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I took some flight tests with different loadings. The find out that the fuel amount makes drammatic changes in the CoG of this plane. I wish we had an indicator showing the changes in the CoG with loading something like as in MS-FSX.

 

Then maybe this discussion might never existed.


Edited by Europa
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I took some flight tests with different loadings. The find out that the fuel amount makes drammatic changes in the CoG of this plane. I wish we had an indicator showing the changes in the CoG with loading something like as in MS-FSX.

 

Then maybe this discussion might never existed.

 

Remember my suggestion some posts above ? :-)

 

Not only fuel loading but also amno.

Flight Simulation is the Virtual Materialization of a Dream...

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Remember my suggestion some posts above ? :-)

 

Not only fuel loading but also amno.

 

I made the tests with and without ammo and fuel after you. Thank you again. If it was possible to visually see how the CoG moved with different loadings it will be more clear I believe.

 

I have a rough idea for the fuel as I know the quantity and place of the tank but not sure about how much the ammo loading will displace the CoG.


Edited by Europa
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  • 4 years later...

Can a Developer post a side picture of the COG please, where is the COG located at 100% fuel and ammo in DCS? And how the COG shifts at 1% fuel? Please

Usually the COG should be at the point where the Payload mount is located, but DCS feels more like COG is somewhere in the middel between the Wings and the Elevator.

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These posts pop up from time to time, somewhere on the forums those images were posted time ago. CoG was about at the pilot IIRC which makes sense since you're sitting on top of the fuel tank.

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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6 hours ago, Jafferson said:

Can a Developer post a side picture of the COG please, where is the COG located at 100% fuel and ammo in DCS? And how the COG shifts at 1% fuel? Please

Usually the COG should be at the point where the Payload mount is located, but DCS feels more like COG is somewhere in the middel between the Wings and the Elevator.

 

6 hours ago, Ala13_ManOWar said:

These posts pop up from time to time, somewhere on the forums those images were posted time ago. CoG was about at the pilot IIRC which makes sense since you're sitting on top of the fuel tank.

 

Yes I know, it's a never ending story. From time to time i come back to the 109. Some years ago I modified my pitch axis nose down and stopped caring. But still feels wrong. The rudder is producing drag, the nose down attitude of the plane is producing drag.

Yes the Pilot is sitting on top of the fuel tank... and the fuel tank is sitting on top of the wings. Everything heavy is in front and on top of the wings, the Prop, Engine, Radiators, landing gear, oxygen, cockpit, Pilot, ammo and fuel.

14.gif

The only thing is MW50 in the back of the seat with 85kg. The engine is in Front and  have a weight of near 800kg, the fuel tank got a capacity of 400kg. The tail is never this heavy, what is the weight at the tail wheel real one?

For example, in this picture we can see the cable is mounted near the COG. It's still nose heavy so they had to add a cable at the nose.

bf109g-6_ha-1112-m1l_spanishaf_g-awhs-4_

I think the 109 armed and fueled, the COG is between the landing gear at payload mount. Should be able fly level with 0 trim.

YoYo was right with the data and the range of the elevator. But today i think, something is not right with the weight balance of this plane.

Ok it's maybe only a model, however this guy show's how to set up the COG for his plane, but it's still the same aerodynamic frame.

 

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9 minutes ago, Jafferson said:

For example, in this picture we can see the cable is mounted near the COG. It's still nose heavy so they had to add a cable at the nose.

bf109g-6_ha-1112-m1l_spanishaf_g-awhs-4_

I think the 109 armed and fueled, the COG is between the landing gear at payload mount. Should be able fly level with 0 trim.

Nope, sorry, that's a really, really, reaaaaalllyyyy bad mockup (Emil tail and tailwheel, awfully wrong nose trying to depict a weird G-14, c'mon mate 🙄). That's no example for nothing but awful museum pieces which shouldn't exist. Not to mention, even if it were a real 109, which it isn't, it's clearly hollowed, no engine, no cockpit, no nothing, hence no CoG any related to an aircraft in flight order and the model we discuss here.

