Properly modelling the Extra, and Pitts...

[jcomm 5,974]

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 like IRL with these aircraft as can easily be observed in a myriad of sources like those in youtube on aerobatic performances...

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 ( thx @lupedelupe) same applies to knife edge...

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 ?

Edited October 1, 2020 by jcomm

[lupedelupe 315]

And try as I might the Extra 330 will not hold knife-edge flight. 🤨

[jcomm 5,974]

Just now, lupedelupe said:

And try as I might the Extra 330 will not hold knife-edge flight. 🤨

Right, that's another one I forgot to list :-)

[Waldo Pepper 1,953]

I've wondered how realistic that behavior is.   (I'm not an Extra pilot irl)   

According to the manual I downloaded for the real aircraft, recommended entry speed for knife edge is 150 knots.  If I read it correctly,  it's rated at 150 knots entry and 10 seconds of duration for the maneuver.

My gut feeling is that the rudder doesn't have quite enough authority at the correct speeds,  but I'm going to investigate further.

The other thing with the Extra is it's spin behavior.   I can make it spin at will,  but I wish it was a bit flatter.   I end up needing full aileron and a bit of power to flatten it out.    Still working on inverted spins.

[robert young 2,897]

10 minutes ago, Waldo Pepper said:

I've wondered how realistic that behavior is.   (I'm not an Extra pilot irl)   

According to the manual I downloaded for the real aircraft, recommended entry speed for knife edge is 150 knots.  If I read it correctly,  it's rated at 150 knots entry and 10 seconds of duration for the maneuver.

My gut feeling is that the rudder doesn't have quite enough authority at the correct speeds,  but I'm going to investigate further.

The other thing with the Extra is it's spin behavior.   I can make it spin at will,  but I wish it was a bit flatter.   I end up needing full aileron and a bit of power to flatten it out.    Still working on inverted spins.

It's not a spin. It is a spiral dive with lots of induced drag to hold the speed increase. To make an aircraft spin in FS2020 requires a lot of tweaking.

[Waldo Pepper 1,953]

22 hours ago, robert young said:

It's not a spin. It is a spiral dive with lots of induced drag to hold the speed increase. To make an aircraft spin in FS2020 requires a lot of tweaking.

I'm not a pilot IRL,  and I'm not here to dispute your words.   Just to clarify my personal experience in this sim, the E330 in this sim will enter a "Steep Mode Spin" reliably,   but won't enter a "Flat Mode Spin".

The Pitts,  is no where near as cooperative in that respect.

 

 

[robert young 2,897]

2 hours ago, Waldo Pepper said:

I'm not a pilot IRL,  and I'm not here to dispute your words.   Just to clarify my personal experience in this sim, the E330 in this sim will enter a "Steep Mode Spin" reliably,   but won't enter a "Flat Mode Spin".

The Pitts,  is no where near as cooperative in that respect.

If you look at the differences shown in the excellent video you've linked to, you'll see that a spin as opposed to a spiral has equal amounts of yaw and roll. The yaw revolves through 360 degrees just as the roll does. A spiral is not really a spin and has little or no yaw, and the movement is almost all roll. A "flat" spin is almost all yaw (shown near the end of the video). You can make sim aircraft flat spin but you need to shift the C of G way back and have tons of elevator authority. This is a bit of a cheat because the whole point of a spin is that up elevator should have little affect as the spin generally moves the air stream so the elevator is ineffective.

Most GA aircraft spin with nearly equal amounts of yaw and roll but do not increase airspeed as the drag cause by the spinning motion equals the gravitational force that would normally accelerate the aircraft. The "tuck in" is a key element in the start of a spin. It is yaw tucking the nose of the aircraft through and around its initial drop in attitude.

You are right when you say your feeling is that some of the sim aircraft do not have sufficient yaw authority to spin. In fact some of them nearly do but they also have too much yaw stability at high angles of attack. You can encourage a better spin by use of a table/graph which adjusts yaw VS aoa.

Edited October 2, 2020 by robert young

[jcomm 5,974]

I would like to bring back this thread , which now contains a wealth of excellent posts on different subjects regarding the flight dynamics in MFS, because there are some interesting additional insights into what might be the cause for such "mushing" recovery from high roll rates in aerobatic / light aircraft in MFS, just as it was the case in previous versions of the simulator.

I am thankful to all of those who have contributed to dig deeper into the possible causes of this limitation in MFS, specially the author of the two videos linked bellow, but also Murmur and Alexis which I am proud to share daily simmer talk with at Discord and other forums.

There's also a thread I initiated at FSDeveloper on this same subject, and of course another one at the flightsimulator.com forums, and in the MFS ZenDesk.

Murmur has given us a very interesting possible interpretation of this limitation in one of his posts on the Discord group.

The author of the two videos I link bellow ( from the FSDevelopers thread ) very clearly shows the difference in the way higher roll rates ( increasing or decreasing ) appear to get truncated in MFS, as opposed to X-Plane, and Aerofly FS 2 for that mater...

https://youtu.be/6aTb5BZ9nBM

https://youtu.be/stunk175e6I

So, it may well be that, just as other issues, MFS is copying from previous versions stuff that is no longer required or should be addressed in the new "Modern" fdm...

Let's hope they find a way around it - I would really like to be able to finally get decent aerobatic aircraft modelled in MFS !

 

Edited October 5, 2020 by jcomm