In 1948 North American began work on the NA-163 turboprop-powered derivative of the AJ-1 Savage, two prototypes being ordered in September of that year. The US Navy specified major changes, including deletion of the Allison J33 booster engine, and the first prototype North American XA2J-1 did not fly until 4 January 1952. Development was hampered by problems with the Allison XT40-A-6 engines, each of which comprised two T38 engines driving contra-rotating propellers through a gearbox, allowing either T38 in each unit to be shut down for long-range cruise. The three-man crew was provided with a pressurised cabin and defensive armament comprised two 20mm guns in a remotely-controlled barbette. Maximum offensive load was 4911kg of bombs. The completed second prototype was never flown.