Thanks Jan, good tip. Deflections are fine, however plane does not move as expected. But, as others stated, this has always been so in XP and it seems that LR thinks it's still properly modeled. It's not that I would call taxiing impossible, just not realistic as it seems.

Thanks Jan, good tip. Deflections are fine, however plane does not move as expected. But, as others stated, this has always been so in XP and it seems that LR thinks it's still properly modeled. It's not that I would call taxiing impossible, just not realistic as it seems.

 

Yeah, there has been some debate as to how realistic it is. I can not chime in, I don´t have any time in C-172s, only about 200 hours in Beech F33As - most of that time in no more than light to moderate winds.

 

I would argue that pilots with considerable experience flying C-172s in higher crosswinds (>12kts) are rare. Most recreational pilots would not go out on days with strong crosswinds (good judgment!) and the C-172 isn´t widely used in commercial or scheduled air services, where the need to fly outweighs the risk in averse conditions.

 

The airline industry has acknowledged that even high-time airline pilots are NOT proficient in handling crosswinds at or around the limitation of their aircraft. These conditions are simply too rare.

 

I can count the times I have landed a 737, 747 or A320 in crosswinds of more than 30 kts on the fingers of my two hands - in 20 years of flying airliners. So am I a capacity in judging if a simulator feels right in high-crosswind situations? Well, I was too busy staying on the centerline and timing my decrab to take notes of yoke and pedal positions or look at the drift angle pointer... so no.

 

I can say that X-Plane´s airliners tend to raise the upwind wing way too much when rolling down the runway with a good crosswind - almost as if there was no weight to it. So I think the calculation of forces in a sideslip (lifting the wing) is flawed - but this is not surprising, that whole airflow scenario with the wind coming from the side, flowing over and under the fuselage, etc - is highly complex and way beyond a desktops CFD capabilities.

 

Jan

 

 

mpossible. The weathervaning on the ground has existed forever with XP and it is not fixed in B6 nor is it just a C172 problem. It's all airplanes.

When you start to taxi, does the airplane go straight with no rudder input? If it does, you've hit the lottery or something.

 

The weather vaning at one point in the betas was such that in a 15knt wind the plane would just pirouette - sometimes with the hand brake on it would just be pushed across the apron.  Now in such winds the 172 is stable. I am not saying it does not need any rudder to go straight with a full crosswind component but it is now totally manegeable in a 15knt corsswind, at least with my hardware (PFC C2 Pro and PFC GA Rudder Pedals). I did video both sitting on the apron with brakes on an off and a separate one taxing out, one full circuit and taxi back, but YouTube just didn't want to upload yesterday. Will try again today.

 

It is certainly more sensitive than the PA-38 Tomahawk I fly in real life, you can obviosuly feel the weight which you just can't on flight sim.  However  the one time I took that out at near the max crosswind component (15knts) it certainly was lively and needed both aileron and rudder inputs whilst taxing depending on angle to wind and one whole lot of rudder input whilst on the take off roll.

 

Here's a link to some Cessna 172 pilots takling about max crosswind - http://www.cessna172club.com/forum/ubbthreads.php?ubb=showflat&Number=67758 which is gives some insight.

 

cheers

Peter

Everyone keeps getting stuck on high crosswinds and it's missing the point.

Taxiing in no winds is still wrong. You should not need any opposite rudder to taxi in a typical situation, yet you do in XP.

 

I can load up no wind, see the windsock totally limp, double-check it on the data-ref that it says 0 wind, and still need right rudder just to taxi to the runway. I don't think this behavior is even really related to the wind. I think Murmur has it right. It has something to do with the prop and how it's modelling over the control surfaces even at low RPMs. The wind is just another variable that makes already present behavior worse.

 

In fact, just to confirm this, throttle up the 172 to 1000 RPM (set no wind in the sim). Start to taxi hands off. The plane will go left and require right rudder to stay straight. BUT, if you cut the power, and take your hands off, it'll suddenly roll straight with no input like you'd expect it should for a moment. Then it'll settle back into a left pull.

