Captain Jack (Updated: 8/8/2016):
Development - Fitter-B
The Su-7 (NATO codename of "Fitter-A") was a capable aircraft in its own right. However, there were glaring deficiencies in its operational range - no thanks to a thirsty powerplant - and ordnance-carrying capabilities. Sukhoi and Soviet authorities sought other improvements that would make the Fitter series a much more capable and versatile battlefield component. As such, a Su-7BM production model served as the demonstrator for the testing of a new swing-wing variable geometry system development. The new wing would essentially be made up of two parts - a fixed wing root/wing glove and the positional swing-wing portion making up half of the wing (at about mid-wing span). The new prototype became the Su-7IG ("IG" for "Izmenyaemaya Geometriya", also internal designation of "S-22I"). First flight was achieved on August 2nd, 1966. The working prototype/technology demonstrator showed enough promise during this testing phase, improving on both field performance and range of the Su-7, that it was selected for production.
A two-seat Su-7U long-fuselage trainer was then revised. The rear instructor's cockpit would make way for additional avionics and fuel while housing the new wing component. The swing-wing configuration was devised as a way to increase the Su-7's inherent range while at the same time allowing the aircraft to carry more weaponry along its fixed wing portion without the need to implement heavy and complex swiveling weapon stations to maintain aerodynamic integrity in full sweep. A limited production run appeared under the base "Su-17" designation, these being fitted with the Lyulka AL-7F-1 turbojet powerplant of 22,046lbs thrust. Production of this early Fitter-B would run from 1969 to 1973.
The Su-17K became the export version of this base Su-17, though this was only received by the Egyptian Air Force. NATO assigned the new aircraft design the codename of "Fitter-B", sequentially relating this new design with that of the original Su-7 it originated from.
The Rest of the Su-17 Fitter Variants - Beginning with Fitter-C
The Su-17M (S-32M) became the first quantitative production version of note and was known to NATO as "Fitter-C". The aircraft was fitted with an afterburning Lyulka AL-21F-3 engine of 24,800lbs output and was given an onboard SRD-5M range-finding radar (same as the one found on the Su-7BMK production models). A new navigation and attack system was installed for her intended ground attack role. The fuselage was also given a pair of forward-mounted pitot pressure measurement tubes. An Angle-of-Attack (AoA) vane was affixed as was a rear brake parachute, the latter promoting shorter landing runs. First flight was achieved on December 28th, 1971. In addition to her primary battlefield roles, some Su-17s were developed into a limited-production - though still capable - reconnaissance variant under the Su-17R designation featuring reconnaissance pods with applicable equipment. Production of the improved Fitter-C began in 1972 with official introduction occurring in 1973. Production ceased in 1975.
The export version of this ground attack model became the Su-20. The prototype Su-20 first flew on December 15th, 1972. Egypt, Poland and Syria were the primary export customers of this new aircraft. The Su-20R was the export reconnaissance equivalent of the base Su-20 line.
The Su-17M2 was the next definitive development and was assigned the NATO codename of "Fitter-D". She was essentially an improved production form of the former types and was known internally at Sukhoi as S-32M2. The nose assembly was extended by 15 inches and revised to incorporate more of a downward slope to improve the pilot's "out-of-the-cockpit" forward visibility - a plus in the low-level strike role. This new Fitter also deleted the ranging radar but incorporated the Fon-1400 laser rangefinder as well as additional combat-related avionics. A DISS-7 Doppler navigation radar was installed into a fairing under the nose and first flight of the aircraft was achieved on December 20th, 1973. Production began in 1974, lasting until 1977, and the Su-17M2 officially entered Soviet service in 1975. The Su-17M2 featured a fixed shock cone.
The Su-17M2D was another Fitter-D development but fitted with a Tumansky R-29BS-300 series engine of 25,335lbf with afterburning in a revised rear fuselage (this being a defining feature of the variant) and shorter overall fuselage. The engine offered little in the way of improved performance and limited range so was therefore only offered in forthcoming export deliveries. First flight was achieved on January 31st, 1975 and production lasted from 1977 to 1978.
Fitter-E - the Trainer
The Su-17UM was the two-seat trainer form developed from the S-52U prototype and given the NATO codename of "Fitter-E". Production began in 1976, with the aircraft entering service that same year. Production lasted until 1978. This new aircraft featured a deeper revised airframe to make room for the addition of the second cockpit for the instructor. This also resulted in the deletion of some internal fuel space thus limiting the aircraft's range. The original avionics of the production model were maintained while the portside cannon was omitted. The vertical tail fin was enlarged to counteract the effects of longitudinal instability (when in a high AoA). First flight was achieved on August 15th, 1975.
The two-seat Su-17UM went under the export designation of Su-22U and fitted a Tumansky R-29 series powerplant.
The Su-17M2D export model became the Su-22 which fell under the internal Sukhoi designation of S-32M2K. The Su-22 was afforded the same K-36D ejection seat system as found on the modern-day MiG-29 "Fulcrum" and Sukhoi Su-27 "Flanker" jet aircraft series and was powered by a Tumansky R-29 engine. The Su-22 also featured a fixed shock cone, laser rangefinder and Doppler radar.
The Lyulka-powered Su-17UM3 (S-52UM3, NATO codename of "Fitter-G") was a revised conversion trainer with the deeper fuselage and revised vertical tail fin. It fitted the avionics suite of the Su-17M3 and achieved first flight on September 21st, 1978. Production lasted from 1978 until 1982.
The export form was offered as the Su-22UM3 and the Su-22UM-3K, each differing by their use of the Tumansky R-29 and Lyulkin AL-21 series engines respectively.
The Su-17UM two-seat trainer airframe was also used in the development of the S-52, becoming the Su-17M3 ("Fitter-H"). The instructor's cockpit position was naturally removed and made way for additional avionics and fuel stores, the latter benefitting range. The external Doppler radar fairing was moved into an internal position and provision for AA-2 "Atoll and AA-8 "Aphid" along two hardpoints under the wing gloves were added. First flight was achieved on June 30th, 1976. Production lasted from 1976 until 1981. The Su-17M3 (and its related export derivatives) model became the most quantitative Su-17 Fitter development of the series, numbering nearly 1,000 production examples in whole.