The Sukhoi Su-15 is a twinjet supersonic interceptor aircraft developed by the Soviet Union.
It entered service in 1965 and remained one of the front-line designs into the 1990s.
The Su-15 was designed to replace the Sukhoi Su-11 and Sukhoi Su-9, which were becoming obsolete as NATO introduced newer and more capable strategic bombers.
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 air brake, the Su-15 abandoned the shock-inlet cone nose intake for side-mounted intake ramps with splitter plates 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 double-delta wing 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 (750 ft/s), a very important parameter for an interceptor aircraft.
Take-off and landing speeds were comparatively high, with a take-off speed of 395 km/h (245 mph) for early delta-winged ‘Flagon-A’s and 370 km/h (230 mph) 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 (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.
Variants
T-58
Prototype of Su-15.
Su-15 (Flagon-A)
First production version.
T-58VD (Flagon-B)
One-off prototype using three Kolesov lift jets in the centre fuselage to provide STOL capability.
Not mass-produced.
Su-15UT (Flagon-C)
Trainer version without radar and combat capability, in use since 1970.
Su-15 (Flagon-D)
Version with extended wingtips built since 1969.
Su-15T (Flagon-E)
Version equipped with Volkov Taifun radar.
Su-15TM (Flagon-F)
Improved Su-15T version equipped with Taifun-M radar and additional aerodynamic modifications, in use since 1971.
New radome design for improving radar performances.
Su-15UM (Flagon-G)
Trainer version of Su-15TM without radar but with combat capability, built between 1976 and 1979.
U-58UM
Prototype of Su-15UM with Taifun-M radar, not entered serial production.
Su-15Sh
Proposed supersonic ground-attack aircraft, offered in 1969, Not built.
Su-15-30
Proposed version sharing the radar and missiles of the MiG-25, not built.
Su-15bis
Converted Su-15TM with R-25-300 engines of 69.9 kN (15,652 lb) afterburning thrust for improved performance; approved for series production, but not built because of a shortage of the engines.
