Beta 6 is out

[Janov 2,383]

Look, the weathervaning is very easy to demonstrate. Follow these steps:

 

1. Load the default C172 on a runway facing 90 deg. East.
2. Hit "B" once for brake on.
3. Make sure any weather injection plugins are off.
4. Go into the weather menu, set a 5 kt wind from direction 0 deg. North.
5. Hit the "C" key for free camera, move the view up and directly over the plane so you're looking down on it.
6. Now hit "B" again for brakes off.
7. Plane will rotate to the left.

 

Now reset the flight by choosing that runway location again, hit "B" for brakes on, go to the weather menu and change the wind direction to 180 deg. South. Use the same overhead camera position, and remove the brakes. The plane now rotates to the right, into the wind, at about the same rate as it rotated left before. And with a five knot wind!

 

This should demonstrate that something is going on with wind-induced weathervaning that isn't related to prop wash, torque, P-factor or anything similar.

 

This is an age old phenomenon and has been explained many times. In the range between 0.001 and 1.5 kts there is a transition from the static to the moving ground model. In this range you get excessive weathervaning that can only be stopped with a good application of rudder/nosewheel.

 

It is a flaw, a limitation of the current way the simulator handles static and rolling friction and tire steering slippage. I doubt it will be adressed soon, and it is really not a showstopper.

 

Jan

[Humpty 751]

Even the tyre friction tweak could be in that. i feel the idle RPM may still be a bit high. don't know. 

[sd_flyer 6,042]

Oh, give me a freaking break. The first part of the video is at idle and just releasing the brakes. It's pulling left immediately at idle with no input.

 

 

Whether it's bug or not you still taxi fast. It's like doing runup without breaks to prove the point  

[Paraffin 2,197]

This is an age old phenomenon and has been explained many times. In the range between 0.001 and 1.5 kts there is a transition from the static to the moving ground model. In this range you get excessive weathervaning that can only be stopped with a good application of rudder/nosewheel.

 

No, it's not just something that kicks in within that range. Do that same test with crosswind increased to 10 kts. Then again at 15 kts. The speed of rotation is much faster. The amount of rudder that needs to be applied to taxi straight increases proportionally. This is not just something that only occurs below 1.5 kts.

 

 

It is a flaw, a limitation of the current way the simulator handles static and rolling friction and tire steering slippage. I doubt it will be adressed soon, and it is really not a showstopper.

 

It's a showstopper if you're trying to taxi or take off in a crosswind that the aircraft is rated to handle, and it's not behaving like the real thing. This isn't just a minor effect that's easy to ignore.

[bonchie 2,305]

Even the tyre friction tweak could be in that. i feel the idle RPM may still be a bit high. don't know. 

 

 

 

It is still too high and it's too powerful at a given setting.

 

It's idling at 800 RPM and even with no wind, that breaks the plane free to roll to a fairly high speed. Trying to use 1000 RPM (a normal taxi power setting) results in a lot excess speed and having to ride the brakes.

 

BUT, I'm less concerned with that. These are default planes so I don't expect perfection in individual modeling. The issue I'm bringing up applies to the core flight modeling that affects all piston/single aircraft.

Whether it's bug or not you still taxi fast. It's like doing runup without breaks to prove the point  

 

Can we stay on topic? The video showed idle from a dead stop to the speed building at just 1000RPM. It pulled left at the same rate regardless of speed. If you want to discount anything you saw past a certain speed, go ahead. You can still see the pull left even from a dead stop at idle. I did not want to apply brakes too early in each run because I then couldn't gurantee I wasn't indirectly applying turning forces via the rudder/differential braking. After the speed got too high, I spun the plane around to a dead stop again.

 

So while I appreciate you telling me I'm taxiing too fast in the video, it's irrelevant to what was being shown.

 

I'm well aware of how to taxi an airplane. Trust me.

[Humpty 751]

It is still too high and it's too powerful at a given setting.

