Center of Gravity

[DD_Fenrir]

Jafferson - You assume fuselage alignment = AoA.

It doesn’t.

There’s a thing called angle of incidence. I suggest you do some further reading.

[Jafferson]

14 hours ago, Jafferson said:

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

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.

I can agree speed can push a nose a little bit, but not this much.

12 hours ago, kablamoman said:

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

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.

 

the horizon at 30.000 feet is lower

12 hours ago, razo+r said:

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.

 

So you guys try to tell me the misdesigned wings caused the pitchup and the unnatural attitude? never

Ok let's keep it simple what's the physics behind the pitchup behavior?

Edited June 7, 2022 by Jafferson

[razo+r]

11 hours ago, Jafferson said:

I can agree speed can push a nose a little bit, but not this much.

Then try to fly any airframe at its lowest and at its highest speed and see how much difference there is. 

Speed has an immense influence on the attitude of an aircraft. 

11 hours ago, Jafferson said:

the horizon at 30.000 feet is lower

Doesnt matter where the actual horizon is when you care more about the "artificial" horizon and level flight. 

11 hours ago, Jafferson said:

So you guys try to tell me the misdesigned wings caused the pitchup and the unnatural attitude? never

Ok let's keep it simple what's the physics behind the pitchup behavior?

 

Then why dont you explain what the pitchup (what do you even mean with pitchup) is causing? Its definitly not the Cg. An aircraft wont simply fly nose down or nose high because the Cg is too much forward or aft. 

[IIIJG52_Otto_]

On 6/4/2022 at 9:22 PM, Jafferson said:

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.

You are right,... and it was confirmed by Volker Bau a test pilot of Flugmuseum Messerschmitt.

[Jafferson]

11 hours ago, IIIJG52_Otto_ said:

You are right,... and it was confirmed by Volker Bau a test pilot of Flugmuseum Messerschmitt.

Thank you very much for this video, all right its confirmed by a 109 pilot, level flight is at Trim 0

 

And i got new evidence too, this is a historical document with content about a pre dive configuration.

Page: 9

Sorce: http://www.airwar.ru/other/manuals/[aviation] - [manuals] - Betriebs und Rustanleitung - Me-109E mit DB601.pdf

Digital Sorce: https://ww2aircraft.net%2Fforum%2Fattachments%2Fbf109e-handbuch-pdf.89212%2F&usg=AOvVaw3tAVNEfMKbKknLJc45lLBM

Translation:

VI. Flight under special conditions

a. dive

1. Adjust the horizontal-stabilizer trim so that the aircraft can only be kept in the nosedive by gently pressing . This condition is best created by turning from level trim to 1/2° tail-heavy trim. If it is detected during the dive that the Hand strength for the horizontal-rudder direction "push" decreases, then stop the dive immediately.

2. Throttle in idle position.

3. Make sure that the temperature of the lubricant and cooling water does not drop below 40°C. Depending on the weather, close the water cooler flaps halfway or fully.

4. Propeller position about 9.30 a.m.

Danger ! Maximum allowed engine speed for dive 3000 rpm.

Meaning: Its crystal clear, dive configuration was tail heavy. They pulled out the dive when the stick force decreased.

 

It's probably a misconception of reading the raw data, its also possible a unnoticed + or  - value in the FM is inverted. We also need to take into account how the dive test and Stick Force data was created, a weight scale was installed at the front instrument panel and we need to understand how this experiment works. A plausible explanation is the horizontal-stabilizer was trim full forward to create a counter force at the horizontal-rudder, the stick was placed at a weight scale to read the needed Stick force in Kg at a certain speed. The Stick Force experiment was not performed to make a depicton of flight charecteristics, the experiment shold only show how much Stick Force was needed to maneuver the Aircraft at a certain speed.

Edited June 7, 2022 by Jafferson

[Ala13_ManOWar]

On 6/7/2022 at 9:33 PM, Jafferson said:

Thank you very much for this video, all rght its confirmed by a 109 pilot, level flight is at Trim 0

Just for your knowledge, that individual is a (sadly for me) well known troll here with a new account, but still spilling idiocy everywhere over his bigotry about the subject (an "it's impossible that the almighty 109 flies like I don't like" kind). His blindness makes him say one thing and the opposite a second later about the subject talked here, but he finds no issue with that. Don't feed the trolls or use their lack of arguments making you a troll either .

