Fuel density, expressed either in kilograms per litre or pounds per US gallon.
The discriminated shape forces the call site to name its unit explicitly. This
prevents the classic silent bug where a caller passes a bare density number in the
wrong unit (lb/gal and kg/L differ by a factor of ~0.12) and gets a plausible-looking
but badly wrong weight. US flight-planning materials typically publish fuel density
in lb/gal; SI and European sources use kg/L.
Fuel density, expressed either in kilograms per litre or pounds per US gallon.
The discriminated shape forces the call site to name its unit explicitly. This prevents the classic silent bug where a caller passes a bare density number in the wrong unit (lb/gal and kg/L differ by a factor of ~0.12) and gets a plausible-looking but badly wrong weight. US flight-planning materials typically publish fuel density in
lb/gal; SI and European sources usekg/L.