The category is fixed under EASA, ref-
Cat.op.mpa.320 aircraft categories
(a) Aircraft categories shall be based on the indicated airspeed at threshold (VAT) which is equal to the stall-ing speed (VSO) multiplied by 1.3 or one-g (gravity) stall speed (VS1g) multiplied by 1.23 in the landing con-figuration at the maximum certified landing mass. If both VSO and VS1g are available, the higher resulting VAT shall be used.
(b) The aircraft categories specified in the table below shall be used.
table 1: aircraft categories corresponding to Vat values
aircraft category Vat
A Less than 91 kt
B From 91 to 120 kt
C From 121 to 140 kt
D From 141 to 165 kt
E From 166 to 210 kt
(c) The landing configuration that is to be taken into consideration shall be specified in the operations man-ual. (d) The operator may apply a lower landing mass for determining the VAT if approved by the competent authority. Such a lower landing mass shall be a permanent value, independent of the changing condi-tions of day-to-day operations.