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tutmeister

When are they going to fix ground handling in windy weather?

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Loaded up real weather at Manchester Barton EGCB today (weather too bad to really fly from there today) and could barely taxy down the airfield. Default 172 kept trying to swap ends. After run ups I lined up using proper grass field procedure with the yoke all the way back to reduce pressure on the nose wheel and prop strike risk. Opened the throttle and the thing was pitching up almost immediately and it wasn't THAT windy!

I'm assuming I'm not the only one who thinks it is still a joke. It's even mentioned in the active sky manual that there are inherent serious problems with ground handling and wind on the ground with options in active sky to mitigate the crosswind problems.

Why is it taking this long for laminar to sort it? It's been like this for ever. It's one of the biggest problems stopping me moving from a2a and prepared and really spoils the claim that it is a serious sim.

Edited by tutmeister
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42 minutes ago, tutmeister said:

Loaded up real weather at Manchester Barton EGCB today (weather too bad to really fly from there today) and could barely taxy down the airfield. Default 172 kept trying to swap ends. After run ups I lined up using proper grass field procedure with the yoke all the way back to reduce pressure on the nose wheel and prop strike risk. Opened the throttle and the thing was pitching up almost immediately and it wasn't THAT windy!

I'm assuming I'm not the only one who thinks it is still a joke. It's even mentioned in the active sky manual that there are inherent serious problems with ground handling and wind on the ground with options in active sky to mitigate the crosswind problems.

Why is it taking this long for laminar to sort it? It's been like this for ever. It's one of the biggest problems stopping me moving from a2a and prepared and really spoils the claim that it is a serious sim.

So the plane was doing a wheelie, is that what you are saying?


AMD Ryzen 7 1800x, 1080GTX, Ram - 32GB, 32" 4K Monitor, WIN 10, XP-11 !

Eric Escobar

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Ha ha yep pretty much. But also trying to lift off at much too low an airspeed and being blown around while taxing. I was using real world weather and it was pretty windy but not hurricane level.

I know there is not really anything to be done about it, I was just having a rant because it is still broken but they are more bothered about getting metal and pbr in than fixing basics.

Edited by tutmeister

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Interesting to know what teh wind was seems 15kts crosswind  is no go for 172.

 

Planes flying while standing still, not xplane

 

Look Mum no pilot most fuel efficent engined plane in te hworld

 

 

Edited by mjrhealth

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What was the actual wind speed and what direction relative to the runway heading? I know XP11 has had issues with this, but it's hard to evaluate your post without a wind speed and direction. A C172 isn't an all-weather plane.

I fly with injected real weather from ActiveSkyXP, but with the settings tailored to back off the real weather to make sure I can takeoff and land, with the light GA planes I like to fly. Up here in the PNW, there are days where I just couldn't fly otherwise!

 


X-Plane and Microsoft Flight Simulator on Windows 10 
i7 6700 4.0 GHz, 32 GB RAM, GTX 1660 ti, 1920x1200 monitor

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Yeah I know, primarily it was me whinging because it still isn't fixednand I desparately want XP11 to just get it rught.

I'll try it again later using the same weather but I'm off to the cinema with the family to watch avengers and then lunch watching the Baku F1 GP. After than I'll try it again.

Cheers.

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For what its worth, I (and those at Laminar at the decisive positions) feel that the crosswind handling and capabilities of the default C-172 is fine. If you get "blown around" it is very likely due to having too much wind, insuficient runway state, poor control setup (hey, some people still fly with mouse or without rudder pedals!) or just simple plain piloting technique deficiencies 😉.

You can rant all you want, but don´t hold your breath for this getting changed. These threads usually end when I post a video of me taxiing the C172 (or other aircraft being declared "totally unrealistic") at 1.5x official crosswind limit winds just fine - and then the OP usually disappears 😁.

So - while there are still some things under review (like the propwash effects on stabilizers), the general crosswind behaviour of X-Plane is "in the ballpark".

Cheers, Jan

 

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Hi Jan, I don't have a pc right now so no access to XP, what is the max xwind speed you can consistently safely take off with the current C172?


