Experimental aircraft commonly use engines which consume AVgas (Lycoming / Continental / Franklin and equivalent types) or engines running Mogas (Rotax, Subaru, Jabiru etc). Some engines are capable of running either fuel, although with restrictions. Purpose built diesel aircraft engines are designed to use JET and can run on normal diesel too. In this section we delve deeper into aircraft JET fuels also called AVtur.
Diesel is a light oil with density of around 850 gr/l and releases 40,9 MJ of energy per liter. It is obtained at 200 °C to 350 °C in a fractional distillation unit. JET / kerosene is derived from the same source at 150 °C to 275 °C but has 5% less energy.
The basic properties compare so much that either fuel can be used in a diesel engine. Main difference is that the lubrication properties of diesel are much better and as the fuel is sometimes used as lubricant for the high pressure pump, running only on JET can ruin this pump if precautions are not taken.
Mixing JET with about 2 to 5% biodiesel will aid in increasing lubricity for the high pressure fuel pump thereby prolonging engine life.
Todays kerosene fuels have been developed from the illuminating kerosene used in the early gas turbine engines. These engines needed a fuel with good combustion characteristics and high energy content. The kerosene type fuels used in civil aviation nowadays are mainly A-1 and A. The latter has a higher freezing point (maximum minus 40 °C instead of maximum minus 47 °C) and is available only in North America. The color is straw like clear.
Typical JET - Diesel fuel types suitable for aircraft diesel engines are:
Some typical JET - Diesel properties are:
Property | JET A/A-1 | JP-5 | JP-8 | Diesel #1 | Diesel #2 |
API Gravity @ 60°F | 44.3 | 41.1 | 45.6 | 43 | 39 |
Flash point in °C | 38 | 62 | 45 | 38 | 52 |
Viscosity cSt @ 40°C | - | 1.5 | 1.2 | 1.2-2.4 | 1.9-4.1 |
Cloudpoint °C | -40/-47 | -46 | -47 | -7 | -20 |
Sulfur, %mass | 0.3 max | 0.4 max | 0.4 | 0.05 | 0.05 |
Cetane number | - | 42 | 45 | 45-50 | 45-50 |
Heat content Btu/Gallon, Net. | 123608 | 125270 | 123069 | 130000 (typical) | 129500 |
JET / kerosene weighs 6.76 lbs/US gallon or put another way: 0.81 g/ml at standard temperature (15°C).
Learn more by reading about JET-A fuel specifications here, and the details on JP-8 specifications (both by ConocoPhillips).
Detailed information on aviation and diesel fuels in these documents from: Chevron Aviation Fuels or from: AeroShell Aviation Fuels.
Written by EAI.