Moreover, Mr Volker, as you can see in that video, had no idea what they were asking for (you see the amazingly good English from him, the one talking off camera at the end), nor they understood at all what he was answering. He meant the aircraft is nice, stable and pleasant to fly by being gentle at the controls (and not using more than 1.3 Ata, ahem), then they immediately get the conclusion that the aircraft should stay stable even when they mistreat throttle and controls, and that's not going to happen.

Anyhow, don't be fooled by these people, they don't really care about realism in the 109 or DCS at all, they only care about they getting the allegedly invincible 109 they wet dream of, and that's not going to happen either .

Edited June 9, 2022 by Ala13_ManOWar

[DD_Fenrir]

109 Fanboi: *quotes Bf 109E flight manual as citation for Bf 109K flight characteristics.*

Me: 

Edited June 8, 2022 by DD_Fenrir

[DD_Fenrir]

Sorry, but Jafferson, do you have ANY idea how irrelevant your arguments are?

 

Let's take a look at the differences between the two models shall we?

	Bf 109E-3	Bf 109K-4
Length (m)	8.74	9.02
Wingspan (m)	9.86	9.92
Wing Area (m2)	16.7	16.08
Empty Weight (kg)	2,125	2,800
Gross Weight (kg)	2,603	3,362
Horsepower	1,100	1,850

 

The gross weight alone of the K-4 is almost 30% above that of the E-3.

The max power output with MW-50 is 68% more!!

The prop is essentially a gyroscope stuck at one the ends of the aircraft farthest from the CoG; even a basic understanding of physics will tell you the more power you put through that, the more destabilising effect it has on the aircraft. That should instantly tell you that the K-4 is going to be notably more unstable at higher power settings, especially as airspeeds drop and the control surfaces become less effective.

The wing was drastically re-designed. The tail heavily redesigned.

Then you have additional tankage for the MW50 and it's plumbing behind the CoG.

Then I suspect some ballast in the tail to attempt to counter the additional weight of the DB605 vs the DB 601 in the nose.

All of which adds up to an aircraft of massive difference to the E-3.

Your assumptions are wildly off the mark.

It's not just a CoG issue btw; some of the tail heaviness of the K-4 comes from a different effect, one that comes into play at lower airspeeds and thusly increasing Angles of Attack.

In a nose up, power on situation there is increasing pitch instability as airspeed bleeds - with each degree of AoA increase a greater portion of your thrust line is now directed into the vertical, wanting to lift the nose for no pilot input. With a longitudinally stable aircraft this effect is counteracted by natural tendency to nose drop as speed decays. Not so with a neutrally stable aircraft such as the Bf 109K-4 (and incidentally the Spitfire).

 

Edited June 8, 2022 by DD_Fenrir

[fapador]

6 hours ago, DD_Fenrir said:

drastically

 

6 hours ago, DD_Fenrir said:

massive

 

6 hours ago, DD_Fenrir said:

wildly

Hyperbole level 100.

Your effort to prove a misleading point is admirable...

Lets shoot E-4 vs K-4  facts down 1 by 1.

- 8cm of length ( yah right it will lead to massive handling differences. Almost certain this is bacause of the new Larger Prop Cone cover blending with fuselage)

-Wow! 6 cm more Wingspan only to be caused by the elliptical addition to reduce induced drag WoW Totally different airframe!

-62 cm^2 more Wing Area maybe some difference here but again irrelevant as Center of lift remains exactly the same. I suspect this was changed to support an overall heavier airplane.

-Empty Weight : 675 Kg Heavier.... Irrelevant, as their distribution is what  matters the most and as far as I know, E model had Oxygen tanks further aft than the newer models and also newer models deleted heavy Tail supports, + some other changes that I cant recall precisely  atm

- Gross weight same as above..

- 750 Hp more .  Only difference would be on take of roll, cruise speed, Max speed and engine systems and management. + all 109 models after E-4 had a smaller more efficient lighter prop if I recall correctly.. ( Equilibrium maintained to balance for heavier engine)

So only the MW-50 Tank addition might perhaps change Aerodynamical handling which I highly doubt since other changes were made to counteract this, like E-4 Wing Guns deleted etc

+

BF-109 E-4 vs K-4 has almost exactly same CoG location...

 

Its like telling me a Cessna 152 flies differently than a Cessna 172

or a Piper Warrior III flies differently than a Turbo Arrow IV.

I have flown all 4 of these two sets of aircraft and they don't fly differently..  most importantly they don't display angle of attack differences in between them at each flight regime compared....

Only difference they display in a nutshell are Speeds they achieve, Engine management, Use full loading capability, and max Range.

