Monday, March 16, 2015

Foreign Fitters

Russian aircraft builders display great ingenuity in wringing every last ounce of performance from existing machines. The long-lived Su 17 is such an example, and it continues to be upgraded and employed long after the basic design became obsolete.

In 1956 the Sukhoi design bureau created its first tactical jet bomber, the Su 7, a modern-looking machine built in large numbers to offset its relative simplicity. It was a capable fighter-bomber and ruggedly built but also somewhat underpowered. Moreover, it suffered from long runway rolls and rather short range. In 1967 the Sukhoi bureau decided to upgrade this family of bombers by adding variable-geometry wings to enhance takeoff, landing, and load-carrying abilities. Early on it was judged impossible to fit wing-retracting equipment into the narrow fuselage, so engineers compromised by making the wings pivot midway along their length. The added lift increased the Su 7's takeoff performance, and operational radius and ordnance payload were improved as well. Commencing in 1971 the new Su 17 became operational in large numbers, and they were deployed by Warsaw Pact allies and Soviet client states. It has since received the NATO designation FITTER.

During the past three decades, the basic Su 17 design has undergone numerous modifications and upgrades that render this marginally obsolete machine still useful as an attack craft. The latest variant, the Su 17M, is distinguished by a close-fitting clamshell canopy with a high spine ridge running the length of the fuselage. The tail fin is also somewhat taller and employs a single airscoop at its base. This model has been exported abroad as the Su 22, with somewhat lowered-powered avionics, but otherwise it remains an effective bombing platform. After the breakup of the Soviet Union in the late 1980s, many former Warsaw Pact countries were eager to unload their aging Sukhois, but Russia alone seems content to maintain its stable of 800-plus Su 17s. Their rugged design, combined with good reliability and performance, ensures a long service life.



Su-7IG (S-22I, "Fitter-B")

Su-7BM variable geometry wing demonstrator.

Su-17 (S-32, "Fitter-B")
Limited production run based on the longer fuselage of the two-seat Su-7U trainer, with bulged dorsal spine for extra fuel (4,550 L/1,200 U.S. gal total). Retained Su-7s Lyulka AL-7F-1 engine. Manufactured 1969-1973.

Su-17K - export version of the Su-17 for Egyptian Air Force.

Su-17M (S-32M, "Fitter-C")
First major production version, introduced Lyulka AL-21F-3 engine, twin pitot tubes, new navigation and attack computer (retaining Su-7BMK's SRD-5M ranging radar), angle of attack vane, single brake parachute. Variable-position intake centerbody providing maximum speed of Mach 2.1. First flight: 28 December 1971 with V. S. Soloviev at the controls. The export version was designated Su-20, first flying 15 December 1972 with A. N. Isakov at the controls. Manufactured 1972-1975, entered service in 1973. Exported to Egypt, Poland, and Syria.

Testbed for Kh-28 (AS-9 Kyle) anti-radiation missile.

Testbed for Kh-25 (AS-10 'Karen') and Kh-29 (AS-14 "Kedge") missiles.

Small number of Su-17M aircraft equipped to carry reconnaissance pods. Equivalent export version designated Su-20R.

Su-17M2 (S-32M2, "Fitter-D")
Nose extended 38 cm (15 in), deleting ranging radar and 'drooping' to improve pilot visibility. Fon-1400 laser rangefinder/marked-target seeker (LRMTS). ASP-17 and PBK-3-17s aiming avionics. RSBN-6S short-range navigation and instrument landing system. Undernose fairing for DISS-7 Doppler navigation radar. First flight: 20 December 1973 with V. S. Ilyushin at the controls. Manufactured 1974–1977, entered service in 1975.

Test-fit of the Tumansky/Khatchaturov R-29BS-300 engine (shared with some MiG-23s), with 112.7 kN (25,335 lbf) afterburning thrust, in a bulged rear fuselage. Due to lack of performance advantage and decreased range due to higher fuel consumption, it was decided to offer this engine as an export version only. First flight: 31 January 1975 with A. N. Isakov at the controls. The export variant was designated Su-22 (factory code S-32M2K, NATO "Fitter-F"), manufactured 1977-1978.

