Fw 190 AoA

[Charge]

Exactly what Stoney said. The NACA profile of 190 can maintain lift up to 15-16 degrees of AoA at certain Reynolds number, add to that 2 degrees washout at wingtips and you get the point of max AoA around 17-18 degrees.

There has been talk about the wing structure change (A6 onwards) and its effect on premature stall so that the FW's wing would flex and thus have the effect of less effective washout but I don't agree with such speculations. If there would be change in roll performance between A5 and A8 (without added weight in wings) that would support claim of bad effects of wing flexing on max AoA.

Anax: the weight of cowl guns is almost at the centre of CoL so their effect is quite small on a/c balance.

-C+

[Krusty]

MG131s aren't an issue.

The CoG issue has been brought up in the history of the 190a8. Read up on it. They had to move the ETC rack forward 8 inches or so to re-balance it. It was thought to be dangerously unstable (like the P-51 with full aft aux tank, for a contemporary comparison). The ETC rack is about 130lbs I believe. This moves the CoG forward.

If you don't think the CoG is important, take a 190a8 to 10k, burn off your entire forward tank, dive bomb something down to 3k, pull up. You'll be missing both your wings about now. Do the same, but drain your AFT tank first. This time you'll have no problem.

Our 190A8 is overweight by a large margin. [EDIT several hundred pounds] It's almost as if they modeled the heavy sturmbock variant but WITHOUT any of the armor modeled into the damage system.

Here's the thing: The A8 is no more sturdy than the A5 in-game. The F-8 is modeled with more armor (you'll rarely get an oil leak in that thing!) but is the heaviest 190 in the game. The 190a8 as-modeled has too much weight for no added benefit.

As for making-do with what we have, you can mix it up even without resorting to flying on fumes. I just took a 4x 20mm A8 package up last night and landed 5 kills with it, most of it against n1k2s, las, spits, p38s, and other capable rides. I wasn't alone, but I was mixing it up. I've had the 2-gun package before and held my own against superior foes at times, as well. I had a very hard-fought fight with a yak9u in a 2-gun 190a8 once, and it was a 5-6 minute long stalemate of turns, scissors, overshoots, etc. I made a mistake, almost got killed, a country-mate made the yak break and I was able to remerge and got the kill.

For reference:
Discussion of 190a8 weights in-game, including how we got the ETC weight added to the A8:
http://bbs.hitechcreations.com/smf/index.php/topic,228970.0.html

Discussion about 190a8 weights as-modeled in AH, across 190 models:
http://bbs.hitechcreations.com/smf/index.php/topic,197645.0.html

[Anaxogoras]

Oh, I have no trouble with the A8.  I've landed 9 kills in it without rearm (no vultching), and could probably do more if I were a better pilot or a more skilled marskman.

What's a good way to test AoA in the game?  I'd love to tie a piece of string to my wingtip, but I don't think HT will let me do that.

[Stoney]

If you don't think the CoG is important, take a 190a8 to 10k, burn off your entire forward tank, dive bomb something down to 3k, pull up. You'll be missing both your wings about now. Do the same, but drain your AFT tank first. This time you'll have no problem.

I didn't mean for anyone to interpret that CG is not important, merely that using a description of an "Aft CG" to explain poor turn performance is imprecise.  Again, center of gravity affects stability only. 

I can't explain why the wings depart on an Aft CG pullout versus a forward CG pullout.  An aft CG would make the elevator more effective, so perhaps you are able to load up the wings so fast that they depart?  That's not a function of CG directly, but more of a G-load issue.

[Krusty]

Stability is important in turning tightly, Stoney. Do you recall the pre-2.06 update where the airflow code was updated? Before that point the 190s were so unstable that you could not pull any AoA (even if level, not banked) without instantly snap-stalling 180 degrees inverted, below the speed of 230mph or so. Even near this speed it was dangerous to manuver. The issue was stability. The wings snap-stalled, insta-dropped, flopped about. That has a MAJOR impact on your ability to sustain a tight turn, if you're fighting the ride more than the enemy.

