Broken stall dynamics

Bug Reporting Hub Resolved
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1

In all the cases below:

  • All assistance settings OFF,
  • Flight model set to modern,
  • ISA conditions,
  • No wind.
  • CG on AFT limit.

Full Stall in Clean Configuration

The stall characteristics are still broken, you can still stall the Cessna 172, power off, keep the yoke all the way back and steer using ailerons. You could rock the wings using FULL aileron deflection without dropping a wing! When adding the slightest bit of power the aircraft starts to roll to the left, which I assume is supposed to be the torque effect, but the effect is way too strong in that case (you can see this at the end of the video), I tried to arrest the left roll by using ailerons (which you should never do in real life obviously).

Conditions: power idle, yoke full back, rocking the wings left to right using full aileron input, no rudder used at any moment. Power added at the end of the video.

Stall in Climbing / Descending Turn

In real life the outer wing is supposed to stall during a climbing turn while the inner wing is supposed to stall during a descending turn. In MSFS, nothing really happens, no wing drop:

Accelerated Stall (60 degrees AoB steepturn)

Tried to determine the 1g stallspeed in the beginning which isn’t really clear as there is no clear stall break. Accelerated stall in 60 degree steep turn, the stall warning seems to be activating earlier, that part is correct at least. The stall characteristics are broken still so no proper stall or drop of the inner wing (by the way, nice coastline):

Everything past 1:30 is just fooling around


Cessna 172 CG envelope.

Uhmmm


Picture1
Picture12000×1125 156 KB

Stall while side-slipping (full rudder, opposite ailerons)

And a stall in side-slip, using full rudder and opposite ailerons. No wing drop or spin. You can see that for a moment the wrong wing actually drops.

Conditions: full right rudder, ailerons opposite, full up elevator.

Beechcraft G36

I found the same issue with the G36, at maximum take-off weight however it does start to behave a little more as it should. Still, the correct wing doesn’t stall in a climbing or descending turn and it is not really possible to induce a wingdrop with ailerons:

50% payload + 50% fuel:

Max. TOW:

At the end of the second video the wing with the aileron deflected down finally stalls, but this might also be the torque effect or coincidence. For some reason the inner wing always stalls in turns, no matter if it is a climbing or descending turn and no matter which aileron is deflected.

Airliners are not performing any better in this regard, in the above video you find the A320 in direct law mode trying to enter an accelerated stall, instead the aircraft loops end over end when keeping the sidestick pulled full back. You can observe the aircraft flying a loop with the speed dropping below 40 kts (?!) on a positive angle of attack without stalling at some point, this is something straight out of GTA.

It seems to me, all aircraft are pitching up to CLmax and then just stay there for some reason. It doesn’t matter what aircraft, weight or configuration you test, aircraft pitch up to CLmax until running out of energy, even when stalling the aircraft transition into falling leafs instead of really making a clean stall break, wing drop etc. Its almost like there is some AOA limiter installed limiting the AOA to just below stalling angle.

Edit: I think I found atleast one of the issues, when looking at the elevator deflection it is somehow depending on the airspeed, so full back sidestick at Vmo only means a few degrees of elevator deflection. I think this is due to another “improvement” they’ve incorporated to make make planes behave more “realistic”. I believe this was explained in some developer Q&A, but I can’t find it.

They’ve explained something like, its harder in real life to pull the stick full back due to the feedback from the flight control system and G-forces so they’ve limited something. Just tested on the Cessna 172, exactly the same thing going on, no full elevator deflection at high speed. This would explain the weird stall dynamics and inability to pull the aircraft in an accelerated stall, it does however not explain or solve the sensitivity issue.

The implementation is done very poorly, to the point that you can’t even stall an aircraft anymore, can’t maintain altitude during a 45 or 60 degree steep turn etc. From the video below, you can see the elevator deflection above my mouse pointer. When inside the cockpit you have no hind that this is even happening as the yoke position mimics your joystick position and is unrelated to the actual elevator position!!! Not how it works in real life at all of course, totally unrealistic.

Asobo, please, please remove this or make it an option!!!

