Spitfire's torque effects ?....

[Guest deleted@50488]

Or, the absence of it....

 

Would really like to see someone from the Devs team offer oppinion on this.

 

The IL2 GB  Spitfires are - IMO - modeled in a rather "faint" way regarding prop effects...

We can perfectly takeoff, even setting the rudder trim tab to it's neutral position, climb at the highest possible slope angle, and it's suprising to find that initially it even appears to "want" to roll right after leaving the ground, and then you practically don't have to add any stick ( right stick ) to level your wings (?) or rudder to avoid sideslipping  (?)

 

Tried it at various fuel & amno configurations, clipped wing version too, and it's the same... You can get to extreme AoAs, and just a tad before stalling does some Anti-Clockwise rotation start to develop ?

 

Given that I have IL-2 GB on a high mark regarding flight dynamics, I would like to be told this is the correct behaviour, because at least common sense tells me it is plain wrong...

Edited August 10, 2018 by Von-Target

[ZachariasX]

At 1100 kW and 3000 rpm you have 3500 Nm torque. 3 m out in the wing (maybe where the center of lift is, this makes 1150 or so N, reflecting 115 kg or so of added „asymmetrical mass“, about 4% of total lift required.

 

No, don‘t expect much work on the ailerons, unless your plane is on the edge of stall, and then it‘s too late.

[Guest deleted@50488]

Thx ZhacariasX,

 

but appart from the "pure" torque, there's also the P-factor and the asymmetric slipstream hit of various aircraft surfaces, all contributing to a left yawing tendency (*) and, I believe, also some induced roll ?

 

If you get the time please give it  a try. You can start from an Autumn map, fuel at 65%, no amno. Takeoff and pitch it up to the limits, keeping around 100 MPH IAS in your climb...

 

Make sure you turn the rudder trim to neutral. I usually hit the "reset trimmers" key and then add only the pitch trim before starting the takeoff run...

 

(*) although actually the vertical fin & rudder being hit portside could actually partly compensate the left rolling tendency...

Edited August 10, 2018 by Von-Target

[ZachariasX]

Oh, next week I‘ll be back near my sim rig and I will give it a try.

 

About P factor, this requires significant AoA to really give a left pull (in case of the Spit), this when the tail still sits down and the plane sitting heavy on the wheels, meaning the undercarriage carries most of the torque as well at that point. If you accellerate and the moment you bring up the tail, you will notice p-factor disappearing and you have to adjust the RUDDER to compensate the difference. Still in this moment, the aircraft is somewhat on its wheels and you will not have any induced roll.

 

The moment you lift the aircraft off the ground, the ailerons will have to compensate for the sometimes rudder input to keep the plane straight, especially if the engine is powerful and lots of rudder is needed to maintain flight attitude in *climb configuration*. The more the aircraft is suceptible to adverse yaw, the more aileron is required.

 

Personally, I doubt the Spitfire has much adverse yaw compared to other types.

 

For completeness sake in climb, the plane starts to yaw because the airsream is corkscrewing around the aircraft behind the propeller, resulting in the vertical stabilizer getting airstream somewhat from the side, pushing the tail sideways. If you had vertical stabilizers upward and downward in the slipsteam, then the corkscrew slipstream would push the upper section from one side and the lower section from the other side, inducing a rolling force. In a Do-335 for instance, you‘re more in to trim your climb configuration with the aileron trim than with the yaw. Remember, despite opposite turning props, the tailplane is still in the slipstream of only one propeller.

 

[Guest deleted@50488]

Exactly Zacharias, and thx for going to try it ?

 

I mentioned the corkscrewing effect ( called it slipstream ) and in those climbs maintaining next to 100 MPH or even less, at full power / rpm, sometimes even keeping the undercarriage down, I do believe really high AoAs are reached.

 

Then again, sometimes there appears to be also very faint need to use the rudder to clear the resulting sideslip. I'd say these Spitfires appear to be very benign in as far as prop effects at high power / rpm and AoA go...

