A pitch drive for turning at least one rotor blade (6a, 6b, 6c) of a wind turbine, the pitch drive comprising a pitch drive controller which analyses if a first error situation or a second error situation occurs in a pitch drive unit (9a, 9b, 9c) of the pitch drive controller and wherein the pitch drive controller is adapted to react: - to the first error situation in absence of the second error situation and a third error situation with a first error procedure, wherein the first error situation comprises a failure of a resolver for controlling a pitch motor (93a, 93b, 93c) of one of pitch drive units (9a, 9b, 9c); - to the second error situation in absence of the first error situation and the third error situation with a second error procedure; - to a fourth error situation where the first error situation and the second error situation occur in absence of the third error situation at the same time with a third error procedure that is different to the first error procedure and the second error procedure; characterized in that the second error situation comprises a failure of a blade encoder for measuring position of a rotor blade (6a, 6b, 6c) of the pitch drive unit (9a, 9b, 9c); and that the pitch drive controller is further adapted to react: to the third error situation in absence of the first situation and the second error situation, with a fourth error procedure, wherein the third error situation comprises a failure of an emergency power backup system for the pitch drive; - to an error situation where the first error situation, the second error situation and the third error situation occur at the same time, with the third error procedure; - to an error situation where the first error situation and the third error situation occur in absence of the second error situation at the same time, with the first error procedure and the fourth error procedure; and - to an error situation where the second error situation and the third error situation occur in absence of the first error situation at the same time, with the second error procedure and the fourth error procedure. - to the first error situation in absence of the second error situation and a third error situation with a first error procedure, wherein the first error situation comprises a failure of a resolver for controlling a pitch motor (93a, 93b, 93c) of one of pitch drive units (9a, 9b, 9c); - to the second error situation in absence of the first error situation and the third error situation with a second error procedure; - to a fourth error situation where the first error situation and the second error situation occur in absence of the third error situation at the same time with a third error procedure that is different to the first error procedure and the second error procedure; that the second error situation comprises a failure of a blade encoder for measuring position of a rotor blade (6a, 6b, 6c) of the pitch drive unit (9a, 9b, 9c); and that the pitch drive controller is further adapted to react: to the third error situation in absence of the first situation and the second error situation, with a fourth error procedure, wherein the third error situation comprises a failure of an emergency power backup system for the pitch drive; - to an error situation where the first error situation, the second error situation and the third error situation occur at the same time, with the third error procedure; - to an error situation where the first error situation and the third error situation occur in absence of the second error situation at the same time, with the first error procedure and the fourth error procedure; and - to an error situation where the second error situation and the third error situation occur in absence of the first error situation at the same time, with the second error procedure and the fourth error procedure.