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Murmur

FSX A2A C172's FM vs X-P

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(LOL at the topic title).

 

Reading the forums, I understand that A2A has gone great lenghts to assure that its new C172 has a flight model as accurate as possible, doing a lot of flight tests, doing accurate measurements of maneuverability and performance, etc. So the consensus seems to be that the A2A C172 flight model is the most accurate for FSX.

 

Now, it's really interesting to note that the common early "complaints" about its flight model are _exactly_ the same complaints have historically been made about X-Plane flight models:

 

.) "too twitchy", "flight controls too sensitive" (read this topic: http://a2asimulations.com/forum/viewtopic.php?f=107&t=36223&sid=bf7ea5d47014302795d20197852a1a50 )

 

.) some roll due to torque (recent Jcomm's posts in this forum on this issue)

 

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I think the A2A model is out of rig.... :smile:

 

It must be. All of sudden, sim land is believing that these 172's are sensitive, and want to always slightly roll. In reality, they're about as easy to fly, as it gets. Unless it's out of rig of course. I've previously mentioned, the trip I took, to ferry a 172 back, that had a bird strike, and took out most of the front wind screen. It was repaired, but just flew out of wack. It was an older plane.

 

My RV was sensitive, the Pitts was more sensitive. 172s are not sensative. None keep trying to roll, either.

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I think the A2A model is out of rig.... :smile: It must be. All of sudden, sim land is believing that these 172's are sensitive, and want to always slightly roll. In reality, they're about as easy to fly, as it gets. Unless it's out of rig of course. I've previously mentioned, the trip I took, to ferry a 172 back, that had a bird strike, and took out most of the front wind screen. It was repaired, but just flew out of wack. It was an older plane. My RV was sensitive, the Pitts was more sensitive. 172s are not sensative. None keep trying to roll, either.

 

Maybe on the lateral axis. I hardly think that an out of rig condition makes it more sensitive/twitchy, though. All of this tends to strenghten my belief that the A2A C172 has an accurate flight model (in terms of the "hard numbers"), but its apparent handling results far more twitchy than the real one due to various limitations in feedback between being in front of a screen with a spring loaded stick, and being in a real aircraft. But this issue has been brought many, many, many times in the past...

 

Or maybe, the people at A2A have flunked all their flight test measurements...

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They actually did the test on two different C172s, not just one :-)

 

Both exhibited exactly the same bahaviour :-)

 

Meanwhile I talked to a great friend of mine, who flies this exact model, very well represented in one of the skins available for the A2A C172 and he confirmed exactly the same about the evident roll to the left at high power settings, during takeoff, initial climb or even at cruise when throttle is increased from normal cruise settings!

 

As some pilots I have asked about this subject commented, he also added that most of the time pilots aren't even aware of the corrections they are doing to their controls while flying. They're flying the aircraft, not paying attention to what we simmers can sometimes spend time doing...  When I am flying a glider, I just look at the instruments when entering the base leg... or for checking that thing called flight computer :-/

 

Also, the kind of forces associated with yoke / manche aileron inputs is usually a lot less than the force we have to apply on the rudder, so, it's easier to notice that one than probably the corrections we keep doing to the roll axis.

 

Flying the Mu2 with that mod I suggested in the Art Stab can be very interesting if you observe the inputs that the Art Stab system does... looking a lot like what we see in most RL videos.

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Great post jcomm!

 

Also, the kind of forces associated with yoke / manche aileron inputs is usually a lot less than the force we have to apply on the rudder, so, it's easier to notice that one than probably the correction we keep doing to the roll axis.

 

This can be (partly) simulated even in X-Plane and even without a force feedback joystick: just use full non-linear (full right slider) for pitch and yaw axis, and use full linear (full left slider) for roll axis. This way, you'll need less stick deflection (and hence less spring force) for roll axis, compared to the other two.

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Honestly by now you know in more of an FSX fan but I don't like the FM in the a2a sky hawk.

 

My primary gripe is with elevator control. And ya from my limited c172N time, in a stable trimmed config, the elevator is far too sensitive.

 

Especially after AP disengagement - touch the yoke and wow what a reaction!

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Honestly by now you know in more of an FSX fan but I don't like the FM in the a2a sky hawk.

 

My primary gripe is with elevator control. And ya from my limited c172N time, in a stable trimmed config, the elevator is far too sensitive.

 

Especially after AP disengagement - touch the yoke and wow what a reaction!

 

There you have it, directly from A2A developers:

 

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Another thing to consider is travel on a real yoke/stick is greater then most controls for the PC Sims, so movement is condensed, which can add to the twitchy/sensitivity feeling in XP/FSX

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Another thing to consider is travel on a real yoke/stick is greater then most controls for the PC Sims, so movement is condensed, which can add to the twitchy/sensitivity feeling in XP/FSX

 

Exactly.... talk about sensitivity? Every fsx or even xpx simmer should really try how sensible the controls are on the DCS P51d!!!

 

I am using the "STICK_SENSITIVITY_MODE=0" entry in FSX,cfg to override FSX's internal smoothing / massaging of control inputs, and even FSUIPC for setting and calibrating the main axis, but even that way MSFS applies a "softening algorithm" to all inputs, and that's why it is very difficult to build a realistic aerobatic aircraft of high roll rate / stop rate :-)  for it....

 

X-Plane does a better job in this area, but also has other shortcomings. I use control phase-out to fine tune control response, and so far am satisfied with the results.

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There you have it, directly from A2A developers:

 

Have you flown the A2A 172?