"The problem with quotes on the Internet is that it is hard to verify their authenticity." [Abraham Lincoln]

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Post GP I'll have a play around but it wasn't that windy. I'm using properly calibrated yoke and pedals and whilst not the greatest pilot in the world I know how to taxy and take off on grass field all be it in a warrior and not a c172.

If you have active sky xp and have read the manual there is a paragraph where they highlight the deficiency in the xp crosswind and ground handling.

I'm pretty sure it is flawed in even moderate wind but let's leave it until I can get back on my pc and try again.

 

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18 hours ago, tutmeister said:

Loaded up real weather at Manchester Barton EGCB today (weather too bad to really fly from there today) and could barely taxy down the airfield. Default 172 kept trying to swap ends.

XP real weather imported winds were between 15 and 25KTS gusting up to 33 pretty much anywhere in the UK in the past 2 days.  That's a tall order for a 172, in particular for the XP default one. 🙂

4 hours ago, Janov said:

For what its worth, I (and those at Laminar at the decisive positions) feel that the crosswind handling and capabilities of the default C-172 is fine. If you get "blown around" it is very likely due to having too much wind, insuficient runway state, poor control setup (hey, some people still fly with mouse or without rudder pedals!) or just simple plain piloting technique deficiencies 😉. 

You can rant all you want, but don´t hold your breath for this getting changed. These threads usually end when I post a video of me taxiing the C172 (or other aircraft being declared "totally unrealistic") at 1.5x official crosswind limit winds just fine - and then the OP usually disappears 😁.

So - while there are still some things under review (like the propwash effects on stabilizers), the general crosswind behaviour of X-Plane is "in the ballpark".

That depends on how you define "ballpark", or what ball and what park we're talking about.  I've joined a few discussions about that, made a lot of experiments and tried to devise a method of finding out what's wrong since I bought XP11, and last week I could gather some pretty solid indications (if not evidence) that the widespread perception that at least the default 172 is pretty off can be explained and even proven.  IMO the default 172 is very much off for 2 main reasons:

1.) There is a distinct lack of rudder authority making (strong) crosswind handling more difficult than it should be.  Many pilots agree that around 20KTS crosswind component is the point where 172s run out of rudder, the default 172 doesn't have enough rudder authority to reach the demonstrated 15KTS.  But this lack of rudder authority is shared by all XP GA planes (3rd-party or not) I have, most of which have higher demonstrated crosswinds than a 172.  This points to an underlying issue with a yet unknown parameter/component, an issue that - if I understood that right - has been acknowledged by Austin (who is apparently just as puzzled about that) and led to the famous "model fuselage" photo.  

On the Easter weekend I finally had a chance to assess how much rudder authority some (real) C-172 actually has by performing a few simple side- and forward slip tests and comparing that to the XP 172s I have:

A) how does the 172 respond to full rudder at a defined speed (85KTS in that case) anyway (how much yaw, how fast does it get there...),

B) how much yaw angle will there be at full rudder deflection at that airspeed, while maintaining the ground path using aileron/bank angle and

C) how much bank angle is needed to stop the rotation around the yaw axis anyway.  

The (generously rounded, because my data acquirement method wasn't exactly thought through very well yet) results are

A) much smoother, much faster, much more than the XP 172,

B+C) somewhere between 20-30° of yaw and >10° of bank angle, while the default 172 delivers 10-15° of yaw and <10° of bank angle.  If you translate that to a crosswind landing situation, it's pretty clear why you can't kick away a wind correction angle of e.g. 20° during a sideslip/wing down flare, or properly sideslip over the centerline in first place.  Tweaking the .acf to get that rudder authority needs such high deviations from the default numbers that I think the lack of authority might just be a symptom of another, underlying problem.

1a) Of course everything "flying sideways" is affected by this, you can't expect a realistic forward slip behavior when you can't yaw and bank enough metal into the relative wind in first place.  This also affected the REP 172 so far and gets currently worked on, and that's how I got into this discussion again.  The default 172 lacks all means to perform a forward slip that actually affects speed or sink rate substantially, and the rudder also has an odd lack of roll response (even when brutally tweaked to have more effect) so you need barely any opposite aileron to maintain the needed attitude, so that's yet another thing I'd consider "at least not in *my* ballpark".

