Gas turbine engine and method for introducing oil in a gearbox arrangement

A gas turbine engine for an aircraft, having:

• an engine core which comprises a turbine, a compressor and a turbine shaft which connects the turbine to the compressor and which is in the form of a hollow shaft;
• a fan which is positioned upstream of the engine core, wherein the fan comprises multiple fan blades;
• and
• a gearbox which receives an input from the turbine shaft and which outputs drive for the fan for the purposes of driving the fan at a lower rotational speed than the turbine shaft, wherein
• the gearbox has a sun gear which is driven by the turbine shaft, and
• the turbine shaft and the sun gear form a spline connection which is lubricated with oil,
• wherein the turbine shaft has, on its radially inner side, at least one indentation which is suitable for receiving oil, and the turbine shaft has at least one bore which extends from the indentation to the radially outer side of the turbine shaft and which is suitable for transporting oil from the at least one indentation to the radially outer side of the turbine shaft as the turbine shaft rotates.