We All owe Murmur a Beer! Make it a Diner !...

[jcomm 5,961]

http://forums.x-plane.org/index.php?showtopic=89958

 

Austin's post in the thread is here:

 

http://forums.x-plane.org/index.php?showtopic=89958#entry958066

 

Sooooo, thx to Murmur, finally the "torque bug" was found

[Sesquashtoo 2,846]

DANG!   Here's a Sam Adams!

[Murmur 3,944]

LOL! :smile: So the torque felt by propeller aircrafts is double what it should be. Austin said it should be fixed in 10.50. I wonder when was it introduced though? X-Plane 10? 9? 8?

 

There also seems to be some other inaccuracies in the flight model, that could contribute to discrepancies in the response of the aircrafts, and that I hope to track and analyse thanks to a custom plugin I made.

 

So hopefully they could be fixed in the future.

[CarlosF 1,243]

Outstanding work Murmur,  :Applause:  Thanks!

 

 

  

[jcomm 5,961]

The torque bug started somewhere along version 9. I still remember it, and Austin announcing he had finally started to computer prop torque...

[x-plane 123 61]

So, in the last few weeks you've given us improved clouds, improved fog, and found the torque bug  ! Great work Murmur, thank you so much!

[Ianrivaldosmith 5,317]

Is this when the aircraft is pulling to the left? After takeoff.... 

[Jimmy RFR 406]

After reading through the linked post, that's some very impressive work there... good job!

[Phantom88 3,287]

Muchas Gracias!!! :smile: 

[LAdamson 240]

Is this when the aircraft is pulling to the left? After takeoff.... 

No. The airplane should pull to the left on the takeoff run & initial climb. As airspeed builds the need for right rudder diminishes.  X-Plane's torque problem has to do with the plane wanting to roll left. It also means constant roll corrections with power changes. In reality, there can be very noticeable  torque, when the plane heads down the runway. The left wheel will push down. It's mostly noticeable when quickly adding power with slow airspeeds, such as go-arounds, or touch & goes. By the time we're to normal flying speed, the torque is overun by the wings lift.  Some X-Planes give the impression that the pilot has to be holding the yoke to the right, so the airplane won't be rolling to the left on takeoff. It also gives the impression, that this torque force will even be more powerful with larger engines.

 

In reality, we should be using right rudder on takeoff, and not holding the yoke or stick against a perceived roll from engine torque. It's a fact, that torque can completely roll an airplane over, when too much power is added to quickly, while the airplane is barely flying (low airspeed). This would often happen on WWII type aircraft carriers, during a wave off. P-51 Mustangs are also well known for it. But the P-51 takeoff, doesn't require aileron trim. It calls for right rudder trim, and a foot on the right rudder. Get up to airspeed in the correct manner, and the airplane won't want to roll to the left, as soon as you leave the ground. Even with the high powered P-51 engine, the torque is still overpowered with the wings lift. The spiral airstream will still call for right rudder, until airspeed is high enough to counter it with rudder trim, and/or an offset vertical stab. Without offset vertical stabs, or fixed/adjustable rudder trims, or offset engines, or a combination of all...................these airplanes will always yaw to the left, with a clockwise turning prop, from the cockpit view. 

[jcomm 5,961]

But beware that there is a LOT more behind the scenes....

 

Murmur has been working, using pure scientific method, to seek for other quirks... As he wrote in this thread, he has developed a set of scripts that runs a detailed evaluation of various aerodynamic parameters, and compares them to rw data, allowing to check how close a given aircraft model has those values in X-Plane.

 

The torque bug may not be the only "problem". A prop aircraft, but any other aircraft as a mater of fact, is dependent on so many factors in terms of design and how it's aerodynamic properties characterize it's way of flying that it's difficult for a generic flight simulator to properly model any specific model accurately. Mumur's scripts will probably give the developers further insight into what has to be adjusted on a given model.

 

To all I recommend reading the many interesting sources with a wealth of great information available, for instance, at the FlightLab's site, under "Download Courses".

 

Read, at least, chapter 4 on Lateral and Directional stability, and understand, among other things, why aircraft, including prop aircraft, compensate for the torque effect itself, making it secondary, as dynamic pressure, slipstream effects, dihedral, weathervane stability and other factors become prevailing...

 

Let's look fwd for whatever Murmur's finding about the "torque bug", and other aspects of X-Plane's FDM can bring developers for the future of the sim... We're getting there, slowly, but with sound steps!

[tonywob 4,770]

Awesome work Murmur, have a virtual beer on me.

 

I'm also quite amazed Austin responded to the post, it means they do actually read the forums in-spite of what many people actually say

[Murmur 3,944]

I'm also quite amazed Austin responded to the post, it means they do actually read the forums in-spite of what many people actually say

 

Keep in mind though, he has been informed via private emails on that thread, so I think they don't usually follow the forums.

[Old_As_Dirt 160]

Thanks to Murmur, jcomm, and several others who have persisted in bringing this to the forefront. I also read (on Sesquashto's post) and found to be true that going into the airfoils folder in your main x-plane folder and clicking (at the top) the line saying something like bring to current standards, it will update all your aircraft to the latest 10.41 airfoil standards. It is said to greatly improve rotor-wing aircraft, but adjusts all the others as well.

 

Great information coming from this community!

 

John

[tonywob 4,770]

Either way, I'm glad somebody found and pointed this out, otherwise I think it would have been a long time before it was actually fixed :-)