Sukhoi Su-15 - Design

Design

Although many components of the Su-15 were similar or identical to the previous Su-9 and Su-11 (NATO reporting name "Fishpot"), including Sukhoi's characteristic rear-fuselage airbrakes, the Su-15 abandoned the shock-cone nose intake for side-mounted intakes feeding two powerful turbojet engines, initially the Tumansky R-11F2S-300. The change allowed room in the nose for a powerful search radar, initially the RP-22 Oryol-D (NATO 'Skip Spin'). The early Su-15 ("Flagon-A") had pure delta wings like its predecessors, but these were replaced from the 11th production series onward by a new 'kinked' delta planform of increased span and area, with a small wing fence above each outer pylon and blown flaps to improve landing characteristics. This was accompanied by a new tail of greater anhedral and a vertical fin of reduced height.

The Su-15 had maximum speed of Mach 2.5 and a rate of climb of 228 m/s. Take-off and landing speeds were comparatively high, with a take-off speed of 247 mph (395 km/h) for early delta-winged 'Flagon-A's and 231 mph (370 km/h) for the larger-winged 'Flagon-F.' While the controls were responsive and precise, the aircraft was unforgiving of pilot error.

Despite its powerful radar, the Su-15, like most Soviet interceptors before the late 1980s, was heavily dependent on ground control interception (GCI), with aircraft vectored onto targets by ground radar stations. It was fitted with the Lazur-S datalink system, which transmitted instructions to the pilot to accomplish the interception. The later Su-15TM had a Vozdukh-1M datalink and SAU-58 (sistema automaticheskogo upravleniya, automatic control system) capable of carrying out completely automatic, 'hands-off' interceptions until the last moments of the interception.

Primary armament of the Su-15 was the R-8/K-8 (AA-3 "Anab"; later R-98) air-to-air missile. Early models carried two missiles, but 'Flagon-D' and later versions could carry four. Like most Soviet missiles, the R-98 was made in both infrared and semi-active radar homing versions, and standard practice was to fire the weapons in pairs (one semi-active radar homing, one IR homing) to give the greatest chance of a successful hit. The IR homing missile was normally fired first in order to prevent the possibility of the IR missile locking on to the radar homing missile. Later 'Flagon-F' models often carried two R-98s and one or two pairs of short-range R-60 (AA-8 'Aphid') missiles. Late-model 'Flagons' also sometimes carried a pair of UPK-23-250 23 mm gun pods on the fuselage pylons, each containing a two-barrel GSh-23L cannon.