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Fly Eagle Jet F-14 Crash (video)

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Fly Eagle Jet F-14 Crash (video)

Old 06-08-2013, 10:30 AM
  #1976  
Falcon 64
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Default RE: Fly Eagle Jet F-14 Crash (video)

I know, Paul..
The willingness of the rudderstabs! to flutter is a harder task to solve.
The cure is better bulkheads of course and wider distance between the carbon shafts (wich will lift the level of reconance). Rigidity as the R/stab structure itself, a third case.
As I know it, flutter in the R/stabs have not yet been an issue? And I assume therefore they aren`t the problem. That brings us back to the main-issue, the elevons with the HC bulkheads.
IF you fly the Tomcat as it is out of the box, I`m not surprised it would come down after a number of flights. The subject you mention aeroflexibility, is the core here. Because the elevons are constantly trying to outlive it`s own world, wich is fluttering wildlessly. This create a incredible amount of torcue and it`s never brought to silence since they have not all elements of it to do so. AND this constant factor of an attempt to flytter is the cause to build enough slop in setup AND components such as alu servo-rigs and so on. When big enough, the linkage, slop in servo, bulkhead or any other loaded component WILL fail. And it might not be noticable for the modeller to discover it before it`s too late. That`s how big these forces are. If we could measure the amount of torque created by the elevons before and after balancing, it would be a jawdropping experience..
Then we have you last element in your post, the structure rigidity of the fuselage in roll, the need to give up on twisting forces when using the elevons as ailerons. If that really is a issue with the huge span of the tailerons, the bulkheads must be soft as biscuit, and perhaps it is.
Solving that can`t be done another way than making the formers/bulkheads stiff and strong enough with mass in them, but since we can take the main issue away, it also reduces the stress to a minimum, meaning the stress there is left is another world than before.
I DO NOT defend FEJ in making bulkheads behind trailing edge out of HC, misunderstand me correct!..
They should be made of the highest quality ply with carbon on both sides (like my big FEJ F-16), nothing less on a model in this size and type. Since mine just came with that, I also assume this is the way they always will make them from now on. Meaning they are listening..

One more thing, the big FEJ F-18 which masterly landed lately, was saved just because the bulkheads was made of ply, and of course a expert pilot.
But then again, this plane was not either balanced...or am I wrong? Don`t think so.

Old 06-08-2013, 10:58 AM
  #1977  
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Default RE: Fly Eagle Jet F-14 Crash (video)

And the HC in the fuselage itself, I`ve never seen a fuselage more sturdy to resist twisting than this.
My fuselage is bone stiff. But will also ripp apart easier once hell broke loose.
Therefore, align the forces and be safe. Those who has HC bulkheads can still be safe, thing is that none of you have done it yet, but still climb the fences and says it won`t cure a thing.. And that really amazes me..
It even counts for them who never had the problem, because it reduces unnessacery stress to a absolute minumum. Done in minutes, costs nothing.
My efforth in this have been trying to help fellows with potensial bombs.
Doing so is like pouring water on the gunpowder, I promise..!
Old 06-08-2013, 11:38 AM
  #1978  
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Default RE: Fly Eagle Jet F-14 Crash (video)

F-16 fuse is a big tube. The F-14 is much different in that it is wide and thin in the center, so comparing the ability to twist between the two is apples and oranges. You have been helpful with your input around stab balancing, that has been accepted. So what else are you being helpful about?
Old 06-08-2013, 11:59 AM
  #1979  
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Default RE: Fly Eagle Jet F-14 Crash (video)

That question goes to many others than me Dantley, and you know it, but you choose to give me that question. You have no other choice than to make me feel I will shut my mouth another time some help is obvious.
But I know you are a good man, and maybe say so was to save face and pride, however i must say I`m disappointed..infact I regret it now.
But that`s what life is about, up & downs..

