Originally Posted by
industry insider
Concentric
There are 2 types of gear with different part numbers -06 and -07. Each gear has bearings from a different manufacturer. -07 gear bearings have a different span and shape and a corresponding greater contact pressure on the outer race (inner rig of the gear) than -06 gear bearings.
It is thought that the greater contact pressure of the bearing in the -07 gear causes spalling. The -06 gear bearing is not known to suffer spalling according to AH.
Any metal on the plugs or in filter at the 10 hour inspection must be analysed. Any presence 16NCD-13 metal would indicate spalling of the -06 gear bearing. The -06 gear / bearing / cage combination has been in the L and L1 for some time and are regarded as the reliability benchmark.
Industry Insider, a technical question:
In AAIB report on G-REDL, page 17, it is written that second stage on AS332L2 increased the dimension of planet gears and reduced their number from 9 to 8. So, it is really possible to install a -06 gear and its bearing in the L and L1 and their carrier?
Besides, is 16NCD13 steel the material of the planet gear only? Maybe other power gears, apart the bevel shaft of 2012 memory (in steel 32CDV13), are made from the same material.