What is the total moment for the baseline configuration with full fuel?

• A. 180,000 in-lb
• B. 136,080 in-lb
• C. 170,640 in-lb
• D. 159,000 in-lb

Answer: (C)

Total moment comes from adding up the moments of every item about the reference datum. A component’s moment is simply its weight multiplied by its arm (in-lb). In the baseline configuration with full fuel, you include the full fuel weight at its designated arm plus the moments of all other standard items (empty airplane weight, crew, baggage, etc.). Sum all those individual moments to get the overall moment for the configuration. When you do that with the given data, the total moment comes out to 170,640 in-lb. This quantity is what you use, along with the total weight, to locate the center of gravity. If the fuel amount changed, the fuel’s weight would change and so would its contribution to the total moment, shifting the CG accordingly.