Btw, the fuselage shape don`t matters as long as once a HC tube gets stiffer than an ordinary lay-up on the same shape.
All shapes would be stronger then, the background of HC, why they invented it..
Old 06-08-2013, 12:07 PM
  #1980  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Not asking you to shut your mouth. I was asking what else you thought can be improved aside from just balancing the stab. Sorry if you took my question the wrong way.
Old 06-08-2013, 12:55 PM
  #1981  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Ok, misunderstood you then...sorry!

Since I`ve not even seen it, it`s hard for me to say.
But as my impression is about the issues I`ve already mentioned, balancing, bulkheads, there won`t be much I guess. I for mine will balance ailerons/flaps too.
Ali thinks about rebuild the elevon mecanism on his F-16. I won`t because it leaves out any torque on the pivot, the way it is.
I just stick to reason for this thread.

There are "always" room for improvement on brand new models, and things in them will nessacerily vary from a small to a bigger version. Someone made a DF of it and made it lighter.
I`m really not there to say pro/con to that.
An absolute pro+ would be the HC fuselage, there is nothing stiffer than HC compared to weight.
It just have to be used correct wich is a big + for FEJ here, speaking fuselage.
I wouldn`t hesitate a milli-second to fly it, if balanced.


Old 06-08-2013, 07:28 PM
  #1982  
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Default RE: Fly Eagle Jet F-14 Crash (video)

I have been reading this daily and think there may be a chance for my FEJ F-14 yet. I have only got as far as installing the Fins and the Elevators with the operating mechanisms. As mine is all HC also I have decided to strip it all out again and remove most of the HC former at the rear/aft and install ply sandwiched with CF. also intend to "lock in" the aluminium block with a piece of CF top and bottom glued to the former. One thing i know nothing about is the balancing of the elevators. I am used to building and flying BVM and YA jets so having to re work a new out of the box model is new to me but can't bring myself not to do it. Can I get some advice and guidance on how to balance the elevators/stabilisors. Thanks. Tom.
Old 06-08-2013, 08:32 PM
  #1983  
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Default RE: Fly Eagle Jet F-14 Crash (video)

TJ,

Olnico just put a great article on Stab balancing on his UltimateJets website that is very helpful along with alot of math explaining forces, aerodynamic vs static balancing.... I dont have the link but do a search on Threads he has posted or look at the Ultimate Jets Website as its a blog there...

I was just in Malaysia... Where do you guys fly there?


ORIGINAL: tj coleman

I have been reading this daily and think there may be a chance for my FEJ F-14 yet. I have only got as far as installing the Fins and the Elevators with the operating mechanisms. As mine is all HC also I have decided to strip it all out again and remove most of the HC former at the rear/aft and install ply sandwiched with CF. also intend to "lock in" the aluminium block with a piece of CF top and bottom glued to the former. One thing i know nothing about is the balancing of the elevators. I am used to building and flying BVM and YA jets so having to re work a new out of the box model is new to me but can't bring myself not to do it. Can I get some advice and guidance on how to balance the elevators/stabilisors. Thanks. Tom.
Old 06-09-2013, 04:19 AM
  #1984  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Tom, the method I use is very simple.

You need some lead hail, a disposable coffe-cup, epoxy (moulding epoxy is best because of it`s voscosity).
Some tape, a book which has a thickness slightly bigger than the shaft/pivot, and a scale to measure the accurate weight.
A heavy but hard item like my vase here or something similar.

Arrange the elevator as on picture (this is a balanced one) and it will drop the TE straight down.
Now just pour lead into the cup so it balances horisontal.
The arrangement has a close to none resistance as the pivot has glass and the edge of the table to rotate against.

Measure the weight (can be dropped if you repeat it on the other one) and mix the lead hail with epoxy.
You can also warm the epoxy with a hair dryer to get the viscosity as thin as possible, but if you use ordinary 1 hour glue here,
time suddenly appears as a critical factor, as the cure speeds up rapidly when heated!
Do not use more epoxy than nessacery, meaning the mass is ment to be at least sticky. I use abit more than that because it eases the further process.

Pour the mix into the 8 mm - 1/3" hole you made 4" from LE on the root chord, and hold the elevator upright, nose down.
When finished, be sure all the hails are well stuck in the extreme front part of the elevator.
This can be done by swinging the elevator in loops with you hand to create more G.
Put it away for curing, nose down.