In that regard, CoG is very important for turn fighting, and is one major reason not many turn fight the Ta152 (bad CoG on that one) The turn radius is okay, the AoA is okay, but the instability when trying to utilize either prohibits it.

Don't get me wrong the 190s are way better than they used to be. Much of the bugs have been ironed out. It's just that the CoG is probably very important for those that dogfight this thing effectively.

[bongaroo]

"Its what the luftwaffe did" oh really?
Krusty, pls find some pics of 190s with a fuel tank rack without a fuel tank for us pls.
*Edit good point about the A8's other tank still being there though.


AH Fw190s and AOA
190s have roll rate in here, but the turn rate, instant and sustained, sux terribly. In AW3, it used to be able to do 'few second sharp turns' without much penalty to speed / energy. After the few secs tho, speed/energy dropped off fast. With the instant turn rates, one could get snap shots off, also could throw off trailing planes for a min to get speed back.

In aw3, what you couldn't out run, you needed to try to force to fly past you. This was done by fast rolling and short duration high g turns. Hence: balance three angles, your direction (towards your friends or base) and your angle on horizon (if about to stall, get nose down, if got extra speed, then can nose up) with the angle of the enemy behind you's nose with your plane (to stay out of his front / bullets), all the while looking out back window to see his bullets. Land is very wavy in AH, so ya have to look forward alot also if not over water. In here the acceleration of 190s seems so poor that once ya give up speed, nm trying to out run. And since turn rate is so bad, nm trying to force overshoot. Just bail out! Doomed! SUX!
And peeps yell 'picker' and 'come back skilless dweeb'

Aceshigh A5's are too slow, no acceleration, can turn if leave outer guns at home. Can get peeps mad at you if out turn em, I've had a few aces upset since they couldn't figure out what i was doing... (no outer guns and low gas) lol. IF enemy just flys straight, they out run me in secs, even with my weak amo hitting! SUX!

Aceshigh A8's are too slow, no acceleration, can't turn with or without outer guns. This plane could have won the war if they just put the guns facing backwards, sigh SUX! Aw3 book says they were fast.

Aceshigh D9's are faster than other 190s, but still slow compared to any late war contender - plenty stuff in the sky is still faster, no acceleration, weak amo means you have to give up speed to saddle. So in combat in the MA, a d9 might get a kill, but he lucky if has time to accelerate up to speed again.

Aceshigh Ta152 ... i've seen employed as a ground attack... sigh. Soo fragile that only a fewl would spend an hour getting to 30k just to be downed by a bombers tail gun in first seconds.
Btw, WHY??? do the d9's seem like no springs in the gear at all while the Ta's bounce more than rubber ball.

SHawk had a tough time keeping his P47 behind my 190a5 last night.  If you can't force the overshoot using that amazing roll rate with some clever rudder slips and throttle control you just need more practice.  It isn't always easy; but it is certainly possible.

Your breakdown of 190s is obviously reliant upon your previous experience in a different game.

[Cthulhu]

Exactly what Stoney said. The NACA profile of 190 can maintain lift up to 15-16 degrees of AoA at certain Reynolds number, add to that 2 degrees washout at wingtips and you get the point of max AoA around 17-18 degrees.

There has been talk about the wing structure change (A6 onwards) and its effect on premature stall so that the FW's wing would flex and thus have the effect of less effective washout but I don't agree with such speculations. If there would be change in roll performance between A5 and A8 (without added weight in wings) that would support claim of bad effects of wing flexing on max AoA.

Anax: the weight of cowl guns is almost at the centre of CoL so their effect is quite small on a/c balance.

-C+

Charge, I agree. I don't see how increased wing twist could possibly affect lift (via a change in washout) and not have a serious effect on roll performance (up to and including aileron reversal at high speed). And I don't think any of us have seen that. Given the 190's impressive roll response, I'd guess the torsional stiffness of the wing is pretty high.

