Lack of Inertia in MSFS?

I find most if not all MSFS planes very sensitive and “twitchy” on the controls, especially the rudder. On bigger aircraft the lack of inertia is very apparent, especially in turbulence and gusts. It doesn’t feel like there is much mass going down that flight path. In real life, when there are so many metric tons moving along a flight path, its not gonna instantly react to control inputs, turbulence or gusts and change flightpath due to its inertia. I’m not a developer by any means so I have no idea how to properly test this, I can only compare the flight model with real life experience. I came up with a couple of “Mickey Mouse” ways to compare the MSFS flight model to the real world, you can’t take any accurate conclusions from those “tests” other than proving the MSFS flight model has serious flaws and lacks inertia.

All assistances off and modern flight model

Rudder Hard-over Test

By no means something you can take reliable conclusions from, its just speculation. Regarding the lack of inertia, I decided to compare the A320 in a hard-over rudder scenario against a video I’ve seen on the internet concerning a Boeing 737. I know different aircraft etc. so not a reliable test:

From minute 12:15 (time stamp is wrong):

Default A32N, at MTOW (as much inertia as possible), flight computers OFF (direct law mode). First time full opposite aileron while pushing slightly forward on the stick, second attempt while pulling up.

The rudder hard-over itself doesn’t look completely unrealistic. It seems a little too responsive on the rudder, especially in the beginning, in the first video it seems like yaw and roll are much more in balance while in MSFS the initial yaw rate is much higher than the resulting roll rate. The elevator effectiveness is way too low in my opinion, it seems to be the same problem which plagues the default C172 amongst other planes, not being able to force the aircraft into a (accelerated) stall. The barrel roll at the end using full rudder and aileron is totally unrealistic though, I don’t see a 79t aircraft doing that. Regarding the broken stall characteristics I think this topic might be related:

Designed Maneuvering Speed Test

I’ve used the A32NX development version (flight model itself seems to be the same as the default A320), flight computers off to do design maneuvering speed test. I have found the table below on the internet, although not knowing for which exact A320 model and for what weight those speeds are.

Idea is to fly 250 kts at FL100 and pull the sidestick full back, the g-loading can be seen on the bottom of the lower ECAM display and should peak at 2.5g.

At MTOW: peak g-load = 1.9g
At 59.8t: peak g-loading = 2.4g
At 43.5t: peak g-loading = 2.8g

I never intended to do those loops until I noticed the aircraft didn’t stall at all during my design maneuvering speed tests, so I thought, lets see what happens when you keep pulling the side stick full back… I’m not familiar with the A320, haven’t flown it in the real world, I do fly the Embraer 190/195 and have loads of hours on a 737-400 level D sim, they are build essentially the same so I don’t expect their behavior in direct law to be much different. I don’t know where my theory stands but it goes something like this to explain this odd behavior:

  1. In real life there is a lot of mass following that flightpath, the aircraft does fairly quickly respond to flight control inputs causing roll, pitch or yaw rates, but the flightpath does not suddenly change direction and / or speed due to inertia. For example, if you fly straight and level in cruise and suddenly decide to yank the yoke full back, the nose pitches up while the aircraft continues down the original flightpath for a moment. The aircraft flight path will be lacking behind the nose-up pitching moment and therefore AOA will be increases and stalling angle will eventually be exceeded. I don’t see these effects on any aircraft, not on the C172 and neither on the Boeing 747. The aircraft instantly responds and the flightpath does not lack behind the pitch rate sufficiently to enter an accelerated stall.

  2. Something which might have an influence on this is the effectiveness of the horizontal stabilizer and elevator, I think it became aerodynamically limited after some update. I’m speculating that this is the “improvement” they implemented to have the tail plane stall at large elevator deflections, I think they might have overdone this, you can see the aircraft pitching up more sharply in the initial moments after applying full up elevator, after which elevator effectiveness seem to reduce. The horizontal stabilizer is having a negative AOA during straight and level flight and while the AOA increases (becomes more negative) when moving the elevator towards the up position, the angle of attack decreases as the tail starts to move down (nose moving up), I doubt the horizontal stabilizer will stall before the wing does while performing these sharp pitch-up manoevers. The elevator authority is seriously limited, it suffers from the same issue as the Cessna 172 and a lot of other (if not all) MSFS aircraft, even with the stick full back you can’t force the aircraft into a stall. When trying an accelerated stall during a steep turn you can’t physically maintain altitude until stall, with the stick full back the aircraft starts descending. It seems impossible to force exceed the stalling AOA.