Done!
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Old 06-09-2013, 08:36 PM
  #1985  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Falcon. Thanks very much for that. I didn't realise it was that simple. Same method as I used on My Avonds F-15.
Rush, we fly the jets at Bernam River airfield which is close to Slim River off the North South highway. About 1 1/4 hours from KL. Great spot. I've been travelling so much recently haven't been there for a year. Hopefully maiden by BVM UB there soon. Tom.
Old 06-09-2013, 11:54 PM
  #1986  
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Default RE: Fly Eagle Jet F-14 Crash (video)

He he, it`s enough and when done you`ll see it`s at a perfect ballance..
Bearings would be the high-end method . The only "hard" task here is to get the mixture inside without spilling.
Old 06-10-2013, 07:52 AM
  #1987  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Falcon64 you are incorrect in stating that those with HC bulkheads can still be ok. The only way they can be ok is to replace the bulkheads with aircraft ply like 1/4 inch. Being an engineer that has dealt with composite structures I can tell you that the construction of the bulkheads the way FEJ has done it is completely incorrect. It would be ok for the fuselage form but not bullheads. Early on in this thread I attached a link on how to use the HC properly.
Old 06-10-2013, 08:53 AM
  #1988  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Exactly.

The root problem here is the insufficient torsional and longitudinal rigidity of the airframe structure as constructed by FEJ. Any flutter tendency only accelerates the failure.

I firmly believe that the torsion loads imposed by the horizontal stabs in high roll-rate deflections, coupled with the known and observed lateral flexing of the vertical tails in high AOA maneuvering, will eventually lead to failure of the aft fuselage in the FEJ HC F-14, regardless of the presence of stab flutter.

Sluggo
Old 06-10-2013, 09:45 AM
  #1989  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Taileron flutter should not be the problem, it must be the HC tail structure.

Why? Unintenionally I did a flutter test of one taileron on my First Generation (non HC) Tomcat during flight last week. On the 48th flight I managed to to stupid to fix the taileron correctly. The rotating pin was not all in as I set the four screw holding the Taileron. I missed this because the moving test I did by hand was without power on the servos.

Directly after departure I recognized that something was wrong. The plane was unstable and it was not possible to trim it for a straight and level flight. Finishing the second trafic pattern I was able to land without damage. Me and the other guys at the field have not seen any flutter. After landing I checked what was wrong and was shocked. The left taileron could be moved up and down by hand approximately 10 degrees with very light force.

Rudi


Old 06-10-2013, 09:56 AM
  #1990  
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Default RE: Fly Eagle Jet F-14 Crash (video)

The method employed by Falcon64 is to statically balance the stabs on the the pivot rod in its currently installed location.

This suggested "solution" does not address the fundamental concerns as to:
1) whether the stab pivot is in the correct location with respect to the MAC;
2) the engineering basis of balancing the stab behind the centre of pressure;
3) concerns regarding bolting the stab mechanism through the honeycomb material causing core compressive failure; and
4) structural concerns regarding the rear fuselage torsional loading.

As such, is likely not a "solution".

Regards,

Jim
Old 06-10-2013, 12:06 PM
  #1991  
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Default RE: Fly Eagle Jet F-14 Crash (video)

I showed how to static balance a taileron/elevator since I had the impression there was more than one that wondered how to.
It`s up to you if you think the rest is ok I think. And I mentioned bulkheads some posts further up on this page..
It`s enough now





Old 06-10-2013, 12:48 PM
  #1992  
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Default RE: Fly Eagle Jet F-14 Crash (video)

Well rudi has proven that their isnt a balance problem with his latest post, atleast in his model with un balanced stabs...
Old 06-10-2013, 01:39 PM
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Default RE: Fly Eagle Jet F-14 Crash (video)


ORIGINAL: invertmast

Well rudi has proven that their isnt a balance problem with his latest post, at least in his model with un balanced stabs...
Yes, one reason may be that in Rudi's case, he removed the other factor in flutter that Falcon conveniently ignores, the spring constant of the control linkage.

