An agricultural harvesting machine including a transverse fan assembly comprising: an air plenum having associated therewith an air inlet thereto and an air outlet therefrom; and a transverse fan disposed within and extending across said air plenum and being rotatable about an axis of rotation, said transverse fan having an outer periphery, the resultant air flow pattern from said air outlet across the expanse thereof being dependent, in part, upon the pattern of air flow from said air inlet, a supplementary air feed inlet including an air chamber open at at least one location (304/306) to a source of supplemental air and having an aperture at at least one other location along said air chamber open to said air inlet of said air plenum at a given location along the expanse thereof, rotation of said transverse fan about said axis of rotation thereby drawing air from said source of supplemental air into and through said air chamber to said aperture in said air chamber and therethrough for introduction into said air inlet and said air pathway therethrough at the location of said aperture, said introduction of said supplemental air into said air inlet and said air pathway therethrough at the location of said aperture producing a volume of air flow into an air inlet entryway near said location of said aperture across the expanse thereof, said volume of air flow into said air inlet entryway near said location of said aperture across the expanse thereof effecting a resultant air flow pattern across the expanse of the air outlet that differs from the resultant air flow pattern that would otherwise be realised across the expanse of the air outlet in the absence of said volume of air flow in the air pathway in said air inlet, whereby a desired air flow pattern across the expanse of said air outlet is realisable by providing supplemental air from said supplementary air feed inlet to said air inlet to effect an infill of air flow into the air flow pathway to said transverse fan near said aperture along said air chamber of said supplementary air feed inlet, characterised in that said air chamber includes a first side extending adjacent to said air inlet, said first side including first and second separation members extending inwardly towards one another from said opposed open ends and an opening between said first and second members along said first side, said opening permitting the passage of air therethrough from said air chamber to said air inlet. an air plenum having associated therewith an air inlet thereto and an air outlet therefrom; and a transverse fan disposed within and extending across said air plenum and being rotatable about an axis of rotation, said transverse fan having an outer periphery, the resultant air flow pattern from said air outlet across the expanse thereof being dependent, in part, upon the pattern of air flow from said air inlet, a supplementary air feed inlet including an air chamber open at at least one location (304/306) to a source of supplemental air and having an aperture at at least one other location along said air chamber open to said air inlet of said air plenum at a given location along the expanse thereof, rotation of said transverse fan about said axis of rotation thereby drawing air from said source of supplemental air into and through said air chamber to said aperture in said air chamber and therethrough for introduction into said air inlet and said air pathway therethrough at the location of said aperture, said introduction of said supplemental air into said air inlet and said air pathway therethrough at the location of said aperture producing a volume of air flow into an air inlet entryway near said location of said aperture across the expanse thereof, said volume of air flow into said air inlet entryway near said location of said aperture across the expanse thereof effecting a resultant air flow pattern across the expanse of the air outlet that differs from the resultant air flow pattern that would otherwise be realised across the expanse of the air outlet in the absence of said volume of air flow in the air pathway in said air inlet, whereby a desired air flow pattern across the expanse of said air outlet is realisable by providing supplemental air from said supplementary air feed inlet to said air inlet to effect an infill of air flow into the air flow pathway to said transverse fan near said aperture along said air chamber of said supplementary air feed inlet, characterised in that said air chamber includes a first side extending adjacent to said air inlet, said first side including first and second separation members extending inwardly towards one another from said opposed open ends and an opening between said first and second members along said first side, said opening permitting the passage of air therethrough from said air chamber to said air inlet.