Su-17UM (S-52U, "Fitter-E")
First two-seat trainer version, based on the Su-17M2, but with a different, deeper fuselage with windscreen moved forward; same length as the original Su-17M. Internal fuel capacity reduced and port cannon deleted, but retained full avionics and armament. First flight: 15 August 1975 with V. A. Krechetov at the controls. Test flights revealed longitudinal instability at high angles of attack which was remedied by enlarging the tail fin. Export version with the R-29 engine was designated Su-22U. Manufactured 1976-1978, entered service in 1976.

Su-17M3 (S-52, "Fitter-H")
Based on the revised airframe of the Su-17UM, but with an avionics bay and an additional fuel tank in place of the rear cockpit, increasing the internal fuel capacity to 4850 l (1,280 U.S. gal). Doppler radar moved internally, removing the fairing. "Klen-P" laser rangefinder/target designator. A launch rail for K-13 (AA-2 "Atoll") or R-60 (AA-8 "Aphid") was added between the two existing pylons on each wing. First flight: 30 June 1976 with V. A. Krechetov at the controls. Export version with the R-29 engine and downgraded avionics (equivalent to Su-17M2) was designated Su-22M (factory designation S-52K, NATO "Fitter-J") and first flew on 24 May 1977 with E. S. Soloviev at the controls. An export version with Su-17M3 avionics was designated Su-22M3 (factory S-52MK). Su-17 manufactured 1976-1981, Su-22Ms were manufactured 1978–1984. Su-17M/Su-22M/Su-22M3 was the most numerous variant with almost 1,000 built.

Su-17UM (S-52UM)
The initial trainer version with the same avionics suite as the Su-17M.The export version was designated Su-22UM3 with R-29 engine, and Su-22UM3K with the AL-21 engine. Manufactured 1978-1982.

Su-17UM3 (S-52UM3, "Fitter-G")
Revised trainer with the same avionics suite as the Su-17M3. First flight: 21 September 1978 with Yu. A. Yegorov at the controls. The export version was designated Su-22UM3 with R-29 engine, and Su-22UM3K with the AL-21 engine. Manufactured 1978-1982.

Su-17M4 (S-54, "Fitter-K")
    Final production version with considerably upgraded avionics, including RSDN navigation (similar to LORAN), beacon navigation, inertial navigation, a more powerful (Klyon) "Kлён-54" laser rangefinder, radio compass, and SPO-15LE ("Sirena") radar-warning system. Additional fuselage inlets (including ram-air inlet at the base of the fin) to improve engine cooling airflow, fixed air intake shock cone. Many aircraft were equipped for the use of TV-guided missiles and BA-58 Vjuga pod for anti-radiation missiles. AL-21F-3 engine. Export version was designated Su-22M4 (factory S-54K). First flight: 19 June 1980 with Yu. A. Yegorov at the controls. Su-17M4 was manufactured 1981–1988, Su-22M4 was manufactured 1983-1990.

    The initial export version of the Su-17M, (S-32MK).

    A Russian-French upgrade package offered for existing aircraft with modernized cockpit, HOTAS, improved avionic systems. Deletes the laser rangefinder in favor of Phazotron/Thomson-CSF 'Phathom' radar.

    The S-52U two-seat combat-trainer, export version of the Su-17UM, with a completely re-designed nose housing the tandem cockpits for student and instructor.

    Gun pods such as the GSh-23 based UPK-23 and SPPU-22 were utilized by the Su-17, Su-20, and Su-22. The SPPU-22 ground attack variant featured 30 degrees of traverse.

    An experimental version of the Su-20 was built with fixed wings attached to an Su-17M fuselage, in an effort to increase Payload/range performance by eliminating the weight of the wing sweep system. Good results were obtained in flight tests in 1973 but further development was cancelled.

    Tactical Reconnaissance versions of all variants could be made by fitting the KKR (Kombinirovanny Konteiner Razvedy – combined reconnaissance pod) on the centre-line pylon.

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