 

It's idling at 800 RPM and even with no wind, that breaks the plane free to roll to a fairly high speed. Trying to use 1000 RPM (a normal taxi power setting) results in a lot excess speed and having to ride the brakes.

 

BUT, I'm less concerned with that. These are default planes so I don't expect perfection in individual modeling. The issue I'm bringing up applies to the core flight modeling that affects all piston/single aircraft.

 

 

Agree that the addons models can overcome that issue if i am correct,  but when the base FDM engine itself has flaws / bugs / wrong calculations etc.. then the addon devs will face a problem and there will be flaws again with their models.

 

Sometimes i want to throw Xplane away but i like XPlane . 

 

Let's wait till the next beta and hope these things do get fixed. 

 

Have to try the 109 G6 , haven't touched the tail dragger in XP11 not sure how the tail dragger would perform. 

[Murmur 3,941]

So, now we have too much propwash effect when on ground, and too little propwash effect when airborne...

[sd_flyer 6,042]

 

 

Can we stay on topic? The video showed idle from a dead stop to the speed building. It pulled left at the same rate regardless of speed. If you want to discount anything you saw past a certain speed, go ahead. You can still see the pull left even from a dead stop at idle. I did not want to apply brakes too early in each run because I then couldn't gurantee I wasn't indirectly applying turning forces via the rudder/differential braking. After the speed got too high, I spun the plane around to a dead stop again.

 

So while I appreciate you telling me I'm taxiing too fast in the video, it's irrelevant to what was being shown.

 

I'm well aware of how to taxi an airplane. Trust me.

 

I'm staying on the topic. What it looks to me in your the video is lack of directional control with high taxi speed. It's hard to judge whether it's lack of input or bug problem . Now saying this, I do believe something is not quite right with taxi modeling, but it's hard to judge it based on your video.

 

How you really know to taxi airplane is not really my concern, unless of course I need to sign your log book   Don't take my comments as criticism of your taxing skills. I just think your video can be interpreted different ways - not quite the way you meant it

So, now we have too much propwash effect when on ground, and too little propwash effect when airborne...

 

I somewhat noticed it as well 

[bonchie 2,305]

I'm staying on the topic. What it looks to me in your the video is lack of directional control with high taxi speed. It's hard to judge whether it's lack of input or bug problem . Now saying this, I do believe something is not quite right with taxi modeling, but it's hard to judge it based on your video.

 

How you really know to taxi airplane is not really my concern, unless of course I need to sign your log book   Don't take my comments as criticism of your taxing skills. I just think your video can be interpreted different ways - not quite the way you meant it

 

I somewhat noticed it as well 

 

Again...The video starts at idle from a dead stop. From...a...dead...stop. It pulls left at idle RPM (800 in this case) with no control input and netural rudder/nosewheel as shown by the data-ref.

 

Ignore the higher speed portions at the end of each run if you'd like, but I have no idea why you continue to ignore the portions shown from a dead stop where the speed is not high at all. You can see the left turning from the very beginning no matter what the speed is.

 

Go test it yourself. It'd take all of 3 minutes.

Just to stop the arguing, here's a video at idle RPM, very low speeds, with no input. Just releasing the brakes with the rudder and nosewheel reading completely neutral. Wind at 0 so it's not a variable.

 

http://sendvid.com/x8ne8q54

 

So, now we have too much propwash effect when on ground, and too little propwash effect when airborne...

 

That's my suspicion and it would make sense.

 

But I wouldn't say "now." This was in XP10 as well.

[sd_flyer 6,042]

Only if you are being purposefully obtuse.

 

Again...The video starts at idle from a dead stop. From...a...dead...stop. It pulls left at idle RPM (800 in this case) with no control input and netural rudder/nosewheel as shown by the data-ref.

 

Ignore the higher speed portions at the end of each run if you'd like, but I have no idea why you continue to ignore the portions shown from a dead stop where the speed is high at all. You can see the left turning from the very beginning no matter what the speed is.

