Experienced BF-109 pilots - help needed - right roll level flight

 

Again, it is quite simple physics. The motor is turning a large propeller. Newton's third law is operative.

 

 

 

Engine torque does not produce yaw. It is a rotational force translated into yaw when the aircraft is in contact with the earth, through the gear.

 

(...)

 

 

DCS P-51 has no torque

 

 

 

DCS Bf-109 has some torque but not enough.

 

 

 

Are they in a ratio that basically reproduces relative performance? Maybe

 

 

 

Are they correct? Not even close.

 

 

 

So where did you fly a real life P-51D and BF.109 K4 as you seem to have experienced the yaw effect and torque in the planes in real life, considering your statements.

In the Sim at least, I feel a considerable torque along the longitudinal axis if I get near stall speed and induce too much torque when pushing the throttle...

How much torque was there in the real life plane you flew and how the hell did you survive the experience? Really interested in a real life BF.109 K4 pilots input on that. ;)

The documents you list were just a few of the many used, but also weigh more than your hunches. You can question all you want, but they aren't worthy questions if you have no fact to back up your arguments.

1) The plane used was an Bf.109 F with G Wings and no mentioning of the engine used.

2) according to the document the plane was tested in a dive starting at 10.7 Km MSL and an overall weight (Fluggewicht) of 2,900 kg.

Before we discuss any of these document's "findings" and “adapt" them to the simulated BF.109 K4, I would like to ask everyone to recreate these conditions, especially the WEIGHT.

Our simulated K4 has an empty(!), as in NO FUEL weight of 6395 lbs or 2900,72 Kg... unless they glided the plane into a dive and landed it afterwards, either the weight of "our" K4 is wrong, what I doubt, or the F used in the tests has a different weight/is a different aircraft/likely has a different engine. Anyway with a different weight/different CoG etc. , the whole comparison is pretty much useless, I guess.

I wonder, why none of our "forum specialists" here with "engineering background" did not point that out, as they sure must have thoroughly read them papers before comparing the results to the simulated K4 ?!

Or am I missing something, that explains the weight difference?

Because there is no problem and the following quotes make it clear that discussing anything aircraft related in this thread is a waste of time. How does aircraft weight in the fuselage influence high speed roll characteristics, just interested?! 7-8 kN are 700-800 kg/m^2 in your mind? God almighty... Stickforces of 300-400 kg? Jesus!

If you want to tell us, that it's totally easy to pull the stick against a force of roughly 7-8 KiloNewton (700-800 kg/m2) at 450 km/h against at least half a squremeter of elevator, with both hands, cramped into the cockpit with your knees bent and against the pedals, we can discuss.

 

 

Let's assume the elevators give you a counter force of "just" 350 - 400 Kg, I consider a bit of "stiffening" pretty realistic... but that's just my interpretation of the original charts and I may be wrong. :dunno:

 

Source:

https://forums.eagle.ru/showthread.php?t=200423

Because there is no problem and the following quotes make it clear that discussing anything aircraft related here is a waste of time. 7-8 kN are 700-800 kg/m^2 in your mind? God almighty... Stickforces of 300-400 kg? Jesus!

Well, not exactly in my mind, it's what the unit KiloNewton stands for: 1,000 Newton which is roughly a force equal to 102 kg (per squaremeter).

You can Google KiloNewton.

I roughly halfed the force to 300 to 400 kg as the elevators together are more 50*100 cm sized or a bit less, so even if we make it only a quarter of the measured 7 to 8 kN it's still 150 to 200 kg.

And you did not answer how you did set the K4 to 2900 kg gross weight in DCS, when conducting your "verification of the flight model based on the paper you provided"? So you make assumptions based on research that's obvious made with a different plane, to make a point while trying to throw smokescreens to cover this little discrepancy and waste our time?

7-8 KiloNewton (700-800 kg/m2).

Well, not exactly in my mind, it's what the unit KiloNewton stands for: 1,000 Newton which is roughly a force equal to 102 kg (per squaremeter).

