Weight, Arm, and Moment Calculator
| Item | Weight (lbs) | Arm (in) | Moment (lb-in) |
|---|---|---|---|
| Front Seats | |||
| Rear Seats | |||
| Total |
Here’s a comprehensive table summarizing the key concepts of Weight, Arm, and Moment in aviation weight and balance calculations:
| Concept | Definition | Formula | Unit | Notes |
|---|---|---|---|---|
| Weight | The force exerted by gravity on an object | – | Pounds (lbs) | Sum of all weights = Total Weight |
| Arm | The horizontal distance from the datum to the center of gravity of an item | – | Inches (in) | Datum is a reference point chosen by the manufacturer |
| Moment | The product of weight and arm, representing the item’s tendency to rotate the aircraft around the center of gravity | Moment = Weight × Arm | Pound-inches (lb-in) | Often divided by 100 or 1000 for simplification |
| Center of Gravity (CG) | The point at which the aircraft would balance if suspended | CG = Total Moment ÷ Total Weight | Inches from datum | Must be within the aircraft’s CG limits |
| Datum | An imaginary vertical plane from which all horizontal distances are measured | – | – | Often at or near the nose of the aircraft |
| Station | A specific location in the aircraft, measured as its distance from the datum | – | Inches (in) | Used to determine arms for various items |
| Moment Index | Simplified moment value to make calculations easier | Moment ÷ 100 or 1000 | – | Check the aircraft’s manual for the correct index |
To calculate weight and balance:
- List all items (aircraft empty weight, fuel, passengers, cargo, etc.)
- Determine the weight of each item
- Find the arm for each item (usually provided in the aircraft manual)
- Calculate the moment for each item (Weight × Arm)
- Sum up all weights and all moments
- Divide total moment by total weight to find the CG location
- Verify that the CG is within the aircraft’s allowable range
Remember to always refer to the specific aircraft’s Pilot’s Operating Handbook or Weight and Balance Manual for accurate data and procedures.