An edge flap arrangement for an aircraft, the edge flap arrangement comprising an hourglass bearing assembly, the hourglass bearing assembly comprising: an inner raceway defining a radially outwardly facing convex surface having an inner raceway radius of curvature (Ri); an outer raceway defining a radially inward facing convex inner surface (122A, 122B) having an outer raceway radius of curvature (Ro), the outer raceway being positioned around the inner raceway; a plurality of rollers disposed between the inner raceway and the outer raceway, each of the plurality of rollers having an hourglass shape and being in rolling engagement with the inner raceway and the outer raceway; each of the plurality of rollers having: a circular cross section symmetrical about a longitudinal axis; a first axial end and a second axial end; an exterior surface extending between the first axial end and the second axial end; the exterior surface defining a concave engagement surface extending outwardly from a central portion of the roller, characterised in that: the concave engagement surface has a first radius of curvature extending from the central portion to each of two first transition zones positioned on opposing sides of the central portion and the concave engagement surface has a second radius of curvature extending outwardly from each of the two first transition zones to each of two second transition zones; and the second radius of curvature is greater than the first radius of curvature; and the first radius of curvature is between 50 percent and 95 percent of the second radius of curvature, wherein the inner raceway radius of curvature (Ri) is between about 95 percent and 100 percent of the first radius of curvature and the outer raceway radius of curvature (Ro) is between about 95 percent and 100 percent of the first radius of curvature. an inner raceway defining a radially outwardly facing convex surface having an inner raceway radius of curvature (Ri); an outer raceway defining a radially inward facing convex inner surface (122A, 122B) having an outer raceway radius of curvature (Ro), the outer raceway being positioned around the inner raceway; a plurality of rollers disposed between the inner raceway and the outer raceway, each of the plurality of rollers having an hourglass shape and being in rolling engagement with the inner raceway and the outer raceway; each of the plurality of rollers having: a circular cross section symmetrical about a longitudinal axis; a first axial end and a second axial end; an exterior surface extending between the first axial end and the second axial end; the exterior surface defining a concave engagement surface extending outwardly from a central portion of the roller, characterised in that: the concave engagement surface has a first radius of curvature extending from the central portion to each of two first transition zones positioned on opposing sides of the central portion and the concave engagement surface has a second radius of curvature extending outwardly from each of the two first transition zones to each of two second transition zones; and the second radius of curvature is greater than the first radius of curvature; and the first radius of curvature is between 50 percent and 95 percent of the second radius of curvature, wherein the inner raceway radius of curvature (Ri) is between about 95 percent and 100 percent of the first radius of curvature and the outer raceway radius of curvature (Ro) is between about 95 percent and 100 percent of the first radius of curvature. a circular cross section symmetrical about a longitudinal axis; a first axial end and a second axial end; an exterior surface extending between the first axial end and the second axial end; the exterior surface defining a concave engagement surface extending outwardly from a central portion of the roller, characterised in that: the concave engagement surface has a first radius of curvature extending from the central portion to each of two first transition zones positioned on opposing sides of the central portion and the concave engagement surface has a second radius of curvature extending outwardly from each of the two first transition zones to each of two second transition zones; and the second radius of curvature is greater than the first radius of curvature; and the concave engagement surface has a first radius of curvature extending from the central portion to each of two first transition zones positioned on opposing sides of the central portion and the concave engagement surface has a second radius of curvature extending outwardly from each of the two first transition zones to each of two second transition zones; and the second radius of curvature is greater than the first radius of curvature; and the first radius of curvature is between 50 percent and 95 percent of the second radius of curvature, wherein the inner raceway radius of curvature (Ri) is between about 95 percent and 100 percent of the first radius of curvature and the outer raceway radius of curvature (Ro) is between about 95 percent and 100 percent of the first radius of curvature.