You can Google KiloNewton.

This makes me sad. You clearly don't even know what a Newton is and then tell me to Google it. A pressure is not the same as a force... And where on earth did you find this pressure in the first place? Non of the documents in yoyos past talk about pressures, yet you quote his post?

This makes me sad. You clearly don't even know what a Newton is and then tell me to Google it. A pressure is not the same as a force... And where on earth did you find this pressure in the first place? Non of the documents in yoyos past talk about pressures, yet you quote his post?

Still wondering how you did set the weight to 2900 kg in DCS for the "verification flights you did". Any input on that?

You are absolutely far from the real prop physics and PRACTICE. The real world physics sometimes is more complex than a school book or an old vanilla Il-2 FM. If you take a look at the trim diagrams for the most powerful WWII fighters you could see that small aileron input is used only at very low IAS and the PRIMARILY counteracting factor is RUDDER.

exactly i dont use aileron trim at all (i think p-51 is only one wich have aileron trim in dcs from props) i use rudder for it :). you want coordinated flight so ball must be in the middle you cant do it by aileron trim. Ofc not all planes react to rudder trim like that but in warbirds it was rather intentional. and as far as i know vertical stabilizer is fixed trimmed to counter tourqe of the engine so probably in very low power cruise or when plane reached its max speed for given power setting it dont need rudder trim. when i dive with low power setting and get high speed in p-51 i have to trim rudder to the left it looks for me that p-51 has fixed vert stab trim

A Newton is actually an acceleration acting on a mass, but if I did read the left axis of the chart correct there was a scale of kN related to the pressure measured on the elevator?

 

Still wondering how you did set the weight to 2900 kg in DCS for the "verification flights you did". Any input on that?

Newton is unit of froce i think

"acceleration acting on mass" something i dont like in this sentence

Regardless of the reason of the previous discussion and probable language nuances...

As it is the same simple formula, sometimes. in non-inertial systems you can look at it from this point of view: inertia force acting to mass is proportional to its mass and acceleration.

As your car decelerats at known rate, the force your body encounters from the seat belt, for example. :)

 

Or, the weight is force and it is equal mg, where g is acceleration, though fictional in this case.

not alwayes you can feel it for example in free fall you dont feela thing but you are accelerating preaty fast

not alwayes you can feel it for example in free fall you dont feela thing but you are accelerating preaty fast

For the purpose of this discussion, try opening the door of a car at 120 km/h and then correlate how much "force" you may need at 300, 400 or 700 km/h...

You will feel it the moment you connect with the ground and Earth's mass "decelarates" you with the accumulated Newton.

For the purpose of this discussion, try opening the door of a car at 120 km/h and then correlate how much "force" you may need at 300, 400 or 700 km/h...

im here only becopuse Newton, not fluid mechanics

First of all, this is not my fight. I think everything is correct about the rolling characteristics after YoYos revision a few years ago.

2) according to the document the plane was tested in a dive starting at 10.7 Km MSL and an overall weight (Fluggewicht) of 2,900 kg.

Before we discuss any of these document's "findings" and “adapt" them to the simulated BF.109 K4, I would like to ask everyone to recreate these conditions, especially the WEIGHT.

The non liquid weight close to the longitudinal aircraft axis has absolutely negligible influence on roll characteristics. So if all I do is put a 500kg radio and/or a 50kg heavier gun in the fuselage which sits on the longitudinal axis, my roll characteristics dont vary a thing.

I also never said I did any "verification flights" at 2900 kg. Why would I? What I am supposed to verify with that? If you are talking about the elevator discussion, all I needed was CG in %MAC. But since you still havent understood the basic concepts, it is moot explaining why. I verified the power off curves of the soviet G-2 tests.

YoYo has accepted himself now that how double trim tabs were set in the high speed trials increase maximum nose down trim and that the K gearing ratio changed. Judging by the comments in that thread, the community seems to be hopeful that the elevator problematic finally gets resolved. No more discussion needed on that topic. So back to this topic.

