Weight Model

Weight & Balance Summary

SummaryLoad an aircraft

Choose or drop a JET11 fileExcel .xlsm/.xlsx or JET JSON export

Load a JET11 file to calculate the CG envelope.

Editable weight locations · top view

Load an aircraft to position editable weights.

Marker centers use equal-scale aircraft X/Y coordinates in feet. Wheel to zoom; double-click to reset.

Static-margin travel through flight

Forward, aft, and nominal CG paths will appear here.

The envelope independently varies every element categorized as fuel or expendable payload from its imported value to zero. The nominal path burns all fuel elements proportionally and releases expendable payload at 50% fuel remaining. Land w/ Payload retains all expendable payload through landing. Trapped Fuel holds one named tank full while the other tanks drain nominally; payload release remains at 50%.

Weight calculation

Item name	Weight calculation					Volume calculation
Item name	Reference meas.	×	Weight factor	=	Calculated weight	Reference meas.	×	Volume factor	=	Calculated volume
No file loaded

Amber inputs are overrides; clear an amber field to restore the ordinary model. Blank volume cells mean no volume model is provided. Yellow rows are expendable items used for the CG envelope.

Weight model configuration & references

Usable fuselage volume assumptions

Geom!S47 is a total-aircraft loft volume: its station areas sum fuselage, wing, pitch-control, vertical-tail, nacelle, and strake contributions. This calculation intentionally isolates the fuselage outer mold line before deducting the inlet path.
Gross volume is integrated from the actual fuselage-section perimeter polygons, not width-by-height approximations. Current JET11 loft sections and AircraftDesigner's FUSELAGE.Definition.Type = "Spline" format are both accepted.
Only the inlet flow path through the compressor-face station that intersects the fuselage is removed. A uniform 2-inch sleeve is added around that flow path before intersection; inlet volume outside the fuselage is not deducted.
Overlapping twin inlet branches are treated as a union so their merged region is not subtracted twice.
The default 0.80 packing factor is applied after the inlet deduction. It is an early-design allowance for structure, pumps, baffles, lines, access, and unusable pockets; replace it with a layout-derived value as the design matures.
Virginia Tech aircraft-design guidance, citing Nicolai and Carichner, gives preliminary fuel packaging factors of 0.80 for a shallow integral fuselage tank, 0.85 for a deep integral fuselage tank, and 0.75 for a fuselage bladder tank. This tool uses 0.80 as the conservative initial setting.
NASA OpenVSP fuselage guidance supports defining smooth fuselage bodies from positioned cross-sections and skinning; the spline adapter follows that section-based geometry approach.
An explicit Weight.Fuselage.Model.Overrides.Volume value from a future detailed packaging model takes precedence.

Shared weight-model factors

Average Component Weight Charts

Table 8.1 · Structural weights

Table 8.2 · Component weight fractions

Shared parameters are stored in WeightModel; each element stores its calculation and optional overrides in Weight.<element>.Model. The inlet flow path is excluded from fuselage usable volume and is not also counted as a separate volume item.

Static margin = (neutral point - CG) / MAC. Positive values place the CG ahead of the neutral point.