[Stoney]

Stability is important in turning tightly, Stoney. Do you recall the pre-2.06 update where the airflow code was updated? Before that point the 190s were so unstable that you could not pull any AoA (even if level, not banked) without instantly snap-stalling 180 degrees inverted, below the speed of 230mph or so. Even near this speed it was dangerous to manuver. The issue was stability. The wings snap-stalled, insta-dropped, flopped about. That has a MAJOR impact on your ability to sustain a tight turn, if you're fighting the ride more than the enemy.

In that regard, CoG is very important for turn fighting, and is one major reason not many turn fight the Ta152 (bad CoG on that one) The turn radius is okay, the AoA is okay, but the instability when trying to utilize either prohibits it.

Don't get me wrong the 190s are way better than they used to be. Much of the bugs have been ironed out. It's just that the CoG is probably very important for those that dogfight this thing effectively.

This isn't stability in its aerodynamic definition Krusty.  What you're describing here is loss of lift--snap stalls, accelerated stalls, etc caused by pulling too hard (too much AoA) during turns.  If one wing tip stalls, the root doesn't, and the other wing doesn't, it can cause this type of phenomenon.  Given the taper of the wing and airfoil, the wing tips stall before the rest of the wing.  In a turn, the inside wing-tip stalls first, causing the "insta-flop" you describe.  Its similar to the handling of the plane when the wing-tip has been blown off.

Aerodynamic stability is expressed as static (positive, neutral, negative) and dynamic.  I won't get into a discussion about what it is since this article:  http://www.owlnet.rice.edu/~mech594/handouts/aircraft_stability_control.pdf articulates it much better.  But, I will restate that CG affects stability only.  Turning performance is more a function of lift.  I can look up the mathematical equations to illustrate that statement, but not until I get home.

My point is that to discuss the issue properly, you have to use the proper terminology.  The proper way to describe the "insta-flop" tendencies would be to say "...at high angles of attack, the FW190 displays high static instability along the roll axis..."  But, the foreward and aft movement of weight that you described as a result of fuel load, or the external pylon position are factors that affect pitch stability.  Factors that affect pitch stability are, generally speaking, the distance of the center of gravity from the center of lift, the distance between the elevator/horizontal stabilizer from the center of lift, and the size of the horizontal stabilizer in relation to the size of the wing(s).

[Krusty]

In-game the CoG is the point around which the plane pivots in pitch. This is why you rip your wings off if you drain the FWD tank first in my dive bombing 190a8 example, but you don't if you drain the AFT first.

If the CoG is towards the center of lift, the aircraft can manuver without disrupting that same lift you were talking about. It's like a flatbed cart at Home Depot, only one wheel in the center. If you are careful and the weight is over that pivot point, you can get around easier. If your single point, your wheel, is at the rear end, and the weight is in the same point in the center, you now have to push a lot more of the front end around, swinging it back and forth rather than turning it.


So, say hypothetically the pivot point (CoG) of a plane is in the middle of the wing. The wing can pitch up and down normally. Now say the pivot point is at the trailing edge of the wing. Let's take it further to show what I mean. Let's say the pivot point is well past the wing's trailing edge. Now to pivot the same amount you're not just pitching the wing. Now you have to push the wing into the wind or pull it out of the wind for any pitch movement you need. All of a sudden it becomes a sail, an oar, a paddlewheel. The AoA may remain the same, but the force of pushing the entire wing upwards into the air stream (assuming a "pull stick back to turn" motion) you're disrupting the air a hell of a lot more than you would if the wing's main spar were the pivot point.


So maybe the AoA is still the same, but the rest of the flight characteristics are affected by this CoG shift?

Just a thought. I don't know all the physics involved, all the forces and how they interact (quite complex interactions no doubt). All I know is that rearward-oriented CoGs are not good for dogfighting. This from experience, and having read a comment or two regarding real planes that says the same thing.

