scope:

Description of Driving Event:

A wind turbine was lowered from its tower and secured to a ground level assembly stand. A blade tip was then removed and the work crew broke for lunch. After lunch the rotor brake was released. Personnel on the ground realized the unbalanced rotor condition as the blade came rapidly to the ground.

The direct cause of the accident was a failure of several knowledgeable personnel in the immediate area to realize the unbalanced conditions of the rotor. A crane operator was available in the immediate area. The crane should have been used to secure the unbalanced rotor and slowly lower it to the ground. This procedure of lowering an unbalanced rotor has been standard procedure in many blade, spool piece, and tip changes in the past.