So again, this bug has nothing to do with the wind. That's just a secondary variable. What is happening is that the prop itself is causing the left turn. A 172 (or most any piston single I've flown) does not have left turning tendencies that require opposite rudder at taxi power settings. But in XP, the prop planes do. That's the issue.

I think it's about airflow and not the torque modeling, but the symptoms are similar to experiencing way overdone torque at low RPMs and that's the easiest way to describe it.

 

Don't mis-understand me. None of this means I taxi my 182P in real life with no feet on the pedals. But I'm holding neutral pressure in a taxi to keep from going squirrely, not opposite rudder to counteract a hard left pull. In a simulator, when the axis is centered, that should be the equivalent of neutral even though you don't feel the forces or have to hold it.

 

 

In fact, just to confirm this, throttle up the 172 to 1000 RPM (set no wind in the sim). Start to taxi hands off. The plane will go left and require right rudder to stay straight. BUT, if you cut the power, and take your hands off, it'll suddenly roll straight with no input like you'd expect it should for a moment. Then it'll settle back into a left pull.

 

Interesting!

You can watch this very low quality video (wanted to just be able to upload it quickly) here to qualify what I'm talking about:

 

http://sendvid.com/nuajtupf

 

The video is blurry, but you can still see the movements and when the RPM needle goes up and down. The wind was set at 0 and is confirmed in the data-ref (even though it's too blurry in the video to see).

 

This is the breakdown of what I do:

 

1) Idle RPM, release the breaks, no input = plane pulls left

2) 1000 RPM, no input = plane pulls harder left

3) Pull RPM to idle, no input = plane tracks straight until the engine settles and then it starts to pull left again

4) I spin the plane around

5) 1000 RPM, no input = plane pulls left

6) I jerk the rudder right and release it = plane pulls back left

7) I spin the plane around

8) 1000 RPM, no input = plane pulls left

9) Pull RPM to idle, no input = plane tracks straight until the engine settles and then it starts to pull left again

 

The reason I turned the plane around several times was to show that direction nor wind has anything to do with it. These tendencies are coming from the prop somehow.

 

Just to reiterate, I checked the data-refs and this happens with wind at 0, steering at 0.0, rudder at 0.0, and rwheel at 0.0. So it's not a controller setup issue nor is it an issue of the control surfaces not being centered for some reason. This is an a prop issue unrelated to control surface deflections. It's also not a 172 issue. It happens with all prop planes.

I love X-Plane, I really do, and fly it daily.  But, I do chuckle that at even version 11 after 20+ years, we still struggle with getting a plane to taxi properly.

 

I really like XP11 as well and totally converted from P3D.  I've only flown a real 172 once and it was so much easier to taxi than it is in XP11 where I am all over the place!

If you are having weathervaning problems, do this:

 

Go to Settings, then Data Output and enable the following data displays (click leftmost buttons) for these parameters:

 

Weather (#5)

 

Joystick aileron/elevator/rudder (#8)

 

Flight controls aileron/elevator/rudder (#11)

 

Landing gear steering (#134)

 

Now you can take the guesswork out of what is going on.

 

You can see if you ACTUALLY have the wind that you set up (many people have much higher winds, because they set a strong wind at 30.000 but X-Plane assumes this to be valid to the ground)

You can see if you ACTUALLY get full joystick rudder deflection (it needs to go from -0 to +1 and be at 0 when not steering)

You can see if you ACTUALLY get full nosewheel and rudder deflections (they need to go from -20 to +20 and -1 to +1, respectively).

 

I can taxi, take off and land in a straight 16kt crosswind. Taxiing is competely uneventfull, takeoff and landing need a bit of forward elevator to increase nosewheel grip.

