Recognizing the limitations of the earlier Su-9 and Su-11, the Sukhoi OKB quickly began the development of a heavily revised and more capable aircraft. A variety of development aircraft evolved, including the T-49, which shared the fuselage of the Su-9 (including its single engine), but used cheek-mounted intakes to leave the nose clear for a large radome for the 'Oriol-D' (Eagle) radar, and the T-5, essentially a heavily modified Su-11 with a widened rear fuselage containing two Tumansky R-11 engines.