Effects of CG Position on Aircraft Performance

Understanding CG Position in Aircraft

The centre of gravity (CG) is the point where the aircraft's total mass is considered to act. Its location along the longitudinal axis is crucial: it must always remain within specified limits for safe operation. CG limits are published in the aircraft's flight manual and are checked using loading graphs or by calculation (CG = sum of moments / total mass).

Effects of Forward CG

A forward CG position increases longitudinal static stability, making the aircraft more resistant to pitch changes. However, this comes at a cost:

• Higher stall speed
• Increased drag and fuel consumption
• Longer take-off and landing distances
• Higher rotation and approach speeds (V1, VR, V2, VREF)
• Reduced rate of climb and ceiling
• Heavier stick forces, making pitch control more difficult

Effects of Aft CG

An aft CG reduces stability but enhances performance:

• Lower stall speed
• Reduced drag and fuel burn
• Shorter take-off and landing distances
• Improved climb performance and higher optimum altitude
• Lighter stick forces, increasing manoeuvrability However, if the CG moves beyond the aft limit, the aircraft can become dangerously unstable, risking loss of control.

Operational Significance

Pilots must ensure the CG remains within limits for all flight phases. The CG position affects pitch control, optimum altitude, and overall aircraft behaviour. Proper mass and balance calculations are a fundamental part of pre-flight planning, directly impacting safety and efficiency.