The Swedish Defence Materiel Administration (Försvarets materielverk, FMV) project which evaluates biofuels in bilateral cooperation with the United States has taken another step. This time, it was a biofuel produced by Swedish Biofuels that was tested in the Saab JAS 39 Gripen multirole fighter aircraft engine RM12 at GKN’s facility in Trollhättan. Prior to the test, FMV, with the help of the Swedish Armed Forces (Försvarsmakten) mixed the biojet fuel in barrels with the Swedish Armed Forces’ standard fuel Flygfotogen 75 into a 50/50 mixture. Swedish Defence Materiel Administration analyzed the mixture to be able to verify that it was approved to be delivered to the engine test at GKN by tanker. No change in thrust or fuel consumption was detected. Following the current FOI exam, 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.
The biofuel based on alcohol was mixed in the ratio 50/50 with the normal fuel for the Gripen engine RM 12, known as Flygfotogen 75. A 50% mixture of biofuel is today the highest permitted according to the fuel specifications for aviation fuel. The test was the first where this particular biofuel was tested in a larger aircraft engine. The test was carried out in a test rig at the company GKN Aerospace Engine Systems Sweden in Trollhättan. In total, the engine was run for almost three hours with a 50/50 mix. After several engine starts and ignitions of the afterburner, the engine worked without remarks. No warnings or indications emerged that could be due to differences between the different fuels. The Swedish Armed Forces’ Materiel Administration procures, develops and delivers materiel and services to the Swedish Armed Forces. This is how Swedish Armed Forces meet the needs of the Swedish defense – in peace, crisis and war. Final report to the Armed Forces will take place in 2021.
In total, the engine was run with 50/50 mixture for 2 hours and 49 minutes, of which 14 minutes with lit afterburner, eight engine starts and 25 ignitions of the afterburner. In the test, which was carried out in GKN Aerospace Systems’ test rig in Trollhättan, engine function and engine performance were compared with a 50/50 mixture of a Swedish biofuel and Flygfotogen 75 with only aviation kerosene. Briefly, the results from the tests with the 50/50 mixture compared to Flygfotogen 75 showed:
— Very similar thrust and fuel consumption in relation to thrust and times for engine transition;
— No indications of combustion-related pressure disturbances
— Same characteristics for engine start and restart.