More on XP12 flight dynamics...

[jcomm 5,929]

Wow!  Just WOW !!!

https://forums.x-plane.org/index.php?/forums/topic/262336-x-plane-12-flight-model-update-–-supersonic-transition-delta-wings-and-mass-properties/

[Pastaiolo 1,688]

Before reading a technical post made by Austin

[Murmur 3,941]

I actually never thought about the effect of entrained jet flow on horizontal stabilizers, but I guess the effect must be there!

Another good news is that he has improved the ground effect in terms of downwash flattening. I presume that should improve the excessive nose down tendency just before touchdown which many XP aircraft exhibited.

 

[jcomm 5,929]

4 minutes ago, Murmur said:

I actually never thought about the effect of entrained jet flow on horizontal stabilizers, but I guess the effect must be there!

Another good news is that he has improved the ground effect in terms of downwash flattening. I presume that should improve the excessive nose down tendency just before touchdown which many XP aircraft exhibited.

 

Again, also thanks to your contribution and that of Alexis in the emails sent to Austin with interesting flight data !

[Biology 1,347]

There is one important thing to point out, what Austin did is not just a mere tweak of the .acf file, but instead it is a rework of the flight dynamics engine to make the F-4 fly accurately when accurate data is fed. In other words, he is not simply tweaking the F-4 .acf file until it flies right by using inaccurate values, instead he is improving the flight dynamics engine using phyiscal principles so that the results are accurate when accurate data is used. Therefore this will improve the experience for not just the F-4 but all aircraft. I think airliners will especially benefit from that as they tend to fly at transsonic region and X-Plane has been using an approximation called Prandtl-Glauert transformation for compressible flow effects, but it gets rather inaccurate as Mach number approaches 1 and eventually leads to Prandtl-Glauert singularity at Mach 1. Given Austin is working on supersonic flight, he likely made that better too.

Edited February 23, 2022 by BiologicalNanobot

[Bjoern 1,157]

If the F-4B is also getting some polish inside and outside and considering that VSKYLABS is working on an "E" model, XP12 is going to be a Phantom driver's paradise. And I subtly wonder if VSKYLABS was involved in that e-mail ping pong as its chief designer used to be a F-4 instructor as well.

I thoroughly enjoyed that read and for some reason have a craving for an XP12-compliant F-104 now.

 

In case anybody needs a primer on high speed flight (subsonic, transonic, supersonic):

https://www.youtube.com/watch?v=LSmqsg0DbTY

https://www.youtube.com/watch?v=ciIv_7WkPxQ

Edited February 23, 2022 by Bjoern

[jon b 2,047]

BOOM..as Austin says.

[Gary1124 181]

On 2/23/2022 at 8:19 AM, BiologicalNanobot said:

There is one important thing to point out, what Austin did is not just a mere tweak of the .acf file, but instead it is a rework of the flight dynamics engine to make the F-4 fly accurately when accurate data is fed. In other words, he is not simply tweaking the F-4 .acf file until it flies right by using inaccurate values, instead he is improving the flight dynamics engine using phyiscal principles so that the results are accurate when accurate data is used. Therefore this will improve the experience for not just the F-4 but all aircraft. I think airliners will especially benefit from that as they tend to fly at transsonic region and X-Plane has been using an approximation called Prandtl-Glauert transformation for compressible flow effects, but it gets rather inaccurate as Mach number approaches 1 and eventually leads to Prandtl-Glauert singularity at Mach 1. Given Austin is working on supersonic flight, he likely made that better too.

I flew the Blackbird at Mach 3.2 in X-plane 4 or something in the 01 to 05 span

 Thought he already had supersconic.

[mSparks 2,086]

20 minutes ago, Gary1124 said:

Thought he already had supersconic.

There is "moving over the ground at greater than 330ms"

Then there is "moving through the air at >330ms".

First is really simple.

Second is 

 

territory.

[Gary1124 181]

8 hours ago, mSparks said:

There is "moving over the ground at greater than 330ms"

Then there is "moving through the air at >330ms".

First is really simple.

Second is 

 

territory.

So, basically he is working on the fluid  dynamics of the atmosphere to go along with the speed which is already simulated?

Edited February 27, 2022 by Gary1124

[mSparks 2,086]

3 hours ago, Gary1124 said:

So, basically he is working on the fluid  dynamics of the atmosphere to go along with the speed which is already simulated?

transonic behaviour isnt accurately modelled in XP11, air behaves differently between mach 0.8 and mach 1.2 (see the video I posted)

aiui XP11 just has a hard transition boundary at mach 1.0. 

Also its talking about fixing the delta wing behaviour. See the OP for more detail.

 

 

Edited February 27, 2022 by mSparks

[Bjoern 1,157]

On 2/23/2022 at 3:16 PM, Bjoern said:

And I subtly wonder if VSKYLABS was involved in that e-mail ping pong as its chief designer used to be a F-4 instructor as well.

Confirmed. So we may get a polished default F-4B from Laminar and a more complex third party F-4E from VSKYLABS in XP12, both behaving as close to spec as possible.