General Maintenance Issues of Horizontal Axis WPPs:
1. Gearbox failure.
2. Misalignment between generator and gearbox.
3. Problems related to lubrication.
4. Variation among the components by manufacturer, configuration and operating environment of such items such as generators, power converters, gear box.
5. General routine maintenance related about tower, storage devices, wiring, charging gear oil, brake pads, filters, bearings, sensors, actuators. 6. Bearing failure issue.