SUKHOI Su-27 FLANKER | CHECKSIX - the military aviation journal

PLANES OF FAME: Sukhoi Su-27/30/34/35 FLANKER

Update: 2020/09/29 by Robert Kysela / CHK6

Some airplanes become true legends in their own lifetime and one such aircraft to which this statement certainly applies to is the Sukhoi Su-27 (NATO Code: FLANKER). Hardly any other aircraft combines such an aggressive design, brute power and phenomenal maneuverability as this mighty Russian fighter. It’s also hard to believe that the first prototype Su-27 made its maiden flight over 40 years ago! Reason enough to take a closer look at the development and history of this fascinating aircraft!

A Soviet response to the West's new air superiority fighters was to be commissioned in the late 1960’s

R. Kysela

Fighter plane development during the 1950’s focused primarily on one aspect, speed! Maneuverability was seen as a secondary requirement, while cannon armament was steadily being abandoned in favor of missiles as the way of the future. During the Vietnam War the Americans also realized they did not have an adequate fighter that could stand up in a dogfight to smaller and relatively more agile Soviet designs such as the Mikoyan & Gurevich MiG-17 (NATO Code: FRESCO) and MiG-21 (NATO Code: FISHBED). At the time, the then most modern and powerful fighter in the U.S. Air Force inventory, the McDonnell Douglas F-4 PHANTOM II, did not poses any form of integrated gun and therefore had to be quickly retrofitted with one. In return, Soviet models suffered from relatively short range and rigid operational doctrine, requiring strict coordination from a ground control station. Both sides drew their lessons from this conflict, these were lessons that have had a lasting influence on the development of combat aircraft to this very day. On the U.S. side, these lessons resulted in the McDonnell Douglas (now Boeing) F-15 EAGLE and the General Dynamics (now Lockheed-Martin) F-16 FIGHTING FALCON. A Soviet response to the West’s new air superiority fighters was to be commissioned in the late 1960’s.

When the Soviet military began to receive information about the next generation of U.S. fighter aircraft, it was clear to them they could do little against the new evolving threat with the models currently in service such as the Yakovlev Yak-28 (NATO Code: FIREBAR), Mikoyan & Gurevich MiG-23 (NATO Code: FLOGGER) or the Sukhoi Su-15 (NATO Code: FLAGON). The design offices (OKB = Opytno Konstruuktorskoye Byro – Office for Experimental Design) of Mikoyan & Gurevich, Yakovlev and Sukhoi therefore received the order in 1969 to develop a new type of fighter aircraft. The specification for Perspektivnyyy Frontovoy Istrebitel (roughly: Future Frontline Fighter) envisaged a machine with outstanding maneuverability and long range, which was to be superior to U.S. models in all respects. This tender was divided in 1971 into a heavy long-range fighter (Su-27) and a light interceptor, which in turn served as a counterpart to the General Dynamics YF-16 and the McDonnell Douglas YF-17 (predecessor to the F/A-18 HORNET). This second program was named Perspektivnyy Lyogkiy Frontovoy Istrebitel (roughly: Future Light Frontline Fighter) which finally became the Mikoyan & Gurevich MiG-29 (NATO Code: FULCRUM).

A key element of the design was its ogive wings, which were flush with the fuselage segment (a so-called Blended Wing Body)

R. Kysela

At the beginning of 1970 a project team led by Yevgenj Iwanov of the Sukhoi OKB commenced the first design drafts for the new fighter aircraft. To achieve the required performance the designers had to break new ground in many areas. A key element of the design was its ogive wings, which were flush with the fuselage segment (a so-called Blended Wing Body). To improve aerodynamics and maneuverability the front wing section was therefore pulled far forward by employing LERX (Leading Edge Root EXtensions or STRAKES – Known in Russia as Sablya or Sabre). The fuselage thus contributes to lift which not only greatly improves the overall aerodynamic capabilities but above all also ensures the cockpit, which is located considerably forward, provides an element of additional lift. The LERX also allows for very high angles of attack and a positive effect on the overall agility of the machine.