Yep, and I just had the time to try recreating the test from the "document ( Diving_Test_109F_W.Nr.9228_ger_eng.pdf )" presented and while started reading through the German originals I noticed two interesting facts, already.

1) The plane used was an Bf.109 F with G Wings and no mentioning of the engine used.

What an interesting fact you noticed there... The aircraft used was Bf 109 V34b and therefore we know all about its history and engine and whatnot. Well at least one of the two of us seems to know. It also had an ejection seat and was one of the permanent DVL Versuchsträger aircraft at Rechlin rigged with measurement equipment. However, for roll comparison all that needs to be known is that it was a 109, had the stiffended G wings and standard G control column.

A Newton is actually an acceleration acting on a mass, but if I did read the left axis of the chart correct there was a scale of kN related to the pressure measured on the elevator?

 

Still wondering how you did set the weight to 2900 kg in DCS for the "verification flights you did". Any input on that?

Sure you can set the weight to 2900 kg, but what for?

First you talked about dynamic pressures on the elevator (I guess?). Now you switched to a force in kN. Would you mind telling me which chart in YoYos post you are talking about? Because I cant find any listing something in kN and it wouldnt make any sense either considering how the measurements in the test were done.

If you want to tell us, that it's totally easy to pull the stick against a force of roughly 7-8 KiloNewton (700-800 kg/m2) at 450 km/h against at least half a squremeter of elevator, with both hands, cramped into the cockpit with your knees bent and against the pedals, we can discuss.

 

Let's assume the elevators give you a counter force of "just" 350 - 400 Kg, I consider a bit of "stiffening" pretty realistic... but that's just my interpretation of the original charts and I may be wrong.

The only chart adressing dynamic pressures is the german one. Lets forget about that kN nonsense and check what the chart really tells us... at 450 km/h we have a dynamic elevator pressure of 1000 kg/m^2 and that translates to about 12 kg of stickforce! Are you honestly saying you cant move 12 kg? What are you?

We dont need to assume anything, especially not your 350-400 kgs of stickforce. How on earth do you think that by halving dynamic elevator pressure you get the stickforces??? It is not even the correct unit... You even misread the dynamic pressure against the airspeed, with both parameters being on the same damn axis! This is soooo sad, I dont know what to say. At least you got the last sentence correct...

I am totally not sure if you are trying to troll us into an angry reaction or if you are really that incapable.

Or am I missing something, ...?

Pretty much everything.. Jesus Christ..

The problem is you mistake some yaw effects for engine torque. And it doesn't seem like you are willing to consider that possibility.

Nope. Rather, the problem is there seems to be something badly off-kilter at your end.

For those who doubt the validity of how DCS TW aircraft behave, and the difficulties they simulate, I can say with some authority that they are pretty much spot on. Therefore, the problems being described on these forums are also very much representative of the real world. The thing that sets DCS apart from other PC based simulations, and a number of commercial simulators, both leisure and certified which I have experienced, is that so many of these factors deemed undesirable in the real world, are faithfully modelled, along with the challenges they bring.

What do I know about it? Well, I have spent a significant proportion of my professional flying career teaching both experienced and novice pilots how to fly and handle tail-dragging aircraft.

https://forums.eagle.ru/showpost.php?p=2989273&postcount=1

And he's not the only guy in the know who has said our warbirds are pretty good. Not even near. But you're not interested in that. No, you're only interested in being right, without giving even a red second's thought to the possibility that there may actually be something wrong at your end.

Out for now.

First of all, this is not my fight. I think everything is correct about the rolling characteristics after YoYos revision a few years ago.

 

 

 

The non liquid weight close to the longitudinal aircraft axis has absolutely negligible influence on roll characteristics. So if all I do is put a 500kg radio and/or a 50kg heavier gun in the fuselage which sits on the longitudinal axis, my roll characteristics dont vary a thing.

