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jcomm-il2

Spitfire elevator...

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It appears to be dflected slightly down inflight, on pretty much every video of real Spitfires flying.

 

In game, even if we set the pitch trim to neutral ( 0% in techno chat ) and look at the tail, there will be no sign of deflection, and if we momentarilly apply stick fwd to counter any pitching up tendency, the defcetlion is unperceptible.

 

Maybe I'm being too picky, but it's very noticeable in the real aircraft.

 

Example, among many:  fast fwd to when Lord Sugar get's the controls, the camera focuses on the tail, and it's pretty much noticeable, but many videos abound at YouTube and other sources where this "peculiarity" can be seen:

 

https://youtu.be/ZvGt1sW7c3g?t=385

Edited by jcomm

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On 8/25/2017 at 11:12 AM, Von-Target said:

It appears to be dflected slightly down inflight, on pretty much every video of real Spitfires flying.

 

I think it is the same in the game, however for some reason the 3D model is made such that it is depictes straight.

 

Look here, just noticed today:

spittrim.jpg

 

The plabe goes about 300 mph, and as you can see I have trimmed it 50% nose down to make it fly hands off (a considerable nose down trim). In any plane that I could think of, setting the trim tabs other than "neutral" (0% in game), it will produce a deflection of the control surface. This means, with 50% down trim, the elevator shouldn't be flush with the horizontal stabilizer. It should much rather point downwards and the horns slightly upward. Exactly like in all those pictures:

 

White-Cliffs-Spitfire.jpg

 

 

I think by simple  adjustment of the 3D model, we shoukd actually be reproducing the characteristic elevator down situation as it is so typical for the aircraft.

 

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Keep these threads coming. If visual representation is connected to FM in any way the Spit is off. The Spitfire is one of my favorite aircraft and it even "feels" funny using force feedback.

I'd like to see a comment from the devs on the Spit. As such an iconic aircraft it's only natural to be so picky.  :P

 

Thanks BoX devs. When you have a moment, please have a look at our Spits.

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9 hours ago, 7./JG26_Smokejumper said:

I'd like to see a comment from the devs on the Spit. As such an iconic aircraft it's only natural to be so picky.  :P

 

Thanks BoX devs. When you have a moment, please have a look at our Spits.

 

You gotta send a report to the devs if you want them to look at it. A forum topic isn't enough.

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There is no way my Mk IX can fly hands off at 300mph with nose down trim if I am reading the cockpit indicator:  it needs about one tick (out of four up and four down) nose up.  On the technochat that is about 0% IIRC - the middle of the trim setting in the Spitfire is not at 0% on the technochat.  One tick nose down is about -50% on the technochat.  This is Kuban map, sea level, take off with 100% fuel and ammo.

 

I also have none of the FFB issues Smokejumper has reported. 

 

Interesting that our experience can be so different.   

 

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30 minutes ago, unreasonable said:

There is no way my Mk IX can fly hands off at 300mph with nose down trim if I am reading the cockpit indicator:

I noticed this on Berloga the other day. The 300 mph are a rough guess, I can make more precise IAS measurements, but this wouldn‘t be really too relevant as whatever the speed, with 50% nose down trim, the elevator should point down slightly and not be flush, or the rigging of the plane or CoG would really be weird.

 

Fact is that I always have to fly the Spit at 25% to 50% nose down at „combat speed“ (Berloga is not the server where on average you fly fastest) in order to be trimmed for straight flight. If you fly at neutral trim or even slight up trim, you‘re free food. You don‘t need to watch the speedometer. It is more useful to check „turn and bank“ to be sure she‘s straight. (But the beauty needs very little rudder work...)

 

To me, it appears that the Spit internally is rather correct, but the 3D model of the elevator is not set to match it. But who knows.

 

Now before I was to pester Han with a report, I thought it might be useful to see how other people have the setting when flying the Spit. It I found something that‘s agreed on, then I would forward the issue.

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Well, I tried using 50% ( technochat ) nose heavy trim with no success - had to constantly pull the stick, and had to trim it back to near true neutral inflight... Will check again.

I do not have FFB.

 

How can we send reports to the Devs ?

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@ZachariasXI agree completely about the visual inspection of the elevator position. Very hard to get it showing any downwards deflection in level flight.  In addition to the pictorial evidence, my understanding of the Spitfires is that they flew a bit like WW1 aircraft, eg the FC Dr.1, although in a less exaggerated manner, so they needed a little  forwards stick pressure to fly level within a normal range of trim.  Let go of the stick and they want to loop. The BoX Spitfire does not do that either without a great deal of nose up trim.  So I agree that it's handling is slightly off compared to the descriptions.