You can take a surface that does not flutter on its own because of static and dynamic balancing, and cause it to flutter by introducing "springiness" in the control linkage.

Bob
Old 06-10-2013, 02:38 PM
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Default RE: Fly Eagle Jet F-14 Crash (video)


ORIGINAL: rhklenke


ORIGINAL: invertmast

Well rudi has proven that their isnt a balance problem with his latest post, at least in his model with un balanced stabs...
Yes, one reason may be that in Rudi's case, he removed the other factor in flutter that Falcon conveniently ignores, the spring constant of the control linkage.

You can take a surface that does not flutter on its own because of static and dynamic balancing, and cause it to flutter by introducing ''springiness'' in the control linkage.

Bob
No, you can`t.
Old 06-10-2013, 02:50 PM
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Default RE: Fly Eagle Jet F-14 Crash (video)

A stabilized elevator will float in itself and relax like I will.

Gone salmon-fishing for a week tomorrow
Old 06-10-2013, 03:54 PM
  #1996  
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Default RE: Fly Eagle Jet F-14 Crash (video)


ORIGINAL: Falcon 64


ORIGINAL: rhklenke


ORIGINAL: invertmast

Well rudi has proven that their isnt a balance problem with his latest post, at least in his model with un balanced stabs...
Yes, one reason may be that in Rudi's case, he removed the other factor in flutter that Falcon conveniently ignores, the spring constant of the control linkage.

You can take a surface that does not flutter on its own because of static and dynamic balancing, and cause it to flutter by introducing ''springiness'' in the control linkage.

Bob
No, you can`t.

But you could cause a unbalanced and "stabilized" control surface to flutter due to balancing it improperly.
Old 06-10-2013, 09:20 PM
  #1997  
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Default RE: Fly Eagle Jet F-14 Crash (video)

I doubt that very much..
Once you move the CG location forward, even if it`s not in ok balance, you also improve flutter velocity indeed.
At a perfect balance, the flutter speed will be higher than the engine can take the model (depends on MAC).
A nose heavy elevator pushes the limit even further. I`ll give you an example..

What is the optimum way to discover flutter? It is to have a very loose binding to the thing that holds it in place, agree?.
Like holding it in you hand.. 45 km/h was all it took unbalanced. If you took the same elevator and tested it on the fuselage, the speed would be significantly higher. And add a strong digital servo to force it to be still, we climb even higher in speed to have flutter, but we may get there. That is the way you know it.
Thats why the flutter come so suddenly, it creates enough power to finally get the freedom it strives for, because its held in place with a snug fit, "no slop" in the pivot tube /bearings (not speaking linkage to servo, that comes as an addition because we are without servo here).

Then we take the same elevator which I in my case fluttered in 45 Km/h before, now WITH balance..
In my hand at 150 Km/m down the 2000 meter runway, it`s just floating at ease, no tendensies to flutter.
And we move this balanced elevator back to the airframe without any servo, we get a even higher velocity before flutter, perhaps 250-300 km/h, and that`s before it fluttered in the first place at 150 Km/h. THEN we attach a strong digital servo to it, where do you think we are heading now..?

The plane can`t fly that fast...other things will come off first, like ailerons or flutter in r/stabs or rudder, wing-flutter, you name it..

Gaula River, here I come!




Old 06-11-2013, 03:09 AM
  #1998  
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Default RE: Fly Eagle Jet F-14 Crash (video)


ORIGINAL: Falcon 64

I doubt that very much..
Once you move the CG location forward, even if it`s not in ok balance, you also improve flutter velocity indeed.
At a perfect balance, the flutter speed will be higher than the engine can take the model (depends on MAC).
A nose heavy elevator pushes the limit even further. I`ll give you an example..

