A hub enclosure (6), e.g. a spinner, for a hub (4) of a wind turbine is disclosed. The hub enclosure (6) comprises an aperture defining an aperture area and at least two aperture covers (10). The aperture covers (10) are arranged to cover substantially separate parts of the aperture area. Each of the aperture covers (10) is movable between a first position and a second position. In the first position the corresponding part of the aperture area is closed, and in the second position the corresponding part of the aperture area is open. The aperture covers (10) are positioned relative to each other in such a manner that neighbouring aperture covers (10) are arranged to cover adjacent parts of the aperture area. Thus, when two neighbouring aperture covers (10) are both in the second position, an opening is defined having an area which corresponds to the sum of the areas covered by the two aperture covers (10). Thereby a passage opening of a desired size can be obtained, simply be moving an appropriate number of neighbouring aperture covers (10) to the second position. This allows objects of various size to pass through the aperture without compromising the strength of the structure.
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