Su-15

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.
These led to the T-58, which combined the twin engines with a modified version of the T-49's nose, but with side inlets further back, behind the cockpit. It was approved for

production on 5 February 1962, as the Su-15, and the prototype first flew on 30 May 1962. It entered service testing 5 August 1963, but its service entry was delayed by

political infighting with the Yakovlev OKB over production line capacity in Novosibirsk, which was also building the Yakovlev Yak-28P. The Su-15 proved to be superior in most

respects other than range, and it was officially commissioned on 3 April 1965. Series production began the following year, and it entered service with the PVO in 1967, replacing

Su-9s, Su-11s, and Yakovlev Yak-25s. The initial Su-15 received the NATO reporting name 'Flagon-A.' A simplified trainer version, the Su-15UT (NATO 'Flagon-C'), with no

radar or combat capability, entered service in 1970.
Initial delta wing Su-15s had poor take-off and landing characteristics, and so Sukhoi investigated a new wing design with extended wingtips (increasing wing area) and

boundary layer control. Su-15s with the new wing went into production in 1969. They were dubbed 'Flagon-D' by NATO, although the Soviet designation was unchanged.