A pilot is planning a flight and determines the aircraft's total weight is 2,200 lbs with a center of gravity (CG) at 82.0 inches aft of the datum. To bring the CG within limits, 50 lbs of baggage must be moved. If the baggage is moved from a station at 95.0 inches aft to a station at 65.0 inches aft, what is the new CG of the aircraft?
- A80.6 inches aft
- B83.1 inches aft
- C82.7 inches aft
- D81.3 inches aft
Show answer & explanationAnswer & explanation
Correct answer: D. 81.3 inches aft
First, calculate the original total moment: 2,200 lbs * 82.0 in = 180,400 lb-in. Next, calculate the moment change due to moving the baggage. The change in arm is 95.0 in - 65.0 in = 30.0 in. Since the baggage is moved forward, the moment decreases. The change in moment is 50 lbs * 30.0 in = 1,500 lb-in (subtracted). The new total moment is 180,400 lb-in - 1,500 lb-in = 178,900 lb-in. The total weight remains 2,200 lbs. The new CG is 178,900 lb-in / 2,200 lbs = 81.318 inches, which rounds to 81.3 inches aft.
Why the other options are wrong
- A. Incorrect calculation; potential error in the moment change or final division.
- B. Incorrect calculation; likely an error in the moment change or its application.
- C. This would be the result if the baggage was moved aft instead of forward, or if the moment change was added instead of subtracted.
Weight Shift CG Change
Moving weight within an aircraft changes its center of gravity. The amount of CG shift depends on the weight moved and the distance it's moved.
- CG shift = (Weight moved × Distance moved) / Total weight.
- If weight moves forward, CG moves forward.
- If weight moves aft, CG moves aft.
- Used to adjust CG to be within limits without changing total weight.
Memory trick: Move Weight, Shift CG: Moment change, divide by total.