To try to make sense of some earlier information:
- Ab initio nav training ends 2011 (source: PN's source)
- GR4 OSD 2018 (source: an earlier poster; seems reasonable)
- GR4 OCU stands down 2016 (source: KeyPilot assumption - platform OSD minus 2 years)
=> where does the supply of new navs to the GR4 OCU come from during 2011-2016? Thoughts?