Abstract: A system for variation of the pitch angle position of rotor blades of a wind energy installation includes drive units, closed-loop control devices, and system control connections. The drive units are in each case individually associated with the rotor blades. The closed-loop control devices are in each case individually associated with the drive units. The system control connections are switchable by switching means. By way of the system control connections, in the event of a failure or a malfunction of at least one closed-loop control device a drive unit which is associated with the at least one closed-loop control device is operated in parallel with and at the same time as another drive unit, by means of a closed-loop control device which is associated with the other drive unit.