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- during climb throttle was idle

- at close to zero speed throttle was slammed to max.

- no control input was made until the plane has stabilized itself in the following dive.

No need to climb at idle. You can/should climb with full throttle for the complete maneuver.

That way it's easier to note that you don't need any aileron input.


Edited by bbrz

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I didn't tell you any conclusion, because I wanted you to watch the track :)

 

I think, that in this particular situation there is plenty of torque, especially with the 109, but I am not a warbird expert by any means.

 

Here are the other tracks I have just made with the 109 and the Spit, using the same method, although I could not firewall the throttle in the 109 as it would kill the engine instantly for some reason, so there is some more torque left in that machine...

BF-109 Torque Test.trk

Spitfire Torque Test.trk

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No need to climb at idle. You can/should climb with full throttle for the complete maneuver.

That way it's easier to note that you don't need any aileron input.

 

 

Aileron input does not matter in that sitaution, since there is almost no airflow, and it is outside of the flow generated by the prop. But there was no aileron input anyway.

 

 

The main idea is to get the aircraft into a situation, where it is more or less free from any other aerodynamic effects, and then, unleash the torque.


Edited by HWasp
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Next Test:

 

 

The go around after a bounced landing, that should kill me.

 

As source here is real vintage P-51B instructional video:

 

 

According to this (27:40) I should EASE the throttle forward in case of a low speed, high AoA go around following a bounced landing or a crash is likely.

 

 

In the track I have slammed the throttle full open (prop forward) at 100 after intentional bounced landing, and the plane was still almost fully controllable.

I was about to test it again, but sudden engine failure has made that a full stop landing instead. :)

 

I did the same with the 109, terrible approach, bounced landing, slam throttle (prop at 12:00) and very little effect.

TF-51 landing go around Test.trk

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But there's torque certainly present when I operate the bird at least, because if there wasn't, I wouldn't have to input right rudder etc. at all. So for me at least the effects are there, and thus, I've got no need to disprove anything you say per se.

 

The need for right rudder is NOT torque except on the ground. DCS does do some modeling to simulate some of the symptoms of torque but that doesn't mean torque is modeled.

 

On the ground the engine torque drives the left main gear down, so much so that the left main on the P51 wears much faster than the right. This downward force produces friction drag during the takeoff roll that must be compensated for with rudder and a bit of aileron as speeds builds. This happens in EVERY single engine prop aircraft and in multis without counter rotating engines.

 

This rotational force does not disappear when the aircraft becomes airborne and one can easily see in DCS there is no torque force present as soon as the aircraft breaks ground.

 

 

 

 

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Maybe because it does and it complies?

 

I mean, seriously, one doesn't even need to fly warbirds in DCS to see torque is modelled - just starting the engine on the runway and revving it up and down with parking brakes, while observing wingtips, clearly shows Third Law in action, with the plane rolling on gear shocks. Obviously it's way more visible in Spit and 109 with their narrow gear.

 

In flight, at any speed and in any DCS warbird extreme changes in throttle or RPM also result in combined roll and yaw opposite to torque from prop and the engine. Amount of response being dependent on the speed obviously. One can discuss if the values are correct for various speeds, but it's there allright.

 

As for your "experiment" - be my guest, I took Mustang and Spit and adjusted throttle and trims to fly level at 130 mph IAS, then throttled to max making sure I keep controls exactly as they were. The planes always pitch up a little, roll to the left beyond 90 degrees and dive to the ground unless corrective action by right stick and rudder is started. Doesn't matter if I do it at 2600 or 2900 RPM. Now, pre-stall buffeting is indeed present, though both planes are way above clean config stall speeds of 90-100 mph range, not to mention that roll is much slower compared to the actual snaproll caused by stall, as it is modelled in DCS. But even if it was "only" a stall as you imagine, why do you think it's always to the left even without adverse yaw by dead centered ailerons?

 

I don't even want to dwell on the "Il-2 does it better" argument, or rather misinformation, as everyone who has both platforms can take BoX Spit IX now for a spin and make a comparison. Hint - in the same conditions (clean, 2850 RPM, decelerate to 130, firewall the throttle, keep controls fixed), BoX Spit rolls left only up to 20 degrees as per markings on artificial horizon. Compared to way over 90 in DCS, It's obvious which sim has stronger reaction to torque changes.

 

But why do I bother... It seems you don't read replies in this thread anyway, and it's questionable if you actually fly the sim with game fligh model off and auto rudder off.

 

You can see in my video that it is simulator mode with takeoff assist and rudder assist off. I specifically included those points for folks like you.