The maiden flight of the new fighter, designated T-10-1 took place on 20 May 1977 at the flight test center at Zhukovsky. At the controls was chief test pilot Vladimir Ilyushin, son of well-known aircraft designer Sergey Ilyushin. It soon became apparent that the prototype did not meet its expectations with performance data, at times, far outside the specified parameters. Adding to this catastrophic situation, the second prototype (T-10-2) crashed on 07 July 1978, killing the pilot, Yevgenji Solowjew. The evaluation of the flight tests showed the T-10 was laterally unstable however, it was (and contrary to plan) relatively stable around its longitudinal axis, this in turn had a negative effect on its overall maneuverability. Additionally, the engines would overheat as the fan blades were not actively cooled – All issues adding to a growing list of shortcomings that began to exceed an acceptable level. These deficiencies were to become so great that any minor improvements would be insufficient to remedy them. There were actually only two options available, either to stop the entire project or redesign the aircraft in its entirety. Fortunately for Sukhoi, OKB got the green light for the redesign. The first prototype T-10-1 found its way to the museum in Monino, where it can still be admired today.

With assistance from the renowned SibNIA (Sibeerskiy Nauuchno Issledovatel`skiy Instituut Aviahtsii – Siberian Aviation Research Institute) in Novosibirsk, the T-10 airframe was completely redesigned. It must be said that at the time engineers in the Soviet Union had little or no experience with LERX and therefore had to do some basic research to find the right aerodynamic shape. With the exception of its approximate size and designation (T-10S), the newly developed prototype had little in common with the previous version. The wing tips were flattened, the overall wing shape was simplified and the double vertical tail was further extended (the original design had the tail units located centrally above each engine).

The new prototype first flew on 20 April 1981, again with Vladimir Ilyushin at the controls and despite the fact that a prototype of what was to become the Su-27 had progressed, luck did not hold out for Sukhoi OKB. On 3^rd September of the same year the first prototype was involved in an accident, fortunately Ilyushin was able to save himself utilizing the ejection seat. The second prototype crashed only a few months later (on 23rd December 1981). The pilot, Aleksandr Komarov, unfortunately was not so lucky and was killed in the accident. Despite these setbacks however, the development team was on the right track. This certainty was particularly evident by the fact that the production facilities in Komsomol’sk- on-Amur (KnAAPO) had already begun preparation for series production, even though the test phase was not fully complete.

Therefore the future Su-27 was classified as RAM-K, the MiG-29 received the designation RAM-L and the Su-25, which was also under development, was classified as the RAM-J

R. Kysela

In the West, there was a long period of uncertainty about not only the existence, but above all the performance of the new fighter plane. The first satellite images appeared at the end of January 1980. With a lack of a correct formal designation (or the respective manufacturer/OKB involved), the machines were given the code designation RAM (RAM stood for Ramenskoje – Western intelligence services long believed that the flight test center in Zhukovsky was named after the nearby town of Ramenskoje). Therefore the future Su-27 was classified as RAM-K, the MiG-29 received the designation RAM-L and the Su-25, which was also under development, was classified as the RAM-J. Western analysts could not get much information from available photos with the approximate size and the wing geometry being the only parameters that provided any information until the mid 1980s. This left much room for speculation and misinterpretation. Not only did analysts tend to see these new machines as simple (and of course poor quality) copies of modern US-American designs, they even believed the RAM-K (Su-27) utilized swing wings.
The first usable pictures of the new Soviet fighter were provided by a Lockheed P-3B ORION of No. 333 Sqn / ROYAL NORWEGIAN AIR FORCE in 1987 when it was intercepted by two Su-27s near Murmansk. For the first time there were razor-sharp images of the Su-27, which henceforth was to become known in the west by its NATO designation: FLANKER. On the basis of these images, one could roughly calculate some performance parameters and at least guess the rest. A big shock came just two years later when for the first time a Su-27 was demonstrated in flight at the international trade fair at Le Bourget, demonstrating maneuvers considered impossible by many experts beforehand. Even if though its aerobatic demonstration is still controversial among experts today (especially Western experts who like to point out again and again that the famous COBRA maneuver has no use whatsoever in combat), they still impressively demonstrated the considerable agility of this new large fighter.

