Heavy-fuel engine is a manufacturer of compression-ignition and spark-ignition engines that run on diesel and kerosene-based aviation fuels. A heavy-fuel engine (HFE) runs on the heavier distillates: diesel and kerosene-based aviation fuels such as Jet A-1 or the military JP-8. Many military and civil operators prefer a single fuel for all equipment, and kerosene has a higher flash point than gasoline, which lowers fire risk during storage and handling.
Two routes exist. Compression-ignition engines (diesel cycle) burn these fuels naturally and give the lowest BSFC among piston engines. Spark-ignition engines, including rotary designs, can be adapted with heated intake, fuel injection and modified ignition to burn them, at the cost of less efficient combustion, usually a higher BSFC than on gasoline, and more care over cold starts and cooling.
Heavy-fuel engines are used as the prime mover for long-endurance fixed-wing and large rotary-wing unmanned aircraft, and as the generator engine in series hybrid propulsion for heavy-lift drones and eVTOL concepts.
On a datasheet check the approved fuels list (for example Jet A-1, JP-5, JP-8, diesel), the rated power in kW and rpm, BSFC, dry mass, cold-start limits, altitude rating and time between overhauls. Also check the oil type and consumption.
A frequent mistake is assuming that an engine marketed as multifuel performs equally on all fuels. Power, BSFC and overhaul interval are normally stated for one reference fuel, and other fuels may need derating or different lubricants. Verify the fuel on which the quoted figures were measured.
