Rotary assembly for an aviation turbine engine, the assembly comprising a separate fan blade platform mounted on a fan disk

A rotary assembly for an aviation turbine engine, the assembly comprising:

• a fan disk comprising at least one tooth with an upstream face;
• at least one platform mounted on the tooth of the fan disk;
• and
• a shroud mounted at the upstream end of the fan disk,
• wherein, at the upstream end of the platform, the platform includes a step with a radial portion that is extended by an axial portion giving the step a longitudinal section that is substantially L-shaped, the axial portion being for radially retaining the platform against the tooth of the disk, the radial portion extending along the upstream face of the tooth of the disk and including an opening for having a fastener element passing axially therethrough to mount the shroud on the fan disk, and
• wherein a face of the shroud facing the upstream face of the disk tooth includes an element that projects from said face of the shroud, said element passing through the opening and coming into contact with the upstream face of the tooth of the disk, said element extending from said face of the shroud over a length that is longer than a thickness of the radial portion of the step of the platform.