Geared gas turbine engine

A gas turbine engine for an aircraft comprising:

• an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
• a fan located upstream of the engine core, the fan comprising a plurality of fan blades;
• and
• a gearbox that is configured to receive an input from the core shaft, and output drive to a fan shaft via an output of the gearbox so as to drive the fan at a lower rotational speed than the core shaft;
• wherein:
• the fan shaft connects the output of the gearbox to the fan;
• a gearbox output position is defined as a point of connection between the fan shaft and the gearbox;
• the fan has an axial centreline;
• a fan-gearbox axial distance is defined as an axial distance between an axial position of the gearbox output position and the axial centreline of the fan;
• and
• the fan-gearbox axial distance divided by a moment of inertia of the fan is in a range from 5.3×10−10 m/kgmm2 to 8.8×10−9 m/kgmm2.

A gas turbine engine for an aircraft comprising:

• an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
• a fan located upstream of the engine core, the fan comprising a plurality of fan blades;
• and
• a gearbox that is configured to receive an input from the core shaft, and output drive to a fan shaft via an output of the gearbox so as to drive the fan at a lower rotational speed than the core shaft;
• wherein:
• the fan shaft connects the output of the gearbox to the fan;
• and
• a product of:
• (the radial bending stiffness of the fan shaft at the output of the gearbox)×(the moment of inertia of the fan)
• is in a range from 2.0×1014 Nkgmm2m−1 to 1.4×1018 Nkgmm2m−1.