An aircraft with an empty weight of 1800 lbs and an empty weight CG of +31.5 inches was altered as follows: two 15-lb pax seats located at +72 were removed; structural modifications increasing the weight by 14 lbs at +76; a seat and safety belt weighing 20 lbs were installed at +73.5; radio equipment weighing 30 lbs was installed at +30. What is the new empty weight CG?

An aircraft with an empty weight of 1800 lbs and an empty weight CG of +31.5 inches was altered as follows: two 15-lb pax seats located at +72 were removed; structural modifications increasing the weight by 14 lbs at +76; a seat and safety belt weighing 20 lbs were installed at +73.5; radio equipment weighing 30 lbs was installed at +30. What is the new empty weight CG?

• A. +31.61 inches
• B. +31.00 inches
• C. +32.10 inches
• D. +30.90 inches

Answer: (A)

Calculating the new empty-weight CG means updating weight and moment and then dividing the total moment by the new empty weight. The aircraft starts with 1,800 lb and a moment of 1,800 × 31.5 = 56,700 in-lb. Changes in weight and moment: - Remove two 15-lb seats at +72: weight −30 lb, moment −30 × 72 = −2,160 in-lb. - Structural modifications add 14 lb at +76: weight +14 lb, moment +14 × 76 = +1,064 in-lb. - Install seat and belt 20 lb at +73.5: weight +20 lb, moment +20 × 73.5 = +1,470 in-lb. - Install radio 30 lb at +30: weight +30 lb, moment +30 × 30 = +900 in-lb. Net change: weight +34 lb, moment +1,274 in-lb. New empty weight = 1,800 + 34 = 1,834 lb. New total moment = 56,700 + 1,274 = 57,974 in-lb. New CG = 57,974 / 1,834 ≈ 31.616 inches, i.e., +31.61 inches. This value matches the option listed as +31.61 inches. The CG shifts aft slightly because the net moment increased.

Calculating the new empty-weight CG means updating weight and moment and then dividing the total moment by the new empty weight. The aircraft starts with 1,800 lb and a moment of 1,800 × 31.5 = 56,700 in-lb.

Changes in weight and moment:

• Remove two 15-lb seats at +72: weight −30 lb, moment −30 × 72 = −2,160 in-lb.

• Structural modifications add 14 lb at +76: weight +14 lb, moment +14 × 76 = +1,064 in-lb.

• Install seat and belt 20 lb at +73.5: weight +20 lb, moment +20 × 73.5 = +1,470 in-lb.

• Install radio 30 lb at +30: weight +30 lb, moment +30 × 30 = +900 in-lb.

Net change: weight +34 lb, moment +1,274 in-lb. New empty weight = 1,800 + 34 = 1,834 lb. New total moment = 56,700 + 1,274 = 57,974 in-lb.

New CG = 57,974 / 1,834 ≈ 31.616 inches, i.e., +31.61 inches. This value matches the option listed as +31.61 inches. The CG shifts aft slightly because the net moment increased.