Sukhoi Su-27 ‘Flanker’

A Su-27 ‘Flanker-B’ of the 582nd Fighter Aviation Regiment, part of the Soviet 4th Air Army based at Chojna, Poland, in 1990. In the same year this unit withdrew its 32 Su-27s from Poland and relocated to Smolensk, Russia, where it disbanded in 1992.

Sukhoi’s Su-27 family represents the most potent fighter/attack aircraft in the Russian inventory, equipping several branches of the Russian military.

MiG-29 and Su-27 Backstory

In about 1969 all three of the Soviet Union’s Fighter Design Bureaux began to look at ideas for a fourth-generation fighter. Part of the work involved analysing the operational experience of current types in various regional conflicts so that the design teams might be able to give their new aircraft enhanced capabilities. Much of this effort was stimulated by the appearance of the American F-X fighter programme, which brought forth the McDonnell-Douglas F-l5. The Soviets monitored the progress of this programme very closely because their response would have to be more than a match for the American aircraft, an immensely difficult objective to achieve.

In 1971 TsNIl-30, a division of the Soviet Ministry of Defence, issued the first General Operational Requirement for a fourth-generation fighter, which tentatively was designated PFI (perspektiunyy frontovoy istrebeetel or advanced tactical fighter). The aircraft’s primary tasks would be to deal with enemy fighters in close-in combat using new short-range AAMs or an internal gun, or to intercept aerial targets at more distant ranges and destroy them with new medium-range AAMs; the latter would be achieved either by using the aircraft’s own ‘look-down/shootdown’ radar or with guidance from ground control stations. The aircraft would also undertake other duties, such as ground attack, and compared to previous types it would be more agile and manoeuvrable and carry a set of all-new avionics. Maximum speed had to be at least 1,400km/h (870mph) at sea level and 2,500km/h (1,554mph) at 11,000m (36,089ft) and the maximum Mach number was to fall between 2.35 and 2.5. Sea level rate of climb had to be at least 300m/sec (984ft/sec), service ceiling 21,000m (68,898ft), maximum range without drop tanks 1,000km (622 miles) at sea level and 2,500km (1,554 miles) at height, and the takeoff thrust-to-weight ratio had to be between 1.1 and 1.2.

In 1972, after having revised the Operational Requirements, the WS issued a request for proposals for new fighters. Mikoyan submitted two versions of its MiG-29 project, Sukhoi’s entries were the T10-1 and T10-2 projects and Yakovlev entered the Yak-451 light lighter and the Yak-47 heavy fighter. These designs and their background are described below and the outcome was to be a mix of light and heavy fighters for the Soviet Air Force. The seeds for this result came from some references made in 1971 by the Government’s research establishments, which stated that the fighter fleet planned for the 1980s should be based on two types, one heavy and one light. This move followed American practice where it was becoming clear that the US Air Force’s heavy F-15 Eagle would be complemented by a new lightweight fighter in a competition eventually won by the General Dynamics F-16 Fighting Falcon.

Sukhoi began work on its T-10 design in 1969 with the aim of creating a highly agile fighter that possessed a very long range, heavy armament and sophisticated sensors. In order to maximize manoeuvrability, the fighter was planned from the start to be unstable, and therefore required a fly-by-wire (FBW) control system. The first prototype of the T-10 took to the air in May 1977 and received the NATO reporting name ‘Flanker-A’. However, in its initial form the four original T-10 prototypes displayed a number of serious deficiencies and the aircraft required a wholesale redesign, re-emerging as the radically reworked T-10S-1 of 1981.

The T-10S entered series production in 1982, and received the in-service designation Su-27 (NATO ‘Flanker-B’). Service entry followed in 1984 and the single-seater was joined by the Su-27UB (NATO ‘Flanker-C’) fully combat-capable two-seater that first flew in 1985. By the end of the Cold War, a total of just over 400 Su-27s of both versions were in Soviet service.

As in the 1950s, Sukhoi was assigned the bigger aircraft. The T-10-1 prototype flew before the first MiG, on 20 May 1977. Powered by AL-21F-3 engines, almost identical to those of later Tu-128s, it was impressive, but as testing of later T-10s progressed they ran into severe and sometimes fatal problems. Some redesign was necessary, and General Designer Simonov told the author, ‘In the end, we managed to retain the main wheels and ejection seat’ (he was not really joking). What followed, starting with the T-10S, became the Su-27, perhaps the most beautiful, and certainly most impressive, fighter ever built. When it appeared, Western analysts predictably wrote things like, ‘A cross between the F-15 and F/A-18’. Simonov said, ‘You can’t win if you just copy.’ Once Western pilots were allowed to fly the Su-27 one heard comments like ‘What an airplane! If only I could afford to buy one.’ Most production versions have the outstanding AL-31F engine, which among other things can tolerate having its inlet rotate nose-up through up to 135° in what is called the Cobra manoeuvre (which no Western fighter has yet been able to do). Later Su-27 versions, including the Su-30, 33, 35 and 37 (note, not the S-37), have later engine versions, some of which have a fully vectoring engine nozzle, and in many cases canard foreplanes. Virtually all production today is for export, though small numbers of naval and land-based bomber versions have been delivered, and advanced variants are being produced under licence in China and India.