Anyway being able to loop a fully loaded A320 does not seem very plausible, this looks like something straight out of GTA V. Note that at some point the aircraft is flying upside during one of the loops with only 40 kts indicated airspeed (!) without stalling, an aircraft can fly up to almost zero speed without stalling, but in the video the angle of attack is clearly positive, giving full up sidestick, trying to pull it out of the loop. I found this video on Youtube, Airbus A320 in either direct or alternate law? Doing unusual attitude recoveries. You see how difficult it is to recover without entering an accelerated stall, you can hear and see the wing buffeting during recovery. In real life you would feel the g-forces so its probably a lot easier to feel what is going on and not exceed the critical AOA.

There are more videos like this on Youtube, you can see how easy it is to exceed the critical AOA when being too aggressive on the pitch. I don’t know if these things can be modified in the individual aircraft flight model or if it is a problem with the core flight model? The only experience I have with these events in real life on transport category aircraft is the Upset Prevention Recovery Training (UPRT) in level D sims. After recovering from a nose low unusual attitude I find it very easy to enter an accelerated stall in those level-D sims, at least on the aircraft types I have experience with. If you end up nose low at high speed, you need to very gently pitch up as not to enter an accelerated stall, yanking the stick (full) back as I did in MSFS would immediately cause a stall and wing drop instead of looping end over end.

Boeing 747 Accelerated Stall Test

Trying to pull the Boeing 747 at max. take-off mass into an accelerated stall here:

First of all you can see the wrong force balance I’m talking about where the CofP is in front of the CofG with an up-force on the horizontal stabilizer to counter the resulting nose-up pitching moment, this is completely opposite from the real world. The CofP moving backwards with increase in AOA and vice versa is also wrong.

I might have discovered something interesting, it seems like Asobo made the aircraft feel heavy and respond sluggish by reducing the flight control reactivity. The flight control surfaces (also the yoke itself when using cockpit view) are moving really slowly. Maybe they used this trick to correct for the missing inertia? The reactivity slider in the sensitivity settings does not seem to influence this.

I used full up elevator to force the aircraft (unsuccessfully) into an accelerated stall, the second attempt I used full up stabilizer and full up elevator, again unsuccessfully. I have to admit, I don’t know exactly what is illustrated in the developer mode but it seems the angle of attack does not correspond to the angle of attack indicator on the dashboard. If you look at the angle between the airflow and the box which represents the wing, it is no where near stalling angle while the aircraft is exceeding the critical angle of attack according the AOA indicator with no loss of lift, the aircraft keeps climbing at an insane rate.

And note the weird acceleration in stabilizer trim when trimming for more than a few seconds. Also unrealistic. I assume the white wing box is supposed to be the wing aerodynamic chord? No idea why it moves though. The angle between this box and the relative airflow shows almost no angle of attack whatsoever during most of the maneuver until running out of energy at the top. It looks like the pitch rate and rate of change of the flightpath remains in synch and the AOA therefore remains within limits.

Again, what we should have seen is an increase in pitch while the aircraft continues down the original flightpath initially due to its inertia, increasing the angle of attack passed the stalling angle. It seems to me, all aircraft are pitching up to CLmax and then just stay there for some reason, never really exceeding the critical angle of attack. It doesn’t matter what aircraft, weight or configuration you test, the aircraft pitches up to CLmax until running out of energy, even when stalling the aircraft transitions into a falling leaf instead of really making a clean stall break, wing drop etc. Its almost like there is some AOA limiter active limiting the AOA to just below stalling angle.


