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Old 26th December 2016 | 16:02
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Genghis the Engineer
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At forward CG you have increased longitudinal static stability gradients, and generally speaking an increased directional static stability gradient and margin also.

Further aft, the reduction in LSS gradient as the CG approaches the neutral point, so the elevator displacements to give a required airspeed or Nz change will also reduce. One impact on this, particularly with an old fashioned reversible controlled aeroplane is reduced stick force per g. That is termed "manoeuver stability", but to equate it directly to manoeuverability is overly simplistic

Directionally, things are a bit more complex. With a further aft CG, the directional static stability reduces. This will tend to have no advantage for manoeuverability, it will have impact on other things. The aeroplane has a reduced correcting yawing moment in the event of sideslip. The impact of that is greater need for active rudder input to ensure zero sideslip in turns, but it is easier to fly deliberate sideslip if you want it. A further and undesirable secondary effect of this is that the wing drop at the stall tends also to be greater (you can take my word for that, but I doubt you'll find it in any ATPL textbooks).

If you want to go into this in more depth than the acceptable, but admittedly superficial treatment of most ATPL courses, Anderson's "Introduction to Flight" is the best and most accessible book widely used at present in university undergraduate courses (and vastly more accessible than Houghton's "Aerodynamics for Engineering Students" that I learned from a quarter century ago.)

https://www.amazon.com/Introduction-...HJZ0KG09FHMHN4
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