An empty aircraft is weighed with the main gear net weight of 3,540 pounds at an arm of 195.5 inches and the nose gear net weight of 2,322 pounds at an arm of 83.5 inches. The datum line is forward of the nose. What is the empty CG in inches?

• A. 149.0 inches
• B. 151.1 inches
• C. 152.3 inches
• D. 150.5 inches

Answer: (B)

Center of gravity is found by taking the sum of the moments about the datum and dividing by the total weight. Use the arms measured from the datum, with moments in in-lb.

Total weight = 3,540 + 2,322 = 5,862 lb.

Moments:

• main gear: 3,540 × 195.5 = 692,070 in-lb

• nose gear: 2,322 × 83.5 = 193,887 in-lb

Sum of moments = 692,070 + 193,887 = 885,957 in-lb.

CG = 885,957 / 5,862 ≈ 151.1 inches.

The empty CG is about 151.1 inches from the datum line, which lies between the two gear positions and is closer to the heavier main-gear location due to its greater weight.