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Fw190 Stabilator / stab trim - Still not there :-/


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The stab trim was moved forward by 1.009, and remains there in 1.010.  Instead of being at neutral, it is set way ahead, in a "nose heavy" setting instead of neutral.

 

This was, I believe, done to avoid the strange flick-roll and mostly unrecoverable flat spin that resulted from pitching down more aggressively before, and indeed you get that same behavior if you set the stab trim to the position it should be set by RL manuals - neutral for takeoff...

 

So... why not change the stab incidence ?  Wouldn't it be a better / more close to real way of working this out?

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It is set to cruise for the air starters. If it was set to neutral it would have adverse pitch down effect on those guys. You can set it to neutral for ground starts. It is an acceptable compromise. 

 

 

Are you sure about that??  I'm pretty sure I have to hold the nose up in an air-start otherwise the the aircraft has a tendency to drop into a dive.

 

I think jcomm's right.  I don't think the trim is right yet.  

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I believe the Fw190 could be flown without touching the trim under a wide range of speeds

What is exactly your belief?

If you mean the Fw190 could be flown without touching the trim and the stick (when stabilized) at a "wide range of speeds" (and altitude also?).... then your belief does not correspond to any existing plane.

If you mean the Fw190 could be flown without touching the trim with light pressure on the stick at a "wide range of speeds" (and altitudes ?)..... then maybe you're correct, but then the trim isn't the reason for it, the govern lightness and balance is.

That's something you can't feel in a sim, since you use a Joystick, and even with a goof FF, you can't really simulate the balance and the lightness of the governs... it would be a full simulation in itself, and only concern peoples with FF sticks (and they would probably anyway "ignore" the simulation by tunning themthelves the FF level).

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Even a for plane with neutral pitch stability (so between stable and unstable), a speed variation create an incidence variation.... so you can't fly level without action on the stick and without adapting the trim if you change the speed.

A plane with neutral pitch stability will only "wooble" more than a plane with positive pitch stability, if you change her incidence by changing her speed (but you will still have to trim the elevator if you want your plane to "wooble" around a level line)...

 

So what you mean is that you're finding the Fw190 isn't woobling enough around the longitudinal axis?

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This is what the test pilot Eric Brown had to say about the use of trim on the 190 A-4.

 

 

"A remarkable aspect of this fighter was the lack of retrimming required for the various stages of the flight. There was no aileron trimmer in the cockpit, but if the external adjustable trim tab had been inadvertently moved as a result, for example of a member of the groundcrew pushing against it, an out-of-trim force of considerable proportions could result at high speed. Decidedly the most impressive feature of the German fighter was its beautifully light ailerons and its extremely high rate of roll. Incredible aileron turns were possible that would have torn the wings from a Bf 109 and badly strained the arm muscles of any Spitfire pilot trying to follow. The aileron maintained their lightness from the stall up to 400 mph (644km/h), although they heavied up above that speed.

The elevators proved to be heavy at all speed and particularly so above 350 mph (563 km/h) when they became heavy enough to impose a tactical restriction on the fighter as regards pull-out from low-level dives. This heaviness was accentuated because of the nose-down pitch which occurred at high speeds when trimmed for low speeds. The critical speed at which this change in trim occurred was at around 220 mph (354 km/h) and could easily be gauged in turns. At lower speeds, the German fighter had a tendency to tighten up the turn and I found it necessary to apply slight forward pressure on the stick, but above the previously-mentioned critical figure, the changeover called for some backward pressure to hold the Focke-Wulf in the turn."

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"A remarkable aspect of this fighter was the lack of retrimming required for the various stages of a flight." 

 

"The elevators proved to be heavy all speeds and particularly so above 350 mph (563 km/h) when they became heavy enough to impose a tactical restriction on the fighter as regards pull-out from low-level dives.  This heaviness was accentuated because of the nose down pitch which occurred at high speeds when trimmed for low speeds.  The critical speed at which this change in trim occurred was around 220 mph (354 km/h) and could easily be gauged in turns.  At lower speeds, the German fighter had a tendency to tighten up in the turn and I found it necessary to apply slight forward pressure on the stick, but above the previously-mentioned critical figure, the changeover called for some backward pressure to hold the Focke-Wulf in the turn."

 

Capt. Eric Brown.

 

As I recall from 260 mph (418 km/h) on up no retrim was required at all.*  The most interesting thing we can take from the above is that as the 190 accelerates we have to start dialing in some NOSE UP trim.  Definitely not your average bear.

