Sukhoi Su-15

Sukhoi Su-15

Company type	Military aircraft
Industry	Aerospace
Founded	1962
Headquarters	Soviet Union
Products	Supersonic interceptor aircraft

This article is about the supersonic Su-15 "Flagon". For the earlier subsonic interceptor, see Sukhoi Su-15 (1949).

The Sukhoi Su-15 (designated by NATO as Flagon) is a twin-engine supersonic interceptor aircraft developed within the Soviet Union. It was introduced into operational service in 1965 and remained a key frontline asset through the 1990s. The Su-15 was created to succeed the aging Sukhoi Su-11 and Sukhoi Su-9, which were becoming inadequate against newer and more advanced strategic bombers deployed by NATO.

Development

Due to the shortcomings of the earlier Su-9 and Su-11 in countering the advanced Boeing B-52 Stratofortress, particularly regarding radar capabilities and overall aircraft performance, the Sukhoi design bureau rapidly initiated development of a significantly improved interceptor. This effort produced several experimental models, including the Sukhoi T-49, which retained the Su-9 fuselage and single-engine configuration but featured cheek-mounted air intakes to clear space in the nose for a large RP-22 Oryol-D ("Eagle") radar system (NATO codename "Skip Spin"). Another variant, the T-5, was essentially a substantially modified Su-11 with a broader rear fuselage housing two Tumansky R-11 engines.

These prototypes culminated in the T-58 design, which combined twin engines with a revised nose based on the T-49 but relocated side air intakes further aft behind the cockpit. The design received production approval on 5 February 1962 under the designation Su-15, with its maiden flight occurring on 30 May 1962. Although it began service trials on 5 August 1963, entry into active duty was postponed due to political disputes with the Yakovlev design bureau over manufacturing capacity at the Novosibirsk facility, which was also producing the Yak-28P. The Su-15 demonstrated superiority over competitors in most areas aside from combat radius and was officially commissioned on 3 April 1965. Serial production commenced in 1966, and by 1967 it had been deployed with the PVO, replacing earlier models such as the Su-9, Su-11, and Yakovlev Yak-25. The original Su-15 variant was assigned the NATO reporting name "Flagon-A". A streamlined trainer model without radar or weapon systems, designated Su-15UT (NATO "Flagon-C"), entered service in 1970.

Early delta-winged versions of the Su-15 exhibited unsatisfactory takeoff and landing performance. To address this, Sukhoi developed an updated wing design featuring extended wingtips that increased wing area combined with boundary layer control via blown flaps. Aircraft equipped with this wing modification began production in 1969 and were referred to by NATO as "Flagon-D," although their Soviet designation remained unchanged.

Also starting in 1969, testing commenced on an enhanced model known as the Su-15T fitted with the Volkov Taifun ("Typhoon") radar system—a derivative of the powerful RP-25 Smerch-A ("Tornado") radar used on the MiG-25. However, due to technical difficulties, only ten units were produced before discontinuation. This was succeeded in December 1971 by the Su-15TM (NATO "Flagon-E"), which incorporated an improved Taifun-M radar (NATO "Twin Scan") along with provisions for either a UPK-23-250 gun pod or short-range air-to-air missiles such as the Molniya R-60 (AA-8 "Aphid"). Aerodynamic requirements necessitated redesigning the radome into an ogival shape, resulting in a new NATO codename "Flagon-F," while Soviet designations remained consistent. A corresponding combat-capable trainer version, the Su-15UM (NATO "Flagon-G"), was introduced from 1976 onward. The final batch of Su-15UM trainers, representing the last production run of any Su-15 variant, rolled off assembly lines in 1979.

Several proposals from the design bureau aimed at upgrading the Su-15 with enhanced engines and aerodynamic improvements to meet a Soviet Air Force requirement for a long-range tactical fighter were ultimately rejected in favor of selecting the Mikoyan MiG-23 fighter instead.