 

That does not mean that it's performance measured by numbers is off - just that it feels different on the elevator, although the sensitivity to elevator changes is modeled pretty well IMHO.

I still find it fun to fly - that wing!  But I would not mind if it were tweaked to be a little more like  the Dr.1 in FC: although by Chill's account this shows too much down elevator! Fine margins here, I expect.

 

1 minute ago, Von-Target said:

Well, I tried using 50% ( technochat ) nose heavy trim with no success - had to constantly pull the stick, and had to trim it back to near true neutral inflight... Will check again.

I do not have FFB.

 

How can we send reports to the Devs ?

 

I agree. Anyone can email Han, but it needs to be documented as clearly as possible to have any chance of traction, assuming that he has time to read it.  Ideally we could conscript some one with prior links to the team, who is more likely to be listened to, perhaps a tester, who is known to Jason....

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42 minutes ago, unreasonable said:

, although in a less exaggerated manner, so they needed a little  forwards stick pressure to fly level within a normal range of trim. 

I would really doubt that, as the trim *always* should be able to take any pressure from your stick.

 

But I think what we are seeing might be a different issue althogether. I suspect that trim tabs do not cause the elevator to move *in any aircraft*, as opposed to the stabylo trim that very much so is present with the animation of the tailplane.

 

What trim tabs do, is they ultimately cause a certain deflection on their respective control surface. By doing so, they are de facto producing a stick input. This means, as soon as you move your elevator trim, your stick neutral position (the position where the airflow keeps it as opposed to the flush pusition with the fixed section) should move as well. (FFB sticks should do that.) The stick is more forward with down trim if you let go the stick. If you trim the tabs nose up, the stick will creep back according to the nose up trim.

 

I check now with other aircraft as well.

 

Edit:

 

The trim tabs cause control surface deflection in case of the Yak, here @ 480 km/h or so IAS:

yak_480_kmh.jpg

 

In case of the Spit, the elevator does not really move with different trim tab settings, see here @ 300 mph, 40% down trim:

spit_300_mph.jpg

 

At a mere 130 mph, I have 25% nose up trim:

spit_130_mph.jpg

 

My conclusion is a very boring one. The Spit is WIP and with the release of BoBP, things should be fixed.

 

Edited by ZachariasX

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Before it can be fixed, someone has to prove that it is wrong. What we do know, (see NACA report for instance) is that the elevator change needed to go from level flight to maximim Cl was under 5 degrees. In a turn, it was only 3 degrees before pre-stall buffeting.  Both NACA and the PN remark that the Spitfire elevator is exceptionally sensitive, as is it's trim tab, so comparisons with the Yak are not really convincing.

 

The NACA report does say that the Spitfire (Va but no so much difference) can be easily trimmed (elevator) at any speed. I cannot remember where I read that wartime Spitfire pilots usually flew with a little forwards pressure: perhaps they just liked to fly like that because they  knew that turning was their point of difference: it was not as though they ever had to fly for very long like a P-51, given their limited range, so trimming to be hands off was not really important for them any more than it would have been for a Camel, although presumably they could have doen so.

 

I do think it would be good to ask Gavrick (who seems to have been the Spitfire guru) what is going on here and if there is actually a problem.

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We know it is wrong for instance also from the NACA report, where you can see that downward elevator is needed throughout the speed range. Also, push forces if trimmed neutrally. In addition to this, the attitude of the Spitfire is wrong in game, it should be fairly stronlgy nose down at high speeds, much more than it is. Imho these two issues are linked. Evidence for this is all over the internet or archives, but out of reach for me at the moment. 

 

For what it's worth, including the proper polar gave us the proper elevator/trim behaviour when we reworked the Spitfire FM in Il-2:1946. It's a much older engine, so it should have nothing the BoX engine isn't capable of, which means the current FM is very wrong not just with trivial things like trim or graphic representation of control surfaces.

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5 minutes ago, JtD said:

We know it is wrong for instance also from the NACA report, where you can see that downward elevator is needed throughout the speed range. Also, push forces if trimmed neutrally. In addition to this, the attitude of the Spitfire is wrong in game, it should be fairly stronlgy nose down at high speeds, much more than it is. Imho these two issues are linked. Evidence for this is all over the internet or archives, but out of reach for me at the moment. 

