Military Aviation

Sukhoi Su-27 'Flanker'

The Su-27 'Flanker' represents one of the jewels in the Soviet aerospace industry's crown. A modified version of the aircraft shattered 27 world records (taking most from a similarly modified example of its Western equivalent, the F-15 Eagle), and in countless displays the aircraft has demonstrated manouevres which no Western fighter can emulate, and has done so reliably and safely, at airshow altitudes. The aicraft's reputation is nonetheless tarnished by doubts about its avionics, by doubts about its agility at operational weight, and by an early history of problems severe enough to require a total redesign. Work on the T-10 design began in 1969, when the Sukhoi OKB began work on a new interceptor for the IA-PVO, working closely with TSAGI, the MM Saturn engine design bureau and a number of research establishments. The design team was led by Yevgeny Ivanov, although Sukhoi himself took a close interest in the aircraft until his death in 1975. The requirement was for a highly manoeuvrable fighter with very long range, heavy armament and modern sensors. It was to be capable of intercepting low-flying NATO attack aircraft and high-level bombers, and to be able to meet agile fighters like the F-15 on equal terms.

Sukhoi Su-27 Flanker image1 Early production Su-27s had simple strakes on either side of the tail sting, rather than the box-like fairings which on later aircraft house chaff/flare dispensers. They also retain small anti-flutter weights on the leading edge of each tailfin.

In many ways, the Su-27 could be regarded as a scaled-up MiG-29, although Mikoyan and Sukhoi arrived at similar configurations because they were designing similar highly-agile fighters which were to be able to explore hitherto impossible parts of the flight envelope, and were relying on input from the same research institutes. The aircraft was thus designed around a highly-blended forebody and high-lift wing, with ogival leading-edge root extensions.

To maximase the manoeuvrability, the T-10 was designed from the outset to be unstable, and therefore required a computer-controlled fly-by-wire control system at least in pitch. The OKB was able to draw on the experience it had accumulated during the T-4/Su100 Mach 3 bomber programmem for which a FBW control system had been designed. The first prototype T-10, powered by a pair of AL-21 F-3 turbojets, made its maiden flight on 20 May 1977 in the hands of chief test pilot Vladimir Ilyushin. The provisional reporting name 'Ram-J' allocated then was eventually replaced by the appelation 'Flanker-A'. The first four prototypes (T-10-1/4) were constructed at the bereau's own experimental shop in Moscow, and five more (T-10-5, -6, -9, -10 and -11) were built at Komsomolsk-na-Amur. From T-10-3 the aircraft were powered by Saturn (Lyul'ka) AL-31F turbofans, which gave about 12 per cent more thrust and much better specific fuel consumption.

Sukhoi Su-27 Flanker image2This late-production Su-27 carries an individual aircraft excellence award on the nose, together with a series of small red stars. It is seen on approach to Chojna, once home to the 582nd IBAP and one of two Frontal Aviation 'Flanker' bases in Poland. The two-tone radome is noteworthy, the lighter color denoting the extent of the Su-27's twist cassegrain antenna.

The early flight development programme revealed serious problems. The second prototype was lost in a fatal crash, the aircraft weight escelated and fuel consumption proved higher than expected. Furthermore, the F-15 entered service, and it became clear that the T-10 as it was would be an inferior aircraft. Accordingly, the new designer general, Mikhail P. Simonov, supervised a total redesign. The T-10-7 was completed as the first prototype of the new design, under the designation T-10S-1, making its maiden flight on 20 April 1981. This was effectively a completely new aircraft, with a redesigned wing which had a straight, slatted leading edge and cropped wingtips incorporating missile launch rails. The latter also doubled as antiflutter weights.

Ailerons were deleted, to be replaced by flaperons and differential tailerons, while the entire fuselage was redesigned, with a deeper spine and shallower nose. The mainwheel door airbrakes were replaced by a spine-mounted airbrake and the undercarriage was redesigned and repositioned. The nosewheel was moved aft to improve taxiing characteristics and to minimise foreign object ingestion on take-off or landing. The tailfins were moved outboard from the tops of the engine nacelles to booms which lay alongside them. These changes were sufficient to prompt NATO to allocate a new reporting name of 'Flanker-B'.

Sukhoi Su-27 Flanker image3 This Lipetsk-based Su-27 is fitted with wingtip Sorbitsya ESM pods. 'Red 10' is seen diving on a ground target during a strafe attack, demonstrating the aircraft's secondary attack role. It sports a gaudy sharkmouth on each engine intake and carries a five-round 130-mm rocket pod under the starboard wing.

The original T-10s were used in the flight test programme alongside the T-10S-1, and preparations were put in hand for series production. Before production could begin, more problems had to be solved, the most serious being a wing fault which killed one pilot and nearly destroyed a second aircraft. Reducing the area of the leading-edge slats proved to be the answer.

The Su-27 finally began to enter operational service during the mid-1980s. although deliveries were at one stage held up by delays with the aircraft's advanced new radar. This led to completed but radarless Su-27s being stockpiled outside the Komsomolsk factory for several months. The earliest Su-27s delivered had a frameless rear canopy section and square-topped tailfins, but later aircraft added a frame behind the pilot's ejection seat headrest and cropped off the rear top corners of the fintips. Later still, prominent spikes on the fin leading edges (thought to be anti-flutter devices) were removed.

