Pitch, Roll, Yaw MOI, Is there a scientific way to calculate?

[MSFS 2020] Questions & Community Discussions Aircraft
1

I’ve experimented a lot with these values to see how much of a difference they
make. But now I wonder if there is a more scientific way to calculate these?
What values do I need to obtain in order to calculate them? If I don’t have
these values, can I estimate them? empty_weight_pitch_moi = ; Empty pitch
moment of inertia, Jxx (SLUG SQ FEET) empty_weight_roll_moi = ; Empty roll
moment of inertia, Jzz (SLUG SQ FEET) empty_weight_yaw_moi = ; Empty yaw
moment of inertia, Jyy (SLUG SQ FEET) empty_weight_coupled_moi = ; Empty
transverse moment of inertia, Jyz (SLUG SQ FEE
https://docs.flightsimulator.com/html/Content_Configuration/SimObjects/Aircraft_SimO/flight_model_cfg.htm

2

I also want to say that I am a complete beginner when it comes to model
aircraft. But I am trying with the limited data I have to improve an already
existing flight model.

3

This is from the CJ4 Before sim update 12: empty_weight_pitch_moi = 69403
; Empty pitch moment of inertia, Jxx (SLUG SQ FEET) empty_weight_roll_moi =
13434 ; Empty roll moment of inertia, Jzz (SLUG SQ FEET) empty_weight_yaw_moi
= 75997 ; Empty yaw moment of inertia, Jyy (SLUG SQ FEET)
empty_weight_coupled_moi = 100 ; Empty transverse moment of inertia, Jyz (SLUG
SQ FEET) This is from the CJ4 After sim update 12: empty_weight_pitch_moi
= 124220 ; Empty pitch moment of inertia, Jxx (SLUG SQ FEET)
empty_weight_roll_moi = 17781 ; Empty roll moment of inertia, Jzz (SLUG SQ
FEET) empty_weight_yaw_moi = 75997 ; Empty yaw moment of inertia, Jyy (SLUG SQ
FEET) empty_weight_coupled_moi = 100 ; Empty transverse moment of inertia, Jyz
(SLUG SQ FEET) Should I consider anything with this depending on CFD on or
off?

4

I can see this page:
https://docs.flightsimulator.com/html/Samples_And_Tutorials/Tutorials/Defining_A_Flight_Model.htm
I have set the numbers it gave me.

5

Yes there is an accurate/mathematical/scientific way - split the aircraft into
individual sections with own size and weight, and calculate MoI for each
section CoG, and then use parallel axis theorem to calc MoI for each section
at aircraft empty CoG. It’s a bit of work and very error-prone. A number of
approximation / average tools are mostly useless. MoI’s for MSFS are regularly
estimated too low.