 

For what it's worth, including the proper polar gave us the proper elevator/trim behaviour when we reworked the Spitfire FM in Il-2:1946. It's a much older engine, so it should have nothing the BoX engine isn't capable of, which means the current FM is very wrong not just with trivial things like trim or graphic representation of control surfaces.

 

OK so at least I did remember correctly about the push force! ;)    Sounds like you are just the person to send in the report when you have time....

 

 

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8 minutes ago, unreasonable said:

OK so at least I did remember correctly about the push force!

If trimmed neutrally and there was no push force required, the elevator would be flush. Trimming it nose downwill make elevator deflection without the pilot having to push. The stick will go forward "by itself".

 

Flight attitude is indeed a further matter. But since some basic mechanics have not been included yet, I supoose there will be further revisions to the Spit. At least I hope that.

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46 minutes ago, ZachariasX said:

If trimmed neutrally and there was no push force required, the elevator would be flush. Trimming it nose downwill make elevator deflection without the pilot having to push. The stick will go forward "by itself".

 

Flight attitude is indeed a further matter. But since some basic mechanics have not been included yet, I supoose there will be further revisions to the Spit. At least I hope that.

 

I do not understand what you are saying.  To me "trimmed neutrally" could mean either trimmed for level flight at a  given speed, etc, or  it could mean that the elevator is flush with the stabilizer.  It could only mean both of these at the same time at a single speed. 

 

What I take JtD to be referring to is the NACA Spitfire report, figure 9-10, which show, for a trim tab at 3.1 degrees nose heavy, the elevator force required. This is a "push" force at anything over 120 mph CAS, the push force increasing as speed rises as you would expect.  In other words, if you trimmed a Spitfire to neutral on the trim indicator, you would need far more push force to hold the nose down. (or at least the NACA one which might have been a Lemon for all I know).  Or if you wanted to trim out the push force you would need more than 3.1 degrees more down trim at speeds over 120 CAS. 

 

Unfortunately, I am not sure what 3 down degrees corresponds to on the cockpit dial - maybe that is the centre of the range.

Edited by unreasonable
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13 minutes ago, unreasonable said:

What I take JtD to be referring to is the NACA Spitfire report, figure 9-10,

Ah, I misunderstood.

 

In my musing, I assumed trimmed neutral to equal 0% trim or in consequence the trim tab to be flush with the elevator that in principle should make the elevator being flush with the stabilizer. Thus, just the technical side of it. But makes sense what you are saying.

 

AFAIK, the cockpit dial should point to the centre if there is no trim tab deflection.

 

Just as a comment, I think flight attitude seems to be something really hard to do right. But looking at the images on the web, it doesn't apprer to me that the Spit is markedly nose down attitude, at least not more than other planes. But I might be looking at the wrong images, people mostly are pulling up and rolling toward the camera to show off their ride.

 

On the Fw-190, there should be a distinct nose down attitude (same as the Hellcat). Something that is also masked a bit by the infamous refraction issue, that actually would lift the line of sighting considerably. Looking straight through the visor then makes for a much better view over the nose. But for this, many things had to be changed and I am not counting on that. But it would be nice if the Spit trim tab actually moved the elevator as well.

 

 

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S!

 

Bf109 also flew with a nose down attitude. Several Finnish pilots who flew it said it did so when trimmed. And gave better view over the nose.

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Posted (edited)

[EDIT] I have sent Han a PM on this matter...

 

Since the neutral point of the elevator trim is way above the horizontal mark ( 3 o'clock ) of the pitch trim gauge, then the aircraft is flown most of the time trimmed  nose heavy, and we should actually see the elevator slightly down, hence it's side panels showing slightly up from the horizontal stab plane when looking back from the cockpit… This is how I see it in most videos in shots of RL Spitfires cruising... ( expl: https://www.telegraph.co.uk/news/2016/05/20/the-last-of-the-few-stunning-photographs-of-spitfires-in-flight/the-last-of-the-fewnew-book-captures-the-last-spitfires-in-stunn20/ ) as well as in the DCS World Spitfire IX.

 

There's definitely something wrong either graphically or aerodynamically with this elevator incidence and trim... As pointed out before, if we trim the aircraft so the elevator looks like in those shots it will start diving rapidly...

 

BTW, on a completely different but maybe bug-related matter, I also find something strange with the need for full tail heavy trim when landing ( but not only ... ) for instance the P-40E... 

