Only AFPS 75 offers the sort of commutation that TomJoad is referring to.
AFPS 05 allows you to give up some or all of your tax free lump sum to improve your taxable pension.
AFPS 15 allows you to give up all of your tax free EDP lump sum to improve your taxable pension. AFPS 15 does not give an automatic pension lump sum but it allows members to surrender some of their pension to generate one.