[Stoney]

In-game the CoG is the point around which the plane pivots in pitch. This is why you rip your wings off if you drain the FWD tank first in my dive bombing 190a8 example, but you don't if you drain the AFT first.

Explain how an aft shift in weight makes the plane more likely to shed its wings?

Let's say the pivot point is well past the wing's trailing edge. Now to pivot the same amount you're not just pitching the wing. Now you have to push the wing into the wind or pull it out of the wind for any pitch movement you need. All of a sudden it becomes a sail, an oar, a paddlewheel. The AoA may remain the same, but the force of pushing the entire wing upwards into the air stream (assuming a "pull stick back to turn" motion) you're disrupting the air a hell of a lot more than you would if the wing's main spar were the pivot point.

From the article that I posted:  "Note that while drag plays an essential part in performance determination, its
role is small for stability and control. Its value is much less than that of the lift, and its acts not too far from the center of gravity, so its effects are often neglected."

All I know is that rearward-oriented CoGs are not good for dogfighting. This from experience, and having read a comment or two regarding real planes that says the same thing.

No doubt, but not because it affects the turn performance.  It affects the pitch stability of the aircraft.  Most notably pitch stability is lessened, which means that the plane will be harder to recover from a spin and will be much more difficult to trim (which is not an issue with CT).

[Cthulhu]

Just a thought. I don't know all the physics involved, all the forces and how they interact (quite complex interactions no doubt). All I know is that rearward-oriented CoGs are not good for dogfighting. This from experience, and having read a comment or two regarding real planes that says the same thing.

Krusty, moving the CG aft (but still forward of the aerodynamic center) simply reduces pitch stability, making the plane more "darty" and a crappy aiming platform. The plane is still stable, but less so. A downward force is still required from the horizontal tail to counteract the moment generated by the couple of weight and wing lift.



This isn't to be confused with moving the CG aft of the aerodynamic center, in which case you're now unstable and pushing a rope.

Explain how an aft shift in weight makes the plane more likely to shed its wings?

Yeah, I want to hear that one too.

[Krusty]

Stoney, you ever play with a styrofoam plane? Or a piece of card paper? Twist it back and forth -- very little wind resistance. Now flap it up and down like a fan -- a lot more resistance, more work.

Twisting is with the CoG (pivot point) in the middle. Flapping is with the CoG (pivot point) shifted off center. All this while still moving forward through the air mind you. One requires more effort, pushes harder on the wings (the flapping) and that's why the wings will rip off in-game if your CoG is too far aft and you pull a 190 out of a dive. Because you're forcing more pressure on the wings than in an identical situation with the CoG moved forward.

So, with the CoG further back, perhaps you're just pushing harder on the wings at any given AoA, increasing the weight loading and decreasing lift (meaning you turn worse).

The fact that the CoG, when shifted aft, makes a 190 fly worse is not new. Every 190 pilot in the game has verified this over many years of flying this game. This is why in AH2 the fuel tank burn order was re-coded per massive player request to burn the aft tank first (moving the CoG forward). With the CoG shifted forward it is more stable in tight turning situations.


That's how it works. How you explain it is another matter.

[Cthulhu]

Stoney, you ever play with a styrofoam plane? Or a piece of card paper? Twist it back and forth -- very little wind resistance. Now flap it up and down like a fan -- a lot more resistance, more work.

Twisting is with the CoG (pivot point) in the middle. Flapping is with the CoG (pivot point) shifted off center. All this while still moving forward through the air mind you. One requires more effort, pushes harder on the wings (the flapping) and that's why the wings will rip off in-game if your CoG is too far aft and you pull a 190 out of a dive. Because you're forcing more pressure on the wings than in an identical situation with the CoG moved forward.

So, with the CoG further back, perhaps you're just pushing harder on the wings at any given AoA, increasing the weight loading and decreasing lift (meaning you turn worse).