 

I also never said I did any "verification flights" at 2900 kg. Why would I? What I am supposed to verify with that? If you are talking about the elevator discussion, all I needed was CG in %MAC. But since you still havent understood the basic concepts, it is moot explaining why. I verified the power off curves of the soviet G-2 tests.

 

YoYo has accepted himself now that how double trim tabs were set in the high speed trials increase maximum nose down trim and that the K gearing ratio changed. Judging by the comments in that thread, the community seems to be hopeful that the elevator problematic finally gets resolved. No more discussion needed on that topic. So back to this topic.

 

 

 

What an interesting fact you noticed there... The aircraft used was Bf 109 V34b and therefore we know all about its history and engine and whatnot. Well at least one of the two of us seems to know. It also had an ejection seat and was one of the permanent DVL Versuchsträger aircraft at Rechlin rigged with measurement equipment. However, for roll comparison all that needs to be known is that it was a 109, had the stiffended G wings and standard G control column.

 

 

 

Sure you can set the weight to 2900 kg, but what for?

 

 

First you talked about dynamic pressures on the elevator (I guess?). Now you switched to a force in kN. Would you mind telling me which chart in YoYos post you are talking about? Because I cant find any listing something in kN and it wouldnt make any sense either considering how the measurements in the test were done.

 

 

 

The only chart adressing dynamic pressures is the german one. Lets forget about that kN nonsense and check what the chart really tells us... at 450 km/h we have a dynamic elevator pressure of 1000 kg/m^2 and that translates to about 12 kg of stickforce! Are you honestly saying you cant move 12 kg? What are you?

 

We dont need to assume anything, especially not your 350-400 kgs of stickforce. How on earth do you think that by halving dynamic elevator pressure you get the stickforces??? It is not even the correct unit... You even misread the dynamic pressure against the airspeed, with both parameters being on the same damn axis! This is soooo sad, I dont know what to say. At least you got the last sentence correct...

 

I am totally not sure if you are trying to troll us into an angry reaction or if you are really that incapable.

 

 

 

Pretty much everything.. Jesus Christ..

They don't want to accept the evidence. Maybe they're in the denial phase.. :)

The only chart adressing dynamic pressures is the german one. Lets forget about that kN nonsense and check what the chart really tells us... at 450 km/h we have a dynamic elevator pressure of 1000 kg/m^2 and that translates to about 12 kg of stickforce! Are you honestly saying you cant move 12 kg? What are you?

 

One arm, One leg,One eye pilot

One arm, One leg,One eye pilot

Sent from my Redmi 5 using Tapatalk

First of all, this is not my fight. I think everything is correct about the rolling characteristics after YoYos revision a few years ago.

 

 

 

The non liquid weight close to the longitudinal aircraft axis has absolutely negligible influence on roll characteristics. So if all I do is put a 500kg radio and/or a 50kg heavier gun in the fuselage which sits on the longitudinal axis, my roll characteristics dont vary a thing.

 

I also never said I did any "verification flights" at 2900 kg. Why would I? What I am supposed to verify with that? If you are talking about the elevator discussion, all I needed was CG in %MAC. But since you still havent understood the basic concepts, it is moot explaining why. I verified the power off curves of the soviet G-2 tests.

 

YoYo has accepted himself now that how double trim tabs were set in the high speed trials increase maximum nose down trim and that the K gearing ratio changed. Judging by the comments in that thread, the community seems to be hopeful that the elevator problematic finally gets resolved. No more discussion needed on that topic. So back to this topic.

 

 

 

What an interesting fact you noticed there... The aircraft used was Bf 109 V34b and therefore we know all about its history and engine and whatnot. Well at least one of the two of us seems to know. It also had an ejection seat and was one of the permanent DVL Versuchsträger aircraft at Rechlin rigged with measurement equipment. However, for roll comparison all that needs to be known is that it was a 109, had the stiffended G wings and standard G control column.

 

 

 

Sure you can set the weight to 2900 kg, but what for?

