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Guest IanK

Airfile question on low wing assignment

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Hey guys,Where would one put into the airfiles entry that an aircraft is a low wing configuration?I am setting up an airfile using the Cessna 182 template and need to put in this configuration.I noticed in the config file that there is a 'wing_pos_apex_vert=' entry, but I am not sure if that is the actual location of the wing from CG.Many thanks for any input.Kind regards,Bill

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Hello Bill...As you can find within those templates of the "Aircraft" folder,here's the answer for you :wing_pos_apex_vert= 0.0//Feet, vertical distance from Reference point, positive going up,negative going down.Just in case you didn't already know :FlightSim Reference point =(1/4 chord, centerline, waterline)So it's the not the distance from the CoG.Greetings,HB

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Hey HB,Many thanks Sir.I wasnt sure if that was it or not.Bill

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Hello Bill,I recorded that last advice with similar data for the lateral position which someone may find of interest. As with most aspects of Flight Simulator, things are rarely a simple as they seem.The Visual Model Origin (VMO) should represent the point about which the visual model will rotate in pitch as determined by the .mdl file. It needs to be related to the aerodynamic model defined by the .cfg and .air files. Starting at the Visual Model Origin (VMO) the Reference Datum (RD) is defined relative to the VMO. In this case, +83.5 ft forward of the VMO. The position of all the other parts of the aircraft are defined relative to this. As an example, the picture shows that the Wing Apex Longitudinal Position is 58.2 ft aft of the RD, hence the need for the - sign. The Root Chord is 48.4 ft so that the position of the 1/4 chord point is 58.2 + 48.84 ft = 70.4 ft. This isn't the same as the VMO -it's some 13 ft forward - and, in fact, doesn't seem to be directly referenced.The mean aerodynamic chord (MAC) represets the effective average chord of a wing. On an un-swept, un-tapered wing it's the same as the wing's chord. The 1/4 chord point is a reasonable approximation to the centre of lift. This is the point about which the aircraft will rotate in pitch. However with a swept and tapered wing the the MAC can be taken as the average of the root and tip chords, located halfway along the semi-span as shown in the picture. Its 1/4 chord point can still be taken as an approximation to the centre of lift but is obviously further aft as is expected with a swept wing.Note Microsoft's careful wording in the FSEdit SDK - "Typically .... this point is ... 1/4 chord aft of the leading edge."

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The interesting thing I found with the Aero modeling SDK was the MD83 used a reference point in front of the nose of the aircraft. This was totally different then the SDK instructions. It doesn't make any difference, if one understands how to relate the AERO and visual points together.Most Cessna single engines have the CG measured at the engine side of the firewall.Some helicopters use a point in front of the aircraft where the main rotor blade tip extends.Its all in the reference!!W. Sieffert

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Thanks,that was the diagram I couldn't find and was no longer on the AVSIM server. Saved it now!Ian

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