35 minutes ago, PurdueKev said:

It could be - I haven't hand-flown the Airbus much except for takeoff and landing.  But the oscillations show such a normal mode that it can't be the AP reacting to anything. Just seems programmed in with a set frequency that doesn't decay or change.

As an experiment I tweaked the flight model of one of the more stable MSFS aircraft. I turned up every stability parameter by around 400%.and smoothed out every other force that could possibly provide instability. Hand flying it, it still rolled slowly left and right,, and on autopilot it still yawed from side to side like a slowly ticking clock pendulum, ad nauseam.This is undoubtedly a baked in effect.

Seems the flight dynamics issues are very apparent and predictable. I think have found that all of the airplanes that do not have the aircraft.cfg and flight_model.cfg (i.e. the FSXish performance file) are poorer performing. Thus it stands to reason that the G58 and the C700 are the worse airplanes in the sim because they depend the most on Asobo's built in aerodynamics. Those 640 surfaces.

 

Quote

First of all, a new surface elements model has been created to better account for the distribution of lift, drag and side forces over the entire aircraft geometry. Compared to XPlane11, our geometrical discretization is more precise. Indeed our model uses 640 surfaces where XPlane11 web site states that « ten elements per side per wing or stabilizer is the maximum 

It would seem that Asobo has to learn the same lesson that plagued Xplane in the beginning, that is computational Blade Element Theory is not the end all of aerodynamics. Their simple target_performance.cfg also seems to have little to do with tuning the output created by the aerodynamics engine to expected output. In fact the Longitude stalls at a much higher IAS then should be constrained by the target_performance file. 

BTW I doubt it is the autopliot itself. The a/p params are a carbon copy of FSX/P3d Proportional-Integral-Derivative controls (which work quite well generally speaking). I think these baked in movements are imposing themselves on both manual and auto flight.

Edited August 24, 20205 yr by robert young

8 minutes ago, KenG said:

In fact the Longitude stalls at a much higher IAS then should be constrained by the target_performance file. 

But really airplanes can stall at any speed! If we could constrain flight model by critical angle of attack it would be more proper

24 minutes ago, KenG said:

Seems the flight dynamics issues are very apparent and predictable. I think have found that all of the airplanes that do not have the aircraft.cfg and flight_model.cfg (i.e. the FSXish performance file) are poorer performing. Thus it stands to reason that the G58 and the C700 are the worse airplanes in the sim because they depend the most on Asobo's built in aerodynamics. Those 640 surfaces.

It would seem that Asobo has to learn the same lesson that plagued Xplane in the beginning, that is computational Blade Element Theory is not the end all of aerodynamics. Their simple target_performance.cfg also seems to have little to do with tuning the output created by the aerodynamics engine to expected output. In fact the Longitude stalls at a much higher IAS then should be constrained by the target_performance file. 

On further investigation, it looks to me that whether you use the "modern" or "legacy" f/m options, both have a lot of parameters stripped away. But the Legacy model seems to allow for more variation and scope. For example it is extremely difficult to promote a proper side slip using "modern" flight model. But both versions have many tweakable params missing, or they seem to be replaced by a hard coded look up table that either you cannot alter or is extremely difficult to edit. Many lookup tables have been disabled in both lists of params. You can see this clearly because there are lots of "=0.0" next to some quite significant routines.

The now well-known multiple lift points seem to be just for reference unless I've missed something. They appear as vertical lines in debug mode, but as yet I cannot find a way of actually editing them or indeed doing anything except staring at them. Perhaps in the future they might be editable or useful in a practical way, but so far I cannot see anything that is useful about them.

Edited August 24, 20205 yr by robert young

I love this discussion and loved it over in 26 pages of this thread: 

I also posted a lengthy response in the RW pilot thread in the MSFS forum, though won't repeat it all here.

What I think is most interesting is that there are so many different opinions. The biggest challenge developers face is translating what is such a tactile experience in flying a real plane to something you can do in a chair that isn't moving, looking at a screen that isn't moving with controls that have no feedback. For example, it makes me insane that in turbulence, it is annoyingly hard to use the avionics without your mouse losing focus on the knob or switch I want to use...but, this is actually pretty realistic. Try using a GTN750 touch screen in turbulence while hand flying an approach in IMC. It's hard. And the subject of much whining by RW pilots. That's why some of us have stuck with our trusty GNS series and their knobs you can hold on to in turbulence - and occasionally pop off...

In real life, my plane will yaw a few degrees back and forth in turbulence without positive pressure on both rudder pedals, making minute adjustments to try and dampen the effect. There is almost no way to accurately simulate this because my saitek rudder pedals default to 0 deflection and I can't "feel" anything. So, does unpleasant yaw occur in certain RW aircraft in even mild turbulence? Absolutely. Can it be more easily dampened in a real plane? Also yes IMO.