Design

File:Su-15 Flagon A.jpg

Su-15 Flagon A

File:SU-15.jpg

Sukhoi Su-15

File:Su-15 Flagon C.jpg

Su-15 Flagon C

File:Sukhoi SU-15TM 2008 G1.jpg

A Su-15TM displayed at the Ukrainian Air Force museum in Vinnytsia

File:Su-15 Flagen-F.jpg

Located at the Aviation museum of Zhulyany Airport, Kyiv, Ukraine

While many elements of the Su-15 shared similarities or were directly inherited from the earlier Su-9 and Su-11 models, including Sukhoi’s distinctive rear-fuselage air brake, the Su-15 replaced the shock-cone nose intake with side-mounted intake ramps featuring splitter plates, which supplied air to a pair of robust turbojet engines, initially the Tumansky R-11F2S-300. This redesign freed up space in the nose to house a powerful search radar, originally the RP-22 Oryol-D (NATO reporting name 'Skip Spin'). The initial Su-15 variant ("Flagon-A") featured pure delta wings similar to its predecessors; however, starting from the 11th production batch, these were superseded by a larger double-delta wing with increased span and surface area. This new wing incorporated small wing fences above each outer pylon and utilized blown flaps to enhance landing performance. Alongside these changes, the tailplane was redesigned with greater anhedral and a shortened vertical stabilizer.

The aircraft could reach speeds up to Mach 2.5 and boasted a climb rate of 228 m/s (750 ft/s or 45,000 ft/min), a critical factor for an effective interceptor. Both takeoff and landing velocities were relatively high; early delta-winged 'Flagon-A' models required approximately 395 km/h (245 mph) for takeoff, whereas the larger-winged 'Flagon-F' variants had a slightly reduced takeoff speed around 370 km/h (230 mph). Although handling was responsive and precise, the Su-15 demanded careful pilot input as it offered little margin for error.

Despite its advanced radar capabilities, like most Soviet interceptors prior to the late 1980s, the Su-15 relied extensively on ground control interception (GCI), with pilots being directed toward targets by ground-based radar systems. It was equipped with the Lazur-S datalink system, which transmitted interception commands directly to the pilot. The later Su-15TM featured an upgraded Vozdukh-1M datalink and an SAU-58 (sistema automaticheskogo upravleniya, or automatic control system) enabling fully automated, 'hands-off' interceptions until just before engagement.

The primary weaponry of the Su-15 consisted of R-8/K-8 (AA-3 "Anab", later designated R-98) air-to-air missiles. Initial versions carried two missiles, but from the 'Flagon-D' model onward, payload capacity increased to four missiles. Consistent with Soviet missile doctrine, the R-98 was produced in both infrared homing and semi-active radar homing variants; standard engagement tactics involved launching missile pairs—one semi-active radar guided and one infrared guided—to maximize hit probability. Typically, the infrared missile was launched first to avoid it locking onto the radar-guided missile. Later 'Flagon-F' models frequently carried two R-98 missiles alongside one or two pairs of short-range R-60 (AA-8 'Aphid') missiles. Some late-production 'Flagons' were also equipped with twin UPK-23-250 23 mm gun pods mounted on fuselage pylons, each housing a twin-barrel Gryazev-Shipunov GSh-23L cannon.

Operational history

The Su-15 played a crucial role within the V-PVO's interceptor fleet, primarily intended to engage less challenging targets such as the American B-52, the U-2, and the British V bomber series. More advanced threats like the XB-70 and B-58 were typically assigned to the swifter MiG-25P. The Su-15TM’s Taifun radar was specifically engineered to excel in counter-countermeasure scenarios rather than focusing solely on detection range. During interception missions, the Su-15TM operated under autopilot, guided by Ground-Control Intercept (GCI) commands transmitted via datalink. The radar system was activated only when nearing the target, supplying targeting data for radar-guided K-8/R-8/R-98 missiles; its powerful emissions enabled it to penetrate hostile electronic countermeasures. Should these measures fail, infrared-seeking variants of the K-8 missile provided a final engagement option, supplemented by any onboard gun pods.

Designed with high-altitude interception in mind, the Su-15 excelled in rapid climb rates and high-speed flight at altitude but lacked look-down/shoot-down functionality—even with the enhanced Taifun radar of the Su-15TM. This limitation eventually led to the adoption of the MiG-23P, which possessed look-down/shoot-down capability and became favored by the V-PVO, especially after NATO adopted low-level penetration tactics. Despite this shift, the Su-15 remained a vital component of Soviet air defense until the USSR's dissolution.

