A METHOD FOR DISMANTLING OR INSTALLING A WIND TURBINE BLADE OF A WIND TURBINE

A method for dismantling a wind turbine blade (2) of a wind turbine (4) is disclosed. A hoisting arrangement (11) with a main hoisting device (13) and an auxiliary hoisting device (14) is provided at an uptower position of the wind turbine (4). The wind turbine blade (2) to be dismantled is connected to the hoisting arrangement (11) in such a manner that the main hoisting device (13) is connected to the wind turbine blade (2) at a first position and the auxiliary hoisting device (14) is connected to the wind turbine blade (2) at a second position. The wind turbine blade (2) to be dismantled is disconnected from the wind turbine (4), and the main hoisting device (13) and the auxiliary hoisting device (14) are operated in a coordinated manner so as to lower the wind turbine blade (2) while changing an orientation of the wind turbine blade (2) towards a substantially horizontal orientation. A method for installing wind turbine blade (2) on the wind turbine (4) is also disclosed.