datum is forward of the main gear center point 30.24 inches. Actual distance between tail gear and main gear center points 360.26 inches. Net weight at right main gear 9,980 pounds. Net weight at left main gear 9,770 pounds. Net weight at tail gear 1,970 pounds. What is the empty weight CG of the aircraft described above?

• A. 60.31 inches
• B. 55.50 inches
• C. 62.75 inches
• D. 59.00 inches

Answer: (A)

The main idea is to find the empty weight center of gravity by summing the moments about the datum and dividing by the total empty weight. Treat each weight on a wheel or gear as acting at its arm, which is the distance from the datum to the point where the weight acts.

First, determine the arms. The datum is forward of the main gear center by 30.24 inches, so the arm for each main gear is 30.24 inches. The distance between tail gear and the main gear centers is 360.26 inches, with the tail gear behind the main gears, so the tail gear arm from the datum is 30.24 + 360.26 = 390.50 inches.

Now compute the moments about the datum:

• Right main gear: 9,980 lb × 30.24 in = 301,795.2 in-lb

• Left main gear: 9,770 lb × 30.24 in = 295,444.8 in-lb

• Tail gear: 1,970 lb × 390.50 in = 769,285 in-lb

Sum of moments = 301,795.2 + 295,444.8 + 769,285 = 1,366,525 in-lb.

Total weight = 9,980 + 9,770 + 1,970 = 21,720 lb.

Empty weight CG = total moment / total weight = 1,366,525 / 21,720 ≈ 62.92 inches aft of the datum (about 62.9 inches).

So the empty weight CG is roughly 62.9 inches aft of the datum (the closest listed value is the one near 62.75 inches). The given option of 60.31 inches does not align with these data.