Jump to content

Flight Model modification question


Recommended Posts

I have been ignoring DCS since my disappointment with the responses to this thread.

 

There is a basic misunderstanding of what Torque is on display here. (Not just in aircraft, in general physics knowledge)

 

Yes, the P-51 does stall and it does break left pretty consistently at about 100 mph (more under G load greater than 1)

 

That isn't torque. That is an aerodynamic stall.

 

There is no torque modeled.

 

 

First, a discussion of Newton's third law.

 

For every action, there is an equal and opposite reaction.

 

The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object. The direction of the force on the first object is opposite to the direction of the force on the second object. Forces always come in pairs - equal and opposite action-reaction force pairs.

 

Torque is the name applied to the force pair for rotation.

 

Here is a great discussion of that.

 

https://www.4physics.com/phy_demo/newton/newton_rot2.htm

 

Any prop driven single engine aircraft is subject to the force of torque. The airframe MUST rotate in the opposite direction when power is applied.

 

If you start with the aircraft trimmed for level flight at idle power, add full power and do not need to apply any control force to counter rotation around the torque axis, then torque is not modeled.

 

On an aircraft such as the P-51, this torque force should require some pilot action to counter at 130 mph and this is backed up by pilot reports then and now.

 

Right stick and/or right rudder to counter the result of a very basic law of physics. It doesn't need to be necessarily violent but it does need to exist.

 

It does not exist.

 

This is a basic flaw in the flight modeling of the P-51 in DCS and most probably every single engine prop module.

 

There are a few choices as to why.

 

1. Ignorance of basic physics. I deem this unlikely. Russian science education is extremely good.

 

2. The original base FM did not factor in engine torque because jet engines negate torque internally almost completely and correcting the base FM is deemed very low priority because the customer base is conditioned to expect jet like performance. This I deem as highly probable.

 

3. There was a conscious decision to exclude torque modeling for the same reasons as in 2. Also a highly probable option.

 

Modeling proper torque levels in WWII fighters in software titles has been a constant battle I have been personally involved in for over 20 years now. Most "game" titles specifically choose to tone down the torque, rotating slipstream effects, etc because the paying customers, as demonstrated in this thread, do not actually want full fidelity. Even though most tone it down, they generally leave some in. DCS, while proclaiming to be a study sim, has zero torque. For me that is egregious.

 

War Thunder and IL2 both do a better job with torque modeling in general.

 

For me, that statement alone makes DCS WWII modules gather dust.

 

For those that have an overwhelming desire to rebut, carefully consider why. Where is the evidence that DCS has modeled torque? Why are you interested in disproving my claim instead of investigating why the DCS P-51 does not seem to faithfully replicate real world reports or comply with Newton's Third Law?


Edited by pmiceli

 

 

 

 

EDsignaturefleet.jpg

Link to comment
Share on other sites

  • Replies 122
  • Created
  • Last Reply

Top Posters In This Topic

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.


Edited by msalama

The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.

Link to comment
Share on other sites

I have been ignoring DCS since my disappointment with the responses to this thread.

There is no torque modeled.

Since I have no prop driven add-on this applies only to the TF-51. (My one and only DCS prop plane will be the Yak-52).

 

Torque is definitely modeled, but it's between non-existent and weak, inconsistent and difficult to predict.

 

If you e.g. pull up with full power into the vertical there's no torque at all, not at 200mph, not at 100 and not even at 0mph which is definitely wrong.

 

On the other hand if you descent at a constant 150mph at idle, trimmed for a hands off descent and you apply full power, she does noticable roll to the left.

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

Why are you interested in disproving my claim instead of investigating why the DCS P-51 does not seem to faithfully replicate real world reports or comply with Newton's Third Law?

 

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.


Edited by Art-J

i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.

Link to comment
Share on other sites

But why is it that there's not torque effect at all (if the AoA stays close to zero) in a vertical climb? At 0kts or 20kts torque effect should be very noticable.