Here's a quote from over at Beechtalk - there are whole threads dedicated to "tail wagging" and it's a thing...

Quote

I think you will find the V35B without the yaw dampener is significantly more stable in yaw than your C35 was. My first Bonanza was a straight 35 and it was like a leaf in the wind, and it yawed like crazy in the bumps. My second was an E, and it was much better as was my K. I’ve had my S for 21 years now and personally wouldn’t install a yaw dampener. It also helps to keep you feet on the rudder pedals rather than on the floor when in turbulence. The experts say that another casual factor is elevator rigging - if they are out a bit it can exaggerate the tendency to yaw.

From my testing and flying a few aircraft that I have time in, there are three big takeaways that need work, IMO:

1) Control sensitivity - there's no doubt that when comparing control surface deflection in the sim to the real world, the sim is much more responsive to tiny inputs at low speeds. As @Chock notes, this is particularly bad in pitch, exacerbated by the fact that the real world yoke in most of these planes have much more throw or travel than our simulator yokes... Low speed control surface effectiveness is way overdone in the sim - they may be that sensitive at cruise speed, but not on final or right after takeoff.

2) Yaw on the ground - I don't know what to say about this really, but never in my life has any plane I've been flying yawed violently into the wind when the mains touch down - especially the 3 knot winds we have in the US right now in sim. And on takeoff, the yaw is super sensitive - now it is possible to get a little swerving going in a real plane too if there's a strong crosswind and strong P-Factor, but not nearly as easy as it is in this sim. Dumbing down rudder sensitivity helps, but that makes ground steering (taxiing) increasingly difficult.

3) Performance. This should be maybe the easiest to fix. Many of the planes suffer from unrealistic performance - the Bonanza cruises 30kts too slow...the Baron is too fast, etc etc. The problems with turbine depiction are disappointing, but not unexpected. I'm not smart enough to know whether the bits are in place for 3PDs to depict them better than in P3D...

I've submitted tickets on all of this to zendesk, more than once...

The part that I'm not following is this discussion about the induced/fake oscillations. I don't know if it's just different models maybe, but I haven't experienced this. If you take a look at some of the test flights I did in support of the other thread on this subject, you'll see what I mean and I'm genuinely interested in what others are seeing. Is it different from what I'm seeing? Am I just not noticing it?

Flights in the 208:

https://www.youtube.com/watch?v=078ZaALzKPs

https://www.youtube.com/watch?v=tHzfjJ7U9KA

https://www.youtube.com/watch?v=Oz7rzVRf6cY

Flights in the TBM:

https://www.youtube.com/watch?v=0sM9WMpuTdU

https://www.youtube.com/watch?v=SzSLYibjJtU

There are others in the channel, like the KA and Citation.

One thing I really like? In P3D, I found it almost impossible to hold the nose off in any aircraft after landing. Maybe that was just me, but performing a soft field takeoff or landing in this sim is much more true to life, though hard because of the pitch sensitivity issue previously discussed.

14 minutes ago, cwburnett said:

Try using a GTN750 touch screen in turbulence while hand flying an approach in IMC. It's hard. And the subject of much whining by RW pilots. That's why some of us have stuck with our trusty GNS series and their knobs you can hold on to in turbulence - and occasionally pop off...

Ain't that the truth! ....and it's even worse on the smaller 6xx units. I love so much of what the GTN does, but that touchscreen is the thing of IMC nightmares sometimes.

2 hours ago, FlyingInACessna said:

I noticed this! The landing challenges are impossibly and unrealistically hard! The nose goes wherever it wants to and there’s no stability. Planes descend and climb all over the place. Even with a stable approach speed some are impossible to get down.

Interesting point which suggests something not often discussed. If a simulator is harder to pilot than a real aircraft something is wrong. Of course you are not getting the visceral experience, but nor are you always in a driving sim. Most keen sim pilots learn quite good motor skills quickly. But that is not possible if the simulator makes an aircraft harder to control than its real life counterpart. Take the Beech Bonanza for example. This aeroplane was developed and improved over several decades. It has outstandingly good control harmonisation and is very easy to fly.

Aircraft accidents are very rarely the result of poor motor skills or poor aircraft controls. They are nearly always the result of poor decision making, lack of situational awareness, risk taking, poor planning, poor procedures, flying into IMC without ratings, etc etc. The physical flying is the easiest part, so if a sim aircraft is only just about controllable during an approach and landing it is a bad aircraft. I don't know why, but some tend to think that a sim aircraft is somehow inauthentic unless it is a handful. But aircraft designers spend years and years making most contemporary aircraft as easy to handle as possible, so you can concentrate on forward planning, weather, good procedures. The actual flying should be, and usually is, the easy bit.