Edited by jcomm

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There is a way get accurate elevator deflection data without having to rely on the graphical representation. I did that for the Spitfire in flaps down configuration for the collection of FM issues I posted recently. I wrote a script that logs my joystick y axis deflection 10 times per second. I switched to a linear pitch axis profile in-game, loaded the plane in the qmb and flew with the elevator trim untouched. This being a Flettner trim tab, it's use should not alter your joystick input, provided you use a force feedback stick as I do.

 

Following image shows such input. The yellowish background is a diagram from a NACA report about the spitfire stall behaviour. Superimposed in red is a stall test without sideslip, and in blue a stall with sideslip. The huge peaks at around 70 seconds are maximum joystick positive and negative deflections used as reference time points. These can be exactly identified in in-game tracks. The sideslip occurred after the peaks. There, the plane was hardly controllable without sideslip (red curve), and fully stable with sideslip (blue line).

 

The image is just an example of methodology and not pertinent to the issue you mentioned.

 

Screenshot_2019-01-11-06-35-32-324.thumb.jpeg.9cc6c636e5ba0cc6be0bea6e64bf5dc1.jpeg

 

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9 hours ago, JG27_PapaFly said:

This being a Flettner trim tab, it's use should not alter your joystick input, provided you use a force feedback stick as I do.

 

The simulator has to run well with non-FFB joysticks. Hence in the simulator you have to kind of alter the "wiring lenght" between the stick and the elevator, to give it more or less pitch up/down to match a putative trim change for given stick position. If you have to cheat then with shifting joystick centering, this will give you artifacts when you overlay curves directly. And you expect now that this mechanism is changed for the minority running FFB joystick?

 

So please relax a bit when you are getting all too exact here. There's more under the hood than meets your eye.

 

if you truly want to have something done, then compile your flight tests in a way that is requested by the devs instead of throwing in here and there what "is so wrong and totally ruins the game".

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1 hour ago, ZachariasX said:

And you expect now that this mechanism is changed for the minority running FFB joystick?

Welcome to the world my friend. That effect is there and is BTW very well modeled by the developers. I set the elevator trim in the Spit or in any other plane featuring Flettner trim tabs and, low and behold, my ffb stick's neutral point shifts. So while I trim my hand doesn't move, only the stick force goes away. Really nice, just like in real life. In planes where the vertical stabilizer moves as a whole (e.g. FW190), I have to adjust the stick position while trimming. Sweet.

 

1 minute ago, JG27_PapaFly said:

 

Edited by JG27_PapaFly

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On ‎1‎/‎11‎/‎2019 at 4:17 PM, JG27_PapaFly said:

Welcome to the world my friend. That effect is there and is BTW very well modeled by the developers. I set the elevator trim in the Spit or in any other plane featuring Flettner trim tabs and, low and behold, my ffb stick's neutral point shifts. So while I trim my hand doesn't move, only the stick force goes away. Really nice, just like in real life. In planes where the vertical stabilizer moves as a whole (e.g. FW190), I have to adjust the stick position while trimming. Sweet.

 

 

 

Interesting PapaFly. I never used a FFB stick, so I really can't tell.

 

Given this is actually modeled - which sounds great to me - I ask again, if you don't notice the increase in force, in the nose-heavy direction ( forward ), on your FFB stick when flaps are deployed ?

 

I noticed there's actually a slight pitching down which we have to counter by pulling the stick, which agrees with the NACA reports and is associated in this case with the deflected downwash increasing the local AoA at the tail horizontal surfaces...

 

The DCS Spitfire IX, which was initially released without that "nose-heavy" force that the pilot feels on the stick ( stick-fixed condition as usual specially with non FFB sticks ) and having as effect only the "ballooning" when the flaps were deployed, was then updated, just as their Yak-52, and there is now a marked forward displacement of the stick that you can check in the virtual cockpit views, and counter by pulling, but it's a lot more "intense" than what I observe in youtubes or read in the NACA reports. 

 

I find the way it is modelled in IL.2 BoX more subtle and probably more realistic, and now that you mention it feels ok with FFB, even better!  But beware, in this particular case the effect is actually due mainly to the propwash deflection and increase in local AoA at the tail.

 

OTOH I would like to see little details, like the one that actually motivated the OP, fine tuned. It's probably just a graphical glitch... Other aspects like those you exhibited in your video are certainly being checked by the main flight dynamics dev at 1C / 777 and I strongly believe that with the required time - they're certainly busy given the amount of content they poured into the sim during the last year and since it was released - certainly a winner in terms of quantity and in a good part too in quality, for a ww2 combat flight simulator, taking as reference the alternatives - I can't speak for 1946 though, since I never played that one, but I am seriously considering giving it a try...

 

Edited by jcomm

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