"If you look at the last picture you will see a hole passing through the shaft wall the area where the shaft cracked is above that. The weld area is the next change in colour going up the shaft."
The picture is very good, but not that good. Perspective and parallax play their parts and the best I can suggest is that you look up into an actual gearbox. Then it becomes clear that the weld and the adjacent fracture lines are below the bottom of the main rotor shaft bearing.
Here's another thought. Why would a design engineer allow a main rotor shaft to have any kind of weld between its top and bottom support bearings? That shaft in the picture is nowhere near robust enough to take much greater side loads than just the two oil pumps.
I even question why the oil pumps are next to each other, rather than on opposite sides of the driving gear, to mutually counteract sideways reactions to the torque forces driving them. (Excuse my lack of proper engineering terminology.)
Last edited by Colibri49; 20th Nov 2012 at 12:47.