Hatches of nacelle and helicopter hoisting platform

A wind driven power plant comprising:

• a nacelle having a nacelle cover comprising a roof section and a helicopter hoisting platform, the nacelle further comprising a hatch extension and a hatch cover in the roof section, the hatch extension being arranged between the nacelle cover and the hatch cover, the hatch extension having a channel-like shape, the hatch cover being mounted on top of the hatch extension, and the hatch extension providing a distance between the hatch cover and the nacelle cover, wherein the roof section of the nacelle cover comprises a provision flange and an opening inside the nacelle cover, wherein the hatch extension is configured as an adapter having a flange to be coupled to the provision flange projecting from the nacelle cover around the opening so as to extend the opening, and wherein the hatch cover is mounted on top of the adapter, and
• wherein the hatch extension is configured as an integral part of a panel of the roof section of the nacelle cover.