This paper presents information on new technology which has made aerodynamic rotating shroud composite cooling fans a practical reality. This paper will describe the design methodology which creates an aerodynamic blade for just the required performance of the system. The design tool has shown to more than 90% accurate for air flow performance in lab validation tests. This paper describes applying this fan matching software to an application involving railroad switcher locomotives. The new fans are compared to the predecessor fans, and the notable performance improvement is shown. The heavy demand on cooling systems now and in the future will find a very attractive solution in the high performance low noise rotating shroud composite fan system.