The example shown in the following figure uses a calculation in the RHS of the assignment to derive the total weight carried by an Aircraft on the FlightPlan, where the total weight equals the weight of the fuel plus the weight of all Cargos onboard plus the empty weight of the Aircraft itself.

Figure 1. A calculation in a nonconditional expression

The portion that converts a fuel load measured in liters—the unit of measure that airlines purchase and load fuel—into a weight measured in kilograms, the unit of measure used for the weight of the cargo as well as the aircraft and crew:

plan.fuel * 0.812

Note that this conversion is conservative because Jet A1 fuel expands as it warms so this figure is at the cool end of its range. This portion is then added to:

load.weight -> sum

which is equal to the sum of all Cargo weights loaded onto the aircraft associated with this flight plan. The final sum of the fuel, cargo, and aircraft weights is assigned to the flight plan's planWeight. Note that parentheses are not required. The calculation will produce the same result without them. The parentheses were added to improve clarity.