Method for controlling a wind turbine

(canceled)

A mobile controller for controlling a wind turbine, wherein the wind turbine has a central, controller, the mobile controller comprising:

• a first input configured to receive at least one blade angle signal indicative of a blade angle of at least one rotor blade, and
• an output configured to control a rotor arresting device means,
• wherein the mobile control unit is configured not to deactivate the rotor arresting device as long as the blade angles of the at least one rotor blade are not within a predetermined blade angle range.

A method comprising:

• using a mobile controller to control a rotor arresting device of a wind turbine while the wind turbine is not connected to an energy supply grid or during maintenance of the wind turbine such that the wind turbine cannot receive energy from the energy supply grid for controlling the wind turbine,
• wherein the mobile control unit is designed to receive blade angle information relating to one or more rotor blades of the wind turbine and to control the rotor arresting device in dependence on the received blade angle information and to prevent unlocking of the rotor arresting device as long as the blade angles of the one or more rotor blades are outside a predetermined blade angle range.