 

And yes, since it uses frise-type ailerons, the Spitfire should be optimized regarding adverse yaw.

 

Looking fwd for your tests and comments ?

Edited August 10, 2018 by Von-Target

[ZachariasX]

I‘m planning on taking the teon seat Mk.IX in Duxford for a ride next year. I‘ll have a better idea about how the Spit handles then... 

Edited August 10, 2018 by ZachariasX

[Blackhawk_FR]

What is the "P factor"? 

 

To me the FM of the Spitfire looks really strange, or simple (like "work in progress"). 

I would need to make a specific test to be sure but it looks like there is a real lack of power effect. On a straight and level flight at medium speed, your nose doesn't react a lot at throttle changes (while there should be movements on the 3 axis due to torque and helicoidal blast).

 

Also, the behavior on the pitch axis is really strange. The plane reacts like its CG is really centered at the rear. May be it was a real characteristic? But on IL2 it's the only one with this behavior. And once at very low speed, the elevator lose a lot of efficiencies.

Edited August 11, 2018 by F/JG300_Faucon

[Guest deleted@50488]

P-Factor is the asymmetric contribution of the prop blades to the generation of thrust due to their angle of attack, also known as asymmetric disk effect.

It is present whenever there's an angle between the relative airflow and the axis of rotation of the prop.

 

In a CW rotating prop aircraft, and when pitched up, like on a taildragger during the takeoff and while the tail is down this asymmetry translates into the downgoing blades ( or the starboard side as seen from the cockpit ) having a bigger angle of attack than the upgoing ones thus creating more lift / thrust and pushing the aircraft nose to the left.

 

Regarding that description you make of the CoG, I guess you're experiencing the effects of the aircraft showing neutral static pitch stability under most flight conditions.

 

It is nicely modeled in IL2 GB, IMO, although sometimes I have some questions regarding this or that features, but overall I'd say IL2 is actually my preferred feel of flight among the many many flightims I have used for more than 2 decades ?

 

Edited August 11, 2018 by Von-Target

[Ehret]

The P-factor is most visible in helicopters flying with some forward velocity. The advancing side of the rotor will generate more lift.

[E69_geramos109]

Some fms feels quite simple on torque effects. You can check yak also that is allways perfectly trimmed, and it can prop hang with no torque effect or any force that makes difficult the aiming

[E69_geramos109]

On 8/13/2018 at 10:16 PM, LukeFF said:

 

[edited]

Hey luke you are my best fan. Not missing any comment.

Sad that i did not see your answer on time.

[ACG_Smokejumper]

Torque in Spitfires? That would be good. The rudder trim is almost set and forget. Skid isn't as prevalent as anecdotes indicate. Cliffs of Dover I think does this effect very well for the Spitfire. My 2c.

 

I personally believe the SpitV etc need a lookiloo.

[JG27*PapaFly]

I wonder where the gyroscopic prop forces are in the Spit. They are huge in the 190s. I'd expect them in the Spits, since their prop has similar weight and rotates even faster.

[Denum]

This is the necro of necros and I apologize

 

 

But is there any chance to adding more pronounced engine torque on the single engine aircraft?

 

The 109 and Spitfire shouldn't be able to hang on the prop and maintain accuracy as they do.

 

Usually at these speeds these aircraft are desperately trying to kill you at full throttle.

 

With the addition of the Griffon XIV on the spoke, lacking that violent torque the pilots spoke of is leaving a large part of her character on the table. 

 

I do understand that there's a fine line between fun and realism but some of the maneuvers that I can squeak off in the 109 at slow speed feels more inline with a high performance acrobatic plane or biplane then a world war 2 fighter with 1400HP churning away.

 

 

Still love the game and deeply enjoy flying the aircraft. Thanks again for your efforts devs. 

 

Denum

[Oyster_KAI]

I also hope that the torque can be modeled more realistically.
At present, the torque is very weak (even on Tempest, 109K4 etc), any aircraft can take off easily,  and they can make a variety of agile maneuvers without using pedals.
But I think this will requires a lot of work.