 

Go test it yourself. It'd take all of 3 minutes.

 

Without purposefully obtuse you, yes I believe it can happen in real life due to different reasons. And again,  as I stated before, at the same time I do believe there is a problem with taxing prop airplanes in current beta (I'm not familiar with XP versions prior that)

[Murmur 3,941]

We should first of all establish if it's due to inadequate tire friction modeling, or to excessive vert stab/propwash interaction.

[theskyisthelimit 48]

For the weathervaning.. taxing issues with the 172 in XP11.. does this only apply to the default 172.. or to other versions as well (airfoil labs)?  Do those also exhibit the same behavior?

[bonchie 2,305]

Without purposefully obtuse you, yes I believe it can happen in real life due to different reasons. And again,  as I stated before, at the same time I do believe there is a problem with taxing prop airplanes in current beta (I'm not familiar with XP versions prior that)

 

A plane will not pull hard left at idle to 1000 RPM with a centered and neutral rudder/nosewheel in real life. It won't even break lose at idle and move unless it's on an incline or wind is a factor, but that's another issue they seem to actually be working on thankfully. B6 dropped the idle from 1200 to 800 and it was actually correct in B3.

 

I'm not an expert pilot, but I've got time in a myriad of Pipers, Cessnas (currently own a 182), Mooneys, Socotas, and Beeches and not once have I observed a plane pull hard left at slow speeds and low RPMs the way it does in XP, which happens even at idle RPM.

 

The amount of left-turning tendency you see in XP at very low speeds and near idle RPM is similar to the left turning tendency you'd normally see on takeoff at full power in a 160-200HP airplane in real life (assuming wind's not an factor).

We should first of all establish if it's due to inadequate tire friction modeling, or to excessive vert stab/propwash interaction.

 

Maybe I can answer that or at least give you another variable.

 

In my first video, at the end of the first run I pull the throttle and the plane immediately stops pulling left and tracks straight in it's roll. Only when the RPM settles back at idle does the left turning start again.

 

So to me, I'd think that says it's prop related.

[sd_flyer 6,042]

A plane will not pull hard left at idle to 1000 RPM with centered and neutral rudder/nosewheel in real life. It won't even break lose at idle and move unless it's on an incline, but that's another issue they seem to actually be working on thankfully. B6 dropped the idle from 1200 to 800 and it was actually correct in B3.

 

I'm not an expert pilot, but I've got time in a myriad of Pipers, Cessnas (currently own a 182), Mooneys, Socotas, and Beeches and not once have I observed a plane pull hard left the at slow speeds at low RPMs the way it does in XP even at idle RPM. In a real piston single, until you push the throttle in for takeoff and torque/propwash become a factor, left-turning tendencies are basically non-existent.

 

The amount of left-turning tendency you see in XP at very low speeds and near idle RPM is similar to the left turning tendency you'd normally see on takeoff at full power in a 160-200HP airplane in real life (assuming wind's not an factor).

 

When I tried earlier versions of AirfoilLabs 172 that worked in XP11B3 it was taxing about right. I did had problem with right pull on take off with LE DC-3 but the issue were resolved.

I didn't try stock planes in PB6. However, I noticed  add-on Cherokee 140 had an excessive left pull during taxi as well even thought I tried to keep directional control with my CH rudder. I also felt excessive thrust in beta 5. Right now I'm fooling around with ixeg 737. It seems taxi just fine

 

P.S.By the way I used to own 182 F, loved it.

[Paraffin 2,197]

We should first of all establish if it's due to inadequate tire friction modeling, or to excessive vert stab/propwash interaction.

 

If we can demonstrate roughly equal amounts of excessive weathervaning in either direction -- left or right as in my example above by simply by changing the wind direction, then doesn't that rule out propwash effects? Anything related to the prop/engine should favor one direction only.