The fact that the CoG, when shifted aft, makes a 190 fly worse is not new. Every 190 pilot in the game has verified this over many years of flying this game. This is why in AH2 the fuel tank burn order was re-coded per massive player request to burn the aft tank first (moving the CoG forward). With the CoG shifted forward it is more stable in tight turning situations.


That's how it works. How you explain it is another matter.

Explain to me how the bending moment on an aircraft wing is higher if mass in the fuselage is shifted aft? The aerodynamic loads on the wing don't care. Wing loads are reacted into the fuselage structure at the wing root in the same way regardless.

If you were instead shifting weight within the wing (wing fuel, etc) it would make a slight difference since bending moment at the root would be less (provided the weight of the plane remains constant). But moving weight around in the fuselage has no effect on wing loads.

I guess I'll go up to the second floor of the Engineering Bldg here and talk to one of the PhD's in the styrofoam plane group. Maybe they'll enlighten me.

[Stoney]

Every 190 pilot in the game has verified this over many years of flying this game. This is why in AH2 the fuel tank burn order was re-coded per massive player request to burn the aft tank first (moving the CoG forward). With the CoG shifted forward it is more stable in tight turning situations.

I know that it feels more stable this way.  Like you said before, the P-51 is a plane that shares the same phenomenon.  From a "feel" perspective, you are right--the less of a load in the aft tanks, the better the plane handles.  I'm certainly not disagreeing with you about this.  I'm merely trying to get folks (like the OP) to understand and use the proper terminology to explain the forces on the aircraft that cause the "feel" we're discussing.  Just because the plane feels more stable during turns, it doesn't mean that the increased "feel" stability is a result of a more forward CG. 

[Charge]

Having the CoG too far aft in pull up risks that you inadvertently pull too much instantaneous G, i.e. the high speed may amplify the movement of CoG in relation to CoL and control momentum.

"The elevators proved to be moderately heavy at all speeds, particularly at above 350mph (565km/h), when they became heavy enough to impose a tactical restriction with regard to pullout from low-level dives. This heaviness was accentuated because of the nose-down pitch that was evident at high speeds when trimmed for low speeds. The critical speed at which this change of trim happened was around 220mph (355km/h), and it could easily be gauged in turns. Below that speed, the Fw 190 had a tendency to tighten up in a turn, but above 220mph, some backward stick pressure was required to hold the turn. Thus, in combat, the pilot had to be aware that if he dived on the enemy to get enough speed to follow him into a steep turn, he had to ensure that he didn't lighten his initial pull force by using the trimmer. As speed fell off in the turn, he would have a sudden reversal of stick force that could tighten the turn so much that the plane would depart dramatically into a spin. Most of the early Fw 190 pilots were, however, too well-trained to lose their cool to that extent in battle."

"Flying the FW190..." by Eric Brown.

http://findarticles.com/p/articles/mi_qa3897/is_/ai_n8925541

I have read at least of Yak having the same tendency of tightening the turn by itself after certain point which, I presume, is below certain speed meaning that speed has such effect on aerodynamics that some a/c develop a proneness to such behaviour depending of weight division and airfoil design. Spit was known to enter and almost unrecoverable spin which to some degree may be caused by the wing design but probably more by COG moving too far aft of CoL due to centrifugal force in spins.

I think that for a fighter it is optimal to have the CoG located a bit aft of the CoL so that it is still between the CoL and controlling momentum -i.e. tail with its control surfaces. This makes the a/c eager to change its direction i.e. "darty" as Cthulu said earlier or the behaviour can also be described as "maneuverable". In maneuvering this is desirable but in level flight (or while aiming and shooting) an unwanted feature. A plane with CoG too far back can have steady level flight characteristics but this requires aerodynamic compromises which, in turn, may have bad effects on maneuverability i.e. sweep back of wings, location of wings in relation to thrust line etc.

I think that is the beauty of those planes, they all have different approach of how an excellent fighter is done, some succeed in some areas and the others on other areas and there hardly is an optimal design that would excel in all of them. (Or insert your personal preference here... )

-C+