However this lack of rudder authority alone is not that much of a problem yet, it becomes a problem with many (if not all) default XP planes and in particular the 172 because...

2.) ...there is a known problem with wheel/ground friction.  Again, this is old news and has been proven and acknowledged and addressed (unsuccessfully) repeatedly, while some 3rd-party developers have managed to cope with it very successfully (e.g. the REP packages).  

The problem is that the wheels lose friction pretty fast, and once they lost friction they are not getting it back easily, which would be still a physical correct result if the wheels would regain their grip after losing momentum and sideforce particularly on dry asphalt.  Instead they keep on skidding over it sideways even down to pedestrian speeds, any sideforce and the wheels (all of them) lose friction even when still parking and lifting the brake once, the plane starts skidding around like on ice with brakes occasionally rendered ineffective...again, all a known and acknowledged issue with the XP 172.  At some point during the 11.30 beta phase LR tried to mitigate this by automatically applying toe brakes proportional to the rudder deflection, which I called a "kludge" particularly because it was not only ineffective, it made things worse because the wheels started blocking (=losing grip again of course) at the amount of rudder deflection needed.

The chain of events during crosswind landings is like this:  The lack of rudder authority leads to a very high chance that you are going to touch down with some drift/sideforce (because you can't kick the nose straight enough to align it with the centerline, in particular not while needing to maintain a bank angle) and that means whatever wheel will touch down it will lose grip, all other wheels will likely follow and there is little chance to eliminate the side forces long enough that the wheels get some grip again, not only because the rudder is no big help in this even shortly after touchdown.  

While decelerating the rudder will quickly lose even more force so from there on you are again prone to lose all friction due to weathervaning (which is what this combination of issues is often being confused with anyway).  To prove particularly the latter I "hacked" the default 172 at some point to have sufficient rudder authority for the sideslip and could land it at 20KTS of crosswind blowing perpendicular to the runway, and control it sufficiently to touch down aligned with the centerline (no sideforce) and then S-curve all the way down to bicycle speeds while losing and regaining friction all the time.  One of the cascading problems removed = things get considerably better.
 
This is also where the controller plays a significant role indeed, a little jitter or general lack of precision on the yaw axis/nosewheel steering will make you lose grip even more reliably, and of course your technique will be put to the test in a somewhat disproportional way too.  Yes, I can (and I did) make a video that it can be done way beyond 15KTS but that doesn't mean that it's "fine".  In particular with any halfways realistic variation in the wind, the amount of precision, technique, reaction and luck required is way beyond the ballpark, and with the aforementioned flaws stacking up I wouldn't consider any of this "in the ballpark" enough to generally assume a lack of technique or bad controllers when people understandably complain about this.

1 hour ago, Murmur said:

Hi Jan, I don't have a pc right now so no access to XP, what is the max xwind speed you can consistently safely take off with the current C172?

I don't know about Jan but takeoff is a different animal, and IIRC 25KTS was the point where reaching Vr and losing grip happened close enough to deem it "safe". 🙂

 

 

 

Edited by Captain Nuts
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2 hours ago, Captain Nuts said:

XP real weather imported winds were between 15 and 25KTS gusting up to 33 pretty much anywhere in the UK in the past 2 days.  That's a tall order for a 172, in particular for the XP default one. 🙂

That depends on how you define "ballpark", or what ball and what park we're talking about.  I've joined a few discussions about that, made a lot of experiments and tried to devise a method of finding out what's wrong since I bought XP11, and last week I could gather some pretty solid indications (if not evidence) that the widespread perception that at least the default 172 is pretty off can be explained and even proven.  IMO the default 172 is very much off for 2 main reasons:

1.) There is a distinct lack of rudder authority making (strong) crosswind handling more difficult than it should be.  Many pilots agree that around 20KTS crosswind component is the point where 172s run out of rudder, the default 172 doesn't have enough rudder authority to reach the demonstrated 15KTS.  But this lack of rudder authority is shared by all XP GA planes (3rd-party or not) I have, most of which have higher demonstrated crosswinds than a 172.  This points to an underlying issue with a yet unknown parameter/component, an issue that - if I understood that right - has been acknowledged by Austin (who is apparently just as puzzled about that) and led to the famous "model fuselage" photo.  

