A gas turbine engine comprising: a compressor section; a combustor in fluid communication with the compressor section; a turbine section in fluid communication with the combustor, the turbine section including a fan drive turbine and a second turbine, the fan drive turbine having exactly three turbine stages; a fan including a plurality of blades rotatable about an axis; and a speed change system driven by the fan drive turbine for rotating the fan about the axis, wherein the fan drive turbine includes a first aft rotor attached to a first shaft and the second turbine includes a second aft rotor attached to a second shaft and an annular space is defined between the first shaft and the second shaft, wherein the compressor section comprises a first compressor driven by the fan drive turbine through the first shaft and a second compressor driven by the second turbine through the second shaft, characterised in that: a first bearing assembly is disposed axially aft of a first connection between the first aft rotor and the first shaft, wherein the first bearing assembly supports an aft portion of the first shaft, a second bearing assembly is disposed within the annular space defined between the first shaft and the second shaft, wherein the second bearing assembly supports an aft portion of the second shaft on the first shaft; the fan has 18 or fewer blades; and a ratio between the number of fan blades and the number of fan drive turbine stages is between 2.5 and 8.5. a compressor section; a combustor in fluid communication with the compressor section; a turbine section in fluid communication with the combustor, the turbine section including a fan drive turbine and a second turbine, the fan drive turbine having exactly three turbine stages; a fan including a plurality of blades rotatable about an axis; and a speed change system driven by the fan drive turbine for rotating the fan about the axis, wherein the fan drive turbine includes a first aft rotor attached to a first shaft and the second turbine includes a second aft rotor attached to a second shaft and an annular space is defined between the first shaft and the second shaft, wherein the compressor section comprises a first compressor driven by the fan drive turbine through the first shaft and a second compressor driven by the second turbine through the second shaft, characterised in that: a first bearing assembly is disposed axially aft of a first connection between the first aft rotor and the first shaft, wherein the first bearing assembly supports an aft portion of the first shaft, a second bearing assembly is disposed within the annular space defined between the first shaft and the second shaft, wherein the second bearing assembly supports an aft portion of the second shaft on the first shaft; the fan has 18 or fewer blades; and a ratio between the number of fan blades and the number of fan drive turbine stages is between 2.5 and 8.5. a first bearing assembly is disposed axially aft of a first connection between the first aft rotor and the first shaft, wherein the first bearing assembly supports an aft portion of the first shaft, a second bearing assembly is disposed within the annular space defined between the first shaft and the second shaft, wherein the second bearing assembly supports an aft portion of the second shaft on the first shaft; the fan has 18 or fewer blades; and a ratio between the number of fan blades and the number of fan drive turbine stages is between 2.5 and 8.5.