Modern air superiority fighters are designed inherently unstable, at least in the longitudinal axis, otherwise extreme maneuvers such as tight radius turns and high angle of attack maneuvers would be impossible. For pilots to be able to fly such aircraft, flight control computers and fly-by-wire (FBW) systems which implement computer aided control commands at lightning speeds are mandatory. In the case of the Su-27, developers were able to draw on experience gained from the Sukhoi T-4. The first Su-27 (including its prototypes and pre-production models) were equipped with analog FBW systems which only controlled the elevators, the ailerons and rudders via conventional hydraulics. The current version Su-35S utilizes an MNPK Avionika KSU-35 quadruple-redundant digital FBW control system.

The N001 MECH (sword) pulse doppler radar developed by NIIP for the first FLANKER variants was a quantum leap compared to the radar systems used in the MiG-21 but still did not maintain the required parameters to keep up with more modern western radar systems

R. Kysela

Extremely good maneuverability alone is definitely not enough to stand up to another modern enemy fighter plane. It’s not only radar systems, fire control computers or weapon systems, but also the ergonomics of the cockpit that provides the criteria regarding who will ultimately emerge as the winner in a dogfight. This is particularly so especially in regard to radar, as the first Su-27s certainly did not have an edge over its western counterparts. The N001 MECH (sword) pulse doppler radar developed by NIIP for the first FLANKER variants was a quantum leap compared to the radar systems used in the MiG-21 but still did not maintain the required parameters to keep up with more modern western radar systems. While the N001 was able to detect up to 10 targets simultaneously it could only engage target one at a time. The range was between 40 and 65 km for a target with a RCS (Radar Cross Section) of 3 m2 , depending on the mode employed. The latest version Su-35S is equipped with the NIIP N035 IRBIS-E radar system which is a hybrid PESA (Passive Electronically Scanned Array) radar with a maximum range of up to 400km. The IRBIS-E can detect up to 30 targets, of which a maximum of 8 can be engaged simultaneously. With its enormous power output of 18.6 kW (Peak Power/Ppeak), this radar is also more resilient to able to electronic countermeasures (jamming). The next generation Russian radar system is already used in the Sukhoi Su-57 (NATO Code: FELON) (Tikhomirov NIIP N036-1-01 Byelka – Squirrel). Such systems are steadily closing the technological gap with leading western radar manufacturers, such as Raytheon (AN/APG-77/F-22 RAPTOR) or EuroRADAR (CAPTOR-E/Eurofighter EF-2000). An OLS-35 IRST (Infra-Red Search & Track System) with an integrated laser rangefinder and a TV camera also serves to supplement the radar in the FLANKER series of aircraft. This tracking system is insensitive to ECM measures and allows the FLANKER to locate and engage targets at a range of at least 50 km. The western counterpart of the OLS-35 is the EuroFIRST PIRATE of the Eurofighter EF-2000. One thing perhaps needs to be mentioned at this point. The true performance of modern radar and positioning systems is kept in the dark, at least for the general public. Everything that is (and has been) published about these systems is based on assumptions, propaganda and daring comparisons of known data and the limited data released by the manufacturers.

