Sukhoi Su-17

The Sukhoi Su-17 is a variable-sweep wing fighter-bomber developed for the Soviet military. Developed from the Sukhoi Su-7, the Su-17 was the first variable-sweep wing aircraft to enter Soviet service and featured updated avionics. The aircraft also has variants which were designed for export such as the Sukhoi Su-22 and the less popular Su-20.
It was produced from 1967 to 1990. The Su-17/20/22 series had a long career and has been operated by many air forces, including those of the Soviet Union and other members of the Warsaw Pact, countries in the Arab world, Angola, and Peru.
Although the Su-17 was capable of carrying nuclear weapons, it was used in roles ranging from close-air support to ground attack.

Development

Shortly after the Su-7 fighter-bomber was put into service, the Sukhoi Design Bureau was ordered to develop a modernization program. The program would be aimed primarily at updating on-board avionics and takeoff/landing characteristics. The concept of variable-geometry wings - something gaining wider attention at that time - was adopted. The program was to be led by Sukhoi's head designer, Nikolay Zyrin.
In 1963, the Sukhoi OKB with input from TsAGI created a variable-sweep wing technology demonstrator. The S-22I, converted from a production Su-7BM, had fixed inner portions of the wing with movable outer segments that could be swept to 28°, 45°, or 62°. The S-22I first took off on 2 August 1966. It was later demonstrated at the air parade in Domodedovo in July 1967.
Flight testing revealed that the configuration improved both take-off/landing characteristics, range and endurance. Handling was generally better than the fixed wing Su-7, with the exception that buffeting at high angles of attack to warn of imminent stall no longer occurred.
The aircraft was sent into serial production in 1969 by a joint resolution of the Central Committee of the Communist Party of the Soviet Union and the Council of Ministers. The design of the Su-7IG was modified further, eventually with enough difference to justify the S-32 internal designation. The S-32 first took off on July 1, 1969, with Yevgeny Kukushev at the controls.
Serial production started at Yuri Gagarin Aviation Factory in 1969. The 523rd Aviation Regiment, of the Far East Military Okrug, was the first to receive the Su-17. The Su-17 was produced until 1990, producing 2867 units.
The Su-17 resembles its predecessor, the Su-7, with weight-saving measures added at the cost of combat survivability, an example of which is the removal of pilot protection armor.
The prototype S-22I differed little from the Su-7 except for the wing, essentially a technology demonstrator for the variable-geometry wing. It was later lost in an accident.
Following the S-22I, two pre-production prototypes were constructed, designated S32-1 and the S32-2. The two aircraft mounted updated avionics, and replaced the older AP-28I-2 autopilot with the newer SAU-22 automatic control system.
The next series of prototypes were the Su-7-85, with 85 indicating the batch number. The batch of ten aircraft incorporated a redesigned fuselage, a streamlined cockpit, extra, more accessible maintenance hatches, and an upward-opening canopy. The front of the cockpit was protected with a windshield and two electrically heated side windows. The first three aircraft of the 86th batch incorporated clear windshields with warm air blown at them, taken from the 9th stage of the engine compressor. However, this windshield was dropped in favor of the more traditional glazed windshield following tests by the 4th Combat Use and Retraining of Air Force Personnel Center in Lipetsk.
The Su-7-85 was equipped with a modified KS4-S32 ejection seat, capable of safely ejecting the pilot at speeds above 140–170 km/h.
The fuel system was modified from the Su-7, as well; fuel was stored in three lightweight tanks, with provisions for up to four disposable auxiliary tanks each with 600 litres of capacity, or two PTB-1150 tanks with 1150 litres each, mounted on "wet" pylons under the fuselage.
The wing was largely unmodified from the S-22I. The stationary part of the wing was half as long as the rotating part. With wings at maximum sweep, the Su-17 would look virtually identical to the Su-7. A slide-out flap was installed on the stationary part of the wing, while a slat, a rotating flap and aileron were mounted on the rotating part. The sweep angle could be configured between 30° and 63°. The horizontal and vertical tails were swept at 55°.
Flight control was assisted by non-reversing hydraulic boosters, the BU-220DL2 and -220DP2 for the left and right ailerons, the BU-250L and -250P for the stabilizers and the BU-250DRP for the rudder. The flight control systems were spring-loaded to provide feedback on the stick and the rudder pedals.
Three independent hydraulic systems are installed on the Su-17—an actuating system and two booster systems, each with a hydraulic pump. The actuating hydraulic system was responsible for adjusting the sweep angle of the wing, deploying/retracting the landing gear, the flaps and slats, adjusting the intake ramps, the flight control mechanisms used by the SAU-22 autopilot, and the steering front wheel. The booster systems control the flight surfaces. The systems operate in parallel to ensure safe operation in the event of a failure. The remaining operational system would provide power to the flight surfaces, albeit at half the power. The Nr 1 booster system feeds the GM-40 hydraulic motor driving the rotary parts of the wing. All hydraulic systems are fed with the AMG-10 hydraulic fluid, with a standard operating pressure of 215 kgf/cm² for the booster systems and 210 for the actuating system.
A pneumatic system with a 150kgf/cm² pressure operates the normal and emergency brakes on the landing gear as well as the emergency landing gear/flaps deployment system, and was responsible for charging the two NR-30 cannons mounted on the aircraft, pressurizing the cockpit, opening/closing the canopy and pressurizing the hydraulic fluid tanks.
The Su-17 was powered by a modified Lyulka AL-7F1-250 with a slightly uprated thrust of 9600 kgf on afterburners. It was equipped with a compressor actuator with redundancy, and a system for intake adjustment. The aircraft would need to be disassembled into two halves to replace its engine. Jettisonable SPRD-110 RATO boosters are available to facilitate take-off on short runways, providing a momentary thrust of up to 3000 kgf.
On-board electronics are fed by a 28V DC circuit and a 115V, 400 Hz single-phase AC circuit, fed by two GS-12T DC generators, an SGO-8TF AC generator and a 20NKBN25 nickel–cadmium battery.
The Su-17 has the ability to carry free-fall nuclear bombs with a BDZ-56FNM bomb rack. A special code device would be installed in the cockpit, mandating a correct code input before the bomb could be armed and released, to prevent unauthorized uses of nuclear weaponry. The aircraft also has a toss bombing capability for nuclear weapon delivery, with which it could approach the target, initiate a steep climb and release the bomb when pointing almost upright, and then activate afterburners to escape the blast radius. A special IAB-500 bomb was designed specifically for practicing such a bombing technique.

