The total mass of the aircraft can be said to act through one point, called the Centre of Gravity (CG) and the total lift acts through the Centre of Pressure (CP).

The position of the CP changes with speed and as alpha changes, whilst the position of CG changes as load and fuel change. When this happens, new balancing forces and trim changes will be needed.

The relative positions of the CG and CP affect the longitudinal stability of the aircraft. In practice, the CG is usually forward of the CP, thus, the more forward the CG, the more stable the aircraft in pitch. Some stability in pitch is desirable, but not too much, because the extra down force on the elevator effectively adds to the aircraft weight and requires the lift to be increased to counter it. More lift means more drag created by the trim (trim drag) and more drag means higher fuel consumption.

Aircraft manufacturers determine a safe range for the CG. The aft limit is usually just in front of the Centre of Pressure, but it provides less stability than that provided by the forward limit, but a smaller balancing tail moment will be required.

In summary, the effects of a forward CG position are the following:

• Decreases the Rate of Climb and the Climb gradient
• Increases TORR, TODR, ASDR, thus MTOM must be decreased
• The stick forces required will be more
• Rotation will be more difficult
• Stall speed increases, thus ceiling decreases
• Makes flare more difficult during landing, thus increasing LDR and decreasing MLM
• Due to the increased fuel consumption, the fuel mileage (nautical miles covered per kg of fuel mass) decrease