 

Hope this helps to find out what is going wrong for you guys,

 

Jan

 

Thank you. Jan! 

 

I'll try this later today. Was out hiking most of yesterday, So I need to catch up on some neglected errands and chores before spending time flying.

You can watch this very low quality video (wanted to just be able to upload it quickly) here to qualify what I'm talking about:

 

http://sendvid.com/nuajtupf

 

The video is blurry, but you can still see the movements and when the RPM needle goes up and down. The wind was set at 0 and is confirmed in the data-ref (even though it's too blurry in the video to see).

 

This is the breakdown of what I do:

 

1) Idle RPM, release the breaks, no input = plane pulls left

2) 1000 RPM, no input = plane pulls harder left

3) Pull RPM to idle, no input = plane tracks straight until the engine settles and then it starts to pull left again

4) I spin the plane around

5) 1000 RPM, no input = plane pulls left

6) I jerk the rudder right and release it = plane pulls back left

7) I spin the plane around

8) 1000 RPM, no input = plane pulls left

9) Pull RPM to idle, no input = plane tracks straight until the engine settles and then it starts to pull left again

 

The reason I turned the plane around several times was to show that direction nor wind has anything to do with it. These tendencies are coming from the prop somehow.

 

Just to reiterate, I checked the data-refs and this happens with wind at 0, steering at 0.0, rudder at 0.0, and rwheel at 0.0. So it's not a controller setup issue nor is it an issue of the control surfaces not being centered for some reason. This is an a prop issue unrelated to control surface deflections. It's also not a 172 issue. It happens with all prop planes.

 

To me you are taxing way too fast

Taxi is really fast in the video. The issue happens, anyhow, despite your taxi speed.

 

My guess is that this issue is caused by new propeller modeling done by Austin. You probably read this already, from 04/Jan/2017?  http://developer.x-plane.com/2017/01/x-plane-11-propeller-modeling/

 

This has still to be perfected, but that's my guess on what's behind of that.

 

Please fill a bug report here - http://dev.x-plane.com/support/bugreport.html - in case you have not done so already. Describe well the issue, share the video. This will help to perfect it.

Fly with Lua updated for beta 6

http://forums.x-plane.org/index.php?/files/file/35579-flywithlua-for-x-plane-11-and-10-windows-linux-mac-os-x-version/

Here a bit more information about the "push to the left" propeller effect in single engine aircraft, in real life:

- Left-Turning Forces: http://www.pilotwings.org/left-turning-forces.html

- An attempt to answer the frequent question "Why is my aircraft turning left all the time?": http://wiki.flightgear.org/Understanding_Propeller_Torque_and_P-Factor

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.

Fill a bug report. I will do one later myself.

To me you are taxing way too fast

 

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. 1000RPM, even at higher taxi speeds, is not going to make torque or slipstream suddenly a factor that would cause such a pull to the left.

 

I let the speed build up at the end of each run at 1000 RPM so you could see how it reacts when you cut the power.

 

I'm not trying to be a jerk, but I'm tired of all these sidetracks people keep getting on when it comes to this issue.

 

Taxi is really fast in the video. The issue happens, anyhow, despite your taxi speed.

 

My guess is that this issue is caused by new propeller modeling done by Austin. You probably read this already, from 04/Jan/2017?  http://developer.x-plane.com/2017/01/x-plane-11-propeller-modeling/

 

This has still to be perfected, but that's my guess on what's behind of that.

 

Please fill a bug report here - http://dev.x-plane.com/support/bugreport.html - in case you have not done so already. Describe well the issue, share the video. This will help to perfect it.

 

This is a bug from XP10 as well. And probably before.

 

It probably is indeed from the prop model and how it interacts with the surfaces, but it's not the result of some recent tweak by Austin.

 

As to filing a bug report, I'm not wasting my time. This specific issue has been filed to them hundreds of times and they still won't even admit it's a problem. Maybe one day they'll actually work on it.