Aircraft Useful Load vs Payload vs Fuel
Useful load describes how much weight can be added to the aircraft above its defined empty weight before reaching a specified maximum weight. That available weight must be shared among people, baggage, fuel and other items.
Useful load
A common relationship is useful load = maximum allowable weight − empty weight, but the exact definitions depend on the aircraft's approved records and the weight limit being considered.
Payload
Payload usually refers to people, baggage or cargo carried for the mission. It is not always defined identically in every operating context, so use the definition required by the aircraft or operator.
Fuel is part of the loading tradeoff
Adding fuel uses some of the same available weight that could otherwise be used for passengers or baggage. “Full fuel” and “full seats” are not automatically compatible.
900 pounds of useful load, 650 pounds of payload
If an aircraft has 900 pounds of useful load and the people plus baggage total 650 pounds, only 250 pounds remain before reaching that weight limit. The fuel volume that fits within 250 pounds depends on fuel type and density.
Finish the loading example
With 250 lb remaining after people and baggage, an assumed 6 lb/U.S. gal fuel density allows 250 ÷ 6 = about 41.7 U.S. gal by weight. If the airplane carries 50 gal, that fuel weighs 300 lb and exceeds the remaining allowance by 50 lb.
Reducing fuel is not automatically an acceptable solution. Determine the fuel required for the actual flight first, then adjust the mission, payload or aircraft if both fuel and loading requirements cannot be met. Also check usable tank capacity, baggage limits, station moments and CG through fuel burn.
The 6 lb/gal value is an example density, not a universal loading instruction. See the FAA Pilot’s Handbook of Aeronautical Knowledge, Chapter 10 for weight-and-balance principles and use the actual aircraft records for the numbers.
CG matters too
Even when total weight is acceptable, passenger, baggage and fuel locations create moments that can move the CG outside the approved envelope. Weight and balance must be solved together.
Different maximum weights may apply
Aircraft may have different ramp, takeoff or landing weight limits. A loading condition that is acceptable at one phase may require planned fuel burn before another phase.
Related PilotDesk guides
Fuel weight · W&B envelope · Weight conversions