Infact , like the one correct thing you said, all neutral stable planes fly similarly in a manner, that is they maintain their pitch attitude.

Also most planes  have their Center of gravity acting forward than the Center of Lift which makes them also similar

Its why airline pilots start to learn flying in General Aviation airplanes and not Training jets like the military does which mostly likely always have their CoG behind the Center of lift  .

 

Myth Busted!.

Edited June 8, 2022 by fapador

[fapador]

Also Speed which most clueless people here suggest that plays a major role to AoA in level flight is in reality  not so significant in Subsonic Flight. That is because the center of lift or pressure, doesn't change in speeds lower than 0.9-1Mach. Its only the overall lift that is affected. Thus in majority the AOA changes we might see are only because of possible stabilizer design counteracting insufficiencies which again don't happen as abruptly as DCS tries to make us believe

Edited June 8, 2022 by fapador

[razo+r]

28 minutes ago, fapador said:

Also Speed which most clueless people here suggest that plays a major role to AoA in level flight is in reality  not so significant in Subsonic Flight. 

Let's see.

So for level flight, L(ift)=W(eight), right? Good we can agree there.

So, what contributes to lift? Right, L=Cl x q x A.

 

A is constant.

W is for this case also constant.

Cl is mostly made of constants and one thing we can change, AoA. With changing AoA, we can directly influence Cl.

q is something we can also change by changing throttle settings.

 

Still with me I hope. Because now you need to be able to do simple math.

Let's say, we fly slow. q is low, A is a fixed value and Cl is also a specific value. Keep in mind the weight stays the same for now.

Now, if we increase q by flying faster, we have to decrease something for the equation to give the same value again, since our weight is currently a fixed value.

So, W is fixed, A is fixed, q is now higher and we only have Cl left to change. But how do we decrease Cl you may ask. Well, we decrease the AoA to decrease Cl.

Or now the other way around. If we lower q, or simply put fly slower, you have to increase Cl by increasing the AoA to maintain a lift force that equals the weight of your aircraft.

 

Conclusion: Speed directly influences at which AoA you have to fly to maintain straight and level flight.

 

Now let's put this into practical terms, shall we?

You said you are a PPL pilot and have flown various aircraft. Let's pick, for example, the 152. You surely have conducted slow flight training, right? I hope you did otherwise the following part may come as a surprise to you.

So during cruise you have a certain picture of you, your aircraft, the attitude of your aircraft and your environment, right? Now, once you started slowing down, without deploying flaps, what happend? That's right, as your aircraft slowed down, you had to raise your nose to maintain straight and level flight. And during all of this, your 152 only lost minimal amount of weight. If you put this into the little formula above, you can see the same happening I've explained. First, the lift you produced was equal to the weight at any time. Then, as q decreased, you had to increase Cl by increasing AoA to maintain straight and level flight. Or, unless you have a supersonic 152, I do hope this is what happened.

So by your statement, speed does not significantly influence AoA, is first of all wrong and if you are really a PPL pilot, I'd recommend you to go to your instructor and either ask for a refund or re-explanation of the principles of flight.

[DD_Fenrir]

51 minutes ago, fapador said:

 

 

Hyperbole level 100.

Your effort to prove a misleading point is admirable...

Lets shoot E-4 vs K-4  facts down 1 by 1.

- 8cm of length ( yah right it will lead to massive handling differences)

-Wow! 6 cm more Wingspan only to be caused by the elliptical addition to reduce induced drag WoW Totally different airframe!

-62 cm^2 more Wing Area maybe some difference here but again irrelevant as Center of lift remains exactly the same. I suspect this was changed to support an overall heavier airplane.

-Empty Weight : 675 Kg Heavier.... Irrelevant, as their distribution is what  matters the most and as far as I know, E model had Oxygen tanks further aft than the newer models and also newer models deleted heavy Tail supports, + some other changes that I cant recall precisely  atm

- Gross weight same as above..

- 750 Hp more .  Only difference would be on take of roll, cruise speed, Max speed and engine systems and management. + all 109 models after E-4 had a smaller more efficient lighter prop if I recall correctly.. ( Equilibrium maintained to balance for heavier engine)

So only the MW-50 Tank addition might perhaps change Aerodynamical handling which I highly doubt since other changes were made to counteract this, like E-4 Wing Guns deleted etc

+

BF-109 E-4 vs K-4 has almost exactly CoG location...

 

Its like telling me a Cessna 152 flies differently than a Cessna 172

or a Piper Warrior III flies differently than a Turbo Arrow IV.

