An efficient axial flow fan (2) comprises a central hub (6), a plurality of blades (8), and a band (9), and is designed to operate in a shroud (4) and induce flow through one or more heat exchangers (5) - in an automotive engine cooling assembly, for example. The fan blades (8) have a radial distribution of pitch ratio that provides high efficiency and low noise in the non-uniform flow field created by the heat exchanger(s)(5) and shroud (4). The blade (8) has either no sweep, or is swept backward (i.e. opposite the direction of rotation) in the region between the radial location r/R=0.70 and the tip (r/R-1.00). The blade pitch ratio increases from the radial location r/R=0.85 to a radial location between r/R=0.90 and r/R=0.975, and then decreases to the blade trip.