On the Easter weekend I finally had a chance to assess how much rudder authority some (real) C-172 actually has by performing a few simple side- and forward slip tests and comparing that to the XP 172s I have:

A) how does the 172 respond to full rudder at a defined speed (85KTS in that case) anyway (how much yaw, how fast does it get there...),

B) how much yaw angle will there be at full rudder deflection at that airspeed, while maintaining the ground path using aileron/bank angle and

C) how much bank angle is needed to stop the rotation around the yaw axis anyway.  

The (generously rounded, because my data acquirement method wasn't exactly thought through very well yet) results are

A) much smoother, much faster, much more than the XP 172,

B+C) somewhere between 20-30° of yaw and >10° of bank angle, while the default 172 delivers 10-15° of yaw and <10° of bank angle.  If you translate that to a crosswind landing situation, it's pretty clear why you can't kick away a wind correction angle of e.g. 20° during a sideslip/wing down flare, or properly sideslip over the centerline in first place.  Tweaking the .acf to get that rudder authority needs such high deviations from the default numbers that I think the lack of authority might just be a symptom of another, underlying problem.

1a) Of course everything "flying sideways" is affected by this, you can't expect a realistic forward slip behavior when you can't yaw and bank enough metal into the relative wind in first place.  This also affected the REP 172 so far and gets currently worked on, and that's how I got into this discussion again.  The default 172 lacks all means to perform a forward slip that actually affects speed or sink rate substantially, and the rudder also has an odd lack of roll response (even when brutally tweaked to have more effect) so you need barely any opposite aileron to maintain the needed attitude, so that's yet another thing I'd consider "at least not in *my* ballpark".

However this lack of rudder authority alone is not that much of a problem yet, it becomes a problem with many (if not all) default XP planes and in particular the 172 because...

2.) ...there is a known problem with wheel/ground friction.  Again, this is old news and has been proven and acknowledged and addressed (unsuccessfully) repeatedly, while some 3rd-party developers have managed to cope with it very successfully (e.g. the REP packages).  

The problem is that the wheels lose friction pretty fast, and once they lost friction they are not getting it back easily, which would be still a physical correct result if the wheels would regain their grip after losing momentum and sideforce particularly on dry asphalt.  Instead they keep on skidding over it sideways even down to pedestrian speeds, any sideforce and the wheels (all of them) lose friction even when still parking and lifting the brake once, the plane starts skidding around like on ice with brakes occasionally rendered ineffective...again, all a known and acknowledged issue with the XP 172.  At some point during the 11.30 beta phase LR tried to mitigate this by automatically applying toe brakes proportional to the rudder deflection, which I called a "kludge" particularly because it was not only ineffective, it made things worse because the wheels started blocking (=losing grip again of course) at the amount of rudder deflection needed.

The chain of events during crosswind landings is like this:  The lack of rudder authority leads to a very high chance that you are going to touch down with some drift/sideforce (because you can't kick the nose straight enough to align it with the centerline, in particular not while needing to maintain a bank angle) and that means whatever wheel will touch down it will lose grip, all other wheels will likely follow and there is little chance to eliminate the side forces long enough that the wheels get some grip again, not only because the rudder is no big help in this even shortly after touchdown.  

While decelerating the rudder will quickly lose even more force so from there on you are again prone to lose all friction due to weathervaning (which is what this combination of issues is often being confused with anyway).  To prove particularly the latter I "hacked" the default 172 at some point to have sufficient rudder authority for the sideslip and could land it at 20KTS of crosswind blowing perpendicular to the runway, and control it sufficiently to touch down aligned with the centerline (no sideforce) and then S-curve all the way down to bicycle speeds while losing and regaining friction all the time.  One of the cascading problems removed = things get considerably better.
 