 

 

 

 

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You probably shouldn't. Because his haughty demeanour, his constant reminding of how he's been developing these things for another sim himself, and his complete ignorance of any helpful advice and contrary opinions given, kind of tells me he's got an agenda rather than any genuine interest in the sim.

 

None of which means, BTW, that the flight modelling shouldn't be questioned at all. Of course it should, if (and when) any questions arise. But his claiming of the P-51 having no torque at all is just BS regardless and betrays his probable real purpose of being here, which is sowing discord and doubt in the product in order to help an unnamed competitor.

 

So in other words, we've got a troll in our midst.

 

Not a troll. Just looking for an actual simulation of prop driven WWII fighters. It is a long quest. DCS does a great job with the jet simulations but there are serious holes in the props. My original post was directed at finding a way to tweak the FM to make it more realistic (according to my personal real world experience) mainly because I wanted to be able to use DCS as a preparatory tool for folks transitioning into high performance prop aircraft in the real world. With this basic error, it simply does not fill that bill. It would be nice if it did.

 

There is always a contingent that will hold, steadfast, in the belief that flying a WWII era prop driven aircraft is exactly the same as flying as modern jet. Having done both, I can say with no reservations, that they are not the same. Power changes in a jet require pitch trim changes. Power changes in a single engine prop require trim changes in all three axis. In the early fighters without three axis trim, the pilot was the trim device.

 

At present the P-51 is wrong. It is easily demonstrated as being wrong.

 

 

 

 

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If that's the case, then no disagreement from me on that part! Whether it's a question of torque or airflow modelling, it should be investigated closer indeed. I admit I only tinkered with level flight tests, as it's easier to maintain constant flight parameters then. I couldn't reliably perform a straight vertical climb or a proper hammerhead if my life depended on it :D.

 

Questioning and searching for things in FM to improve is always a good thing, I just find it peculiar when the guy tries to teach us what a moment is (as if it wasn't taught on basic physics lessons in high schools already), while even running the engine of a DCS prop plane, stationary on the apron, shows he doesn't know what he's talking about. If all these flight sims he's been battling with for 20 years don't model torque effects to his liking, than maybe, just maybe the problem is located not in the flight sims, but rather somewhere between his chair and a keyboard?

 

In either case, we know Yo-Yo won't change a thing in a code based only on anecdotal evidence, so we have to come up with something more measurable, or at least in-game replays/videos showing weird behaviour, as in your vertical climb example.

 

Your post doesn't make much sense. Over the past 20 years I have had varying degrees of success with convincing flight modelers that torque exists. And just because a title might do some visuals of torque on the ground doesn't mean it carries through the entire flight model and it is incredibly easy to test.

 

If large power changes can be made at any speed without the need for ANY roll input, torque isn't modeled. It should be most dramatic at slow speeds because the control deflection required to counter the torque force is the greatest. However, the same forces are present at any speed and if there is no roll input changes required with power changes, torque is not modeled. Extremely simple really.

 

Once it is modeled, which it generally is in WWII fighter titles, the argument then becomes about degree. Of course, that particular argument really has no end. Based upon my personal experience in real world high performance piston engine singles, very few come close to modeling torque appropriately, for whatever reason. Others may disagree with that assessment and may think a fire breathing Spit XVI flew around with the stick at a neutral position at all power settings. Personally, I know better.

 

This guy is flying the P-51D currently and regularly gives his "opinion" on subjects like these.

 

https://www.facebook.com/groups/thunderboltp47/permalink/10155861902569583/

https://www.facebook.com/groups/thunderboltp47/permalink/10155861902569583/


Edited by pmiceli

 

 

 

 

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Maybe it's 'complicated, nevertheless it's wrong. Furthermore that's still no answer concerning this basic, rather serious bug.

 

I don't think that you will find a single pirep about torque effect way below stall speed and close to and/or at 0kts airspeed for the P-51, but this doesn't mean the effect is not there IRL!

Even on a rather low powered Pitts with it small lightweight prop this effect is noticable and has to be taken into account during vertical maneuvers.

 

This effect exists on all prop planes IRL and is simulated in most (if not all) other flightsims.

 

My expectations for the Yak-52 and it's aerobatic capabilities have suddenly dropped close to zero :(

 

It's hard to believe if it is this wrong? That with all the pilots such as Nick Grey, this would not have been discussed in length? If anyone would want this to be accurate, it would be all the pilots at TFC TF-51D Mustang 44-84847.


Edited by David OC

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Aileron input does not matter in that situation, since there is almost no airflow, and it is outside of the flow generated by the prop. But there was no aileron input anyway.

Of course it does matter. It's essential to observe the need for increased aileron input with decreasing airspeed. Again, it's an important factor in any vertical maneuver IRL.