A core element of the success of the Su-27 are its excellent engines. The AL-31F, originally designed by the Ljulka design office, proved to be a great success. Even the basic version AL-31F1 turbofan engine (with a bypass ratio of 0.59 : 1) has a powerful output of 122.6 kN with afterburner. Again, it is more than just pure performance parameters that tell us about the quality of an engine. In the case of the AL-31F a key feature is the design of the engine intake. The four-stage low-pressure compressor contains 23 variable guide vanes in the forward section, which even in the event of a significant change in airflow prevents a stall in the compressor and as a consequence a flameout in the combustion chamber. This insensitivity to strongly alternating flow enables the FLANKER to perform flight maneuvers such as the COBRA or the TAILSLIDE. In both maneuvers the engine continues to run without any problems and can be ramped up to full power without any noticeable delay.

Both engines are located in two separate nacelles below the fuselage. This arrangement (similar to the Grumman F-14 TOMCAT) not only provides very good access for maintenance, it also has the advantage of significantly reducing the risk of damage to both engines in the event of major damage to one engine with such collateral damage inevitably leads to a total loss of the machine. If one engine remains intact, the pilot can still generally land the aircraft safely. For this reason the interior of the engine nacelles of the Su-27 are reinforced with titanium components.

The 117S engine has a predicted life of 4,000 operating hours, with an MTBO (Mean Time Between Overhauls) of 1,000 hours

R. Kysela

The following engines are used in the current versions of the FLANKER family

NPO Saturn 117S (Su-35S)
AL-31FP (Su-30SM)
AL-31F M2 (Su-34).

The NPO Saturn 117S engine is based on the AL-31F series, although features a newly designed low-pressure compressor (with 19 electronically controlled guide vanes) and an axially symmetrical 3D thrust vector nozzle that can be tilted by up to 15° in all directions. While Russian engines used to have a rather low life expectancy, the 117S has made tremendous progress in this area. The 117S engine has a predicted life of 4,000 operating hours, with an MTBO (Mean Time Between Overhauls) of 1,000 hours. The high dry thrust capacity of 86.3 kN (142 kN with afterburner) allows the Su-35S to be super-cruise capable, i.e maintain supersonic speed without the use of afterburner. Externally, the Su-35S differs from earlier Su-27 variants mainly by the absence of the large air brake behind the cockpit, the double-tired nose landing gear and the lack of a visible pitot tube on the nose tip.

The aforementioned air brake and pitot tube are still present on the two-seater multi-purpose version, the Su-30S, however the Su-30SM employs the use of canards. The Su-30SM is based on the Su-30MKI export version operated by the Indian Air Force, the differences are mainly due to the fact that, unlike the Su-30MK, only Russian avionics were used. The MKI version is, (with the exception of the N011M-BARS Radar) equipped with Western communication and IFF systems as well as a SAGEM Sigma-95 navigation system. The Russian Air Force (Voyenno-Vozdushnye Sily Rossii) currently operate, according to official information, 114 aircraft of the type, while Russian Naval Aviation (Aviatsiya Voenno-morskovo Flota Rossii) are equipped with 22 Su-30SM. The Su-30SM will soon be subject to an upgrade program according to a plan in which, among other things, all AL-31FP engines will be replaced with the more capable NPO Saturn 117S of the Su-35S (this upgrade is also planned for the Su-30MKI of the Indian Air Force).

A look into the cockpit shows the constant development of the FLANKER family. While the first Su-27 series cockpit was mostly equipped with analogue instruments, modern multi-functional displays are now used. Two MFI-35 color displays each with 1400 x 1050 pixel resolution show the pilot all relevant flight parameters. Centrally located is the IKSh-1M wide angle heads-up display which, when slaved to the pilots ZSh-7 helmet, provides a reliable and above all very efficient and effective combination. There is one thing however all Su-27/30/34/35 variants do have in common – the legendary Zwezda K-36D ejection seat. This seat gained considerable fame at the 1989 Paris Airshow when Russian test pilot Anatoly Kvotchur ejected from his MiG-29 (at an 80 degree angle) moments before impact with the ground. This ejection seat is designed for safe egress at speeds of up to 1300 km/h. The K-36 is equipped with two telescopic rods which are fully extended by additional explosive cartridges initiated during the ejection sequence, these rods are equipped with stabilizing parachutes that ensure the seat remains vertical during the ejection sequence. A fully automatic restraint systems prevent injuries to the pilots arms, legs and especially the head during the ejection sequence. Additionally, a protection device is extended during ejection at high speeds to ensure the enormously high strong air flow is deflected away from the pilot.