 

 

First you talked about dynamic pressures on the elevator (I guess?). Now you switched to a force in kN. Would you mind telling me which chart in YoYos post you are talking about? Because I cant find any listing something in kN and it wouldnt make any sense either considering how the measurements in the test were done.

 

 

 

The only chart adressing dynamic pressures is the german one. Lets forget about that kN nonsense and check what the chart really tells us... at 450 km/h we have a dynamic elevator pressure of 1000 kg/m^2 and that translates to about 12 kg of stickforce! Are you honestly saying you cant move 12 kg? What are you?

 

We dont need to assume anything, especially not your 350-400 kgs of stickforce. How on earth do you think that by halving dynamic elevator pressure you get the stickforces??? It is not even the correct unit... You even misread the dynamic pressure against the airspeed, with both parameters being on the same damn axis! This is soooo sad, I dont know what to say. At least you got the last sentence correct...

 

I am totally not sure if you are trying to troll us into an angry reaction or if you are really that incapable.

 

 

 

Pretty much everything.. Jesus Christ..

Let's assume the difference in weight doesn't matter and look at the elevator force, forgetting about kN or 1000 kg/m² for God's sake. As far as I've seen the elevators in the 109 are connected mechanical, with steel rods(?). How big are the combined elevators? I think we can assume roughly half a square meter? That means how much surface against the wind adjusted by the 33-35° deflection?

Now try to open a car door (should be a roughly similar size to the elevator) and try to open it against the windpressure at 120 km/h to a deflection of 30° and try to imagine the the force required at 450 km/h to reach 30° deflection? I dare guess it is more than a mere 12 kg. As far as I understand, that is, why pilots called the plane stick heavy in the dive. But again I maybe just to old and dumb to understand the forces at work and a 7-year old can move the stick in real life...

As for the rest of this discussion, pretty much what msalama said.

P.S. recently put in a bit time to fly the 109, again. I can fly it pretty well. When the tank isn't full any more, after take-off and climbing to altitude, I can trim her quite good, with just keeping a little rudder input and the trim wheel. Landing and take offs still work ok, if I concentrate and don't get overconfident, but that's just me.

You may experience it differently, depending on your prejzdices and learnings from different high fidelity Sims.

Ok, one last try. So you "tested" the flight behaviour of the simulated plane, exactly at the same conditions in the document, correct? You've set the plane to a gross weight of 2900 kg and have flown the whole test with 3kg(!!!) of fuel?

For Gods sake... NO! Let me qoute myself again!

I also never said I did any "verification flights" at 2900 kg. Why would I? What I am supposed to verify with that? If you are talking about the elevator discussion, all I needed was CG in %MAC. But since you still havent understood the basic concepts, it is moot explaining why. I verified the power off curves of the soviet G-2 tests.

I tested against the soviet G-2 docs from YoYos post at different CG in %MAC! What do you you not understand about this?? You do realize that a non gunpod G-2 at CG 28% MAC weighs ~3142 kg? I have made CG tables for G-2 and K-4 and then tested, you could easily do the same. No witchcraft involved...

My point is, that either the weight of the DCS K4 is off, by a couple hundred kilogram or the plane tested was way lighter, likely had a different engine, CoG and what not.

You still lack a basic understanding of CG! It doesnt matter what engine it had. Please, just ask Yo-Yo to explain it to you, or reread his sticky. He explains what he did and I did exactly the same.

Let's assume the difference in weight doesn't matter and look at the elevator force, forgetting about kN or 1000 kg/m² for God's sake. As far as I've seen the elevators in the 109 are connected mechanical, with steel rods(?). How big are the combined elevators? I think we can assume roughly half a square meter? That means how much surface against the wind adjusted by the 33-35° deflection?

