The technologies being developed for the next-generation fuel-efficient propulsion systems – and whose progress Airbus follows closely – are taking shape at all the big aero-engine makers, here we focus on one of these: CFM International’s “open fan” technology. The open fan architecture is a key component of the engine maker’s “Revolutionary Innovation for Sustainable Engines” (RISE) technology development programme – which aims to demonstrate and mature a range of new technologies for future engines that could enter service by the mid-2030s. (....)