One interesting Su-27 sub-variant was the P-42. This had its radar and radome removed and replaced by ballast and a metal noseconem and had ventral fins, fincaps and paint removed. The aircraft was powered by uprated AI-31F engines (designated R-32) and was used to set a series of time-to-height and other records, in the hands of Victor Pugachev, Nikolai Sadovnikov, Oleg Tsoi and Yevgeni Frolov. Because the lightened aircraft's brakes could not hold it against the full thrust of the more powerful R-32 engines, it had to be tethered to an armoured vehicle while it ran up to full power, before being released using an electronic locking device.


Sukhoi Su-27 Flanker image4 Ukraine has about 60 Su-27s in service with at least two regiments: the 62nd IBAP at Bel'bek, as part of the new Air Defence Force's Southern Region, and the 831st IBAP at Mirgorod, which is part of the tactical air arm.

The standard Su-27 fighter is now in service with the Russian and Ukrainian airforces, and serves with Frontal Aviation as well as the old PVO air defence force. It is used primarily in the air-to-air role, although it can carry a range of freefall bombs and unguided rockets underwing, and the air-to-ground role has been practised by some Su-27 units. Even in Frontal Aviation, however, the Su-27 is primarily used as an interceptor or escort fighter and not as a ground attack aircraft.

The Su-27 is equipped with an advanced pulse-Doppler radar, whose large antenna gives longe range, although poor signal processing means that only one target can be engaged at a time. The radar is backed up by a sophisticated EO complex which includes an IRST system and a collimated laser rangefinder. This allows the Su-27 to detect, track and engage a target without using radar. The Su-27 is also compatible with a helmet-mounted target designation system, faciliating the pilot's engagement of off-axis targets by cueing sensors or missile tracker heads onto a target which has not been boresighted.

Sukhoi Su-27 Flanker image5 The sole export customer to date has been China, whose People's Liberation Army Air Force has taken delivery of 24 or 26 'Flankers'. They were delivered in a new medium grey scheme witn an unusual 'cut-out' in the lower part of the radome.



The Su-27 has a total of 10 hardpoints that allow it to carry up to six R-27 (AA-10 'Alamo') and four AA-11 'Archer' air-to-air missiles, giving remarkable degree of combat persistence. Missiles are backed up by a 30-mm GSh-30-1 cannon in the starboard wingroot, with 150 rounds of ammunition. In either the air-to-air or air-to-ground roles, the wingtip missiles launch rails can be replaced by ECM pods.


Su-27s were originally delivered to the integrated armed forces of the former USSR, but most have been absorbed into Russia's armed forces, the CIS having failed to keep central control of unified forces. The aircraft were originally ordered for the IA-PVO air defence force, but were also delivered to Frontal Aviation units. In 1994, approximately 200 serve with Frontal Aviation. Known users include the 234th 'Proskurovskii' Guards IAP at Kubinka, the 159th 'Novorossiisk' Guards IAP at Biesowice (formerly at Kluczewo, Poland), the 831st IAP at Mirogorod (Carpathian Military District), 54th IAP at Vainodo and 689th IAP at Nivenskoye (both Leningrad/St Petersburg MD). The 582nd IAP at Chonja, Poland, moved to Smolensk and disbanded at the end of 1992. Perhaps the best known Su-27s are the aircraft of the 234 'Proskurovskii' Guards Fighter Regiment based at Kubinka, near Moscow, which provides the 'Russian Knights' aerobatic team.

The break-up of the USSR left some Su-27 regiments on non-Russian territory, most such units then being absorbed by the new air arms of the states involved. The 62nd IAP at Bel'bek became part of the Ukrainian air force, and other Ukrainian Su-27 regiments were based at Zhitomir and Sevastapol. In 1994 Ukraine fielded a further Su-27 regiment at Mirgorod.Formerly assigned to the 24th Air Army, the 831st IAP now forms part of the 5th Air Army's tactical assets and retains its previous role of long-range fighter escort for Ukraine's Su-24 'Fencers'. In Byelorussia, Su-27s may serve with the former 61st IAP at Baranovidu. Since all Su-27 production is sentered in Russia, spares support for these aircraft may be difficult, and many may be replaced by types which are easier to support locally.

The first true export customer for the Su-27 was China, ordering 24 aircraft which were delivered from August 1991, following a March 1991 contract signature. The aircraft were initially based on Hainan Island, but were then moved back to mainland. A second similar batch is reportedly sought by China.


Sukhoi Su-27 'Flanker-B'

Sukhoi Su-27 Flanker specs Wing: span 14.70 m; aspect ratio 5.6; wing area 46.50 m2
Fuselage and tail:length 21.90 m excluding probe; height 5.90 m; tailplane span 9.90 m; wheel track 4.33 m; wheel base 5.88 m
Powerplant: two NPO Saturn (Lyul'ka) AL-31F turbofans each rated at 79.43 kN (17,857 lb) dry and 122.58 kN (27,557 lb st) with afterburning
Weights: empty 17700 kg (39,021 lb); normal take-off 23250 kg (51,257 lb); maximum take-off 33000 kg (72,751 lb)
Fuel and load: normal internal fuel about 5270 kg (11,618 lb); maximum internal fuel 9400 kg (20,723 lb); maximum ordnance 6000 kg (13,228 lb)
Speed: limiting Mach No. 2.35; maximum level speed 'clean' at 11000 m 2280 km/h (1230 kt) and at sea-level 1370 km/h (739 kt)
Range: at high-altitude 3680 km (1,986 nm); range at low-altitude 1370 km (739 nm)
Performance: maximum rate of climb at sea level 19800 m per minute; service ceiling 17700 m; take-off run 450 m at maximum take-off weight; landing run 700 m at normal landing weight
g limits: +8

Su-27 landing Click to enlarge

Source: Encyclopedia of World Military Aircraft 1994 © Aerospace
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