 

*No retrim required for speed changes.  Retrim was still required for fuel burn which moved CG forward.


LOL  -  just saw post

Edited by chuter
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But I wonder if even such cruise trim settings are realistic?  I believe the Fw190 could be flown without touching the trim under a wide range of speeds...

Nope, what I mean is that the Fw190, when set for neutral trim, at almost every speed within it's normal flight envelope, will react strangely to pitch down inputs, entering a strange flick-roll followed by a sort of flat, sometimes inverted, spin.

 

If we keep the trim nose heavy, like it now is set by default, we do not experience this bahavior so, I think it may be related to the incidence of the whole stab section corresponding to zero trim.

 

You lost me, I can't see the logic between the two statements.

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*No retrim required for speed changes. 

Really? for other trims than pitch maybe... but:

 

This heaviness was accentuated because of the nose-down pitch which occurred at high speeds when trimmed for low speeds.

 

So the attitude of the plane depended on speed, and should be corrected with pitch trim.... as for every plane.

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Sorry.  That was in reference to:   As I recall from 260 mph (418 km/h) on up no retrim was required at all.  So, above 260 mph there was no retrim required for speed changes, only CG changes.

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Interesting..

 

Decidedly the most impressive feature of the German fighter was its beautifully light ailerons and its extremely high rate of roll. Incredible aileron turns were possible that would have torn the wings from a Bf 109 and badly strained the arm muscles of any Spitfire pilot trying to follow.

Eric Brown notes of the Bf109's weak wings 'if' it try to follow a Fw190 in a roll.. And at the same time, indicates the Spitfire could have followed the Fw190, but it would have required more effort..

 

I wonder if this wing weakness of the Bf109 is why the 'Fletner tabs' were tested on early versions of the 109, but didn't become a production standard on later versions of the Bf109

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As I recall from 260 mph (418 km/h) on up no retrim was required at all.  So, above 260 mph there was no retrim required for speed changes

 

I find it pretty to believe.... especially since:

The elevators proved to be heavy at all speed and particularly so above 350 mph

Who means the smallest change in plane attitude caused by speed change would require pitch trim or lots of pilot muscles.

 

.........Also, if the plane was elevators heavy and had a "neutral pitch stabilty" at the same time, it would have been a nightmare to fly level...

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He says a turn as sharp as with the 190 would tear the 109's wings off, not that the 109 would lose it's wings if it tried to follow the 190 (which it obviously couldn't). Anyway interesting statement on the "trim-inversion" during flight.

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I find it pretty to believe.... especially since:

Who means the smallest change in plane attitude caused by speed change would require pitch trim or lots of pilot muscles.

 

.........Also, if the plane was elevators heavy and had a "neutral pitch stabilty" at the same time, it would have been a nightmare to fly level...

 

 

You're confusing force required to move the elevators with the tendency of  the plane to change center of pressure requiring trim change.  They are very independent.

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He says a turn as sharp as with the 190 would tear the 109's wings off, not that the 109 would lose it's wings if it tried to follow the 190 (which it obviously couldn't).

That is your opinion, and your welcome to it..

 

But, I think Ill stick with Eric Brown's assessment over yours..

 

That, as I read it states..

 

If a Bf109 and Spitfire try to follow a Fw190 in an aileron roll..

 

The Bf109 pilot has to be concerned with 'death' due to the Bf109's weak wings that will most likely come off should he try to follow the Fw190..

 

Where as..

 

The Spitfire pilot has to be concerned with 'mussel cramps' in his arms due to the Spitfires heavier ailerons should he follow the Fw190.

 

Hope that helps!

Edited by ACEOFACES
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You're confusing force required to move the elevators with the tendency of  the plane to change center of pressure requiring trim change.  They are very independent.

No I'm not.

 

Trim is needed at each attitude change (caused by speed or other factors) in order to cancel the forces to be applied on the stick (to cancel pitch and roll changes). Trims have no other use...

If the elevator is very heavy, then the trim is even more necessary (if the governs are light, then the pilot could feel there's no need for trim since he can easilly cancel the change with low muscle forces).

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Interesting..

 

 

Eric Brown notes of the Bf109's weak wings 'if' it try to follow a Fw190 in a roll.. And at the same time, indicates the Spitfire could have followed the Fw190, but it would have required more effort..