 

It's hard to believe if it is this wrong? That with all the pilots such as Nick Grey, this would not have been discussed in length?

This is for sure not documented anywhere since such a 'test' would be meaningless IRL.

There's no use for such a maneuver in a P-51 and I don't think that especially with the high value of these vintage P-51s anyone would even think of trying that.

Furthermore it puts a lot of stress on the airframe, prop and prop shaft.

 

The point I'm trying to make is that the complete lack of torque in this situation is a basic bug in the FM of (at least) the TF-51. This makes me wonder how torque is being calculated in DCS.

 

If this bug lies in the core of the DCS flight modelling, aerobatic planes like Yak-52 and the Christen Eagle wouldn't make much sense if they couldn't be flown in a realistic way.


Edited by bbrz

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OK, not a troll. Accepted.

 

must be compensated for with rudder and a bit of aileron as speeds builds.

 

This is exactly what I have to do with the Mustang, every single takeoff. So the phenomena are there.

 

in a single engine prop require trim changes in all three axis

 

And again, if I change the power settings in any way, I'll need to trim all three axii when airborne in the Mustang. So again, the phenomena are there.

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Of course it does matter. It's essential to observe the need for increased aileron input with decreasing airspeed. Again, it's an important factor in any vertical maneuver IRL.

 

This is for sure not documented anywhere since such a 'test' would be meaningless IRL.

There's no use for such a maneuver in a P-51 and I don't think that especially with the high value of these vintage P-51s anyone would even think of trying that.

Furthermore it puts a lot of stress on the airframe, prop and prop shaft.

 

The point I'm trying to make is that the complete lack of torque in this situation is a basic bug in the FM of (at least) the TF-51. This makes me wonder how torque is being calculated in DCS.

 

If this bug lies in the core of the DCS flight modelling, aerobatic planes like Yak-52 and the Christen Eagle wouldn't make much sense if they couldn't be flown in a realistic way.

 

Wasn't the Yak-52 built for a commercial client for aerobatics etc? If so, these would have been the first things picked up when doing all the testing you would think? Especially considering they did IRL flight testing also.

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Wasn't the Yak-52 built for a commercial client for aerobatics etc? If so, these would have been the first things picked up when doing all the testing you would think? Especially considering they did IRL flight testing also.

Let's wait and see. Certainly not a first day buy anymore for me :(

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Yeah, it was a commercial project for a party training RL Yak-52 pilots. And as such, it must've been developed pretty comprehensively and accurately, or said party wouldn't have accepted it at all. So to assume there'll be, say, no torque modelling present is just ludicrous IMO.

 

And about this complaint here: the guy says there's no torque, yet I need to always input rudder and aileron when taking off + trim for takeoff as per the book, and trim all 3 axii if I change any power settings in flight. Sure, you can always debate whether the effects and symptoms are correctly presented; but claiming none exist is, again, just ludicrous.

 

And that's my $0.0002. Au revoir gents and gentettes ;)

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Of course it does matter. It's essential to observe the need for increased aileron input with decreasing airspeed. Again, it's an important factor in any vertical maneuver IRL.

 

 

We are NOT talking about the same thing here. The purpose of this test is to try and narrow down the problem. I wanted to get the aircraft in a zero speed condition, and then test the torque there. How I got into that situation was NOT part of the test this time!

 

What this shows me, is that the torque itself is there, and if there is a problem, it might be around the effects that counteract torque in flight.

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What this shows me, is that the torque itself is there, and if there is a problem, it might be around the effects that counteract torque in flight.

 

 

Or... not a problem but rather a well programmed feature that doesn't get modeled right in many flight simulators...

 

 

A good example are the slipstream effects, and the asymmetric "hit" in the lower surface of the left wing, left sections of the fuselage and, above all, left vstab and rudder surfaces ( for the areas above CoG )... These all tend to counter torque , in the presence of slipstream, which is actually maximized at high power ratings and lower TAS...

 

 

I still remember well when along it's v9 iteration, Austin introduced torque in X-Plane :-/... It took years to correct, and we're still dealing with the rest of the effects...

 

 

That's why DCS, and sorry but I really have to mention it here too - IL-2 BoX - are light-years ahead of most civil sims in modelling these and other effects.

 

 

I also still remember the first time I met the effects of deflected propwash during takeoffs under strong crosswinds with exactly these same P51d.... Have you tried it ? Get your P51d in the rw with a 10m/s wind from, say, your 10 o'clock, and see what goes on when you add takeoff power ...

 

 

Ah, and BTW, torque should also be countered using RUDDER, not ailerons ! It's obvious if you take into account adverse yaw from the wing the get's it's aileron down to counter the torque ( left in a CW rotating prop aircraft ), and well explained

for instance...