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

But why do I bother...

 

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.


Edited by msalama

The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.

Link to comment
Share on other sites

At 0kts or 20kts torque effect should be very noticable.

 

You're right, it should. Is there none then? Since I've got to admit that I've never checked / paid attention to this myself.

The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.

Link to comment
Share on other sites

I never tested until I came across this thread. If there a basic bug in the torque simulation this would make aerobatic planes like the Yak-52 much less realistic.

 

I have the impression that torque in the TF-51 depends a lot on AoA, but again, that's difficult to judge and I usually don't fly the TF-51.

 

I'm only testing because I'm interested in the Yak-52 ;)

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

But why is it that there's not torque effect at all (if the AoA stays close to zero) in a vertical climb? At 0kts or 20kts torque effect should be very noticable.

 

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.

i7 9700K @ stock speed, single GTX1070, 32 gigs of RAM, TH Warthog, MFG Crosswind, Win10.

Link to comment
Share on other sites

1. 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.

 

2.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.

 

1. +1 I was tempted to ask if he was in game mode as his 'explanation' was somewhat...different...until I tried the vertical climb. Btw. It's way easier to accomplish in the external view with the flight path data etc. displayed ;)

 

2. I know. It took me and other members many posts to convince him that e.g. the flap pitch moment on the F-86 is reversed.

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

  • ED Team

All questions about "torque" are answered in the trim diagrams, where rudder, elevator, and aileron positions are plotted vs airspeed. Ailerons input, as one can see, is very small or nil in wide range of IAS. Only at near-stall speed it needs to add more ailerons to almost full rudder.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

Link to comment
Share on other sites

Only at near-stall speed it needs to add more ailerons to almost full rudder.

This doesn't match with the observation that even way below stall speed, down to 0kts there's no aileron needed….

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

  • ED Team
This doesn't match with the observation that even way below stall speed, down to 0kts there's no aileron needed….

 

The goal is to have slip and turn indicator in 0. Waiting a video as you trim the plane at 130 mph in 2700/46" climb using NO ailerons...

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

Link to comment
Share on other sites

Doesn't the L-39 count as a (motor) glider ;) The only really impressive glider I've seen in many years is the SZD 59 Acro.

 

 

Ah! SZDs I just flew two other great models, the Cobra 15 and the Standard Mucha....

 

 

Regarding the P-51 in DCS, last time I flew it, long ago, t did show excellent torque effects, that I used to compare to the previous best experience I have had with a P-51 in a flight simulator : the A2A P51d Civil and Military versions, which could easily climb without torque effects until speed got down to Vs0...

 

 

Maybe things changed with the latest DCS updates ?

Flight Simulation is the Virtual Materialization of a Dream...

Link to comment
Share on other sites

The goal is to have slip and turn indicator in 0. Waiting a video as you trim the plane at 130 mph in 2700/46" climb using NO ailerons...

Does this mean that you confirm there actually is a very basic bug in DCS?

 

Regarding the P-51 in DCS, last time I flew it, long ago, t did show excellent torque effects, that I used to compare to the previous best experience I have had with a P-51 in a flight simulator : the A2A P51d Civil and Military versions, which could easily climb without torque effects until speed got down to Vs0..

 

Torque effects are very nice on the DCS TF-51 during normal ops, but apparently there's something seriously wrong with the basic torque calculation.

Yo-Yo already mentioned how ED calculated torque and it presently does look like it is (mostly) speed/AoA dependent, which would be plain and simple wrong.

 

I never understood the hype about A2A. IMO people get too easily exited about loosing ailerons, fouling spark plugs and shaking instrument needles.

I've bought their Spitfire which had horrible basic flaws in the FDE (e.g. torque) and the T-6 which shows severe bugs when doing aerobatics like loops.

 

Concerning handling and aerodynamics I still like the FSX FR 109K the most.

Just tested and in a vertical full power climb you have to use quite a bit of aileron to keep the 109 vertical and below 50-60kts you can't stop the 109 from rolling despite full opposite aileron.

