Sukhoi Su-27
The Sukhoi Su-27 is a Soviet-origin twin-engine supersonic supermaneuverable fighter aircraft designed by Sukhoi. It was intended as a direct competitor for the large US fourth-generation jet fighters such as the Grumman F-14 Tomcat and McDonnell Douglas F-15 Eagle, with range, heavy aircraft ordnance, sophisticated avionics and high maneuverability. The Su-27 was designed for air superiority missions, and subsequent variants are able to perform almost all aerial warfare operations. It was designed with the Mikoyan MiG-29 as its complement.
The Su-27 entered service with the Soviet Air Forces in 1985. The primary role was long range air defence against American SAC Rockwell B-1B Lancer and Boeing B-52G and H Stratofortress bombers, protecting the Soviet coast from aircraft carriers and flying long range fighter escort for Soviet heavy bombers such as the Tupolev Tu-95, Tupolev Tu-22M and Tupolev Tu-160.
The Su-27 was developed into a family of aircraft; these include the Su-30, a two-seat, dual-role fighter for all-weather, air-to-air and air-to-surface deep interdiction missions, and the Su-33, a naval fleet defence interceptor for use from aircraft carriers. Further versions include the side-by-side two-seat Su-34 strike/fighter-bomber variant, and the Su-35 improved air superiority and multirole fighter. A thrust-vectoring version was created, called the Su-37. The Shenyang J-11 is a Chinese license-built version of the Su-27.
Development
In 1969, the Soviet Union learned of the U.S. Air Force's "F-X" program, which resulted in the F-15 Eagle. The Soviet leadership soon realised that the new American fighter would represent a serious technological advantage over existing Soviet fighters. "What was needed was a better-balanced fighter with both good agility and sophisticated systems." In response, the Soviet General Staff issued a requirement for a Perspektivnyy Frontovoy Istrebitel. [|Specifications] were extremely ambitious, calling for long-range, good short-field performance, excellent agility, Mach 2+ speed, and heavy armament. The aerodynamic design for the new aircraft was largely carried out by TsAGI in collaboration with the Sukhoi design bureau.When the specification proved too challenging and costly for a single aircraft in the number needed, the PFI specification was split into two: the LPFI and the TPFI. The LPFI program resulted in the Mikoyan MiG-29, a relatively short-range tactical fighter, while the TPFI program was assigned to Sukhoi OKB, which eventually produced the Su-27 and its various derivatives.
The Sukhoi design, which was altered progressively to reflect Soviet awareness of the F-15's specifications, emerged as the T-10, which first flew on 20 May 1977. The aircraft had a large wing, clipped, with two separate podded engines and a twin tail. The 'tunnel' between the two engines, as on the F-14 Tomcat, acts both as an additional lifting surface and hides armament from radar.
The T-10 was influenced by the Sukhoi Aircraft Design Bureau, Central Aero-Hydrodynamic Institute and the Siberian Aviation Research Institute in their development of a new aerodynamic scheme labelled the 'integral scheme', where the aircraft would have optimal performance under a longitudinal instability of 3-5% mean aerodynamic chord while flying in subsonic regimes as well as fly by wire for future heavy fighters. Stability problems present in the development of airframes under similar performance demands such as the YF-22 and JAS-39 Gripen were rectified during the FBW development process through limitation of normal load factor and angle of attack. Controlled high angle of attack maneuverability, known as supermaneuverability, was emphasized after a 1980s study by research teams from Su-ADB and TsAGI showing its effectiveness in close combat.
Air Force
The first batch of flying prototypes were T-10-1 and T-10-2. They were powered by Lyulka AL-21 turbojets and had ogival wings. The aerodynamic layout was found to be unsatisfactory during construction; this was verified starting with T-10-1's maiden flight on 20 May 1977. The aircraft completed trials in November 1983 and donated to the Soviet Air Force Museum in late-1985. T-10-2 first flew on 16 May 1978. On 7 July 1978, it crashed and killed the pilot; the aircraft exceeded its G limit and broke-up in flight after behaving unpredictably when the control stick was pulled back. The prototypes were initially called "Ram-K" by Western intelligence; they were first spotted by Western satellite imagery at the Flight Research Institute's "Ramenskoye" airfield at Zhukovsky; they were later assigned the NATO reporting name "Flanker-A". Komsomolsk-on-Amur Aircraft Plant built second batch - T-10-3 and T-10-4 - starting in 1978. These were the first to be fitted with the intended powerplant, the Lyulka AL-31 turbofan, and their engine nacelles were redesigned accordingly. T-10-3 was initially used for powerplant testing; it first flew on 23 August 1979 after being delayed by engine trouble. In 1982 and 1983, it performed land-based STOBAR tests for naval aviation. T-10-4 was used for avionics and armament testing with the Mech radar. Tests with the T-10-4 and the later T-10-10 revealed serious deficiencies with the Mech radar. KnAAPO built a third batch of "type T-10-5" AL-21-powered aircraft - T-10-5, T-10-6, T-10-9, T-10-10, T-10-11 - for avionics tests. T-10-6 was destroyed in October 1980 in a ground fire caused by a leaking fuel line. T-10-10 and T-10-11 performed radar, weapons control and targeting tests. These prototypes found that avionics weight, AL-31 fuel consumption, and aerodynamics failed to meet requirements.The aircraft underwent a major redesign. Sukhoi accepted greater cooperation from SibNIA, which conducted extensive wind tunnel testing. Contemporary Western aircraft were examined for ideas. The new design - T-10S - bore only a superficial resemblance to the T-10; the design was completed in 1980 and was the precursor to the production Su-27. The first batch of flying T-10S prototypes were T-10-7 and T-10-12. T-10-7 was used for handling, manoeuvring, and AL-31 tests; it had no radar or mission avionics. It first flew on 20 April 1981, and crashed on 3 September 1981 after a critical in-flight failure; the pilot ejected and survived, but the project's chief was replaced and the flight engineer was dismissed. T-10-12 was completed by KnAAPO in March 1981 for fire control testing. On 23 December 1981, it broke-up in flight and killed the pilot. Sukhoi's general designer was dismissed after the crash. KnAAPO produced additional batches in 1982 - T-10-15, T-10-17 to T-10-22 - and 1983 - T-10-23 to T-10-27. T-10-17 was the first aircraft built to full production standard and first flew on 26 May 1982. In 1983, it landed after losing part of a wing and a tail fin from structural failure. T-10-21 crashed on 25 May 1984 after a structural failure of a leading edge flap; the pilot ejected and survived.
