G-REDL
An extensive and complex investigation revealed that the failure of the MGB initiated in one of the eight second stage planet gears in the epicyclic module. The planet gear had fractured as a result of a fatigue crack, the precise origin of which could not be determined. However, analysis indicated that this is likely to have occurred in the loaded area of the planet gear bearing outer race.
LN-OJF
Among the recovered parts were two pieces which together form approximately half a second stage planet gear (ref. Figure 2). Examinations of these parts have revealed features strongly consistent with fatigue. The fatigue appears to have its origin in the outer race of the bearing (inside of the gear), propagating towards the web of the gear teeth. There is sign of spalling in front of the fracture surface.