing rocking tendencies increase too, among other things.

To sum it up... if you are going to attempt high alpha... first and foremost do at three mistakes high (or maybe 6 mistakes high since this jet is bigger) regardless of what setup you choose to implement. Then, really, if you want to pursue high alpha, by all means, do so with THRUST VECTORING NOZZLES installed. Attempting high alpha on non-vectored jets, while possible, is an outright accident waiting to happen. You also don't really want to go there in your first 10 flights, at least if you are not vectored.

And assuming you are using vectored nozzles, then the more reason you have NOT to use nose heavy CG, as you won't ever get stuck in a high alpha condition as long as your nozzles are operative and you retain thrust.

Jets behave much better in high alpha with neutral to aft-CG settings period.
I barely can think of any exception, certainly the MiG shouldn't be one.

Knowing everything precludes the need for actual experience, lol

No kidding, it actually kinda does.
Of course this is an exageration but, point is, engineers don't just build a 100 aircraft out of their own personal fantasies and test them all until they hit the right nail.
One parts from previous knowledge, makes calculations and works to 'forsee' what is going to happen before it actually does. So, of course, experience, once available pretty much supersedes theory, but theory is a very valid starting point, more so for theory that is based on previous experience. And ultimately, experience itself is bound to be misinterpreted, so bear that in mind too.

No model responds well to being forced into high alpha against its will - and it doesn't take experience to know this also being the case with the mig.

If you encounter a red hot oven - of a make and model you have never seen before - do you have to put it to the test in order to know you will get burnt if placing your hand on it?

It is perfectly possible to analyze basic problems based on skills and relevant experience from similar models without requiring hands on experience on a particular model. The mig answers to the same rules of physics as any other aircraft does. And likewise, it is perfectly possible to have hands on experience without necessarily learning a lot from it ;)

Making sure people don't get the wrong idea about a certain measure solving their problems when it does in fact not is important - and not a game.

I know you have flown the model and I haven't. That does not mean that you cannot give poor advice, nor does it mean I cannot give good advice.

The mig abides by the same laws of physics as any other model. Recommending people to make sure they are nose heavy if trying slow flight is, based on simple physics, poor advice prone to leading some into serious problems. It is a lot more risky to try flying high alpha while nose heavy compared to a balanced model. Even slightly tail heavy is safer in that particular aspect.

Aye!
Big +

I had read your post. That was my point.

You clearly omitted in your reply the fact that he did acknowledge first and foremost not to have flown this plane yet.

[Airguardian]

Oh, and for heaven's sake, anyone attempting to fly high alpha on such a jet DO FIRST ENABLE tailerons before attempting to.
And toggle on full taileron throws with great doses of expo.

That should be pretty obvious but guess it is worth emphasizing.

[Gringotuerto]

.... balancing the stabs does help.

It is not hard to estimate this. I thought someone said above it takes 4 quarters and a penny to balance it. A quarter weighs 5.67g. A penny weighs 2.5g. So in total, that's a shade over 25g. I don't have the model yet, but from the photo it looked like these were offset about 6cm from the pivot point. If so, then they are contributing 151g-cm. According to the memo, the original servo was 2.5kg-cm. So the weight-torque is about 6% of the max servo torque. So it seems to me that balancing is not a bad idea - you gain another 6% for free. Not highly necessary, but if you want to do it, it does help, and the help is not completely insignificant.

Another way to look at it is - what are the aerodynamic forces. Well, they are less than the max servo torque, or the servo binds up. In this particular model, we actually have some data - if you use the correct hole it seems to work, and if you don't, it might fail. So I would guess that the max aerodynamic force is pretty darn close to the servo torque when you use the 3rd hole - headroom in that case is approximately zero. So we can estimate that headroom when you use the correct hole is similar to the difference in lever arm between those two holes. Again, I don't have the plane and calipers in front of me, by just eyeballing photos, it looked like that the outer hole is about 30% farther out than the middle hole. So then we can estimate that headroom between max aerodynamic force and servo torque is less than 30% (stock servo, correct hole). When you look at it that way, gaining 6% servo torque is nothing to sneeze at - it can take your headroom from about 30% to about 36%. That could be the difference between surviving or not, if you get into an overload situation (i.e. stupidly dive at full throttle then hit the elevator).

Note that the new servo is 3.5kg-cm, which is 44% higher than the stock servo, so obviously that is a much bigger effect. If the old headroom was around 30%, then the new headroom is around 87% (1.3 x 1.44). So now you're getting in the vicinity of 2x, which I would consider to be very bulletproof margin.

