What is the center of gravity (CG) and why must flights stay within the CG envelope?

• A. CG is the center of gravity
• B. The CG is the point where the aircraft's weight acts; staying within envelope ensures stable handling, adequate elevator authority, and predictable stall characteristics
• C. CG is the aircraft's aerodynamic center
• D. CG is the center of lift

Answer: (B)

The center of gravity is the balance point where the aircraft’s weight effectively acts. Because the entire airplane will rotate about this point, its position relative to the lifting surfaces changes how stable the airplane is and how much elevator authority you have to pitch it up or down. If the CG is too far forward, the ship tends to nose down and you’ll need more elevator to raise the nose or recover from a stall; if it’s too far aft, the airplane can become unstable and you may not have enough elevator authority to control or recover from unusual attitudes. The CG envelope sets safe weight and balance limits so that, in all loading and fuel situations, you retain stable handling, enough elevator authority, and predictable stall characteristics. The center of gravity is not the aerodynamic center nor the center of lift—the latter two move with angle of attack and describe lift and pitching moments, whereas the CG is the fixed weight balance point.