As the wing tanks fuel is consumed during flight, the CG moves aft towards the trim tank (since the fuel in the trim tank is isolated and not being burnt - resulting in a tail-heavy situation).

An aircraft with forward CG is “heavier” and consequently, slower than the same aircraft with the CG further aft. For a forward CG location, a “nose-up” trim is required in most aircraft to maintain level cruising flight. Nose-up trim involves setting the tail surfaces to produce a greater down load on the aft portion of the fuselage, which adds to the wing loading and the total lift required from the wing if altitude is to be maintained. This requires a higher AOA (Angle of Attack) of the wing, which results in more drag and, in turn, increases fuel burn and reduces flight range. Furthermore, if the CG moves forward, the airplane becomes more stable. A forward CG with the increase in stability will make it easier to recover from a stall. However, maneuverability will be reduced.

• The opposite occurs for an Aft CG location. For the same aircraft, an aft CG location results in an increased flight range and maneuverability, and a decrease in drag. However, in this case, fuel will be isolated in the trim tank and the aircraft will be unable to use it. Therefore, flight range will be reduced.

Note that Increasing stability about any axis decreases manoeuvrability and controllability, and increases stick (or pedal) forces.

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