Nobody is expecting study level aircraft or a fully realistic flight model but some flight model aspects in MSFS seem to use physics straight from GTA V. We should at least be able to expect the default aircraft to represent the basic effects, not accurately maybe but at least to some extend, slipstream, adverse yaw, P-factor, propeller drag, inertia, ailerons affecting angle of attack and leading to wing drop. Inner wing stalling during base to final turn etc. I don’t care a thing about needing a little more right rudder in real life, or in real life it feels a little more like this or that, I’m sitting stationary behind a computer with a joystick lacking feedback from a flight control system, with a different range of motion etc. It is never going to be the same as the real deal. But the basics should be somewhat right.


Took a whole afternoon but I think I’ve found the issue, it starts with an A and ends with SOBO:

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!!!

Exposing Asobo since 3/14/2021 :smile:


definetely, 747 in gusts feels oddly light but actual aileron control feels realistic

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Does changing reactivity in the control settings also change how the 747 flies?

I didn’t notice any difference.

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Have you seen the latest developer Q&A? They spent some more time on physics and such. Maybe you can marry your insights with what they discussed? Your analysis coupled with their modeling may help to paint a more-comprehensive picture of what’s in the sim.

Yes, I saw the last Q&A. I did post some questions including some flight model ones, I think only the propeller drag got answered.

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uhhh ladies and gentleman from the flight deck i apologize for the barrel rolls. I’m just doing some inertia testing.

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You are correct. I call the parameters Asobo uses “fake” inertia. Straight out of Asobo B748 cfg files:
pitch_stability = 0.5
roll_stability = 0.5
yaw_stability = 0.5
These are the Asobo A320 values:
pitch_stability = 0.25
roll_stability = 0.25
yaw_stability = 0.25

The “real” inertia is - again first B748, then A320:
empty_weight_pitch_MOI = 76427903; Empty pitch moment of inertia, Jxx (SLUG SQ FEET)
empty_weight_roll_MOI = 19300696 ; Empty roll moment of inertia, Jzz (SLUG SQ FEET)
empty_weight_yaw_MOI = 89315555 ; Empty yaw moment of inertia, Jyy (SLUG SQ FEET)

empty_weight_pitch_MOI = 3027957 ; Empty pitch moment of inertia, Jxx (SLUG SQ FEET)
empty_weight_roll_MOI = 840695 ; Empty roll moment of inertia, Jzz (SLUG SQ FEET)
empty_weight_yaw_MOI = 3507948 ; Empty yaw moment of inertia, Jyy (SLUG SQ FEET)

And last but not least the parameter that makes the airplane “heavy”. I know, “heavy” is no aerodynamics term. Again first B748, then A320:
drag_coef_zero_lift = 0.02300

drag_coef_zero_lift = 0.02370

And yes, if I decrease (L/D)max or increase drag_coef_zero_lift I make the airplane “heavier”. This is the core of my flight model mods. Change (L/D)max to a value that “feels realistic” and then change many other parameters to get other performance parameters again according to spec.

By the way, my B748 mod values are:
pitch_stability = 0.05 ; 0.5
roll_stability = 0.05 ; 0.5
yaw_stability = 0.05 ; 0.5
empty_weight_pitch_MOI = 76427903; Empty pitch moment of inertia, Jxx (SLUG SQ FEET)
empty_weight_roll_MOI = 19300696 ; Empty roll moment of inertia, Jzz (SLUG SQ FEET)
empty_weight_yaw_MOI = 89315555 ; Empty yaw moment of inertia, Jyy (SLUG SQ FEET)
drag_coef_zero_lift = 0.0268 ; 0.02300

You see no more “fake” inertia, but more drag_coef_zero_lift. I think an interesting experiment is to increase “real” inertia by a factor of two and let a real pilot compare this setting to the original setting.

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!!!

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Thank you for the detailed post. I forwarded this on for test to review.

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I created another one which is getting even more extensive, it overlaps a little with the stall dynamics thread and this thread.

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Maybe you want forward to test that I have already 10000 downloads for my flight level mods. Just search on https://flightsim.to for “flight level mod” by Paul Falke.

But up to now: No reaction on emails to msfsim@microsoft.com. No reaction on Zendesk “glitch” reports. Nothing. Hopefully you have more luck !

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This whole thread is forwarded to test. So thank you for linking your tests.

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Let’s hope one day, this second more important bug in MSFS (CTD is n°1) may be fixed.

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