 

I wonder if this wing weakness of the Bf109 is why the 'Fletner tabs' were tested on early versions of the 109, but didn't become a production standard on later versions of the Bf109

 

 

This is getting a bit OT but Eric doesn't say the Spitfire could follow a 190 in a roll.  And in fact, we know that a Spit (a Mk.1-16 - even a clipped wing Spit) couldn't follow a 190 in a roll.  That is why Eric uses the word 'trying' in relation to the Spit.  Trying isn't necessarily the same thing as succeeding.

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This is getting a bit OT but Eric doesn't say the Spitfire could follow a 190 in a roll.  And in fact, we know that a Spit (a Mk.1-16 - even a clipped wing Spit) couldn't follow a 190 in a roll.  That is why Eric uses the word 'trying' in relation to the Spit.  Trying isn't necessarily the same thing as succeeding.

That is your opinion, and your welcome to it..

 

But, your right, the Bf109 weak wings is OT for this thread, so, we will just have to agree to disagree..

 

I do thank you for the quote! I will be sure to use it in the future should the Bf109 weak wings topic comes up again! S!

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I find it pretty to believe.... especially since:

Who means the smallest change in plane attitude caused by speed change would require pitch trim or lots of pilot muscles.

 

.........Also, if the plane was elevators heavy and had a "neutral pitch stabilty" at the same time, it would have been a nightmare to fly level...

 

 

They are not necessarily connected. 

 

Let's say I'm tooling along in my 190, trimmed, at 275 mph and pull the stick back "hard".  The plane pulls up solidly.  I now accelerate the plane to 375 mph and find that no trim change is required.  In every other plane it is but not this one, how odd.  Now I repeat the "hard" pull on the stick but find the elevator much heavier and the pull up much shallower.  The plane was still in trim but the elevator was much heavier.  One might be tempted to use trim to assist high speed handling but that isn't "trim".  This is a very unique characteristic of the 190 and comparing it, in this regard, to other planes only points that out.

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They are not necessarily connected. 

They necessarily are.... heavy governs makes trim more necessary to fly it without fighting the plane.

 

I now accelerate the plane to 375 mph and find that no trim change is required.  In every other plane it is but not this one, how odd.

So You're telling me that a Fw190 with locked trims fly with the exact same incidence angle at all speeds between 400 km/h and 700 km/h (keep 600 if you want)?

I have real hard time to believe it... I don't believe in UFOs

 

You're right to add "how odd".

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To clarify a previous point:

 

 

Now, if the plane was trimmed for 190 mph and I then accelerated to 275 mph I would find that I would need to dial in some (but it doesn't sound like a lot of) nose up trim.  That is backwards to almost every other airplane out there (except the likes of the Lake LA-4 which is DRAMATIC in the trim change required and in the backwardness of it, never quite got used to it). 

 

The biggest changes in trim (physically, as in degrees incidence) seems to be for CG changes, as in fuel and ordinance.

 

 

 --->  Well, Tator - take it up with Eric Brown and the flight test reports.  I have little reason to argue the point.  But if Eric is wrong about the 190 trim he is also likely wrong about the 190/109/Spitire ailerons and Aces won't like that.

Edited by chuter
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Take it up with Eric Brown and the flight test reports.  I have little reason to argue the point.

Maybe you're reading too much in Eric Brown's test report.

I confess I have not readen it, but in the above quote, I've seen no text clearly stating that no pitch trim is required between 400km/h and 700km/h.

I wouldn't say it's impossible. Nothing is impossible, including UFO's...... but having all force momentum (wing lift, tail negative lift, drag of different surfaces, propeller push, prowash effects, gyroscopic effects, etc...) dynamically  perfectly compensenting on 3 angles at all speeds between 400 km/h and 700 km/h has a very, very, very low probability....

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These threads just will nopt stop.. Even if the devs fix what Joe,Bill and Frank want... Bob Jack and Ed are going to complain that it is still not right.. or now it is wrong. I suggest you take the universe you have and learn to use what you have in it.

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These threads just will nopt stop.. Even if the devs fix what Joe,Bill and Frank want... Bob Jack and Ed are going to complain that it is still not right.. or now it is wrong. I suggest you take the universe you have and learn to use what you have in it.

 

 

Well with all due respect, no one is asking for anything other than accuracy.  If accuracy isn't important then this really is just another fantasy video game.

 

The 190 has been improved in recent weeks and that's something everyone in the community should celebrate.  But there is still room for improvement.  