1 Like
15

I have noticed that during low speed, high angle of attack, and odd COG flights that the plane is oddly stable and that during a partial or 1 wing stall the plane doesnt actually stall, not fully at least. I would like a more true to life physics for low speed, or high AOA stalls so that I can properly use the more aerobatic planes in this game. Furthermore I noticed that in higher speeds the game would rather break your plane than stall out, which is fine for a Cub but for the 3rd party Eurofighter it gets in the way of the maneuverability.

Long story short I would like a less forgiving, more rue to life stall model

16

I too have noticed it. I mostly fly airliners and it’s really hard to land without bouncing, and I find myself floating along in a fully loaded 747 at 100kts sometimes xD
And on takeoff too
 takes off a wee bit too early IMO
TLDR, the planes are a bit floaty

This sim is absolutely ground breaking, don’t get me wrong, but this just one of those things I’d love to see fixed :grin:, You know, the icing on the cherry on the icing of the cake (who doesn’t do that?)

17

Sorry Mate
flight dynamics are way down on Asobo’s list to have fixed
after all
this is a scenery simulator
not a Flight Simulator
just check out the latest development update
95% (approx) of the items they are working on as a priority do not relate to aircraft dynamics or performance envelopes. This product is aimed at the gamers market, they love it, so Asobo’s efforts are pushed in that direction. As a real life PPL holder whom , uses Flight Sims for training, I find MSFS fun as a game and very “pretty” to use
 but definitely not suited to serious practice.

1 Like
18

Speak for yourself. The 152 is incredibly realistic.

19

I learnt to fly on the 152
I tried it during the Alpha/ beta stage
but pushed it aside 
I’ll give it another go when I re install MSFS in a few months

20

Man, can you imagine using this in DCS? :smiley:

Who knew the 172 was the sharpest knife in the Phone Booth? (i.e., High-AoA, Near Stall Speed Dogfighting - a.k.a., the Phone Booth) A lot of folks I knew at Nellis and Fallon would have paid good cash to have this kind of performance, LOL.

1 Like
21

I did the same test on the TBM, same same. Doesn’t seem the C172 is the only aircraft affected by this.

2 Likes
22

Not good. I kept wondering why I wasn’t getting punished for certain speed/AoA maneuvers in single-engine. I probably would have crashed and burned more times than I thought.

2 Likes
23

This is an excellent analysis. These showcases are selected very well because they represent real-life threats that a simulator can help students to get familiar with and avoid. Some of these are even taught in advanced flight school.
Adobo should use your tests as a quality reference. If the airplane behaves correctly in these situations, the flight model must be good.

5 Likes
24

Adding my two cents: this is very probably an aircraft specific issue (in this case the default C172 G1000) and it doesn’t mean stall characteristics of the entire sim is broken. Two examples below in the 3rd party Carenado Seminole:

I can easily replicate in the default C172 G1000 what OP described in his original post, but I can’t do the same in Carenado Seminole.

In the words of Matt Nischan, one of the developers of the nearly “study-level” Working Title CJ4:

“There’s no conclusive observation that can be made by looking at one specific aircraft flight model configuration and then applying that conclusion to the entire flight simulation. How well a particular aircraft meets book values is entirely dependent on how well the flight model author adjusted the values to make the book values possible.”

Source: More Physics, More Real Winds - #256 by Bishop398

P.S 1: I am by no means implying that the issues mentioned by the learned OP should not be investigated.

P.S. 2: Carenado Mooney in MSFS exhibits almost the same stall characteristics as the OP described, and therefore a Mooney factory test pilot was consulted regarding the matter who testified by saying that the real Mooney and the one by Carenado exhibit almost the same stall characteristics.

4 Likes
25

Could be only with default FS aircraft indeed, so far all the default aircraft I have tested suffer from this bug (not only C172)


26

Reported up to QA thank you.

5 Likes
27

I found the same issue with the G36, at maximum take-off weight however it does start to behave a little more as it should. Still, the correct wing doesn’t stall in a climbing or descending turn and it is not really possible to induce a wingdrop with ailerons:

50% payload + 50% fuel:

Max. TOW:

At the end of the second video the wing with the aileron deflected down finally stalls, but this might also be the torque effect or coincidence. For some reason the inner wing always stalls in turns, no matter if it is a climbing or descending turn and no matter which aileron is deflected.

