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Von-Target

Spitfire's torque effects ?....

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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 by Von-Target

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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.

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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 by Von-Target

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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.

 

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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 by Von-Target

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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 by ZachariasX
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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 by F/JG300_Faucon

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

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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

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14 hours ago, E69_geramos109 said:

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

 

[edited]

Edited by SYN_Haashashin
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