Btw, it's nice how she smoothly translates into a flat spin during this maneuver.

 

It would be great if someone could test the DCS 109 and/or Spitfire in a vertical climb.


Edited by bbrz

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

Concerning handling and aerodynamics I still like the FSX FR 109K the most.

Just tested and in a vertical full power climb you have to use quite a bit of aileron to keep the 109 vertical and below 50-60kts you can't stop the 109 from rolling despite full opposite aileron.

Btw, it's nice how she smoothly translates into a flat spin during this maneuver.

 

They must have done a really good job, even with all the problems in FSX. The Q400 used an independent Flight Dynamics Engine to be able to get it right for the sim(s), the sim is only for scenery files. I think they used this dynamics engine.

i7-7700K OC @ 5Ghz | ASUS IX Hero MB | ASUS GTX 1080 Ti STRIX | 32GB Corsair 3000Mhz | Corsair H100i V2 Radiator | Samsung 960 EVO M.2 NVMe 500G SSD | Samsung 850 EVO 500G SSD | Corsair HX850i Platinum 850W | Oculus Rift | ASUS PG278Q 27-inch, 2560 x 1440, G-SYNC, 144Hz, 1ms | VKB Gunfighter Pro

Chuck's DCS Tutorial Library

Download PDF Tutorial guides to help get up to speed with aircraft quickly and also great for taking a good look at the aircraft available for DCS before purchasing. Link

Link to comment
Share on other sites

I think in as far as engine / prop torque go, it's being calculated correctly, speed and AoA only contributing to enhance or "shadow" it's effects.

 

P-factor that's a different story, and same regarding slipstream, which I believe is also calculated taking into consideration various interactions.

 

Actually the only aspect I always found a bit overdone ( but have no real world data or experience to base my affirmation in… ) is P-factor. P-fcator plays a very important role at least in the P51d, and it shows during final approach when I always see the nose wanting to wobble around...

 

 

BTW: Believe the OP is referring to what he recorded in this video:

which was recorded at 16k feet!


Edited by jcomm

Flight Simulation is the Virtual Materialization of a Dream...

Link to comment
Share on other sites

  • ED Team

 

 

 

Torque effects are very nice on the DCS TF-51 during normal ops, but apparently there's something seriously wrong with the basic torque calculation.

Yo-Yo already mentioned how ED calculated torque and it presently does look like it is (mostly) speed/AoA dependent, which would be plain and simple wrong.

I never mentioned the ideas you wrote here. Of course, AoA and speed have effect on torque as in RL, but in the calculations for prop effects are very sophisticated in DCS. Torque is not equal to engine torque regarding a single engine prop planes, because of slipstream interaction with the airframe, so, the momentum of the free slipstream behind the plane is much less than it was after the prop.

DCS models slipstream position and velocities distribution in it, then - the interaction with the airframe. So, the model is much more complicated, and, that is important, corresponds either to test reports or real pilots experience. I mean the pilots with hundreds and thousands hours in WWII props.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

Link to comment
Share on other sites

So, the model is much more complicated, and, that is important, corresponds either to test reports or real pilots experience. I mean the pilots with hundreds and thousands hours in WWII props.

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 :(

i7-7700K 4.2GHz, 16GB, GTX 1070 

Link to comment
Share on other sites

Hello guys!

 

 

I have decided to test the torque effect, in close to zero speed conditions on the top of a vertical climb.

 

 

Track is attached!

 

 

- 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.

 

 

It's fun, so Bf-109 and Spitfire will follow soon :)

TF-51 Torque Test.trk

Link to comment
Share on other sites

Hello guys!

 

 

I have decided to test the torque effect, in close to zero speed conditions on the top of a vertical climb.

 

 

Track is attached!

 

 

- 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.

 

 

It's fun, so Bf-109 and Spitfire will follow soon :)

 

What are your conclusions though?

Link to comment
Share on other sites

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...