26 minutes ago, cwburnett said:

One thing I really like? In P3D, I found it almost impossible to hold the nose off in any aircraft after landing. Maybe that was just me, but performing a soft field takeoff or landing in this sim is much more true to life, though hard because of the pitch sensitivity issue previously discussed.

That pitch sensitivity will be a big problem for them on Xbox so I guarantee a fix soon lol.

ive been waiting to invest in some new controllers and got rid of my x52 ages ago because of their issues. In the meantime I’ve been trying out the sim on gamepass and using an Xbox controller.

that sensitivity is horrible. Particularly the yaw, which is almost impossible to balance with an analog stick. even at stall speeds the plane is like a yo-yo on the run way and it’s incredibly difficult to manage with an Xbox controller.  

34 minutes ago, cwburnett said:

I love this discussion and loved it over in 26 pages of this thread: 

3) Performance. This should be maybe the easiest to fix. Many of the planes suffer from unrealistic performance - the Bonanza cruises 30kts too slow...the Baron is too fast, etc etc. The problems with turbine depiction are disappointing, but not unexpected. I'm not smart enough to know whether the bits are in place for 3PDs to depict them better than in P3D...

Most of the engine parameters in MSFS are a carbon copy of FSX and P3d. The Bonanza engine performance is easily fixed. But unfortunately there are other aerodynamic parameters which interact with these engine params that are needed to fine tune things that appear to be missing or changed. If I was to try to convert for example the RealAir Duke Turbine to this sim it would not really be possible at the moment. There are too many subtle and controllable parameters that are missing or obscured. 

Regarding basic controls, let me invite you to try the Extra in MSFS 2020. I quite admire the YouTubers who have demonstrated this because they have amazingly adapted their control skills to somehow make this aeroplane just about flyable. I can't do it! Mainly because I am so shocked by the extreme over control in every axis, and the truly extraordinary bouncing of pitch, yaw and roll I just can't stand it and give up.

The real Extra is one of the most beautifully harmonised aircraft on the planet. You can fly it like it was a 747. It is so tame and easy to control if you input modest (but not tiny) movements. The aerobatic stuff you see are from pilots who are using quite vigorous control movements, often with both hands. The Extra can fly like a friendly pussycat. From the standard back seat, and having no flaps, you have to side slip the Extra on final approach and landing, otherwise you cannot see anything. But it is an absolutely doddle to side slip,. The controls are amazingly easy and beautifully balanced.

I don't see this in the sim. Nowhere near. It is EXTREMELY hard to control and there is no possibility of any finesse. It is so shockingly hard to control and over-sensitive that it is just zero pleasure to load it up.

1 hour ago, sd_flyer said:

But really airplanes can stall at any speed! If we could constrain flight model by critical angle of attack it would be more proper

I was talking about a 1g stall. When the VR for the airplane is 107 KIAS and it stalls at 130 KIAS 1g then something is fundamentally wrong with the flight dynamics. 

3 minutes ago, KenG said:

I was talking about a 1g stall. When the VR for the airplane is 107 KIAS and it stalls at 130 KIAS 1g then something is fundamentally wrong with the flight dynamics. 

Ken, it's the coefficient of lift vs aoa tables that are wrong. In fsx you could define literally a hundred very detailed lift vs aoa points on a visible graph. I'm not sure it you can do this in FS 2020 as so far I've only seen a text format table with only a few entries. Maybe it is possible to add more. But the key bad param here is the top of the slope where the Y value is way lower than it should be at maximum aoa before the stall. So the wings are stalling probably before the proper angle of attack maximum.

1 hour ago, robert young said:

As an experiment I tweaked the flight model of one of the more stable MSFS aircraft. I turned up every stability parameter by around 400%.and smoothed out every other force that could possibly provide instability. Hand flying it, it still rolled slowly left and right,, and on autopilot it still yawed from side to side like a slowly ticking clock pendulum, ad nauseam.This is undoubtedly a baked in effect.

What kind of weather were you in and also, were you around any mountains or buildings that could cause effects to the aircraft. I am just reaching here, but maybe there is something to do with external effects causing too much impact on the aircraft. Thought I would ask because you are an expert with this. 

2 hours ago, Slides said:

I imagine this is similar to how driving in real life, you will feel, hear and even see slight bumps based on the road surface or small potholes all the time.

But if that were to be implemented in a car racing sim to the same degree as in real life, I would imagine car simmers would riot.

Yes, but it would feel even more annoying in a flight simulator. Suddenly on final in good weather and no tough conditions, the left wing drops 20 degrees - without that feeling strange in any way. Without thinking you quickly push the stick to the right for half a second and then back to the middle. To someone beside you it might look like you are struggling to "battle the turbulence" with the stick moving around all the time - but you don't feel that way. It would make a simulator feel rather crazy though 🙂

Does anyone have a real life video example of a light GA aircraft which is perfectly still while flying? So far I have not been to find one.