02/28/2010. Owing to limitations in Sabre engine supply that were used in the B-37 Firebrand TF.Mk.I torpedo-strike fighter, the decision was taken in 1942, to re-engine the Firebrand with the Bristol Centaurus eighteen-cylinder radial engine, in accordance with Specification S.18/43. Two airframes-originally to have been the 10th and 11th Mk.Is (s/n DK372 and DK373), were modified as prototypes for the B-45 Firebrand TF.Mk.III, the pictured example was the first of these Centaurus-powered aircraft flying on December 21, 1943.
By comparison with the B-37, the B-45 embodied extensive redesign, although few major changes were incorporated in the fuselage structure. Twenty-seven production TF.Mk.III torpedo-strike fighters were built, the first of these flying in November 1944 with a 2,400 hp Centaurus VII, and the 11th and subsequent aircraft having the 2,520 hp Centaurus IX. Armament comprised four wing-mounted 0.787 in (20 mm) Hispano cannon and a 1,850 lb (839 kg) torpedo, two 1,000 lb (454 kg) or 2,000-lb (907 kg) bombs, or sixteen 60 lb (27,2 kg) rockets.
Further development resulted in the B-46 Firebrand TF.Mk.IV, the first version to be built in substantial numbers. This differed from the TF.Mk.III primarily in having enlarged vertical tail surfaces and re-tractable wing spoilers. The first TF.Mk.IV flew on May 17, 1945, and production totaled 102 aircraft, 40 of these later being converted to Firebrand TF.Mk.5s which featured detail improvements. Sixty-eight TF.Mk.Mk 5s and TF.Mk.5As (the latter having hydraulically-boosted ailerons) had been built from scratch when Firebrand production terminated at the end of 1947.