Geared turbofan engine and spline arrangement

A geared turbofan engine, comprising:

• a fan stage,
• a fan shaft via which the fan stage is driven,
• a turbine shaft, and
• a planetary gearbox that couples the fan shaft and the turbine shaft to each other, wherein
• the planetary gearbox has a sun gear that rotates about a rotational axis of the geared turbofan engine and is driven by the turbine shaft, wherein the rotational axis defines an axial direction of the geared turbofan engine,
• the turbine shaft forms an outer spline toothing and the sun gear forms an inner spline toothing, and the outer spline toothing and the inner spline toothing form a spline shaft connection of the turbine shaft and the sun gear,
• the spline shaft connection has a toothing area that is lubricated with oil, and
• sealing means are provided, sealing off the oil in the toothing area against axial leaking,
• wherein
• the sealing means have an elastic sealing ring that has variable diameter and is springing outwards, and that is arranged inside a groove that extends in the circumferential direction of the turbine shaft, wherein, with its radially outer circumferential surface, the sealing ring abuts at an inner circumferential surface of the sun gear.