Again, we dont need to assume anything because the charts provide all the necessary information. You still dont understand that dynamic pressure can not be directly translated into stick forces, because of such things as gearing factor eg. Why would you want to deflect the elevator to 35° at these speeds? The airframe would over G and self destruct way before. Makes no sense... The 109 elevator was obviously designed to limit G-forces to survivable levels, just like it is good practice. The charts say at va 650 kph (Mach 0,73) you can pull 2.8° elevator deflection with around 33 kg of stickforce in a 109 G, thats easily above 5Gs load. In a K-4 with different elevator gearing, this would only be 25 kg of stickforces.

Now try to open a car door (should be a roughly similar size to the elevator) and try to open it against the windpressure at 120 km/h to a deflection of 30° and try to imagine the the force required at 450 km/h to reach 30° deflection? I dare guess it is more than a mere 12 kg. As far as I understand, that is, why pilots called the plane stick heavy in the dive. But again I maybe just to old and dumb to understand the forces at work and a 7-year old can move the stick in real life...

And the charts again. You "assumed" at 450kph and 700-800 kg/m^2 the stickforces will be 350-400 kg, ridiculous right? I dont care what you think a car door does or does not do.

As for the rest of this discussion, pretty much what msalama said.

P.S. recently put in a bit time to fly the 109, again. I can fly it pretty well. When the tank isn't full any more, after take-off and climbing to altitude, I can trim her quite good, with just keeping a little rudder input and the trim wheel. Landing and take offs still work ok, if I concentrate and don't get overconfident, but that's just me.

You may experience it differently, depending on your prejzdices and learnings from different high fidelity Sims.

Who cares?! It doesnt change the fact that the DCS K-4 is modeling a G-2 elevator and not a K-4 one. YoYo has said it himself?

The only thing that is really for sure is 30% difference in the gear ratio.

...

And, of course, I agree with two last facts that the trim tabs DO help to maintain dive as 1 15' stab alone was not able - there is nothing contradicting with the scientific approach.

https://forums.eagle.ru/showpost.php?p=3912440&postcount=133

What is your point here? You "feel" its fine, good for you. Its still not a correct K-4 elevator. Now please just stop arguing in this nonsensical way.

To be fair, you did kind of cut what you wanted from Yo-Yo's response, the full response reads a little different, at least to me...

To be fair it says exactly that! YoYo confirmed there is a 30% difference in gear ratio between a G-2 and K-4. Since a 30% difference is not the same the current model obviously must be somehow incorrect, right? He later didnt post anymore, but also agreed that nose down trim was increased in this test. And any other statement wouldnt make much sense anyway because thats exactly what the test was about.

It doesnt change the fact that the DCS K-4 is modeling a G-2 elevator and not a K-4 one. YoYo has said it himself?

The only thing that is really for sure is 30% difference in the gear ratio.

So did that cut make any change in the correct statement? No.

Not really, if you read the rest of it, I still not seeing where Yo-Yo admitted something is wrong, although I am asking him to make sure. I would assume if you proved something wrong it would be slated to be fixed.

Not sure we are reading the same thing Sith? It is absolutely clear! There is a 30% difference in stickforces required and the current elevator model is wrong in several respects. It is funny how he is saying 30% lower stickforces doesnt make a difference, just the percentage of broken wings would increase significantly. Thats how small of a difference it would be, significantly more broken wings. lol :music_whistling:

YoYo knows the 109 elevator model is wrong and it should be corrected. The trim is also wrong, because somebody at ED did not know that the Luftwaffe set cruise to maximum continous power which incidentally is 1,15 ata for a G-2, but 1,35 ata for a K-4. I still have some hope ED cares at least somewhat about accurately modeling an aircraft, this long lasting bug gets finally fixed and the DCS K-4 finally is modeled as close as possible to a real historical K-4.

The only thing that is really for sure is 30% difference in the gear ratio.

The only point I would agree is the 30% increasing of gear ratio, giving 30% decreasing of required forces, but, as I mentioned above, the values of force limits in the simulation are set with a good volutarily approach, so 30% more... 30 less - nothing would be closer to real life taking in account that pilots are very different.

 

And, by the way, if we increase these limits the percentage of broken wings will be significantly higher.