[Denum]

50 minutes ago, Oyster_KAI said:

I also hope that the torque can be modeled more realistically.
At present, the torque is very weak (even on Tempest, 109K4 etc), any aircraft can take off easily,  and they can make a variety of agile maneuvers without using pedals.
But I think this will requires a lot of work.

I whole heartedly agree it is likely a ton of work. 

 

Wish I could help in some capacity but it's not a toilet or boiler. 

 

I'm not much use!

[Bremspropeller]

On 2/28/2021 at 7:42 PM, Oyster_KAI said:

At present, the torque is very weak (even on Tempest, 109K4 etc), any aircraft can take off easily,  and they can make a variety of agile maneuvers without using pedals.

 

What kind of surprises me is the amount of LEFT rudder I need to center the ball on many airplanes (clockwise rotating prop) during maneuvers.

One of them is the 190.

 

Speaking of the 190: A D-9 on Meth will do fancy torque-stuff when slow.

[JG27*PapaFly]

On 3/2/2021 at 2:07 PM, Bremspropeller said:

What kind of surprises me is the amount of LEFT rudder I need to center the ball on many airplanes (clockwise rotating prop) during maneuvers.

One of them is the 190.

That's what you'd expect in order to counter the gyroscopic effect produced by a large ~200 kg propeller rotating at more than 2000 rpm. Apply negative g loads and you must push right rudder.

What surprises me is that, despite the fact that most props of the WWII warbids modeled in our game are in the same ballpark in terms of mass and rpm, some FMs seem to have very little, if any, gyroscopic effects. The Spitfires, Tempest, and Yaks come to mind.

 

Here is what aerobatics and warbird pilot Rick Volker wrote about flying aerobatics in the Spitfire:

"The pitch sensitivity is identical to the SU26. Rudders are powerful, and they are needed to arrest the large gyroscopic forces and p factor from the enormous prop. This is one of several traits that the Spitfire shares with the SU26 more than the Harvard."

 

"Recommended entry speed for a loop is 260mph (max. cruise power). A 4G pull gives 120 mph at the top of a 2000ft. diameter loop. A clean airframe and “freight train” momentum force you to strain for a very long time or risk G-loc. You must get on the rudders all the way around to compensate for gyroscopic forces and p factor."

 

That's definitely not how I'd describe our Spitfires, but close to the 190s. In reality, the gyro forces produced by the prop depend on, among others, following parameters:

• The total mass of the prop (very similar for Spit9 and Fw190 series)
• The mass distribution (very similar for Spit9 and Fw190 series)
• rpm (~3,000 for the spit, and ~2.600 for the Fw190)

Why the Spits have no noticeable gyroscopic effects in-game is beyond me.

[Bremspropeller]

11 minutes ago, JG27_PapaFly said:

That's what you'd expect in order to counter the gyroscopic effect produced by a large ~200 kg propeller rotating at more than 2000 rpm. Apply negative g loads and you must push right rudder.

 

You'd also expect P-factor to significantly eat into the gyro-effects.

 

I'll have to spend more time testing and observing whats happening precisely when.

[ZachariasX]

For normal flight you can take the feet off the pedals and you will not see much gyro incuced yaw in the Spit. The qote mentioned aplies to aerobatics where she certainly needs a good footwork to keep her straight. Then again, if you fly a normal loop with a Bücker 131, you need almost full rudder over the top to keep it in plane. Only if you fly the Spit very slow and at high power ratings (aerobatics) or on takeoff that this becomes noticeable (or acute). The Spit flies as straight as a Cessna in „normal“ flight.

[JG27*PapaFly]

13 hours ago, ZachariasX said:

The Spit flies as straight as a Cessna in „normal“ flight.

