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A few notes about CG: A speed stable aircraft will have it's trim vary a bit over the speed range. If it did not it would not be speed stable, dropping the nose with loss of airspeed and tending nose rise with increasing airspeed. CG changes with loading and often with fuel consumption. So there is no perfect CG that remains involiate.
With an aft CG longitudinal stability is reduced, and can become negative! Forward CG requires a large tail downforce and is very stable, perhaps so stable as to not reduce manuvering capibility, such as being able to execute a flair on landing. FS does not directly model tail force and CG stability, but applies modifiers to the wing moment.
So a plane with a CG such that it requires zero trim for takeoff or iniial climb will have to be trimmed for cruise, and on and on. It really is a matter of coming up with a CG that works for the range of possible loadings and stays within the handling envelope for various speeds and manuvers. Fighter aircraft with straight wings tend to have little CG movement, depending on location of droppables and ammunition and their location. Some fighters such as the P-51 that had aft fuselage tanks had quite a CG movement during flight. A good thing as the handling was quite poor with the initial aft CG. A transport aircraft, such as the DC2, that I worked on, required consultation of a load sheet to set the proper trim setting for takeoff, as loading over a long fuselage could result in widely varying CG's and trim values. By contrast the F4U had most of it's consumables and fuel near the CG and a takeoff set of trim settings could generally be specified.
So the question remains, where in the speed range do you desire the plane to be a zero trim?
Cheers: Tom
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