[janmb]

I love it when we overthink stuff.

Mike

The eternal curse of every single engineer on the planet lol

[Pogo]

It is perfectly possible to analyze basic problems based on skills and relevant experience from similar models without requiring hands on experience on a particular model. The mig answers to the same rules of physics as any other aircraft does. And likewise, it is perfectly possible to have hands on experience without necessarily learning a lot from it ;)

It actually wasn't your lack of experience with this model that I was commenting on. It was your abundance of arrogance.
Tom

[Airguardian]

I don't think I would really label Jan's behaviour here as arrogant (a bit sarcastic maybe, with more or less success at it...) but I would certainly label yours as something pretty much 'less than courteous' at best.
Can't we get to discuss things and agree to disagree without calling each other names? We're supposedly a civilized bunch and all that.

[janmb]

It actually wasn't your lack of experience with this model that I was commenting on. It was your abundance of arrogance.
Tom

Correcting false teachings in a sufficiently clear way to ensure third party lurkers don't get burned by it and at the same time avoid anyone looking at it as arrogance.

I'm not as well versed in dilly dallying around easily hurt feelings as most native English speakers seem to be. Not blaming language, it is more a matter of cultural differences.

I speak my mind - with the purpose of being to the readers' benefit - not necessarily the one I'm directly addressing.

[Jdcrow]

one thing that seems to be common on those crash videos.........not a single pilot pulled back power. WOT ALL THE WAY..

[xviper]

one thing that seems to be common on those crash videos.........not a single pilot pulled back power. WOT ALL THE WAY..

Makes ya kinda wonder, don't it? When mine's about to hit dirt, I try my best to chop throttle ASAP.

[janmb]

one thing that seems to be common on those crash videos.........not a single pilot pulled back power. WOT ALL THE WAY..

Yes, that is indeed an interesting point. Most pilots would do that - even instinctively.

What does the freewing esc do if it loses throttle signal completely? Almost tempted to suspect a burnt bec.

Radio loss would be another candidate, but can't believe so many of them would fail to run proper failsafe. Especially considering most of them use Spektrum - where you pretty much have to deliberately try to mess it up.

[Sekhet]

The eternal curse of every single engineer on the planet lol

That's why most of us end up going into less demanding but just as rewarding second careers.
ie.. I went from designing them full time to flying them full time and so many problems just went away
like:
1) A non engineer boss telling you the wing isn't the correct shape, and when you ask what is wrong with it he says, "make it look prettier".
2) A non engineer, non pilot customer telling you that they want two hundred passenger seats on an aircraft designed for eighty to one hundred, using the smallest pitch seats the Government will sign off on, and then gets angry when the mock up department shows them the extra one hundred seats turned upside down in the one hundred seats already in the plane.
3) Or two engineers fighting over balanced or counter balanced control surfaces.
4) Or designing the same part over a hundred times with slight changes in each because the testing department wants to zero in on the best one only to have them tell you after months of testing and redesigning that your original design is the best!

I could go on for days. Now days the only things I need to think about are, What time do I have to leave the house or hotel to get to the airport on time for my flight, did I get my thermos filled with coffee (just a tip don't drink the coffee made on the plane, it's made with the water from the onboard tanks and they only get cleaned once a month or less depending on the airline), Who is the crew I'm flying with, is the aircraft in good working order, What is the weather doing, what does the passenger and cargo manifest look like, are there any changes to the routing, did we get the right amount of fuel loaded, etc...

So you see there is no time to overthink anything, you just do it, leave it all on the tarmac, go home work on your model aircraft cars and boats and then do it all over again on your next work day. No overthinking needed!

[Airguardian]

one thing that seems to be common on those crash videos.........not a single pilot pulled back power. WOT ALL THE WAY..

There's a possible effect of nose heaviness. If nose is too heavy and you lack elevator authority (reduced throws), the only way to be able to raise the nose is at speed. Otherwise, the jet will just nose down. But from the videos it is pretty clear on some the pilot attempted to pull up and the jet rolls instead. There's a good example of why using big throws with proper expo can be better than reduced tthrows with no expo. Having a gyro on could have helped there too (although they should rather be turned off for maidens, really).

So while I would mostly agree that yes, when there are problems with an aircraft, lowering a bit the speed is a good approach, this doesn't always stay true, as maintaining high speed may in some cases be your only chance at retaining any sort of control over jet attitude.