A fan assembly comprising: a fan rotor comprising a hub, and a fan stage having a plurality of fan blades, each blade extending radially outward from the hub and arranged circumferentially around a longitudinal axis; an arcuate platform located on each fan blade at a radially outward portion of the fan blade, such that a portion of an annular fan inner flow path is defined in the fan assembly between the hub and the arcuate platform wherein the fan blade is adapted to increase the pressure of a fan flow stream flowing through the annular flow path; and an outer fan system comprising an outer fan first stage having at least one outer fan first blade extending radially outward from the arcuate platform and an outer fan second stage comprising at least one outer fan second blade extending radially outward from the arcuate platform and located axially aft from the outer fan first stage; characterized in that the fan assembly further comprises: a convertible fan system operable to provide a variable fan pressure ratio while an incoming airflow to the convertible fan system remains substantially constant; the convertible fan system having a convertible fan located aft of and connected to the fan stage having the plurality of fan blades; the convertible fan having a plurality of convertible fan blades arranged circumferentially around a longitudinal axis on a convertible fan hub; the convertible fan system further having an annular splitter located axially forward from the convertible fan blades and operable to split the incoming flow into an inner flow and an outer flow; wherein each of the convertible fan blades has a radially inner portion and a radially outer portion separated by an arcuate shroud, wherein the inner portion is operable to pressurize the inner flow and the outer portion is operable to pressurize the outer flow; and the convertible fan system further having a convertible fan vane system located axially forward from the convertible fan, the convertible fan vane system having outer vanes operable to change a direction of at least a portion of the outer flow and inner vanes operable to change a direction of at least a portion of the inner flow. a fan rotor comprising a hub, and a fan stage having a plurality of fan blades, each blade extending radially outward from the hub and arranged circumferentially around a longitudinal axis; an arcuate platform located on each fan blade at a radially outward portion of the fan blade, such that a portion of an annular fan inner flow path is defined in the fan assembly between the hub and the arcuate platform wherein the fan blade is adapted to increase the pressure of a fan flow stream flowing through the annular flow path; and an outer fan system comprising an outer fan first stage having at least one outer fan first blade extending radially outward from the arcuate platform and an outer fan second stage comprising at least one outer fan second blade extending radially outward from the arcuate platform and located axially aft from the outer fan first stage; characterized in that the fan assembly further comprises: a convertible fan system operable to provide a variable fan pressure ratio while an incoming airflow to the convertible fan system remains substantially constant; the convertible fan system having a convertible fan located aft of and connected to the fan stage having the plurality of fan blades; the convertible fan having a plurality of convertible fan blades arranged circumferentially around a longitudinal axis on a convertible fan hub; the convertible fan system further having an annular splitter located axially forward from the convertible fan blades and operable to split the incoming flow into an inner flow and an outer flow; wherein each of the convertible fan blades has a radially inner portion and a radially outer portion separated by an arcuate shroud, wherein the inner portion is operable to pressurize the inner flow and the outer portion is operable to pressurize the outer flow; and the convertible fan system further having a convertible fan vane system located axially forward from the convertible fan, the convertible fan vane system having outer vanes operable to change a direction of at least a portion of the outer flow and inner vanes operable to change a direction of at least a portion of the inner flow. a convertible fan system operable to provide a variable fan pressure ratio while an incoming airflow to the convertible fan system remains substantially constant; the convertible fan system having a convertible fan located aft of and connected to the fan stage having the plurality of fan blades; the convertible fan having a plurality of convertible fan blades arranged circumferentially around a longitudinal axis on a convertible fan hub; the convertible fan system further having an annular splitter located axially forward from the convertible fan blades and operable to split the incoming flow into an inner flow and an outer flow; wherein each of the convertible fan blades has a radially inner portion and a radially outer portion separated by an arcuate shroud, wherein the inner portion is operable to pressurize the inner flow and the outer portion is operable to pressurize the outer flow; and the convertible fan system further having a convertible fan vane system located axially forward from the convertible fan, the convertible fan vane system having outer vanes operable to change a direction of at least a portion of the outer flow and inner vanes operable to change a direction of at least a portion of the inner flow.