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MSFS Extra 300 in MFS, and the Pitts too...

jcomm

jcomm

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I was never able, in any version of Flight Simulator from MS tune the aerodynamics of aerobatic aircraft to the point of being able to instantly stop a roll.

There's always a lot of lag / inertia / momentum when I promptly return my HW controller to it's neutral point, and the virtual one follows it at that exact pace.

Tried again in MFS, using the "Modern" flight dynamics, and unfortunately, even after fixing the default data which is filled with bugs ( like fuselage_length = -1 ) and trying to adapt
the editable variables, and using Dev mode in the sim, copying the suggested values obtained through their "virtual tunnel test" into the "flight_model.cfg", but still no go - at least
not even by far as realistic as I get it in X-Plane or Aerofly FS 2 with similar aerobatic aircraft models.

Ah! And btw, same applies to knife edge manouvers...

Any suggestions really appreciated.

A friend told me he had seen something about an "historical problem" with SIM1.DLL ( I even thought this one was no longer being used unless Legacy FM was enabled ? ) and roll physics at higher roll rates ?
 
Last edited:
Roy Holmes

Roy Holmes

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The correct way to "instantly" stop a roll is to apply some opposite aileron before centering the stick. If you are doing a 4 or 8 point roll, you do that as you feed in the appropriate rudder deflection. So if you are rolling left and doing a 4 pointer, as you approach 90 bank you move the stick right through center a small distance to the right then center it as the roll stops. At the same time you put on right rudder by an amount depending on the airplane type. The fore and aft position of the stick when upright or in 90 bank can stay fixed, while when inverted it should be fed forwards to maintain the flight path but with negative lift. When upright or inverted the rudders are central.
For the remainder of the roll the procedure is the same, apply a lot of left aileron to get the roll established and then center it and apply right aileron to stop the roll as you approach the next position.
In some types you need to apply rudder on the same side as the aileron to get the roll going and counter adverse yaw.
Every type needs a slightly different technique depending on its control power and stability characteristics, the Hunter was very crisp and needed no rudder to help establish the roll, the F-4 needed some rudder to counter adverse yaw, the Jet Provost was like the Hunter but with a much slower roll rate.

What you describe in the second sentence above is perfectly natural and correct response to just centering the stick, the rate of roll will take a while to stop.
Roy
 
jcomm

jcomm

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OFC I heard about that guy, New-in-Town or how he's called, and Roy, I am aware and try to replicate the technique, but simply no go, ever, with any version of an Extra or Pitts or similar aerobatic aircraft I was ever able to try and tweak in any version of msfs...

It simply doesn't do it anywhere near real life. What I haven't yet tested was if MFS's EXTRA still climbs in a vertical roll with the engine shutdown, like I had the chance to record in fsx long ago...

 
L

L3M0N

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jcomm said:
There's always a lot of lag / inertia / momentum when I promptly return my HW controller to it's neutral point, and the virtual one follows it at that exact pace.

Tried again in MFS, using the "Modern" flight dynamics, and unfortunately, even after fixing the default data which is filled with bugs ( like fuselage_length = -1 )
Click to expand...

Fuse length being set to -1 isn't a bug or error it just clamps the fuselage length from the nose to the tail.

I've been able to reduce the inertia to the point but right now I can't get rid of it completely. There is some 'lag' value that is being used and I can't figure out where the game is getting that value from.
 
jcomm

jcomm

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portugal
L3M0N said:
Fuse length being set to -1 isn't a bug or error it just clamps the fuselage length from the nose to the tail.
Click to expand...

Hmmm, yes, but isn't that totally irrealistic ? Why would it be done that way ? Aren't we supposed to feed the FDM with as close as possible to the real thing data ?

What are the benefits of such an option ? Never seen it in MS FS before, I must confess, and didn't even know it might make sense ...
 
ThomW

ThomW

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I had already located the cause of the sluggish roll acceleration in FSX.
The accelerations and velocities of the aircraft axes are artificially cut to certain values outside the flight dynamics loop. For the angular accelerations this is 5.23 rad / sec ^ 2, as you can see in the video here.

I had already reported the problem three times that these limitations had to be removed, the reports were all set to "solved", but nothing has happened so far.

Otherwise the only possibility of improvement would be to set the limits to a higher value, e.g. in FSX with a sim1.dll hack.

Here is a video from X-Plane, how the accelerations should look like:
 
L

L3M0N

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canada
What are you using to graph the input and rate of roll? Something through simconnect?
 
WarpD

WarpD

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So... angular acceleration is restricted to about 300° per second squared...
 
Roy Holmes

Roy Holmes

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Interesting, the max roll rate for the S-3 Pitts is 300 degrees per second
Roy
 
jcomm

jcomm

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portugal
BTW, yesterday I tried to vary the fuselage_length parameter inside of "flight_model.cfg" and it surely makes a whole difference, and can be seen when the Dev Mode is enables and aircraft geomeetry visualization is active The orange cylinder is dimensioned according to that as well as to fuselage diameter, and varying those parameters certainly has quite an impact in the aircraft flight dynamics... So, I still don't get the "-1" values seen in some of the default aircraft, like the Extra and the Cessna 172...
 
jcomm

jcomm

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portugal
Just as an additional info, today using one of the windows that can be enables when operating MFS in Dev Mode I was able to see reported roll rates of more than 400 deg / s in the Extra 300.
 
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