Flight Physics: Insufficient Mass/Inertia and Drag Simulation (Air & Ground)

Bug Reporting Hub Aircraft & Systems
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ISSUE DESCRIPTION

I have observed a fundamental issue regarding the physics engine, specifically concerning mass/inertia simulation and aerodynamic drag in MSFS 2024. The aircraft feel extremely lightweight, lacking the sensation of proper weight distribution and momentum.

  1. In the Air (Aerodynamics): Aircraft seem to have an unrealistically high lift-to-drag ratio. When throttle is cut, planes—even heavy ones—glide too easily and retain energy for too long, suggesting that parasitic drag is insufficient. The sensation of “heaviness” and inertia is missing, making the flight feel “floaty.”

  2. On the Ground (Ground Handling): The lack of weight sensation persists during taxiing. Heavy aircraft can turn sharply and quickly without the expected resistance, tire friction, or lateral force effects. It feels like the moment of inertia is not correctly calculated, making a heavy jet handle like a lightweight go-kart with no perceived mass friction against the tarmac.

FREQUENCY OF ISSUE How often does this occur for you (Example: Just once, every time on sim load, intermittently)? Every time on sim load, across various aircraft types.

REPRODUCTION STEPS Please list clear steps you took in order to help our test team reproduce the same issue:

  1. Load a flight with a heavy aircraft (e.g., A330, B737, or even GA aircraft like C172).

  2. Ground Test: Taxi at 15-20 knots and perform a sharp turn. Observe that the aircraft turns instantly with almost no resistance or sense of mass shifting/inertia.

  3. Air Test: Take off, climb to altitude, and cut the throttle to idle. “A320” will stay float under 90 knots before touch down!!?

  4. Observe the speed decay and glide path. The aircraft glides excessively well and takes an unrealistically long time to bleed off energy/speed, indicating a lack of proper aerodynamic drag simulation.

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I concur. Also lack of inertia was noticeable with larger helicopters (but they seem to have at least partially mitigated that now.) And with fixed wing, apart from too rapid response to external or control forces, I find them untrimmable in pitch. With a feeling similar to us trying to balance on a large ball vs the real life much greater stability and dampened responses to a disturbance. These have always been and despite ‘20 and ‘24 having different game engines.

The reluctance to slow down and to glide ‘too well’ is noticeable in ‘24 especially. Form drag and induced drag seem too llittle - especially for GA types - biplanes are a good example. Hopefully some algorithim is ‘correcting’ the raw input of pressure being sensed over 100s of points on each model and if so it might be tweakable.

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it may be one of this or mix together :sweat_smile: i’m not sure:

  1. Incorrect Configuration (FDE/Config): The default aircraft’s Flight Model parameters/values are either wrong or flawed, leading to unexpected behavior.
  2. Outdated Content (Missing Updates): The aircraft package or core simulator files haven’t been updated for too long, leaving legacy bugs unpatched.
  3. Sim Engine Level Bug (Core Issue): The error originates from a fundamental processing flaw within the simulator engine itself, requiring a developer fix.
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This is not an issue in the sim.

It’s poor flight model work.

The majority of add-on aircraft flight_model.cfg files have substantially too low values for Moment of Inertia. Even some hi-end payware ones. Almost to the point of frustration. It also explains what people keep complaining about turbulence being too severe. That can partly be ascribed to the same MOI. I get that MoI is a tricky beast to understand and calculate. But there are online sources for MOI for many aircraft.

The glide performance and energy is another matter. That, too, is basic flight model work. It can easily be set and verified to basic data in the (real) pilot handbook.

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I largely agree with your assessment, though perhaps not 100%. We have to consider that the physics and aerodynamic engines have evolved drastically in MSFS 2020 and 2024 compared to the legacy FSX days. This rapid evolution might be causing some ‘distortion’ in how the current simulator interprets those specific configuration values.

This is exactly why top-tier development teams like PMDG, Fenix, and others rely on custom scripts to essentially bypass the default simulator engine limitations to achieve higher fidelity.

I do believe that if Microsoft addresses these core issues natively, we will eventually see better realistic performance with significantly less effort required from developers to reach that deep simulation level. However, we must remember that ultimately, no code can ever replicate 100% of real-world physics; there will always be gaps and nuances that need to be discovered and patched.

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I mostly agree to that. Mind you, the engine has indeed drastically changed from FSX, to a fundamentally new method, not to everyone’s liking though. And quite a bit of stuff from FSX remains, for example in how jet engines are modelled. When Microsoft tried to make FM development easier and more accessible through the normalization scheme, than that failed IMHO.

The new modular/attachement system in MSFS2024 has strong potential, but has not been used to that effect, as far as I know.

I am aware of custom coded flight models, although I am only certain for a few. Some do hybrid custom/native and many do fully native.

What that does NOT change is the need to properly calculate MOI’s. Regardless of native or custom flight model, MoI are a fixed value (for the empty aircraft) and are still often under-estimated.

Let’s do a small example. Image an aircraft fuselage being a hollow fuselage of diameter 2.5 meters, skin thickness 0.10 meters (incl. padding/isolation), and length 10 meters. The pitch MOI of that cylinder is around 9.000 kgm2. And it weighs 1000 kg.

Now let’s grow that aircraft. It gets 50% longer, to 15 meters, and the diameter grows to 3.5 meters, and the weight grows 50% as well. The skin thickness remains the same. What’s the pitch MOI of the grown fuselage? It’s over 30.000 kgm2…. So a growth in size of ~50% leads to an increase in the MOI of more than 200%. Many don’t get that.

I believe that the simulation core of MSFS is technically correctly implemented, although lacking in the way some things are modelled. MSFS does not have provisions for proper AOA-increase of slats, vortices, aerodynamic interference, Reynolds, etc.

You last statement is spot-on - it’s still a model.

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First of all, thank you for the last reply and the rich information provided.

I have researched this issue further and attempted to edit some figures in the flight_model.cfg file, specifically under the [FLIGHT_TUNING] section. I found that most settings are set to scale = 1, and any significant change above this limit causes the aircraft to deal with other problems, such as Autopilot control issues and the addition of unwanted reactions in the aircraft physics.

Therefore, I maintain my suspicion that the MSFS 2024 physics engine contains design flaws. Even with payware aircraft, one can sense the poverty of drag simulation and tire resistance when accelerating, which makes crosswind control harder than in the real world.

Adjusting the MOI (Moments of Inertia) to match REAL WORLD DATA improved the feeling of weight, but it was not a fundamental solution. There are still many side aspects needed to add realism, such as simulating ground roughness and friction with the tires to make TAXI easy and realistic like in real life, with a damping feel close to reality.

I remember that the Asobo team developed these physics in a previous update for MSFS 2020, but it was not adopted by many developers or developed further. I hope the Development Team reads this comment to start quick procedures to fix the physics structure in the 2024 simulator and move it to a Real Simulator level.

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Would that affect aircraft behaviour on the ground? The reason I ask is when taxiing around at dirt strips where there are rocks, some planes when they hit one will bounce into the air violently like they are made of balsa wood, and light as a feather.

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Yes it should…

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