I have flown all 4 of these two sets of aircraft and they don't fly differently..  most importantly they don't display angle of attack differences in all flight regimes....

Only difference they display in a nutshell are Speeds they achieve, Engine management, Use full loading capability, and max Range.

Infact , like the one correct thing you said, all neutral stable planes fly similarly in a manner, that is they maintain their pitch attitude.

Also most planes  have their Center of gravity acting forward than the Center of Lift which makes them also similar

Its why airline pilots start to learn flying in General Aviation airplanes and not Training jets like the military does which mostly likely always have their CoG behind the Center of lift  .

 

Myth Busted!.

 

Jesus. What a steaming pile of male cow manure. No wonder you rabid 109 fanbois are so indignant; your delusion is so deeply ingrained that you actually believe any of the tripe you just posted.

Wow.

 

[fapador]

17 minutes ago, razo+r said:

Let's see.

So for level flight, L(ift)=W(eight), right? Good we can agree there.

So, what contributes to lift? Right, L=Cl x q x A.

 

A is constant.

W is for this case also constant.

Cl is mostly made of constants and one thing we can change, AoA. With changing AoA, we can directly influence Cl.

q is something we can also change by changing throttle settings.

 

Still with me I hope. Because now you need to be able to do simple math.

Let's say, we fly slow. q is low, A is a fixed value and Cl is also a specific value. Keep in mind the weight stays the same for now.

Now, if we increase q by flying faster, we have to decrease something for the equation to give the same value again, since our weight is currently a fixed value.

So, W is fixed, A is fixed, q is now higher and we only have Cl left to change. But how do we decrease Cl you may ask. Well, we decrease the AoA to decrease Cl.

Or now the other way around. If we lower q, or simply put fly slower, you have to increase Cl by increasing the AoA to maintain a lift force that equals the weight of your aircraft.

 

Conclusion: Speed directly influences at which AoA you have to fly to maintain straight and level flight.

 

Now let's put this into practical terms, shall we?

You said you are a PPL pilot and have flown various aircraft. Let's pick, for example, the 152. You surely have conducted slow flight training, right? I hope you did otherwise the following part may come as a surprise to you.

So during cruise you have a certain picture of you, your aircraft, the attitude of your aircraft and your environment, right? Now, once you started slowing down, without deploying flaps, what happend? That's right, as your aircraft slowed down, you had to raise your nose to maintain straight and level flight. And during all of this, your 152 only lost minimal amount of weight. If you put this into the little formula above, you can see the same happening I've explained. First, the lift you produced was equal to the weight at any time. Then, as q decreased, you had to increase Cl by increasing AoA to maintain straight and level flight. Or, unless you have a supersonic 152, I do hope this is what happened.

So by your statement, speed does not significantly influence AoA, is first of all wrong and if you are really a PPL pilot, I'd recommend you to go to your instructor and either ask for a refund or re-explanation of the principles of flight.

Next lesson will be charged

[fapador]

Further more you are isolating my statement without reading the explanation below. Speed doesn't affect center of lift. AoA increases in SLOW Flight to compensate from loss of lift. I am not examining slow flight characteristics of the BF-109. @Jafferson did tests at 400+ kmh that ain't slow flying....

[grafspee]

@fapador so K-4 weight 700kg more over E/F version won't affect AOA level flight ? Seems weird to me.

Edited June 8, 2022 by grafspee

[kablamoman]

9 hours ago, fapador said:

Its like telling me a Cessna 152 flies differently than a Cessna 172

or a Piper Warrior III flies differently than a Turbo Arrow IV.

I have flown all 4 of these two sets of aircraft and they don't fly differently..  most importantly they don't display angle of attack differences in between them at each flight regime compared....

I don't know what to say.

Granted, it's been many moons since I've flown a light piston single, but as someone who used to instruct on some of these... Go home, you're drunk.

There were differences in handling characteristics between individual models of 172s let alone differences between them and a 152 or a piper. Try spinning a 172 vs. a 152, for instance. You're on crack, mate. I've tried reasoning with you in the past in attempts to clear up misconceptions and misunderstandings but I've come to the conclusion too much if what you contribute is in bad faith and not worth the time.

Good luck.

Edited June 8, 2022 by kablamoman

[fapador]

13 hours ago, grafspee said:

so K-4 weight 700kg more over E/F version won't affect AOA level flight ? Seems weird to me.

Not as much as you think, considering there is also an increase to wing area, a  drag reduction and the weight distribution remains very comparable to an E model . Especially when talking about cruise speed level flight regime.