 

 

So, not saying it's perfect, but it certainly must be really close to it in as far as it is possible with such a program...


Edited by jcomm

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Trying to narrow this down with some further unprofessional tests. See attached track.

 

 

 

1st vertical / power 100% prop. max rpm

 

00:43 - IAS: 100km/h / pitch: 76 / AoA: 10,2 --- stable

00:45 - IAS : 80km/h / pitch: 73 / AoA: 8,8 ----stable

00:47 - IAS: 52 km/h / pitch: 65 / AoA: 15,2 ---stable

 

At this point as AoA goes above 20 rotation to the left starts

 

00:50 - IAS: -46km/h / pitch 74 / AoA -106 --- continous rotation to the left approx 100-180 deg/second (did not measure that)

 

00:52 - IAS: -47km/h / pitch 66 / AoA +178 - continous rotation to the left

 

00:56 - IAS: 123km/h / pitch 1 / AoA -72 - still continous rotation to the left, at this point the nose drops below the horizon

 

00:57 - IAS: 150km/h / pitch -30 / AoA +25 - As AoA is back in range the rotation decreases rapidly

 

00:58 -IAS :187 km/h / pitch -67 /AoA -1 - stable dive, rotation stopped

 

Next vertical without engine power (throttle idle, prop min. rpm)

 

01:38 -IAS :58 km/h / pitch 73 /AoA 15,2 --stable

01:39 -IAS :37 km/h / pitch 72 /AoA 32,3 --stable, no roll

01:40 -IAS :28 km/h / pitch 71 /AoA 63 -- no rotation

01:42 -IAS :-65km/h / pitch 53 / AoA 123 - nose dropping, no roll, no rotation

Nose dropping to stable dive

 

 

I think this shows the following:

 

 

-The continous rotation to the left is caused by the torque, not any other effect, being stalled or anything else (we knew that of course)

 

 

-Being in the 50 km/h speed range, basically zero speed, the rotation due to the torque starts only as the AoA increases above stall AoA.

 

 

Pleas do watch the track and excuse my bad flying.

TF-51 tailslide Test.trk

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Trying to narrow this down with some further unprofessional tests. See attached track.

 

 

 

Excellent data ( even if not "professional" ) .

 

 

I will not be able to try your track, but I agree from the observations that something looks wrong indeed !

 

 

Thx

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Ah, and BTW, torque should also be countered using RUDDER, not ailerons

 

IRL in a (full power) vertical climb you need the rudder and the ailerons to keep/correct the wing position. With the DCS TF-51 I need only rudder and no ailerons.

 

But, after flying the TF-51 and the FR 109 extensively I have to admit that (apart from the discussable torque/low AoA interaction) the TF-51 feels much more like a real airplane than the 109 in FSX and I do concur with jcomm when he says that DCS (don't have IL since many years) flight models are way ahead of other flightsims.

 

edit: corrected weird quote error


Edited by bbrz

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IRL in a (full power) vertical climb you need the rudder and the ailerons to keep/correct the wing position. With the DCS TF-51 I need only rudder and no ailerons.

 

But, after flying the TF-51 and the FR 109 extensively I have to admit that (apart from the discussable torque/low AoA interaction) the TF-51 feels much more like a real airplane than the 109 in FSX and I do concur with jcomm when he says that DCS (don't have IL since many years) flight models are way ahead of other flightsims.

 

edit: corrected weird quote error

 

That's why I love this old post by EvilBivol and link and share it a lot for others that are new to flight sims or just learning what to know more without getting into CFD modelling etc. The guy's here are trying, with some limitations, more than any other sim's, to go as deep as possible with the FM modelling, the aircraft feel more alive to me and the choppers way more than other sims.

 

 

Again, it's ultimately a model and cannot be completely correct or account for every physical phenomenon, but we try to go as deep as possible in terms of real-time modeling and as wide as possible in terms of covering physical effects within reasonable limits of time and money. Otherwise we could work on any one model endlessly, which is probably what some of the devs would like to do. smile.gif

 

Read the full post here

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Again, it's ultimately a model and cannot be completely correct or account for every physical phenomenon, but we try to go as deep as possible in terms of real-time modeling and as wide as possible in terms of covering physical effects within reasonable limits of time and money. Otherwise we could work on any one model endlessly, which is probably what some of the devs would like to do

 

 

I fully agree with these considerations, and let's not forget that the flight sensations that return the aircraft in DCS are unique, that is the result of an excellent work in compliance with the conditions reported by EvilBivol-1 and does not seem to me a thing to little for a consumer simulator.

 

 

 

:thumbup:

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