During WW II there were many Spitfire modifications released, which gradually improved plane's performance. It was a very popular fighter engaged on all fronts of the Second World War. On the Western Front it was the most important opponent to German Luftwaffe. Version IX was a temporary substitution to F Mk.V, no longer able to cope with new FW-109A and BF-109F. Supermarine Spitfire F. Mk. IX C is an all-metal low-wing monoplane with retractable undercarriage, powered by 12 cylinder Rolls-Royce Merlin 61 ( Merlin 63 ) Vee engine , with four-blade Rotol R3 constant speed airscrew with duralumin blades, or R5, R12 with Jablo blades. Armament: two 20mm British-Hispano and four .303 cal Browning machine guns.