 

We're discussing air combat maneuvers. Rick Volker mentioned that considerable footwork is needed to control the plane during mild aerobatics (he uses high entry speeds to vertical maneuvers, limits the g loads to around 4, and also limits the manifold pressure). In-game, the spit can be flown much harsher (higher g loads and turn rates, lower entry speeds, higher manifold pressure) without noticeable gyroscopic effects. 

[CSW_606_Temp]

Other planes in BOX have not torque? Why only Spit? It Is Complex model.

[ZachariasX]

10 minutes ago, JG27_PapaFly said:

We're discussing air combat maneuvers.

Well there for sure. But I'd say it is really speed and use dependent. Both gyroscopic precession and torque are very manageable at high speeds. The corrections are more subtle when you are faster. But if you have a gunsight as reference, moving your nose up and down in strong movements would  surely give you corresponding induced yaw. For good aim, you'd have to correct for that. But I am unsure to what degree you'd notice that as corection of the gyro or take it as simple mean of taking aim.

 

Aerobatics is certainly a special case as you fly say a loop in an exact plane and the gyro of the propeller will bring you off course and you have to correct that as in every (aerobatic) plane. If you do a loop, fly far enough for even a couple of degrees departure making your figure "not nice" At 300 mph, the rudder in a Spit takes a strong leg and you be working that constantly. This way, his comments are familiar.

 

You have TacView? It would be interesting to see ho many degrees your plane does yaw of course during a loop when you do not correct for precession with the foot. I don't have TacView and my "issues" when I'm playing the game are way more basic, so I wouldn't know how much planes are affected. Subjectively, in the game, I don't feel much about it in general. But in essence it should be easy to simulate, as the gyro can be calculated in hard numbers. It is also of note that the moment arm, distance between prop and CoG is also important. I would expect the Mustang to be more affected by gyro precession than the Spit. I hope I can fly a Mustang this August... fingers crossed.

[ACG_Cass]

Prop Torque seems to be modeled very lightly on the superprops and doesn't really differ from the earlier, lower horsepower aircraft. 

 

This is without any rudder input and slightest touch to the ailerons (you can see they barely move). I did a DC K4 and then an F4 for comparison. I actually couldn't get the K4 to properly stall, same with the Spit. Even if you start with the wing dipped in the direction of the torque, it doesn't seem to affect it. 

 

 

Edited March 6, 2021 by Cass

[JG27*PapaFly]

7 hours ago, dogefighter said:

Amazing how people with a JG tag always only whine about Spits or Yaks or other allied planes, while ignoring the fact that 109s and 190s can pull the same kind of (if not worse) BS maneuvers.

Au contraire. Had you watched the video I posted more than a year ago in which I extensively covered global FM issues, you'd perhaps give it a second thought before parading your bias, ignorance, and inanity.

 

 

@ZachariasX
I always correct for gyro precession during ACM. It's essential for good gunnery. The 190 series require at least 50 percent left rudder input during positive g maximum performance turns at 350-400 kph. The Spitfire series require very little, if any, rudder input.  Neither at that speed, nor at it's corner speed, which is way lower. And that's the crazy thing: one the one hand you have planes with higher corner speeds and generally much poorer turn performance (Fw190), with tremendous gyroscopic forces. On the other hand you have the Spitfire series, which are lighter, have similar weight props which rotate even faster than the 190 series props, and have much higher turn rates at slower speeds, yet no noticeable gyro forces. The massive 190 gyro forces are the very reason the 190 series can do gyroscopic maneuvers, like the gyro vertical reversal showcased in my video.

[ACG_Cass]

Awesome video @JG27_PapaFly. Really well put together.

 

There seem to be some glaring issues across the board that are behind all the janky flying we see.

 

My worry is that if each FM is individually developed, then the team don't sound like they have the capacity to go through and actually fix any of these issues as it would require a huge amount of work.

[[-=BP=-]Slegawsky_VR]

With the upcoming Griffon Mk.XIV they will hopefully revise some of the issues such as annoying taxing, gyroscopic prop rpm effect and the list goes on and on.