28

I just tried stalling while in a slip. With full right rudder, and just enough left aileron to keep wings level I applied about fifteen degrees of pitch until I ran out of airspeed. The left wing was first to drop and with the debug forces enabled I could see that the left wing had shorter lift vectors towards the tip of the wing before going into he stall. As I played around with the amount of left elevator while in that slip I saw that the left wing lift vector dropped as I applied more left elevator, this is something you also see in x-plane with the same visualization enabled but there the behavior is that the wing farthest from the relative wind drops first.

What I think is going on here with MSFS is that the changing angle of attack of the wing along the aileron is not sufficiently taken into account. As you deflect an aileron down you change the chord line which affects your angel of attack since the AoA is measured as the angle between the relative wind and the chord line. In the case where you are in a slip with full right rudder you are rolling left with the yoke, this causes the left wing to raise its aileron, this decreases the AoA, and on the right wing you drop the right aileron to lift that wing and in doing so increase the AoA. So because of the difference in AoA between the wings, plus any wind blanking that may happen as a result of the fuselage blocking some wind from the right wing the left wing should stall first. Hopefully that made sense.

The question that shakes out of all of this for me is:

  1. How does MSFS compute AoA for the wings?
  2. Does MSFS take into account the effects of control surface deflections, especially ailerons on the chord line of each surface (wing/v-stab/h-stab)?

References:

1 Like
29

I have taught aerodynamics for ATPL students but you are exactly right, I didn’t want to write it down in such detail as I assume the devs. have some knowledge about aerodynamics themselves.

30

Thanks! I figured I would spell out what I saw both to check my understanding and for anyone that comes across the post and isn’t as familiar.

1 Like
31

Edit: I think I found the issue, when looking at the elevator deflection it is somehow depending on the airspeed, so full back sidestick at Vmo only means a few degrees of elevator deflection. I think this is due to another “improvement” they’ve incorporated to make make planes behave more “realistic”. I believe this was explained in some developer Q&A, but I can’t find it.

They’ve explained something like, its harder in real life to pull the stick full back due to the feedback from the flight control system and G-forces so they’ve limited something. Just tested on the Cessna 172, exactly the same thing going on, no full elevator deflection at high speed.

The implementation is done very poorly however, to the point that you can’t even stall an aircraft anymore, can’t maintain altitude during a 45 or 60 degree steep turn etc. From the video below, you can see the elevator deflection above my mouse pointer. When inside the cockpit you have no hind that this is even happening as the yoke position mimics your joystick position and is unrelated to the actual elevator position!!! Not how it works in real life at all of course, totally unrealistic.

Asobo, please, please remove this or make it an option!!!

4 Likes
32

Now, i’m not trying to say that this is what’s going on here, i’m just bringing up a point that might be relevant: If the plane was ballistic at that point (as in, close to 0g), the stall speed goes down significantly to the point where you could be fully stalled but still retain aileron control. Here’s a video on the topic:

33

Correct, an aircraft can stall at any attitude or airspeed. But during a 1g stall in level flight this isn’t relevant. Issue is that every aircraft I’ve tested transitions into a falling leaf when keeping the stick full back, being able to use up to full aileron input without exceeding the critical angle of attack and inducing wing drop. As long as you keep the stick full back the aircraft does not experience zero g.

A related problem is how Asobo tryed to solve the lack of force feedback and g-loading sitting behind your desk. They have limited the control surface deflection as a factor of airspeed and loadfactor. You have no idea this is actually happening as the in-game yoke or stick mimics your joystick position which is apparently unrelated to the actual control surface deflection.

In my mind your joystick can either directly represent control surface deflection, i.e. the in-game joke mimics your joystick which is directly related to control surface deflection, or your joystick deflection represents a force input and the in-game joke therefore becomes disconnected from the joystick, for example, when pulling the joystick fully back represents x amount of newton force on the controls which at high speed does not correspond to a full up control surface deflection. For some reason they have chosen a weird hybrid of the two methods


One thing is for sure, they have overdone it to the point it becomes impossible to pull the aircraft into an accelerated stall or for example maintain altitude during a steep turn.

That being said, I uninstalled FS2020 when it got stuck in an update loop again and I didn’t bother to reinstall, so I can’t check if they have improved on this.

1 Like