While replacing an unserviceable air driven generator (ADG) on a CRJ-200; a Mechanic reports the spinner was damaged; when performing the ADG ejection jack travel measurements. He and another Technician failed to notice the ADG door control rod had repositioned; even though the rod was disconnected; obstructing the spinner.

Narrative

While replacing an unserviceable ADG assembly the spinner was damaged when performing the ADG ejection jack travel measurement. To take the ejection jack stowed measurement the ADG is stowed with the door actuator control rod disconnected to provide access for recording dimensions of travel. To stow the ADG; one Technician must stand above the open ADG door to operate the stow pump. This is the operation that I was performing when the damage occurred. The second Technician was below assisting the ADG. Prior to performing the task I had replied about clearances of door mechanism when disconnected and second Technician replied that area was clear the mechanism; was positioned out of way and to proceed. During the stowing procedure; the door control rod repositioned and obstructed the spinner of ADG; contacting it and causing damage.By following the procedure for stowing the ADG; for measurement of the travel for the ejection jack; the door control rod assembly should be secured by means of safety.