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FMV tests Swedish biojet fuel in Gripen RM12 engine

The Swedish Defence Materiel Administration (FMV) has provided an update surrounding biojet fuel testing as part of a bilateral Biojet-project collaboration between FMV and USAF/NAVAIR. Biojet fuel produced by Swedish Biofuels AB and blended 50/50 with Jet A1 was tested in the Gripen engine RM12 at GKN Aerospace Engine Systems Sweden AB facilities in Trollhättan. No change in traction and fuel consumption was detected.

Full testing of the 50/50 biojet blend at GKN Aerospace Engine Systems Sweden’s test rig in Trollhättan (photo courtesy GKN).

The biojet fuel provided by Swedish Biofuels is an alcohol-to-jet (ATJ-SKA) type fuel and was blended in the ratio 50/50 with the normal fuel for the Gripen engine RM 12 which is Jet A1 (Flygfotogen 75 – FF75). A 50 percent biojet blend is the highest permitted according to current international fuel specifications for aviation fuel.

The test was the first where this particular biofuel was tested in a larger aircraft engine.

The purpose of the test was to study any differences between the 50/50 mixture and Flygfotogen 75 with regard to engine function and engine performance, said Erik Prisell, a specialist in air propulsion systems at FMV.

The test was carried out in a test rig at GKN Aerospace Engine Systems Sweden, a GKN Aerospace Services Ltd company, in Trollhättan. In total, the engine was run for almost three hours with a 50/50 blend.

The engine performed without anything to remark on. No warnings or indications emerged that could be due to differences between the different fuels, Erik Prisell concluded after several engine starts and ignitions of the afterburner.

After the test, the combustion chamber of the engine core was inspected and no signs could be seen that the 50/50 blend had affected the combustion chamber. Briefly, the results from the tests with the 50/50 biojet blend compared to neat FF75 showed:

  • Very similar traction, fuel consumption in relation to traction, and times for engine transients;
  • No indications of combustion-related pressure disturbances;
  • Same characteristics for engine start and restart

Following the current Swedish Defence Research Agency (FOI) examination, which ends in the first quarter of 2021, FMV’s biojet project will carry out an evaluation and compilation together with its US partners USAF/NAVAIR.

A final report to the Swedish Armed Forces will take place in 2021.

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