 

12 hours ago, kablamoman said:

Try spinning a 172 vs. a 152

Sure will try that on the next chartered flight....

What a reckless statement, What a complete imbecile....,  you say you have ATPL... yeah right,   Yet you invoke someone to go and try aerobatic maneuvers in a non certified airplane.... That's how people in GA planes get killed, from pulling that <profanity>.

Nonetheless if you had a grain of brain you would have realised that I described normal flight regimes. Not extreme handling  maneuvers nor stall characteristics or stall speeds beyond any normal flight envelope...

[grafspee]

3 hours ago, fapador said:

Not as much as you think, considering there is also an increase to wing area, a  drag reduction and the weight distribution remains very comparable to an E model . Especially when talking about cruise speed level flight regime.

I'm really not sure about drag and weight distribution being comparable between E and K

As far as i know E was version with guns mounted in wings, smaller engine no cannon in prop hub on other hand K-4 13 mm mgs above engine, 30mm cannon bigger engine, probably a lot less draggy air frame (lots if aerodynamic improvements applied) i think weight distribution is miles away from Emil configuration. So Emil elevator trim system range would not work in K-4.

I don't know about other things like wings could be moved more forward or angle of incidence changed like you said changes would not be great to be easy picked up by naked eye, at cruise speed very small change will impact noticeably.

Pls don't tell me that those differences won't change things as much as i think, because every god damm plane would fly exactly the same.

Edited June 9, 2022 by grafspee

[fapador]

32 minutes ago, grafspee said:

I'm really not sure about drag and weight distribution being comparable between E and K

As far as i know E was version with guns mounted in wings, smaller engine no cannon in prop hub on other hand K-4 13 mm mgs above engine, 30mm cannon bigger engine, probably a lot less draggy air frame (lots if aerodynamic improvements applied) i think weight distribution is miles away from Emil configuration. So Emil elevator trim system range would not work in K-4.

I don't know about other things like wings could be moved more forward or angle of incidence changed like you said changes would not be great to be easy picked up by naked eye, at cruise speed very small change will impact noticeably.

Pls don't tell me that those differences won't change things as much as i think, because every god damm plane would fly exactly the same.

Numero 1 strike : 7.92 mg17 with more ammo replaced by 13mm with less ammo.

Numero 2 strike : Bf109 f models and all after used a propeller and hub mechanism a lot lighter than emil + as I said read my previous post were its clearly seen that there is not so much difference Weight distribution wise if you consider the sum of all changes. 

Numero 3 strike : Elevator trim range is infact so comparable designers opted to keep exactly the same mechanism with +2 -6 degrees range

Numero 4 strike : wings are exactly on the same position

 

 

It seems you cant see the forest for the trees. You are free to believe whatever you like just don't insist on making others believe what you want.

Nevertheless I would always opt for  a K-4 FM handling like an exact EMIL 109 with more speed rather this absurd FM we have currently with massive AoA differences compared to Emil level flight test data and even G-K flight testimonial reports in relation to yaw and rudder pedal requirements at various speeds.

[fapador]

Also please stop delibaretely choosing to opt out mentions and what they replaced like this:. 

Its very misleading to clueless people reading the posts.

52 minutes ago, grafspee said:

on other hand K-4 13 mm mgs above engine

.

[fapador]

Moreover. that interview with Volker Bau was made by members efforts of a Virtual Squadron known to be very dissapointed with DCS 109 flight handling.

Personally, as I have seen this video before and the ED video showing an Erich Brunotte clearly dissapointed with Fm handling of the Dora, is more than enough for me to doubt the sims Fm's

 

Edited June 9, 2022 by fapador

[fapador]

1 hour ago, grafspee said:

I'm really not sure about drag and weight distribution being comparable between E and K

Never said that the drag is comparable between E-K please don't put words on my mouth.

[grafspee]

4 hours ago, fapador said:

Not as much as you think, considering there is also an increase to wing area, a  drag reduction and the weight distribution remains very comparable to an E model .

I'm not.

[DD_Fenrir]

22 minutes ago, fapador said:

Personally, as I have seen this video before and the ED video showing an Erich Brunotte clearly dissapointed with Fm handling of the Dora, is more than enough for me to doubt the sims Fm's

 

 

Source?

[fapador]

56 minutes ago, grafspee said:

I'm not.

Jesus I said A drag reduction as in general, not drag and weight distribution is comparable.

No wonder its difficult to comprehend...