Austin's Blog...

[Paraffin 2,197]

6 hours ago, Pascal_LSGC said:

I'm not sure wether the enhanced spiraling slipstream has already been implemented. However, in the Flightsimcon presentation he talked about better account of negative wind, which should help taxiing and simulate special aerobatic cases. And the new PT6 engine is for 11.10 as well.

Wait, I thought he was through messing with the PT-6, and the new changes were already in the first 11.0 release? 

If there are any major changes still coming, then it will throw off the work many aircraft designers have already done to adapt their turboprop planes and helicopters to the new XP11 turboprop. That engine model needs to be locked down ASAP, if it isn't already.

[jcomm 5,931]

1 hour ago, Paraffin said:

Wait, I thought he was through messing with the PT-6, and the new changes were already in the first 11.0 release? 

If there are any major changes still coming, then it will throw off the work many aircraft designers have already done to adapt their turboprop planes and helicopters to the new XP11 turboprop. That engine model needs to be locked down ASAP, if it isn't already.

No, there is still work in the Pt-6 modelling approach, and in the spiralling slipstream modelling, but specially the latter will, supposedly, just make prop aircraft flight dynamics model more realistically  the effects of propwash / spiralling slipstream, so, they can only get better...

The same applies to ground physics, which are now clearly flawed and have a chance of, at least, getting better...

This is not as the ancient "Torque Bug" which some developers circumvented using their tricks, through Art Stab or plugins...

[Paraffin 2,197]

19 minutes ago, jcomm said:

No, there is still work in the Pt-6 modelling approach, and in the spiralling slipstream modelling, but specially the latter will, supposedly, just make prop aircraft flight dynamics model more realistically  the effects of propwash / spiralling slipstream, so, they can only get better...

The same applies to ground physics, which are now clearly flawed and have a chance of, at least, getting better...

This is not as the ancient "Torque Bug" which some developers circumvented using their tricks, through Art Stab or plugins...

Well, it still conflicts with what Ben wrote during the last few betas before 11.0, saying they needed to lock down the new engine and flight modeling, so developers could get started on their updated v11 planes. Many have already done that, like the X-Trident Bell 412 and Dreamfoil Bell 407, both using turboshaft engines. Carenado is in the process of updating their fleet to v11, starting with the turboprops, because those are the ones most affected by the changes in XP11.

So now Austin is going to change things again?

I'm hoping that whatever he's still working on is so minor, that it won't send everybody back to the workbench again.

[jcomm 5,931]

I think the changes due for 11.10 are only propwash / slipstream and ground physics related. It appears to me Austin has finished the Pt-6 / jet / turbofan engines updates ( ? )

[Murmur 3,941]

2 hours ago, jcomm said:

The same applies to ground physics, which are now clearly flawed and have a chance of, at least, getting better...

I'm still not sure if the flaw is in the ground physics itself, or in the exaggerated weathervaning + flawed propeller slipstream.

I suspect that the ground physics might be ok, and the only culprits are the other two (both of which are almost certainly not accurate).

 

[strider1 575]

3 hours ago, jcomm said:

I think the changes due for 11.10 are only propwash / slipstream and ground physics related. It appears to me Austin has finished the Pt-6 / jet / turbofan engines updates ( ? )

Slipstream was in beta 4.

http://developer.x-plane.com/2017/01/x-plane-11-propeller-modeling/

[strider1 575]

1 hour ago, Murmur said:

I'm still not sure if the flaw is in the ground physics itself, or in the exaggerated weathervaning + flawed propeller slipstream.

I suspect that the ground physics might be ok, and the only culprits are the other two (both of which are almost certainly not accurate).

 

Probably all of the above !

[Murmur 3,941]

1 hour ago, strider1 said:

Slipstream was in beta 4.

http://developer.x-plane.com/2017/01/x-plane-11-propeller-modeling/

I hope he's still working on it, because the current prop slipstream doesn't seem to be accurately modeled.

[strider1 575]

50 minutes ago, Murmur said:

I hope he's still working on it, because the current prop slipstream doesn't seem to be accurately modeled.

I think whats missing is the P-Factor in the equation. I don't think P-factor is modeled. When flying at a high angle of attack and low airspeed the ball in the inclinometer doesn't move.   

Maybe you could shoot Austin a email Murmur !?

[jcomm 5,931]

P-factor is indeed active at any AoA, provided you're not aligned with the relative wind. 

Yo-Yo ( ED / DCS ) tried to achieve the best possible modelling of it's effects starting with the P51d, where inflight, in a sideslip situation you would clearly feel the pitching up or down moments ( in that case they manifest themselves in pitch instead of in yaw... ) depending on if the sideslip was left or right.

And, on a different matter,  also think Murmur's "thesis" about the origin of the poor ground behaviour of aircraft under x-wind is probably due to an overdone / overcalculated weathervane effect. Maybe it's also being calculated twice :-)

And yes, if the propwash update was in since beta4 of 11.0, than I also hope Austin continues to work on that... The "Visual Flight Model" mode should also allow us to glimpse some of the effects.

 

 

[Griphos 138]

But all of the wind effects -slipstream, prop wash, weathervaning, etc- wouldn't produce such silly results if tires actually gripped the surface with something like the weight and friction they actually have in reality. So ground physics need some attention as well. This is evident on rollout and landing when side pressures are exerted on the gear as well. Just doesn't feel accurate. 

[Murmur 3,941]

20 minutes ago, Griphos said:

But all of the wind effects -slipstream, prop wash, weathervaning, etc- wouldn't produce such silly results if tires actually gripped the surface with something like the weight and friction they actually have in reality. So ground physics need some attention as well. This is evident on rollout and landing when side pressures are exerted on the gear as well. Just doesn't feel accurate. 

I'm not 100% sure. If the weathervaning is much higher than it should be, and if the propeller slipstream is inaccurate and more effective than it should be, the increased aerodynamic forces would then give similar effects as low tire friction. For this reason the only way to establish what's really going on is make controlled experiments with modified aircrafts.

 

[Griphos 138]

Well, if "much higher" than it should be, yes, I can see that also.  And I think you're right about not knowing determinately without careful tests.  But I'm still suspicious of friction values as well.  Fiddling with them in Plane Maker does make significant difference in handling.  

[Murmur 3,941]

This is the default L5 modified with a jet engine to eliminate propeller effects. The behaviour on takeoff and landing seems better, pointing to a flawed modeling of propeller slipstream. Would be interesting to hear opinions. (Since the aerodynamics have not been changed, the weathervaning tendency on crosswind is still the same).

https://drive.google.com/open?id=0B5fyJwRhjar5OGt1bDNaRl91c1k

[jcomm 5,931]

1 hour ago, Murmur said:

This is the default L5 modified with a jet engine to eliminate propeller effects. The behaviour on takeoff and landing seems better, pointing to a flawed modeling of propeller slipstream. Would be interesting to hear opinions. (Since the aerodynamics have not been changed, the weathervaning tendency on crosswind is still the same).

https://drive.google.com/open?id=0B5fyJwRhjar5OGt1bDNaRl91c1k

Murmur,

I can't try it, but that agrees with what I recall having tested with the Cirrus jet in XP11 - that aircraft was a less prone to the weathervane tendency than the C172, or even the C90. 

Maybe it's a combination of various factos, including the way XP11 calculates weathervane effect, propwash,... ( ? )

We can at least hope that it get's better around 11.10 ( ? )