US Patent 11333072 Shaft bearing positioning in a gas turbine engine

An aircraft gas turbine engine has an engine core with a turbine, compressor, and core shaft connecting the turbine to the compressor, a fan upstream of the engine core; and a gearbox. The engine core has three bearings, one forward, two rearward, to support the core shaft, a minor span being the axial distance between the two rearward bearings. A first blade to bearing ratio of the minor span divided by the product of the mass, radius at mid-height, and the square of the angular velocity at cruise for a blade of the lowest pressure set may have a value in the range from 2.0×10