After the collapse of the USSR, ‘Flankers’ were passed on to successor states, and Russia began an export drive for the fighter. First of the export models was the baseline Su-27SK developed for China, basically similar to the ‘Flanker-B’, but with additional air-to-ground capabilities. China also received a ‘Flanker-C’ equivalent, the Su-27UBK. After around 80 Russian-built Su-27SK/UBKs were delivered, China launched licensed production of 95 additional single-seat ‘Flankers’ (designated as J-11).

Vietnam was the second customer, ordering a first batch of six ‘Flankers’ (including one two-seater), and a second batch of two Su-27SKs and four Su-27UBKs. Ethiopia purchased second-hand ex-Russian ‘Flanker-B/ Cs’, while Indonesian acquired two Su-27SKs and three of the improved Su-27SKM single-seater (the latter equivalent to the Su-27SM described later). ‘Flanker-B/C’ exports also included ex-Ukrainian aircraft sold to Eritrea and Ethiopia, while Angola received two ‘Flankers’ from an unknown source, likely Belarus.

While not modular in the hardware sense, the Russian Sukhoi Bureau has come very close to producing an array of types from its baseline T-10. There is the vanilla Su-27 Flanker air superiority fighter and Su-27UB twin-seat trainer stablemate (with full operational capability). The Su-27P single- seater and Su-30 (formerly the Su-27PU) twin-seater are optimized for strategic interception duties and embody extensive data-links for intercommunication and long-range missile guidance. The Su-30M is the basic fighter with added provisions for ground attack. The Su-33 (formerly Su-27K) is the navalized version. The side-by-side seat Su-34 is an advanced strike model (formerly Su-27IB). Probably far from being the definitive version is the canard, digital avionics- equipped Su-35! SEAD radar-smashing, plus Elint and E-0 reconnaissance versions are also being evolved, all from a common set of blueprints, and pushed aggressively by Mikhail Simonov, Sukhoi’s general designer.

The Flanker, represented a quantum leap in technology as well as performance. In particular, the Su-27’s pair of Saturn-Lyulka AL-31F engines are rated at a combined total thrust of 55,125 Ib, making it the hottest twin-engined operational fighter in the world in terms of raw thrust to weight performance. The engines of the Su-33 (formerly Su-27K), the navalized version, are 12-15 per cent more powerful yet. Most significantly, the powerplants can accumulate 2,000-2,500 tactical cycles (each representing the full range of metal-grinding throttle settings normally encountered in an average air combat sortie) between hot-section inspections. In contrast to this, in the West, the latest F100-PW-229 and GE Fll0-100 engines powering the Fighting Falcon and Eagle have been plagued by fourth-stage turbine blade cracks and turbine seal problems. These have caused engine failures after only 200 tactical cycles, and the loss of several aircraft.

‘Hammer and nail’ engine technology has in this instance been superseded by advanced materials technology akin to that available in North America: powder metallurgy. Atomized molten metal is super- frozen into powdery crystals, then bound together and tempered in moulds under intense heat and pressure. The technology was pioneered by Pratt & Whitney, along with ceramic-coated ‘Gatorizing’. Powder metallurgy offers incredible uniformity for highly stressed components such as engine turbine blades, which are twin heat-treated to produce a fine grain, massively strong bore and a coarser-grained rim optimized for greater tolerance to damage.

While Pratt & Whitney are ahead in the game, and are developing even more sophisticated metal matrix composites using carbon fibre reinforcement in a titanium matrix for engine parts for application to the F-22A Rapier’s F119 powerplants, the technology is only just maturing. The latest Russian engines can suffer massive abuse by being speedily throttled up and down. Fast throttling was a feature previously unavailable to Eastern Bloc aircraft which required more gentle persuasion. Many early Fulcrums required new engines after only 1,400 flying hours, as well as regular overhauls at 250-hour intervals. Russian titanium forging for engine bay housings and airframe structural members has also long since surpassed contemporary Western technology. Moving engine production to specialist development factories appears to have paid off in terms of quality control too in recent years.

All of this has produced fighters equipped with powerplants offering phenomenal performance, yet with the durability that was seldom a hallmark of past, cruder design and fabrication methods. Traditional hydromechanical engine controls have similarly been replaced with a DEECS/FADECS-class system, controlling fuel flow and trim digitally. Supercruise (acceleration to supersonic speed and sustained supersonic flight without afterburner engaged) was just possible in the Flanker (given its massive fuel reserves). This was long before Lockheed’s YF-22 and the competing Northrop-McDonnell Douglas YF- 23 battled it out in the skies over California for Full- Scale Development Advanced Tactical Fighter contracts during 1990. But that the Flanker is far from the Mach 1.5-1.6 mil power maximum cruise climb class offered by the new American warplane, and the latest Mikoyan ‘MiG 1.42’ will lag behind a tad. Yet these concepts are flying off the computer-aided design/computer-aided manufacturing (CAD/CAM)) drawing boards and some are already reaching operational service. Surprisingly, nobody really took notice of the CIS hardware much before the pioneering production variants began to appear in large numbers, and then they mostly assumed that they were time-lag copies of the Hornet and Eagle.