Operational history

Soviet Union/Russia

The Su-17 was used during the Soviet-Afghan war during Operation South and launched air strikes on a Mujahideen base at Robat Jaali near the Iranian Afghan border.
The Su-17M3/4 were used during the First Chechen War alongside Sukhoi Su-24s and Sukhoi Su-25s in ground attack and reconnaissance missions.
In a move to eliminate single-engine strike aircraft from its inventory, the Russian Air Force retired its last Su-17M4 along with its fleet of MiG-23/27s in 1998.

Angola

The Soviets supplied the communist government of Angola with 12 Su-20Ms in 1982 or 1983, which formed the basis of the 15th FS. The squadron suffered a swift loss of at least six aircraft – most in mishaps – by 1985, and three more by 1988, and had only two aircraft left when it was reinforced with batch of 14 Su-22M-4Ks and two Su-22UM-3Ks in 1989–90.

Iraq

From 22 September 1980 to 20 August 1988, during the Iran–Iraq War, Iraq used Su-17 export versions alongside older Su-7s. They were mostly used in ground-attack and close air support roles. Iranian Grumman F-14 Tomcats shot down 21 Su-20/-22s, that western sources have confirmed. Eighteen Su-20/-22s were also shot down by Iranian McDonnell Douglas F-4 Phantom IIs. and three by Iranian Northrop F-5s. On 20 October 1980 an Iraqi Su-20 shot down an Iranian F-4E with its 30 mm cannons.
Official Iraqi accounts show no loss of Su-20 aircraft throughout the war against the Kurds and Iran. Twenty Su-22M2s, two Su-22M3s and seven Su-22M4s were lost during the war with Iran, the majority to anti-aircraft fire sustained during low-level bombing raids against Iranian front lines.
In 1991, during the Gulf War, Iraqi Su-22s saw limited active service because the Iraqi regime distrusted the Iraqi Air Force. On 7 February 1991, two Su-20/22s and one Su-7 were shot down by United States Air Force McDonnell Douglas F-15 Eagles using AIM-7 air-to-air missiles when the IQAF was moving its aircraft to Iran.
On 20 and 22 March 1991, two other Su-22s were downed by USAF F-15s in an attempt to protect Kurdish civilians before the start of Operation Provide Comfort to provide humanitarian aid and the establishment of a no-fly zone north of 36th parallel.

Libya

Two Libyan Su-22s were shot down in the Gulf of Sidra incident by United States Navy Grumman F-14 Tomcats on 19 August 1981. One Su-22 launched a K-13 missile head-on at one of the F-14s from an estimated 300-meter closing distance, however the missile was evaded. Both were then downed by AIM-9 Sidewinder missiles.
On 8 October 1987, in the aftermath of the Chadian–Libyan conflict, an Su-22 was shot down by a FIM-92A Stinger launched by Chadian forces. The pilot, Capt. Diya al-Din, ejected and was captured. He was later granted political asylum by the French government. During the recovery operation, a Libyan Mikoyan-Gurevich MiG-23MS was shot down by a Stinger.
A Libyan Su-22 crashed near Benghazi on 23 February 2011. The crew members, Captain Attia Abdel Salem al Abdali and his copilot, Ali Omar Gaddafi, were ordered to bomb the city in response to the Libyan Civil War. They refused, bailing out of the aircraft. Su-22s were heavily used by Libyan loyalist forces against insurgent forces from mid-February to mid-March 2011, when the international mission started and the no fly zone was imposed. Among other missions, Su-22s attacked Anti-Gaddafi positions in Bin Jawad in early March 2011 as government forces retook the town.
One Libyan Air Force Su-22 was destroyed on the ground by a Belgian Air Force F-16AM on 27 March.