What is the optimum way to discover flutter? It is to have a very loose binding to the thing that holds it in place, agree?.
Like holding it in you hand.. 45 km/h was all it took unbalanced. If you took the same elevator and tested it on the fuselage, the speed would be significantly higher. And add a strong digital servo to force it to be still, we climb even higher in speed to have flutter, but we may get there. That is the way you know it.
Thats why the flutter come so suddenly, it creates enough power to finally get the freedom it strives for, because its held in place with a snug fit, ''no slop'' in the pivot tube /bearings (not speaking linkage to servo, that comes as an addition because we are without servo here).

Then we take the same elevator which I in my case fluttered in 45 Km/h before, now WITH balance..
In my hand at 150 Km/m down the 2000 meter runway, it`s just floating at ease, no tendensies to flutter.
And we move this balanced elevator back to the airframe without any servo, we get a even higher velocity before flutter, perhaps 250-300 km/h, and that`s before it fluttered in the first place at 150 Km/h. THEN we attach a strong digital servo to it, where do you think we are heading now..?

The plane can`t fly that fast...other things will come off first, like ailerons or flutter in r/stabs or rudder, wing-flutter, you name it..

Gaula River, here I come!





If it wasnt possible, full scale aircraft manufacturers wouldnt describe in detail the exact procedure and specifications for balancing their flight controls
Old 06-18-2013, 10:49 AM
  #1999  
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Default RE: Fly Eagle Jet F-14 Crash (video)

ORIGINAL: invertmast


ORIGINAL: Falcon 64

I doubt that very much..
Once you move the CG location forward, even if it`s not in ok balance, you also improve flutter velocity indeed.
At a perfect balance, the flutter speed will be higher than the engine can take the model (depends on MAC).
A nose heavy elevator pushes the limit even further. I`ll give you an example..

What is the optimum way to discover flutter? It is to have a very loose binding to the thing that holds it in place, agree?.
Like holding it in you hand.. 45 km/h was all it took unbalanced. If you took the same elevator and tested it on the fuselage, the speed would be significantly higher. And add a strong digital servo to force it to be still, we climb even higher in speed to have flutter, but we may get there. That is the way you know it.
Thats why the flutter come so suddenly, it creates enough power to finally get the freedom it strives for, because its held in place with a snug fit, ''no slop'' in the pivot tube /bearings (not speaking linkage to servo, that comes as an addition because we are without servo here).

Then we take the same elevator which I in my case fluttered in 45 Km/h before, now WITH balance..
In my hand at 150 Km/m down the 2000 meter runway, it`s just floating at ease, no tendensies to flutter.
And we move this balanced elevator back to the airframe without any servo, we get a even higher velocity before flutter, perhaps 250-300 km/h, and that`s before it fluttered in the first place at 150 Km/h. THEN we attach a strong digital servo to it, where do you think we are heading now..?

The plane can`t fly that fast...other things will come off first, like ailerons or flutter in r/stabs or rudder, wing-flutter, you name it..

Gaula River, here I come!





If it wasnt possible, full scale aircraft manufacturers wouldnt describe in detail the exact procedure and specifications for balancing their flight controls

Do not forget full-size fighters are lightyears apart of our game..!
They go supersonic, and are SAFE behind our knowledge and can NEVER! be compared to what we do. If you build a Tomcat in the thought of full-size, you are safe no matter how, but requires the same rigidness and hydraulics.
BUT in modelleing we can`t yet do that, and that answers your reply..and that is where you have questions. Copy a full-size, and you will crasch & burn on and in the terms of the modelling in jets we have done uptil now.

I eeek every time someone compares a full-size aircraft up to their model and think they do it 7 timer smaller, and also think they are in a good path in jets and forces in it, there are dimensions! apart.. PLEASE stop thinking we can compare aerodynamics on our models with supersonic fighters.. ( ! )
Once you do, you are mislead and on your own..and you will loose.!
Our thing happens below 600 km/h, way below subsonic. It`s from there we have to admit our laws exists, not to compare your jet against the original, nothing of it, (!!)... We are dealing model airplanes, the laws there are grewing rapidly once the size/weight and speed grows whith it.
My final words in this thread are :

We have model jets with problems almost all over, made from a various group of manufacturers.
But "none of them" have a clou of what they deliver as almost all of them have fluttered down, at leat none allows a over-motorized setup..
None of them are aware of it until recently, and if they did, we would hear from them a long time ago about it.

