Sustainable aviation fuels for helicopters: Challenges, opportunities, way forward

Abstract

Reduction of CO2 emissions is key in limiting the effect of climate change and Sustainable Aviation Fuel (SAF) is one of the major enablers to achieve the challenging targets of the aeronautical industry. Since the use of blended SAF with conventional JET A-1 is already approved at a ratio of up to 50%, it is necessary to look ahead to understand how to make daily 100% SAF flight possible. Both drop-in and non drop-in pathways can be envisaged. The latter offers additional opportunities, like reduction of non CO2 emissions, but also presents additional challenges. A first flight on a H225 helicopter using 100% HEFA fuel on one engine was performed in November 2021 followed by a second flight in May 2022 using 100% SAF on both engines. Preliminary findings indicate that even if the overall behavior was found acceptable, and that no immediate detrimental effect of the 100% HEFA fuel was observed, some differences in the engine gas turbine temperature dynamics during starting phases, or in the helicopter gauging system were identified. Some were expected due to the fuel characteristic differences, others were not and will need further investigations. In addition, mid and long term impacts of a daily usage of 100% SAF need to be further assessed. Airbus Helicopters already identified several topics among which are engine operation, gauging systems, material compatibility, fuel flammability and volatility, or flame characteristics. Airbus Helicopters’ roadmap to achieve 100% SAF by the end of the decade does not privilege any solution and considers both drop-in and non drop-in pathways. For the first one, activities are centered on the work performed by the existing ASTM task force while for the second one, synergies within Airbus Group will be used to further investigate on the main topics identified previously.