As a key interceptor for the V-PVO, the Su-15 was involved in multiple engagements against foreign aircraft that unintentionally entered Soviet airspace:

• In 1978, Korean Air Lines Flight 902 strayed into Soviet territory and was intercepted by a PVO Su-15 over Murmansk. Although the civilian aircraft sustained a missile strike and was heavily damaged, it managed an emergency landing on a frozen lake; however, two passengers lost their lives.
• In 1981, a Soviet Su-15 based in Georgia collided mid-air with a Canadair CL-44 operated by Transporte Aéreo Rioplatense (TAP), an Argentinian carrier. All three Argentinians and one British national aboard perished. The TAP plane was reportedly transporting arms secretly purchased from Israel by Iran during the Iran–Iraq war when it entered Soviet airspace. While some aviation analysts considered the collision accidental, the Soviet pilot claimed he had been deliberately rammed.
• During the 1983 Korean Air Lines Flight 007 incident, a South Korean Boeing 747 was shot down near Moneron Island after deviating into restricted Soviet airspace. A Su-15TM stationed on Sakhalin launched an attack that disabled the 747’s control surfaces with a direct hit to its tail section. The crippled aircraft subsequently crashed into the Sea of Japan off Moneron Island, resulting in the deaths of all 246 passengers and 23 crew members.

Additionally, the Su-15 was credited with downing five reconnaissance balloons launched by Sweden over Soviet territory in 1975.

Despite its extensive production run totaling approximately 1,290 units across all variants, the Su-15—like many advanced Soviet aircraft—was never exported to Warsaw Pact allies or other nations due to its sensitive technology. Some units were reportedly deployed in Egypt during 1972 but were operated exclusively by Soviet personnel. There was consideration given to adapting the Su-15 as a strike fighter; however, its specialization as an interceptor made this impractical.

Following the collapse of the Soviet Union, the Su-15 was swiftly retired from service within the newly formed Russian Air Force in 1993 to align with obligations under the Treaty on Conventional Armed Forces in Europe. Most aircraft were rapidly dismantled in favor of more modern interceptors such as the Su-27 and MiG-31, although several airframes were retained in reserve for emergency situations. In Ukraine, remaining Su-15s stationed at Kramatorsk and Belbek were withdrawn from operational use by 1996.

Variants

T-58

Initial prototype that led to the development of the Su-15.

Su-15 (Flagon-A)

The first model produced in series.

T-58VD (Flagon-B)

A unique prototype fitted with three Kolesov lift jet engines positioned centrally in the fuselage to enable STOL operations. This variant was not mass-produced.

Su-15UT (Flagon-C)

A trainer variant lacking radar and combat systems, operational since 1970.

Su-15 (Flagon-D)

Model featuring lengthened wingtips, manufactured starting in 1969.

Su-15T (Flagon-E)

Equipped with the Volkov Taifun radar system.

Su-15TM (Flagon-F)

An upgraded Su-15T version incorporating the Taifun-M radar and aerodynamic enhancements, introduced in 1971. It also featured a redesigned radome to enhance radar capabilities.

Su-15UM (Flagon-G)

A trainer version based on the Su-15TM without radar but retaining combat functions, produced between 1976 and 1979.

U-58UM

A prototype of the Su-15UM fitted with Taifun-M radar, which did not enter mass production.

Su-15Sh

A proposed supersonic ground attack aircraft presented in 1969 but never constructed.

Su-15-30

A planned variant intended to use the radar and missile systems from the MiG-25, which was not built.

Su-15bis

Modified Su-15TM powered by R-25-300 engines delivering 69.9 kN (15,652 lb) of afterburning thrust for enhanced performance. Although approved for production, it was never manufactured due to engine shortages.

Su-19 (T-58PS)

An advanced project featuring Tumansky R-67-300 three-spool turbofan engines with 78.44 kN of afterburning thrust each. The design included an ogival wing, improved avionics with a look-down/shoot-down radar, and additional missile pylons. This model was never realized.

Certain Western sources have incorrectly identified the Su-15TM as Su-21 and the Su-15UM as Su-21U. However, these designations were reserved for the Su-17M4 and were never applied.

Operators

Template:USSR

• Soviet Air Defence Forces

Template:RUS

• Russian Air Force phased out all frontline Su-15s by 1994, although some units may still be held in emergency war reserve storage.

Template:UKR

• Ukrainian Air Force retired its fleet in 1996.

Specifications (Su-15TM)

File:Sukhoi Su-15 3-view line drawing.svg

Three-view illustration of Sukhoi Su-15

References

Notes

Further reading

• Butowski, Piotr, Valeriy Pankov, and Vadim Ponomaryev. Su-15 Flagon. Monografie Lotnicze #14. Gdańsk: AJ-Press, 1994 (ISBN 83-86208-04-X) (Polish language).

External links

• Detailed information on the Su-15 at FAS
• Overview of the Su-15 by The Global Aircraft Organization
• Su-15 profile at Military Factory
• Photo walkaround of the Su-15TM Archived 2010-03-18 at the Wayback Machine
• Additional article covering the Su-15