Don’t forget Nimrods! As I recall the following applied to Nimrod personnel.
First ASCs were trained at HSA Woodford.
Then Nimrod experienced Chf Techs/Sgts were trained for approx 3 months at the Nimrod Servicing School (NSS) at Kinloss. Sgts were made Special Acting Rank Paid Chf Techs. During the early/mid eighties? the Nimrod course changed to approx 9 months when non Nimrod trained SNCOs were chosen/volunteered. The course attendees did Halton (A/f, Prop training), Cosford (Elect, Av training) then Kinloss for Nimrod aircraft training, then did 6 months under a mentor on the line.
During their 5 year tour as an ASC most Sgts were promoted to Chf Techs, due to time promotion being the criteria at the time. Only a few reverted to the rank of Sgt.
After the Vulcans/Victors packed in there was a bit of a rebellion as a lot of those Chf Techs reverted to the rank of Sgt, due to the promotion criteria at the time. Then in Jan 1987? trade was changed to Aircraft Ground Engineer (AGE) when volunteers did a 6 months course at Kinloss, with 6 months on the job training on the line. AGEs were normally screened for 5 years. Hope that helps the big picture.