 

Should it be able to fly with 0 trim? Nope, it shouldn't. Well, better said, it does fly hands off (which doesn't mean trim=0), but it does in a certain way while cruising, not in the middle of a combat 1.8Ata running with radiator flaps (auto)opened and everything, that's never hands off until you have FBW. The persistent problem is that IRL you have no problem holding a long stick in the position you want, that's not a problem until high speed when pressure comes to become unsurmountable under certain conditions, specially dives, but that's a very precise scenario. Second persistent no problem, I have absolutely none, zero, not at all, problems holding my long stick here or any other plane, but you have to make your own stick extension or get a commercial one for a proper joystick (Warthog or similar). Neither of those, the difference between real life and a simulator, and your limiting hardware, are actually related to ED which only modelled the thing as it should be as per available documentations extensively shown and explained here to exhaustion. If the infamous post keeps coming from time to time after explaining and showing the documentations to everybody (there's a stuck post somewhere with all of this and probably the chart you asked for) I can't blame ED for not keeping trying to fight an impossible war against not reading or trying to understand the documents shown.

A change for that situation means:

1.- You have unearthed an obscure previously unknown document showing whatever it is and changing everything we know about the aircraft.

2.- You accept your beloved mighty invincible fighter is like that as the factory documents shows and start enjoying how beautiful she actually flies (because she does fly beautifully, only bad tempered if you mistreat her). You wanted a realistic simulation? There you go with one, cope with that.

3.- If we get a Bf109G-6 at some point, it will still be like that, but different prop, weight, and whatever probably means a change and the effect maybe wouldn't be so accused. Just wait.

 

P.S.: should I had known, suspect in the slightest, the apparent innocent CoG question was, again, related to 0 trim and people not liking their home joysticks setups, as usual, I wouldn't even had answered in the first place  😉 .

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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In my opinion K-4 in DCS act like it has very forward moved COG, K-4 require very larger elevator deflection for G, so elevator need to act with great force on the airframe to induce significant G because it has to fight with very forward moved COG, in K-4 trim is done via horizontal stabilizer incidence angle and 0 on the trim dial does not mean that plane will fly straight. But K-4 n dcs definitely does not act like plane with COG in half way from wings to tail section no way:)

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On 6/4/2022 at 10:20 PM, Ala13_ManOWar said:

Nope, sorry, that's a really, really, reaaaaalllyyyy bad mockup (Emil tail and tailwheel, awfully wrong nose trying to depict a weird G-14, c'mon mate 🙄). That's no example for nothing but awful museum pieces which shouldn't exist. Not to mention, even if it were a real 109, which it isn't, it's clearly hollowed, no engine, no cockpit, no nothing, hence no CoG any related to an aircraft in flight order and the model we discuss here.

 

Should it be able to fly with 0 trim? Nope, it shouldn't. Well, better said, it does fly hands off (which doesn't mean trim=0), but it does in a certain way while cruising, not in the middle of a combat 1.8Ata running with radiator flaps (auto)opened and everything, that's never hands off until you have FBW. The persistent problem is that IRL you have no problem holding a long stick in the position you want, that's not a problem until high speed when pressure comes to become unsurmountable under certain conditions, specially dives, but that's a very precise scenario. Second persistent no problem, I have absolutely none, zero, not at all, problems holding my long stick here or any other plane, but you have to make your own stick extension or get a commercial one for a proper joystick (Warthog or similar). Neither of those, the difference between real life and a simulator, and your limiting hardware, are actually related to ED which only modelled the thing as it should be as per available documentations extensively shown and explained here to exhaustion. If the infamous post keeps coming from time to time after explaining and showing the documentations to everybody (there's a stuck post somewhere with all of this and probably the chart you asked for) I can't blame ED for not keeping trying to fight an impossible war against not reading or trying to understand the documents shown.

A change for that situation means:

1.- You have unearthed an obscure previously unknown document showing whatever it is and changing everything we know about the aircraft.

2.- You accept your beloved mighty invincible fighter is like that as the factory documents shows and start enjoying how beautiful she actually flies (because she does fly beautifully, only bad tempered if you mistreat her). You wanted a realistic simulation? There you go with one, cope with that.