The original designation was Su-27IB (Istrebitel Bombardirovshchik = fighter bomber), later the designation was changed to Su-32 and then to Su-34 (the export variant is still called Su-32FN)

R. Kysela

Another variant of the FLANKER family is the Su-34 (NATO Code: FULLBACK). This is a heavy tactical combat aircraft, which differs in many areas from the original Su-27 series. Development began in the mid 1980’s when the first Su-27s entered service. The original designation was Su-27IB (Istrebitel Bombardirovshchik = fighter bomber), later the designation was changed to Su-32 and then to Su-34 (the export variant is still called Su-32FN). In strong contrast to the Su-27UB and Su-30 FLANKER variants where the pilots sit in a tandem arrangement behind each other, the crew of the Su-34 are positioned next to each other. This arrangement also gives the Su-34/32 its very distinctive appearance where in Russia it is often refered to as Utjonok (duckling) because of its duck-shaped nose section.

Another particular feature of the Su-34 is the extensive use of armor plating (made of titanium) for the cockpit area, engine nacelles and fuselage tanks. The latter are also foamed with polyurethane to help prevent an explosion in the event of a direct hit. This is unique for an aircraft of its class and gives the Su-34, in addition to its extensive ECM (Electronic Counter Measurement suite), a considerably higher chance of survival a hostile environment. The increased weight of the armor plating and the enormous payload of the Su-34 (up to eight tons) have made it necessary to considerably reinforce the landing gear. From the 2nd prototype on (internal designation: T-10W-2) a nose landing gear with twin tires was required, while the main undercarriage was completely revised and now consists of a main spar to which a swinging arm with two tires are attached.

In addition to an in-flight refueling probe, the Su-34/32 has a rest area in the rear part of the cockpit where a crew member can rest during the flight. Even meals and hot coffee can be prepared and a toilet is also available. With these facilities, according to the manufacturer, missions of up to 10 hours are possible without any problems. Great importance was attached to a sophisticated information management system. All data/parameters are displayed situationally on five MFI-66 multi-function displays including data relevant to flight operations, weapon deployment and crew survivability. A total of 14 Su-34 took part in the Syrian conflict where the experience gained there is currently being implemented in a combat value enhancement program entitled NVO (Novyye Vozmozhnosti = roughly: New Possibilities). There are currently 118 of the type in service with more to be added and eventually replacing the now obsolete Sukhoi Su-24M (NATO Code: FENCER).

The success of the Su-27 series is far from over as Russia has always well understood how to fully exploit the maximum potential from all its aircraft. While the Su-30SM and Su-35S are known as 4++ generation fighter aircraft, this term can be quite misleading as these aircraft are actually 5th generation technologically, however due to their distinct lack of stealth features they are not fully 5^th generation. This is in fact a very clever marketing strategy as there are many countries that do not require such highly complex weapon systems, particularly those with the stealth properties of the F-22 RAPTOR. What’s more, the full potential of the Su-27 lies primarily in an offensive role. A doctrine based on the pure defence of one’s own territory does not require a stealth fighter, but highly efficient and above all affordable and effective technology. For the same price of a single Lockheed Martin F-22 RAPTOR of 190 million US dollars, a prospective buyer (depending on the purchase quantity and negotiating skills) can get up to four Su-30MK! This gives him a proven, state-of-the-art weapon system that is at least equal to and in most cases even superior to all current competitor models (perhaps with the exception of the F-22).

Robert Kysela / CHK6

PLANES OF FAME: Sukhoi Su-27/30/34/35 FLANKER

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