Retractable tailwheels were fitted as standard .
The majority of the Mk XIs built had the later large - area pointed rudder. 260 Mk XIs were powered by Merlin 61 , 63 or 63A engines , while the remaining 211 used the high - altitude Merlin 70 .
Retractable tailwheels were fitted as standard and the majority of the Mk XIs built had the later large - area pointed rudder. 260 Mk XIs were powered by Merlin 61 , 63 or 63A engines , while the remaining 211 used the high - altitude Merlin 70 .