Calculating Mass MoI of Aircraft Accurately

In summary, The mass moment of inertia for an aircraft is typically calculated by breaking the aircraft into components and transforming their mass into a point mass, or by calculating the integral over the entire mass of the aircraft as point masses. However, CAD software may not accurately account for all components and materials, such as fasteners, fuel, and passenger seats, leading to potentially incorrect results. Accurately calculating mass properties for engineering structures can be a complex and labor-intensive process.
  • #1
SubZer0
19
0
Hi all,

Just a quick question about calculating the mass MoI for aircraft (accurately). Is the whole of the aircraft broken up into pieces, the mass calculated for the component, and then transformed into a point mass? Or the integral calculated over the entire mass of the aircraft as point masses?

Is there any CAD software out there that will do this from models?
 
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  • #2
CAD software should "do" the basic calculations , but the answers may be significantly wrong because of "missing mass" in the models. For example CAD models often don't include all the fasteners joining the various parts, and hundreds or thousands of nuts bolts and rivets can add up to a lot of mass. For an aircraft they probably wouldn't include the mass of things like the cockpit instruments and controls, and maybe not even "bought in" equipment like the passenger seats (not to mention the mass of the passengers!).

The CAD models would probably not contain the mass of fuel, hydraulic fluids, etc, either, and the mass distribution of the fuel between the various tanks will not be constant.

Calculating mass properties accurately for "real" engineering structures is non trivial and often labor intensive - in fact in the company I work for there is a specialist department that does that one task and nothing else.
 

What is the purpose of calculating the mass moment of inertia (MoI) of an aircraft accurately?

The mass moment of inertia is a measure of an object's resistance to rotational motion. In the case of an aircraft, it is crucial to accurately calculate the MoI in order to predict its stability and control characteristics during flight. This information is essential for the design and operation of safe and efficient aircraft.

What factors affect the mass moment of inertia of an aircraft?

The mass moment of inertia is affected by the mass distribution of an aircraft, as well as its shape and size. Generally, a larger and more spread out mass distribution results in a higher MoI. The location of the center of gravity also plays a significant role in determining the MoI.

How is the mass moment of inertia of an aircraft calculated?

The mass moment of inertia of an aircraft can be calculated using the basic formula: I = mk^2, where I is the moment of inertia, m is the mass of the aircraft, and k is the radius of gyration. The radius of gyration is a measure of how the mass is distributed around the center of gravity. It can be determined using the aircraft's physical dimensions and mass distribution data.

Why is it important to use accurate data when calculating the mass moment of inertia of an aircraft?

Small errors in the calculation of MoI can have significant consequences on the stability and control of an aircraft. It is essential to use accurate data, such as the actual mass and dimensions of the aircraft, to ensure the most precise calculation possible. This helps to prevent potential safety hazards and ensures the aircraft performs as expected during flight.

How can the accuracy of mass moment of inertia calculations be improved?

The accuracy of MoI calculations can be improved by using advanced computer software and simulation tools. These tools can take into account various factors, such as the shape of the aircraft and the distribution of its mass, to provide a more accurate calculation. It is also important to regularly update the data used in the calculations to reflect any changes in the aircraft's design or weight.

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