Base Assembly for a Tower Mounted Crane

A base assembly (120) configured to support a tower mounted crane (101) on a nacelle (200) of the wind turbine (300), said tower mounted crane being of the kind comprising a base portion (102) and a boom arm (104), where the boom arm is arranged rotatably about a vertical axis relative to the base portion during normal operation of the tower mounted crane, said base assembly includes a base structure (122) adapted to be mounted to the nacelle, and a support structure (124) configured to engage with the tower mounted crane and support the tower mounted crane in an upright position. In an engagement of the tower mounted crane with the base assembly, a base portion of the tower mounted crane is attached to the support structure. The support structure is movably coupled to the base structure and is adapted to be displaced linearly relative to the base structure in a direction substantially parallel to a longitudinal axis of the nacelle to arrange the tower mounted crane at a plurality of crane mounting positions relative to the nacelle.