Hard facts are often hard to comprehend, but nevertheless a fact.
A hard time for the byer(...!!...), a almos equal hard time after for the rest..friends and likes. I HOPE this thread " dies" into a understanding of the necessity to take a aim at your elevators, even though they have served you right.. Allways.

The solution IS easy. Once flutter occours, we progress/compensate with balance. But those who won`t see it continues the path.
Those who don`t, are on their own.
Allways. Period..
And I promise.. You are flutter-free on those I said..
That`s why i chimed in here at page 32..
Calories.. for a good thing. Dead horse, flutter free..
Remember that when you go down.......
Two cents or 2k kalories, hope it went in where it should..

I`m ready to defend the earodynamics in this , anytime. Just bring it on..
Old 06-18-2013, 02:25 PM
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Default RE: Fly Eagle Jet F-14 Crash (video)


ORIGINAL: Falcon 64

ORIGINAL: invertmast


ORIGINAL: Falcon 64

I doubt that very much..
Once you move the CG location forward, even if it`s not in ok balance, you also improve flutter velocity indeed.
At a perfect balance, the flutter speed will be higher than the engine can take the model (depends on MAC).
A nose heavy elevator pushes the limit even further. I`ll give you an example..

What is the optimum way to discover flutter? It is to have a very loose binding to the thing that holds it in place, agree?.
Like holding it in you hand.. 45 km/h was all it took unbalanced. If you took the same elevator and tested it on the fuselage, the speed would be significantly higher. And add a strong digital servo to force it to be still, we climb even higher in speed to have flutter, but we may get there. That is the way you know it.
Thats why the flutter come so suddenly, it creates enough power to finally get the freedom it strives for, because its held in place with a snug fit, ''no slop'' in the pivot tube /bearings (not speaking linkage to servo, that comes as an addition because we are without servo here).

Then we take the same elevator which I in my case fluttered in 45 Km/h before, now WITH balance..
In my hand at 150 Km/m down the 2000 meter runway, it`s just floating at ease, no tendensies to flutter.
And we move this balanced elevator back to the airframe without any servo, we get a even higher velocity before flutter, perhaps 250-300 km/h, and that`s before it fluttered in the first place at 150 Km/h. THEN we attach a strong digital servo to it, where do you think we are heading now..?

The plane can`t fly that fast...other things will come off first, like ailerons or flutter in r/stabs or rudder, wing-flutter, you name it..

Gaula River, here I come!





If it wasnt possible, full scale aircraft manufacturers wouldnt describe in detail the exact procedure and specifications for balancing their flight controls

Do not forget full-size fighters are lightyears apart of our game..!
They go supersonic, and are SAFE behind knowledge and can NEVER! be compared to what we do. If you build a Tomcat in the thought of full-size, you are safe no matter how, but requires the same rigidness and hydraulics.
BUT in modelleing we can`t yet do that, and that answers your reply..and that is where you have questions. Copy a full-size, and you will crasch & burn on and in the terms of the modelling in jets we have done uptil now.

I eeek every time someone comares a full-size aircraft, and think they are in a good path ( I know). In sailplanes ok, abit close, but in jets and forces, there are dimensions! apart.. PLEASE stop thinking we can compare aerodynamics on our models with supersonic fighters.. ( ! )
Once you do, you are misled and on your own..and you will loose.
Our thing happens below 600 km/h, way below subsonic. It`s from there we have to admit our lawns exists, not to compare your jet against the original, nothing of it, (!!)...
My final words in this are :

We have model jets with problems almost all over, made from a various group of manufacturers.
But ''none of them'' have a clou of what they deliver as almost all of them have fluttered down.
Hard facts are often hard to comprehend, but nevertheless a fact.
A a hard time for the byer..a even harder time after for the rest..friends and likes.

The solution IS easy. Once flutter occours, we progress/compensate with balance.
Those who don`t, are on their own.
Allways. Period..

Who said anything about super sonic fighters in my message? I sure didnt...

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