Question

For an airplane to be statically stable, its centre of gravity must always be

• A. ahead of wing aerodynamic centre
• B. aft of the wing aerodynamic centre
• C. ahead of neutral point
• D. aft of neutral point

Hint:

Neutral point is CG position where static margin is zero — stable aircraft have CG ahead of it.

Answer 1

The Correct Option is C

To understand why an airplane's center of gravity (CG) must be positioned in a specific location to maintain static stability, we must first comprehend the concepts of aerodynamic center and neutral point.

The aerodynamic center is the point on the wing or airfoil where the pitching moment coefficient remains constant regardless of the angle of attack. It is typically located near the quarter-chord point of the wing.

The neutral point is the aftmost CG location where the airplane remains statically stable. If the CG were at the neutral point, any shift aft would make the airplane neutrally stable—or even potentially unstable.

For an airplane to be statically stable, its center of gravity must be positioned such that an increase in angle of attack results in a restoring moment. This means the CG should be ahead of the neutral point.

Therefore, the correct statement is that for static stability, an airplane's center of gravity must always be ahead of the neutral point.