Originally Posted by
Paying Guest
The widely quoted figure of 138 goes back to the time of Initial Gate for the project when that figure, based on 1 for 1 replacement for Harriers, was a planning assumption, so at that time no detailed case for a specific number had been developed.
It seems like the 138 number, defined along the lines of "procured over the programme lifetime", has remained in being for a long while in that case as that was also given in the 2015 SDSR and has only just been called into question (2021). The actual procurement profile has never been detailed (to my knowledge) after the first batches of 16 + 17 + 15 to get us to 48 by 2025. So the 138 figure seems to have been around for quite a while - but with no real detail out into the future that I know of. Only now, Tempest has necessitated a significant rethink so who knows.
Regarding the 138 figure, I do know that some modelling was being done circa 97/98. Of course it was just known as JSF at that time and, IIR, that was just after Main Gate 1. When was the "Initial Gate"? I was supplying some "supportability" data to Farnborough to help feed the various War scenarios so, sadly, I never got involved in the modelling itself. That was done by a great team of boffins at Farnborough who I really enjoyed working with. Certainly one of them has subsequently had a very successful career with DSTL since then which is really very good to see!
What figures they came up with I have no idea but the scenarios were varied and quite in-depth (as in they modelled right back down into the depths of the supply chain, through the carrier deck/hangar capacity to handle certain sortie rates and then on into the battle space itself) in order to derive Fleet numbers to support each scenario. If that supported the 138 then that was derived/proved way beyond a "1 for 1" replacement exercise. Or, just maybe, no-one has ever been able to agree the "requirement scenario/s" so it stuck with the 138 lifetime estimate with a smaller "at any given time" Fleet size, probably as a result of the Farnborough work. I have no idea - others on here may know more!
Anyway, an update?
https://www.airforce-technology.com/...fleet-numbers/