 

We don't bang on about this stuff because we don't like the sim.  It's quite the opposite.  We mention this stuff because we actually do give a monkey's about the fidelity of the experience.  It surprises me that you don't appear to understand that. 

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"One excellent feature of this aircraft is that it is seldom necessary to retrim under all conditions of flight."

 

"The Fw 190 has a high rate of dive, the initial acceleration being excellent. The maximum speed so far obtained in a dive is 580 m.p.h. |934 k.m./h.l True at 16,000 ft [4,880 m|, and at this speed the controls, although slightly heavier, are still remarkably light. One very good feature is that no alteration of trim form level flight is required either during the entry or during the pull-out. Due to the fuel injection system it is possible to enter the dive by pushing the control column forward without the engine cutting."

 

"The fact that the Fw 190 does not require re-trimming under all conditions of flight is a particularly good point. "

 

The above is from "CONFIDENTIAL REPORT ON TACTICAL TRIALS – FW190" http://www.a2asimulations.com/store/fw190/tactical_trials.htm

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Presently I use an Fw190 in another sim that pretty much reflects what the many texts cited here, and other stuff I was able to find on the Internet say about the Fw190. So... you may ask... why don't I simply quit using IL2 BoS and stay concentrated on that other sim ? Because I also like many aspects of il2 BoS, and want it to get better - just that!

 

Another sim you are reffering to has Fw190D model,which is completly different a/c with higher top speed and climb rate,different engine,prop etc then Fw190A-3 in this sim.

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Well with all due respect, no one is asking for anything other than accuracy.  If accuracy isn't important ... 

 

I begin to understand that sometimes those who post about the lack of accuracy on the representation....

 

In order to have a real and fruitfull discussion, the first issue should be to agree on the semantic.

The definition of accuracy I generally use is:  the accuracy is the degree of closeness of measurements of a quantity to that quantity's actual (true) value

 

I'll stop there: I know from experience fruitfull discussions on forums (all forums, this one isn't specific) are exceptionnal.

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Reconsidering what Brown reported regarding the trim inverse during flight I came up with the though the ingame behaviour can only be an issue of the stabilizors aerodynamical model.

 

I sure don't have any polars on hand and therefore can't prove the point sufficiently, so take it as a good guess if you like. But the way Brown describes this destinctive behaviour it actually can only be the stabilizors lift effiiciency effecting the aircrafts balance at different flight speeds.

 

So if I'm right and we take Browns report for correct, the stabilizer should produce more lift at higher airspeeds in BoS to reduce need to retrim (of course not eliminating it) and simulating this inverse behaviour of the trim action.

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Ok Brano, I stand corrected then - so the A3 modeled in BoS couldn't use those tactics to escape Yak-1s and La5s ?... Ok, I am always learning something - thanks!

No,I dint say that.I just wrote that you are reffering to/comparing 2 different a/c.The rest is your personal opinion you are entitled to.Thats all ;)

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Or maybe the incidence of the whole stabilator, at 0º pitch trim settings, needs to be increased ? OTHO assuming that RW datum was used to create the model, it is probably more of what you say...

That may also be the case but does not account for the inverse trim action Brown describes in his report. I guess the real issue is in the middle of both.

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A little more info about this subject from people involved with the design and testing of the fw-190. They talk about extensive testing and considerable attention paid to stick forces and stability of the aircraft both statically and dynamically over a wide range of speeds.

 

 

 

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Maybe they are talking about the other axis (roll and yaw), more when they talk about not need in retriming. It was a known fact that the 109 during that time, required some heavy foot action to compensate for the yaw changes, at different speeds. they say that elevator trim was provided bt adjustable stabilizer.

 

About Eric Brown's quote, in respect to bf109 and spit, he's talking about "aileron turns". From what I read in few places, this is not a simple turn or just a roll, but a combination of 180 degrees roll plus a 90 degree turn. I've seen some diagrams online and some quotes from British pilots, that I think means more than just rolling. I also remember seeing something similar done by fw190, in two allied gun sight films, that looked like a lot of strain may be put on the wings. The roll and turn were combined into some kind of very fast corkscrew maneuver, that could probbably pull the wings of some planes.

Edited by Jaws2002
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But I gave up trying to compare pitch response between the DCS D9 and the BOS A3 because those sources really suggest they're different in as far as this particular feature goes.

Uh... Yeah?

 

The only things they share are an F, a W, the number 190 and Kurt Tank...

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