sklug7685

Dear mgh, dear all, thanks for the comment. I have try this formula for the calculation, but not wirh the same result as FSX or AirWrench. As I understood in the "flight dynamic document" from avsim is the challange to get the LEMAC ( leading edge MAC ). The basic formula for the CG % is: Distance to CG - Distance to LEMAC = Distance CG to LEMAC and (Distance CG to LEMAC / MAC) * 100 = CG % MAC For Example Default B737-800: Variables given: wing_span = 117.42 ft wing_sweep = 27.2° wing_root_chord = 21.0 ft wing_area = 1344.0 ft MAC 14.10 ft ( calculated, same result as AirWrench ) The Calculation: OK 14,41 ft LEMAC, then I will calculate the CG % MAC from empty weight of the B737-800 Arm = 9 ft Then the formula: 9 ft - 14,41 ft = -5,41 ft And: (-5,41 ft / 14,10 ft) * 100 = 38,64 CG % MAC This result is not the same as FSX and AirWrench empty weight CG ( 35.95 % ). Can anyone see the mistake in the calculation ? Best regards Sebastian

Hello, I have a question about CG % MAC. The CG stuff makes me crazy :-). I have many variables for the CG Calculation from aircraft.cfg: max_gross_weight=155500 // (pounds) empty_weight=85710 // (pounds) reference_datum_position=0, 0, 0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline) empty_weight_CG_position=-9, 0, 0 // (feet) longitudinal, lateral, vertical distance from specified datum wing_area=1344.0 //Square feet wing_span=117.42 //Feet wing_root_chord=21.0 //Feet wing_dihedral=5.5 //Degrees wing_incidence=1.0 //Degrees wing_twist=-0.5 //Degrees oswald_efficiency_factor=0.75 //Measure of lift effeciency of wing wing_winglets_flag=1 //Are winglets available? wing_sweep=27.2 //Degrees, wing leading edge wing_pos_apex_lon=6.96 //Feet, longitudinal distance from reference point, negative going aft wing_pos_apex_vert=-3.8 //Feet, vertical distance from reference point, positive going up and the caculated Total Weight and Total Arm for the B737-800 (FSX default). Now the question is, what is the fsx ( or AirWrench ) internal formula for the CG % MAC value? I have tried a lot of formula find via Google. But I never have the same resulat as FSX or AirWrench ( B737-800 with EmptyWeight 35.95 % CG MAC). Thanks in advance for your help ! Sebastian

Hello, I have a question about CG % MAC. The CG stuff makes me crazy :-). I have many variables for the CG Calculation from aircraft.cfg: max_gross_weight=155500 // (pounds) empty_weight=85710 // (pounds) reference_datum_position=0, 0, 0 // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline) empty_weight_CG_position=-9, 0, 0 // (feet) longitudinal, lateral, vertical distance from specified datum wing_area=1344.0 //Square feet wing_span=117.42 //Feet wing_root_chord=21.0 //Feet wing_dihedral=5.5 //Degrees wing_incidence=1.0 //Degrees wing_twist=-0.5 //Degrees oswald_efficiency_factor=0.75 //Measure of lift effeciency of wing wing_winglets_flag=1 //Are winglets available? wing_sweep=27.2 //Degrees, wing leading edge wing_pos_apex_lon=6.96 //Feet, longitudinal distance from reference point, negative going aft wing_pos_apex_vert=-3.8 //Feet, vertical distance from reference point, positive going up and the caculated Total Weight and Total Arm for the B737-800 (FSX default). Now the question is, what is the fsx ( or AirWrench ) internal formula for the CG % MAC value? I have tried a lot of formula find via Google. But I never have the same resulat as FSX or AirWrench ( B737-800 with EmptyWeight 35.95 % CG MAC). Thanks in advance for your help ! Sebastian