MOI Calculator for Flight Simulator. A simple Excel spreadsheet for use with flightsim aircraft. The MOI is moment of inertia, a way to tell Flight Sim how "heavy" aircraft should feel. Many stability problems are fixed using this program. Type in the aircraft's empty weight, the MOI scalar (usually 1.00), and you will get MOI values that usually work well. Tested with everything from regional jets to heavies. Not tested with anything under the size of a regional aircraft. By Matt Duxbury.