Cadet Forces Adult Volunteer
To cut a long story short, some cheeky sod in the ACF wrote to MOD asking why he could only claim 28 days pay (only a few bob) and that the pay wasn't minimum wage. Said person clearly needed his head checked, since cadet forces are a hobby, not a job (though training officers seem to like the word 'your cadet career' these days). However, MOD (as is common when it involves money) promptly shat themselves at the idea of having to pay more to every adult volunteer in the ACF, ATC and CCF ( SCC are a charity so it didn't directly affect them, but they still use the term). Therefore they re-categorised the pay as 'allowance', and created the term CFAV to prove that they are not entitled to employee rights nor minimum wage.
So who are CFAVs? All Officers, SNCOS, Senior Ratings, Civilian Instructors, Unit Assistants, and any other instructional staff (not civilian committees) in the ACF, ATC, SCC and CCF. Despite their assertions that they are part of the RAF with their class A commission, RAFVR(T) officers, are also CFAVs (when it suits the MOD).