 

Like Ryan, I've mostly shelved the plane for the time being, pending further development.  It's got lots of promise and many, many good features, but any suggestion that it's the one true flight model are a bit premature.  Ryan and myself are not the only ones with 172 time who've questioned a few things, side-by-side videos notwithstanding.  Spend time on their support site and you'll see that there is considerable disagreement on many of the flight model's features amongst current and former 172 pilots.  Some seem to like it, others not so much and some are in between.  I'm in the second camp on a few things like the elevator touchiness and how easy it is to map into the average sim yoke's more limited travel and, yes, roll.

 

Things like yoke "feel" are highly controller dependent as well as dependent on how the user perceives the illusion of the simulation, but I've not talked to anyone yet who hasn't felt the need to "tame" the elevator, for example.

 

Please don't misunderstand - I like what A2A are working on and respect their desire to sweat the details, but still... I view the 172's flight model as a work in progress, not (at least not yet) the definitive work.

 

Scott

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A few years back, fifteen or so, I was doing some flight testing with a Cessna 172, to check roll response, and compare it aerobatic type aircraft. This was for beta testing purposes.

 

 

 

Where the aerobatic airplane would just leave it's wing at the angle you deflected it to, for a bit of time.....the Cessna was much different. I'd swing the yoke fully to the left, and let go. The plane had an enormous amount of positive stability. I'd let go, while banked to the left. The plane would instantly roll back right, and actually past level. It would then roll slightly back left to level. It almost seems spring loaded, since it does it without hesitation.

 

 

 

I'd call this stable. There is no aileron trim, in this plane. I find it hard to believe, that "torque" is trying to roll the plane to the left, when it wants to easily spring back to level.

 

 

 

Also bare in mind, that Cessna takes all new aircraft for a test flight. They adjust any wing heaviness out, by adjusting cam bolts on the rear spar. I prefer the term "heavy wing", because the wing just drops lower. It's not trying to roll the plane around and around. My own plane had a heavy wing. It was the right wing, and flew right wing down, if I wasn't holding a bit of left stick. Stick ressure was very light, though.

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There you have it, directly from A2A developers:

 

 

I've already seen that... My flight sim version is far more touchier than that. I know exactly why too: it's because my joystick has FAR less travel than a real yoke. In their FM programming they should have accounted for users' with joysticks. Heck even most the hardware yokes are toys compared to the real thing.

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I am not as qualified as some to comment on the flight model of the a2a 172 ( only a few lessons RL)  but I think it's a lot better for those of us that have yokes. No matter what I do not think any developer can truly get it perfect,  you can FEEL a real plane, you can feel how much force you need to exert on the controls to get the plane to do what you want.   

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Can you adjust the respose curve via fsuipc calibration to help?

 

Sure, and that's exactly what I've done (yoke) and it does help.  It's the most aggressive curve I've put on any aircraft to date.  Others have fiddled with the elevator effectiveness parameter, which in my mind is a bit too sledgehammer of an approach and can cause other issues.

 

As I mentioned, I don't mean to be overly critical on the plane as the flight model has gone through a number of changes with some minor releases from the site and I expect there'll be more.  One of the challenges A2A faces is that they are presenting this product to a far larger group of users who've actually flown the plane IRL than anything else they've ever done.  And we all have opinions, and not all of those opinions match. :-)

 

Scott

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One of the challenges A2A faces is that they are presenting this product to a far larger group of users who've actually flown the plane IRL than anything else they've ever done.  And we all have opinions, and not all of those opinions match. :-)

 

Very true, and we can't forget the myriad of systems, malfunctions, etc... they're actually simulating.

 

This C172 is the first FSX add-on ( prop GA ) that has, for instance, a plausibly implemented Ammeter!  You actually see it charging at higher power settings, specially if not using all the main sources of electrical drain.

 

Strangely I find the latest patch, 1.03, very good in terms of all of the flight controls and their sensitivity. I am also suing FSUIPC but all axis are linear. It probably helped a lot having learned to master the DCS p51d a few months agos :-)

 

OTOH, I still find the way one can fly the A2A C172 under ground effect somehow irrealistic, and think, for instance, that the default C172 in X-Plane 10 does a much better job there too...

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Thanks to this thread, I've gone back to see what updates have occurred since I decided to take a break from the plane.  As I noted earlier, the flight model is still a work in progress, and from the release notes, particularly so when it comes to torque and P-factor.

 

A couple of relevant quotes from the release notes (all emphasis mine). 

 

From the 1.02 notes: "Increased modeling of pfactor (still in testing and development). Should require moderate rudder on roll out, slight taps on takeoff run, slight pressure on a standard climb, increased pressure approaching a stall. Also reverse torque has been simulated. Try flying at a moderate speed, under 80kts ias, and cut the throttle. You should get a very slight roll to the right. The aircraft will always have a slight roll one way based on these power changes (watch how the ball moves). The only time the plane will fly neutral is during cruise operations (when the prop is neither pulling or pushing). The pfactor does pull more than it should while taxiing. This will be remedied in the next update."

 

And 1.03: pFactor and engine torque effect on airframe physics tuned (still in development)

 

As mentioned, I truly appreciate the efforts involved here to do it right and the continued tuning this is getting.  Note the references to rudder for roll out, takeoff and climb and my emphasis on "slight" referring to roll as a result of power changes.  The intent is obviously not to have a plane that feels inherently unstable and twitchy, but does feel alive, responsive and correct.  I've also highlighted that A2A agree that a 172 in level flight at cruise power should be neutral (obviously assuming a reasonably neutral load).

 

That's not how my 172 currently behaves, but based on what I'm reading in the release notes what they're aiming for matches the behavior I've personally experienced in the 172 and most other GA singles.

 

Scott

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