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Mass MoI for aircraft

by SubZer0
Tags: aircraft, mass
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Apr3-12, 06:45 PM
P: 9
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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Apr3-12, 07:34 PM
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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.

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