The T-10S-3 was modified and officially designated the P-42, setting a number of world records for time-to-height, beating those set in 1975 by a similarly modified F-15 called "The Streak Eagle". The P-42 "Streak Flanker" was stripped of all armament, radar and operational equipment. The fin tips, tail-boom and the wingtip launch rails were also removed. The composite radome was replaced by a lighter metal version. The aircraft was stripped of paint, polished and all drag-producing gaps and joints were sealed. The engines were modified to deliver an increase in thrust of, resulting in a thrust-to-weight ratio of almost 2:1.
The production Su-27 began to enter VVS operational service in 1985, although manufacturing difficulties kept it from appearing in strength until 1990. The Su-27 served with both the V-PVO and Frontal Aviation. Operational conversion of units to the type occurred using the Su-27UB twin-seat trainer, with the pilots seated in tandem.
When the naval Flanker trainer was being conceived the Soviet Air Force was evaluating a replacement for the Su-24 "Fencer" strike aircraft, and it became evident to Soviet planners at the time that a replacement for the Su-24 would need to be capable of surviving engagements with the new American F-15 and F-16. The Sukhoi bureau concentrated on adaptations of the standard Su-27UB tandem-seat trainer. However, the Soviet Air Force favoured the crew station approach used in the Su-24 as it worked better for the high workload and potentially long endurance strike roles. Therefore, the conceptual naval side-by-side seated trainer was used as the basis for development of the Su-27IB as an Su-24 replacement in 1983. The first production airframe was flown in early 1994 and renamed the Su-34.
Navy
Development of a version for the Soviet Navy designated Su-27K commenced not long after the development of the main land-based type. Some of the T-10 demonstrators were modified to test features of navalized variants for carrier operations. These modified demonstrators led to specific prototypes for the Soviet Navy, designated "T-10K". The T-10Ks had canards, an arresting hook and carrier landing avionics as well as a retractable inflight refueling probe. They did not have the landing gear required for carrier landings or folding wings. The first T-10K flew in August 1987 flown by the famous Soviet test pilot Viktor Pugachev, performing test takeoffs from a land-based ski-jump carrier deck on the Black Sea coast at Saky in the Ukrainian SSR. The aircraft was lost in an accident in 1988.At the time the naval Flanker was being developed the Soviets were building their first generation of aircraft carriers and had no experience with steam catapults and did not want to delay the introduction of the carriers. Thus it was decided to use a takeoff method that did not require catapults by building up full thrust against a blast deflector until the aircraft sheared restraints holding it down to the deck. The fighter would then accelerate up the deck onto a ski jump and become airborne.
The production Su-27K featured the required strengthened landing gear with a two-wheel nose gear assembly, folding stabilators and wings, outer ailerons that extended further with inner double slotted flaps and enlarged leading-edge slats for low-speed carrier approaches, modified leading edge root extension with canards, a modified ejection seat angle, upgraded fly-by-wire, upgraded hydraulics, an arresting hook and retractable inflight refuelling probe with a pair of deployable floodlights in the nose to illuminate the tanker at night. The Su-27K began carrier trials in November 1989, again with Pugachev at the controls, on board the first Soviet aircraft carrier, called Tbilisi at the time and formal carrier operations commenced in September 1991.
Development of the naval trainer, called the Su-27KUB, began in 1989. The aim was to produce an airframe with dual roles for the Navy and Air Force suitable for a range of other missions such as reconnaissance, aerial refuelling, maritime strike, and jamming. This concept then evolved into the Su-27IB for the Soviet Air Force. The naval trainer had a revised forward fuselage to accommodate a side-by-side cockpit seating arrangement with crew access via a ladder in the nose-wheel undercarriage and enlarged canards, stabilisers, fins and rudders. The wings had extra ordnance hardpoints and the fold position was also moved further outboard. The inlets were fixed and did not feature foreign object damage suppression hardware. The central fuselage was strengthened to accommodate maximum gross weight and internal volume was increased by 30%. This first prototype, the T-10V-1, flew in April 1990 conducting aerial refuelling trials and simulated carrier landing approaches on the Tbilisi. The second prototype, the T-10V-2 was built in 1993 and had enlarged internal fuel tanks, enlarged spine, lengthened tail and tandem dual wheel main undercarriage.