3.- If we get a Bf109G-6 at some point, it will still be like that, but different prop, weight, and whatever probably means a change and the effect maybe wouldn't be so accused. Just wait.

 

P.S.: should I had known, suspect in the slightest, the apparent innocent CoG question was, again, related to 0 trim and people not liking their home joysticks setups, as usual, I wouldn't even had answered in the first place  😉 .

Thank you very much for this long post. If this plane really got no engine no cockpit, we can see, it's still nose heavy 😉

We got data from dive tests, yes they used nose down trim to stay in the dive. But dive configuration is not level flight, there is simply no data about level flight configuration. Not a single offical Luftwaffe document was found. If someone got a Luftwaffe document about level flight configuration and procedures, please show me. It's only assumption they used dive configuration for level flight.

DCS Flight characteristics shows clearly, the COG is somewhere in the aft beyond the pilot seat. If this is the case, we all can agree there is something not right with the COG.

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Somewhat "bad" trimming qualities due to the engineers trying not to kill every pilot diving (as the famous paper you mention shows) doesn't mean CoG is aft of nothing. I can trim backwards any plane and behaviour would be similar. Actually I had the same problem with a Cessna in my baptism due to 4 people in the plane and too much fuel, that's a real CoG issue, though I trimmed later and had no problem with that (only take off and initial climb was a bit cumbersome for me since it was my very first time at the controls). The fact that here it's a CoG issue is only your guess, so all the "clearly shows", "we all can agree", and so stuff is not that clear mate.


Edited by Ala13_ManOWar

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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1 hour ago, Jafferson said:

 😉 Flight characteristics shows clearly, the COG is somewhere in the aft beyond the pilot seat. If this is the case, we all can agree there is something not right with the COG.

Mind you, how could it be, if Yo-Yo showed in the sticky thread that he used Gustav trim curves with COG at 21-25% MAC (+ extrapolation) for K-4 flight model? That still in front of the cockpit.

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Bf109K4 flies great, you only have to know the quirks and use the right procedures. Oh, wait, like in real life aircraft? No way, impossible, how come?

"I went into the British Army believing that if you want peace you must prepare for war. I believe now that if you prepare for war, you get war."

-- Major-General Frederick B. Maurice

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1 hour ago, fapador said:

K-4 fly's like a hog strapped with bricks. I can make paper planes that fly better than the DCS depiction...

Real Pilot with PPL here.

LOL.

Says the guy who was convinced all 109s after E model had aileron droop with flap deployment because he read it in a fine scale modeling book despite all evidence to the contrary and then complained to mods to close his own thread when he was shown to be thoroughly mistaken.

You seem to really enjoy posting disparaging remarks about the hard-researched flight modeling in the game -- maybe it's time to find a new hobby and design a flight simulator of your own?

Real Pilot with ATPL here.


Edited by kablamoman
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2 hours ago, Ala13_ManOWar said:

The fact that here it's a CoG issue is only your guess,

 

Its not guessing, and i prove it with a picture.

20220606171920_1.jpg

Configuration is 100% fuel and MW50 + ammo. She is pointing nose down in level flight, for comparation all other warbirds pointing at the horizon in level. Can someone explain why she does that? Why a Manufacture shold build a fighter aircraft shooting nose down? It makes no sense, its evidence that something is not right here. 100% or 1% fuel makes no difference in this odd behavier. A plane with this attitude would be in a descend, but she is not.

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5 minutes ago, Jafferson said:

A plane with this attitude would be in a descend, but she is not.

Ladies and gentlemen of the jury, I'm just a caveman. I fell in some ice, and later got thawed out by some of your scientists. Your world frightens and confuses me. Sometimes the honking horns of your traffic make me want to get out of my BMW, and run off into the hills... or whatever. Sometimes when I get a message on my fax machine, I wonder: Did little demons get inside and type it? I don't know! My primitive mind can't grasp these concepts...

But there is one thing I do know: An aircraft's attitude in level flight is determined by more than just center of gravity.

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1 minute ago, kablamoman said:

Ladies and gentlemen of the jury, I'm just a caveman. I fell in some ice, and later got thawed out by some of your scientists. Your world frightens and confuses me. Sometimes the honking horns of your traffic make me want to get out of my BMW, and run off into the hills... or whatever. Sometimes when I get a message on my fax machine, I wonder: Did little demons get inside and type it? I don't know! My primitive mind can't grasp these concepts...

