R.A.F. A/c Fatigue Index.
Can anyone enlighten me, please? I have seen an R.A.F. (or Ex-) Bulldog for sale, and in the description is the phrase "Fatigue Index xxx)" .
Does the Fatigue Index replace Engine/Airframe hours, does it work in conjunction with them, or is it not related in any way?
Thanks in advance. N.Z.