The shock wave hit home when the Mikoyan, then subsequently the Sukhoi OKB, showed their wares off at Paris and Farnborough. The crowds were thrilled by amazing tail slides and Cobra manoeuvres which clearly demonstrated the new fighters’ incredible agility, throat-choking engine relights at low-level, and their massive stability at high-AoA. (AoA is usually measured as an index rather than in degrees. It reflects the angular difference between the wings relative to forward motion. The higher the AoA capability, the more forgiving and manoeuvrable is the fighter, it is argued.) The only Western fighters capable of hinting at such antics, apart from the much- delayed F-22A Rapier, are specialized research aircraft or heavily-modified Hornet stock. This gave rise to much balking about the validity of such Russian manoeuvres, probably rooted in not-invented- here petty jealousies.

In aerial combat, the nose-up Cobra and Pugachev’s new Hook (similar, but conducted in the horizontal axis at 90° of bank while pulling 9 #!), in particular, can quickly nullify Doppler radar returns, causing AWACS and air intercept radars to hiccup. Although these antics massively burn up energy and thus may place the aircraft at a severe disadvantage in impending close-quarters air-to-air combat, in the LRI scenario in the counter-AWACS role, they might prove lethal. Of course, such a disadvantage does not necessarily follow. If both combatants have bled off a great deal of energy and are tumbling over each other, struggling for advantage in a horizontal or vertical spiralling barrel roll or scissors motions, the wide FoV of the Russian fighters’ armaments can be brought to bear quickly and decisively in ACM, as we shall discuss shortly.

One tactic Russian pilots used to practise was that of approaching a simulated AWACS and its HavCAP protective Flight at high speed in a couple of closely- welded Para or two-ship Flights. Each wingman was placed 5 ft to the right and 70 ft behind his leader (‘close enough to follow my visual signals but clear of my turbulent engine exhaust and wing vortices’, as one former pilot described it). While still beyond the point where raid assessment signal processing techniques might be used by the defenders to resolve the two acquired tags into four aircraft, the two leaders signal a break the moment just after AWACS or a fighter PD radar lit up their coloured SPO-15 Beryoza RWR systems at full intensity. These then fling themselves out in Doppler-negating Split-S, Cobra or Hook antics, before diving down to low-level, building up energy reserves once more in the process.

Meanwhile the two decoys maintain their headings so as to keep the AWACS computers thinking all was in order, before they, too, ‘knocked it off and withdraw. This introduces some complacency into the minds of the AWACS operators. During these few precious seconds the two snipers close in for the kill at low-level. By the time the AWACS or its minions acquire them and before fighters can be vectored into a firing position, the two swooping snipers close, lock- on passively and launch up to four air-to-air rotordome-homing ARMs (believed to be aerial adaptations of the ramjet-powered Kh-31P ARM), or the first volley from up to a dozen KS. 172 long- ranged AAMs. These go right through the defending HavCap, aimed straight at AWACS, kicking the proverbial wasp’s nest and turning it into a frenzied but uncoordinated communications morass with Flights getting inadequate JTIDS picture calls.

Western pilots have become so dependent on AWACS that this scenario would cause them considerable confusion. It is important to note that Eastern European AAM missile technology – what the Russians refer to as rockets – includes much bizarre hardware optimized for specialist use by highly skilled sniper pilots, including devices designed to pick up the Doppler effect created by swirling helicopter rotor blades. Thus, they can take out low-level SEAD pathfinders, medium-altitude AWACS, and bombers too by means of home-on-jam techniques. AWACS-killing technology, in particular, is very sophisticated. It allows launch-and-leave at extreme range: 60 miles unassisted, and double that with boosters which offer massively increased burn- out speeds, making the rockets tough to intercept before they unleash their deadly cargoes.

Specification (Su-27 `Flanker-B’)

Type: All-weather air superiority fighter

Dimensions: Length: 21.90m (71ft 10in); Wingspan: 14.70m (48ft 2.75in); Height: 5.93m (19ft 5.5in)

Weight: 33,000kg (72,751lb) maximum take-off

Powerplant: 2 x 122.58kN (27,557lb) Saturn/Lyulka AL-31F afterburning turbofans

Maximum speed: 2280km/h (1417mph) `clean’ at 11,000m (36,090ft)

Range: 3680km (2287 miles) at high altitude

Service ceiling: 17,700m (58,071ft)

Crew: 1

Armament: 1 x 30mm (1.18in) cannon and up to 6000kg (13,228lb) of disposable stores including up to 6 x medium-range and 4 x short-range AAMs

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