But there is one thing I do know: An aircraft's attitude in level flight is determined by more than just center of gravity.

Ok than clarify, explain why she does that please.

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1 minute ago, Jafferson said:

Ok than clarify, explain why she does that please.

The aircraft produces so much lift at those high speeds that it requires a negative AoA to produce a Cl to maintain level flight.

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16 minutes ago, razo+r said:

The aircraft produces so much lift at those high speeds that it requires a negative AoA to produce a Cl to maintain level flight.

If this would be the natural attitude of the plane the convergence point of the guns would aim at the horizon and its not. I dont think there is a problem with the convergence point.

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1 minute ago, Jafferson said:

If this would be the natural attitude of the plane the convergence point of the guns would aim at the horizon and its not. I dont think there is a problem with the convergence point.

Maybe try it at a lower speed?

Or maybe up at 30,000 feet?

Anything that has an affect on lift including air pressure, velocity or even things like like wing design and angle of incidence and tail moments will interplay with center of gravity to affect the resultant attitude you end up with for level flight.

 

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13 minutes ago, Jafferson said:

If this would be the natural attitude of the plane the convergence point of the guns would aim at the horizon and its not. I dont think there is a problem with the convergence point.

It is indeed not the "natural" attitude because this aircraft does not cruise around at combat/WEP power or spends most of it's time at ~600kph, so your example depicts a very limited/rare case.


Edited by razo+r
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5 minutes ago, kablamoman said:

Maybe try it at a lower speed?

Or maybe up at 30,000 feet?

Anything that has an affect on lift including air pressure, velocity or even things like like wing design and angle of incidence and tail moments will interplay with center of gravity to affect the resultant attitude you end up with for level flight.

 

At what speed 300 kph 0,8 ATA? is not a combat setting.

1 minute ago, razo+r said:

It is indeed not the natural attitude because this aircraft does not cruise around at combat/WEP power or spends most of it's time at +600kph, so your example depicts a very limited/rare case.

 

She behaves the same at lower speed 400-500-600 kph makes no diffrence.

A Magical lift is not a explanation, where is this lift coming from? The only thing what gets lifted is the heavy tail.

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14 minutes ago, Jafferson said:

At what speed 300 kph 0,8 ATA? is not a combat setting.

Full Throttle with MW-50 at 30,000 and you'll find the attitude for level flight is decidedly nose-high.

14 minutes ago, Jafferson said:

She behaves the same at lower speed 400-500-600 kph makes no diffrence.

Absolutely untrue. The attitude for level flight at 500 kph close to the ground is pretty close to bang-on the horizon. 300 kph is really nose high.

You can't simply say you have an inaccurate representation of the aircraft's center of gravity because you think the attitude is too nose-low in certain conditions.

The reality is that there are many factors that interplay to give you attitudes for level flight, and you are absolutely not going to get the same results between two separate aircraft designs -- making your comparison and assertion a bad one.

The fact is that you don't know what typical attitudes looked like in a 109 because you have never flown them in real life. Even if someone had flown a G6, is it going to behave the same as a K4 in terms of this kind of thing? We don't know.

The devs have at least looked at hard data and have come to certain conclusions. Not to say they can't be mistaken sometimes, but I tend to give that more credence than people randomly pulling stuff out of their ass online.


Edited by kablamoman
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19 minutes ago, Jafferson said:

She behaves the same at lower speed 400-500-600 kph makes no diffrence.

A Magical lift is not a explanation, where is this lift coming from? The only thing what gets lifted is the heavy tail.

At ~430 kph I got an AoA of about 0 degrees, so there is a difference.

Where does this lift come from? From dynamic pressure aka speed and Cl. I suggest you to look at the lift formula, maybe by seeing what variables play a role in the amount of lift you'll get, you'll understand why the airplane has a different attitude at different speeds given level flight.

So you see, less speed requires more AoA to keep the aircraft in level flight. More speed and you need less AoA for level flight.


Edited by razo+r
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