FAA Private Pilot Airplane (PAR)Performance, Weight and BalanceHard
An airplane weighs 2,400 lb with a CG of 86.0 in. The pilot moves 100 lb of cargo from the aft compartment (arm 150.0 in) to the forward compartment (arm 70.0 in), a shift of 80 in forward. What is the new CG?
- A89.3 in
- B82.7 in
- C86.0 in
- D78.0 in
Show answer & explanationAnswer & explanation
Correct answer: B. 82.7 in
Using the weight shift formula: change in CG = (weight shifted × distance moved) ÷ total weight = (100 × 80) ÷ 2,400 = 3.33 in. Since the weight moved forward, the CG shifts forward: 86.0 − 3.33 = 82.7 in.
Why the other options are wrong
- A. This mistakenly shifts the CG aft instead of forward.
- C. This ignores the effect of moving the cargo entirely.
- D. This overstates the forward shift beyond what the formula produces.
Weight Shift Formula
When weight is moved within an already-loaded airplane, the CG shift can be found without recalculating full moments: shift = (weight moved × distance moved) ÷ total weight.
- Shift direction follows the direction the weight was moved
- Formula: ΔCG = (weight × distance)/total weight
- Faster than recomputing total moment from scratch
Memory trick: Move the box, shift the CG the same way.