An aircraft had an empty weight of 2,886 pounds with a moment of 101,673.78 before several alterations were made. The alterations included: removing two passenger seats (15 pounds each) at +71; installing a cabinet (97 pounds) at +71; installing a seat and safety belt (20 pounds) at +71; and installing radio equipment (30 pounds) at +94. The alterations caused the new empty weight CG to move

• A. 1.62 inches aft of the original empty weight CG
• B. 0.75 inches aft
• C. 2.50 inches aft
• D. 0.25 inches forward

Answer: (A)

The reason the CG moves is that the alterations change both the total weight and the moment the aircraft carries. To see the shift, add up the weight changes and the moment changes from all modifications, then recalculate the CG with the new weight and new moment.

Original data: empty weight 2,886 lb with a moment of 101,673.78 lb-in.

Alterations:

• Remove two seats (30 lb total) at +71: moment change = -30 × 71 = -2,130

• Cabinet addition (97 lb) at +71: moment change = +97 × 71 = +6,887

• Seat and safety belt (20 lb) at +71: moment change = +20 × 71 = +1,420

• Radio equipment (30 lb) at +94: moment change = +30 × 94 = +2,820

Net weight change = -30 + 97 + 20 + 30 = +117 lb

Net moment change = -2,130 + 6,887 + 1,420 + 2,820 = +8,997 lb-in

New weight = 2,886 + 117 = 3,003 lb

New moment = 101,673.78 + 8,997 = 110,670.78 lb-in

Original CG = 101,673.78 / 2,886 ≈ 35.23 inches

New CG = 110,670.78 / 3,003 ≈ 36.85 inches

Shift in CG = 36.85 − 35.23 ≈ 1.62 inches aft

So the alterations move the empty weight CG about 1.62 inches aft.