Doing some research into how Moments of Inertia affects the FlightModel in the

MSFS2020 Aircraft, I stumbled onto a weird case of confuse Moment of Inertia

Attribution. In the Flight_Model.cfg it is stated: " empty_weight_pitch_MOI =

60000 ; Empty pitch moment of inertia, Jxx (SLUG SQ FEET)

empty_weight_roll_MOI = 13760 ; Empty roll moment of inertia, Jzz (SLUG SQ

FEET) empty_weight_yaw_MOI = 30090 ; Empty yaw moment of inertia, Jyy (SLUG SQ

FEET) " But this is not a correct mathematical convention, at least to the

material I Have? They state that **Ixx = Moment of Inertia for Roll** **Iyy =**

Moment of Inertia for Pitch **Izz = Moment of Inertia for Yaw** I Wonder if

this is just a simple typo, or somethng that can be affecting internally other

areas of the sim? Worth checking anyway! Regards!

Well spotted Alexis ! Let’s see what they say…

Hey, I don’t know if that helps, but in the Flight Model Physics page, there

is a mention about the axes and referentials used by MSFS. Here is a

screenshot that might answer your question:

It’s a bit confusing since, from the original MS FS SDK documentation one can

get the following: Axis Longitudinal X Positive Forward Lateral Y Positive to

the Right Vertical Z Positive Down i9n FS9/X which agrees with the8old

conventional Ixx, Iyy, Izz notation and moments… Here’s an interesting (old)

post by Tom Goodrick on MOI estimates for MFS aicraft: Calculating MOI’s |

BGA Forums

(proboards.com)

where Tom advocates that in general and for most aircraft designs roll moi <

pitch moi < yaw moi The above example shows that the relation is not valid for

that model, but I really don’t know if it can be justified. Anyway the yaw moi

is lower…

Thank you all for the very good insights on the subject! This page on the SDK

saying MSFS doesn’t follow the usual convention might explain why there are

all swapped. I wonder if that was the case also in previous FSs, or something

that was implemented in Asobo’s Hands. Very good Link Jose! For sure, Yaw is

always bigger on all planes I have seen so far. Disregard my first example, as

that 60.000 in Pitch MOI is just me trying to break the system