Pilot One Academy
Aircraft weight and balance: a step-by-step PPL guide
Quick answer
Weight and balance means checking that aircraft mass and centre of gravity (CG) stay within approved limits throughout the flight. Each load's moment is its mass multiplied by its arm; CG is total moment divided by total mass. Compare the result with the actual aircraft's approved envelope.
Weight, arm and moment
The arm is the distance from the manufacturer's reference datum to a load's centre. Moment is mass × arm. Total mass includes the documented basic empty mass, occupants, baggage and fuel as specified by the manufacturer. CG is the balance point, not necessarily the geometric centre.
Worked example
These figures are invented for teaching and do not describe a real aircraft. All arms use the same datum.
| Item | Mass (kg) | Arm (m) | Moment (kg·m) |
|---|---|---|---|
| Empty aircraft | 600 | 1.0 | 600 |
| Occupants | 150 | 1.2 | 180 |
| Baggage | 20 | 2.0 | 40 |
| Fuel | 60 | 1.1 | 66 |
| Total | 830 | — | 886 |
CG = 886 / 830 = 1.067 m from the datum. This alone does not prove the load is permitted or safe: plot mass and CG on the approved envelope and check compartment, take-off and landing limits.
Before flight
- Use the current empty-weight record and AFM/POH for the individual aircraft.
- Record actual masses and the manufacturer's arms or indices. Keep units and signs consistent.
- Total mass and moments, calculate CG and check the envelope for relevant phases, including fuel burn.
- If a limit is exceeded, change the load or plan and recalculate. Being below maximum mass does not guarantee an acceptable CG.
- Calculate performance separately for the expected conditions; an acceptable loading does not guarantee sufficient runway.
Frequently asked questions
Why does an out-of-limit CG matter?
It can affect stability and control. A forward CG can make rotation or landing more difficult; an aft CG can reduce stability and make stall recovery harder.
Can CG change in flight?
Yes, as fuel is consumed. The effect depends on tank locations and aircraft configuration; check the landing case using the manual.
Can I use a generic calculator?
It can help learning, but use current data and limits for the individual aircraft and check the result against the approved method and your instructor.
Sources and resources
The FAA Weight and Balance Handbook explains arms, moments and CG. Practise related concepts in the PPL question bank. This educational guide does not replace the aircraft manual or flight instruction.
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