This is also where the controller plays a significant role indeed, a little jitter or general lack of precision on the yaw axis/nosewheel steering will make you lose grip even more reliably, and of course your technique will be put to the test in a somewhat disproportional way too.  Yes, I can (and I did) make a video that it can be done way beyond 15KTS but that doesn't mean that it's "fine".  In particular with any halfways realistic variation in the wind, the amount of precision, technique, reaction and luck required is way beyond the ballpark, and with the aforementioned flaws stacking up I wouldn't consider any of this "in the ballpark" enough to generally assume a lack of technique or bad controllers when people understandably complain about this.

I don't know about Jan but takeoff is a different animal, and IIRC 25KTS was the point where reaching Vr and losing grip happened close enough to deem it "safe". 🙂

 

 

 

10

Although there have been improvements with crosswind behavior, I think your assessment is in the 'ballpark' ! Another issue is the lack of 'Left Turning Tendencies' on departure. The 172 should require lots of rudder input when slow at high angles of attack, but the ball shows no deflection in the turn coordinator. Have you contacted Austin with your theory?   

Edit: Ok just been playing around with a 20kt crosswind using the default172 with the EFM(experimental flight model), and had no problem keeping the plane line up on 3mile approach. Plenty of rudder authority! I also tried it with the REP version and it was twitchy, with EFM on and off. EFM with the default 172 seems like the way to go with a crosswind!   

Edited by strider1

AMD Ryzen 7 1800x, 1080GTX, Ram - 32GB, 32" 4K Monitor, WIN 10, XP-11 !

Eric Escobar

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Ok tried again with yesterday’s weather and it was gusting 28 - straight down the runway.

So a quick test. Manually set 270 @ 20 and lined up on 27L. Yoke back, open throttle, wheelie and lift off under 40Kts while veering off right. Recover (mostly luck) and try and tasty at right angles to the wind, yoke back and aileron into wind. Full rudder and nose wheel and I can hardly keep it straight. I know ground friction is dodgy so I try with yoke full forward (something you would NEVER do) still no difference.

Janov, i’m not bashing XP for fun, I just wish it was better in some key areas and as a long term user I get the impression that every time this is raised it is denyed by people connected with or part of the dev team.

Like you I could post a video taxiing round in these conditions but it takes exceptional effort to go where you want it too. Equally I can post a video of the above behaviour and this is using 20kts which is definitely not that far fetched in the real world. As pointed out above with some much more comprehensive arguments that I can make show that rudder authority isn’t right but equally ground friction is definitely still broken. I love flying ga in X-Plane but at the moment it is still only great when CAVOK.

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The precise reason why X-Plane's ground handling is fundamentally wrong (here and here). The simple root cause has never been addressed as far as I know, only piles of hacks to try to fix the unfixable. The details were sent (with the softest gloves) to Austin last autumn, but he never answered. If people like Jan believe it is mostly ok as is, then for sure it is not gonna change any time soon. But from the physics point of view it will remain just an ugly hack around a neat solution of classical mechanics known for more than two hundred years (and readily available in third party open source code...).

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The hardest part for me, is when the 172 will be taxiing around fine, and then suddenly seems to go crazy - very erratic turns for no good reason.  I am learning to work around it, but I have flown with friends, and I know the handling is not "realistic".

Ron

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Kudos to some of the posts in this thread, with special regards to the OP - tutmeister - who I am sure doesn't have a problem with he's controller hw ( quite on the contrary, judging from he's SIG ) and to Oscar Pilote, and thank you Oscar for all your GREAT work with Ortho4XP which is more than enough for anyone to glimpse you do not have an agenda against XP, quite on the contrary....

XP has lost my hopes again and again, version after version... I'm unfortunately not moved by nice-looking sceneries, PBR, and that sort of stuff I see most simmers worried about instead of actually placing their attention in the primary aspects, IMO, of FLIGHT simulation - as sound / accurate as possible flight dynamics modeling - as well as systems modelling.

Not being able to consistently use my "rudder" to overcome torque effects, having to fight  ground physics that leave a lot to be tweaked by others through plugins and tricks, having that full across the spectrum overdone weathervane stability... has killed my otherwise "pleasurable" experience with XP long long ago....

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