An aircraft fuel pump (1) is provided with a centrifugal impeller (2) and a stationary housing (3). A floating annular seal (4) mates with both the stationary housing and the rotating impeller thus providing sealing on two surfaces. The annular seal (4) comprises, in combination, a sealing material (5) positioned radially opposite the surface (6) of the impeller to be sealed, a backing ring (7) radially spaced from the sealing material for axially sealing against a surface (13) on a mating ring (15) of the stationary housing (3), and an elastomer (8) which is bonded to both the sealing material and the backing ring. The sealing material (5) is in the form of sealing material segments (9, 10, 11) which are arranged end to end with expansison grooves (12) remaining between the opposed ends for accommodating differences in thermal expansion between the impeller and the sealing material. The expansion grooves are in the form of a spiral to create a pumping action with relative rotation between the impeller and the sealing material to resist leakage of fuel through the expansion grooves.