I can't spin a spit and FM concerns (vid)

[FLOOB]

I see spits spin all the time.

[colmbo]

Played around with the Spit I this morning using a standard spin entry of idle power, full rudder and full aft stick at the stall.

Using full left rudder the nose first yawed left and bit then hard back to the right, nose staying pretty much on the horizon.  After 90-180 degrees of turn the nose popped up to about 60 degrees nose high, airspeed fell to zero and I fell tail first.  Managed to work the airplane inverted and ended up 40 degrees nose low, IAS 30, elevator had no effect on pitch.  Ailerons would provide roll opposite to correct direction, using aileron and rudder I was about to "rock" the airplane and get the nose to drop more, once airspeed gained it recovered.

Above is pretty standard for what I'm seeing with the Spit spins.

If accelerated at entry and some aileron used it spins more reliably in a more realistic manner.  Even then however it will revert to a spin to the right even with left rudder used.

Spin to right was more normal, "jerky" in yaw rate, nose down 45 degrees or so. 

[Randy1]

A wing-over is not a stall maneuver.  It's simply a steep climb - turn - dive.  Did you mean hammerhead?

I was sure enough.  My bad.

[FLS]

On the P47 wing-over, with hard rudder, the timing of the throttle seems to be critical.  Too soon and it mushes out as you noted.  I do use manual trim.  I can't hit it every-time.  If it mushes, you are in deep po-po. I know that.  Might as well be a Christmas ornament, at a BB gun convention.

Maybe some of the P47 specialist can offer some good advice.  What I said is all I've got.

The critical timing is in the speed where you initiate the yaw. When you are too fast you will skid instead of pivot and the skid will kill your rotation and leave you with your nose high. When you are too slow you won't create enough rotation with the rudder. When you go up make sure it's your wings that are vertical not your fuselage.

When you are on the runway go to F3 and look at your rudder. Note that you can turn your controller faster than the rudder will respond. Controls are affected by high speed and joystick settings but the rudder is always damped regardless of settings so you never get full instant deflection.

[lakc]

When you are on the runway go to F3 and look at your rudder. Note that you can turn your controller faster than the rudder will respond. Controls are affected by high speed and joystick settings but the rudder is always damped regardless of settings so you never get full instant deflection.

But is the input into the flight model correct, and just the graphics delayed, or is the input also delayed?

[FLS]

The control surface graphics come from the flight model. You can see that in high speed dives. The input is delayed and/or limited in order to be correct. Our rudder controllers being easier to move than real rudder pedals.

[colmbo]

Our rudder controllers being easier to move than real rudder pedals.

Hmmmm.

Sitting on the ground in the B-24 you can slap the rudder back and forth easily….same in the B-17.  Moves as easily as the pedals hooked to my computer.  The rudder is over damped in game…one of the reasons it's a bit harder to track during takeoff or landing since you're just "this much" behind the airplane….real life little stabs left and right keep you tracking the center line.  At higher speeds I can see some reduction in rate (it takes more muscle) as well as a possible reduction in throw (again, muscle needed).

[FLOOB]

FLS what's the story behind that motherdiddlying avatar?

[Vinkman]

I've been wondering the same thing for quite a while. My personal hypothesis of it is that there might be excessive gyroscopic precession of the prop working together with the aerodynamic forces at play during a tail slide that cause this somewhat weird behavior. I doubt there's anything wrong with gyroscopic precession code itself but I'm suspecting that the parameters fed into the model might be the cause. For example, a case where the prop mass is too great or the angular velocity of the prop is too high (say, the crankshaft rpm instead the rpm of the prop end of the reduction gear) would cause greater precession force than what would occur in real life.

I want to emphasize that this is just a hypothesis and it would be pretty hard for me to explicitly prove it. One way to test the theory is to try tail slides with the I-16 which seems to have the worst symptoms of this. As the I-16 starts fall backwards at the top of the tail slide, without any control input, it takes a long while for the I-16s nose to drop close to parallel of the velocity vector when the engine is running at idle. With the engine off and prop stationary, the nose swings down quickly and uneventfully.

Before the prop mass of the Brewster was reduced, the plane could fall ~4000-5500ft down more or less tail first from a tail slide maneuver before the nose came down. After the reduction of the prop mass (granted, other changes were made as well) the nose drops down rather uneventfully.

The planes that in my opinion seem to suffer from this problem the most are:

I-16
Spit14
Ta152

Interesting.

I've noticed this most on the Ki-84.

[nrshida]

Interesting.

I've noticed this most on the Ki-84.

Just turn your motor off for a sec dude and she'll come back into line.

[Vinkman]

Just turn your motor off for a sec dude and she'll come back into line.

I will try that. 

[FLS]

Hmmmm.

Sitting on the ground in the B-24 you can slap the rudder back and forth easily….same in the B-17.  Moves as easily as the pedals hooked to my computer.  The rudder is over damped in game…one of the reasons it's a bit harder to track during takeoff or landing since you're just "this much" behind the airplane….real life little stabs left and right keep you tracking the center line.  At higher speeds I can see some reduction in rate (it takes more muscle) as well as a possible reduction in throw (again, muscle needed).

It does seem odd that it's delayed with no airflow. Small corrections are quick but the full travel is noticeably delayed.

[-aper-]

Edit : I'm learning  I learned that what I perceive as 'the screewy behavior' is generated by having the engine on even when at idle. I'm surprised the forces generated by the prop of an engine at idle have so much influence on the FM :
https://www.youtube.com/watch?v=586lFSpIxsw

If the forces generated by prop so strong that they prevent plane falling into left spin normally the plane should entered the right spin with no problem. Is it right?

BTW I tested Spitfire stall/spin behavior in WarThunder and the plane entered left/right spin with no problem at all with engine idling at low rpm at near-stall speeds and full left/right rudder applied.

To recover from left spin it was enough to release controls to neutral position. To recover from right spin full rudder counterclockwise had to be applied.

https://www.youtube.com/watch?v=IikIyblYxkA