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Tuesday, October 25, 2016

Threat Analysis: Su-35S

Image 1: Su-35S

Author’s Note: I had originally planned to release an article detailing a hypothetical engagement between 12 F-22As and 48 Su-35s this week, but decided I needed more time to thoroughly research basic fighter maneuvering and variables associated with within visual range engagements. In the meantime, I will publish a two part series on the Su-35.

Introduction – Divergent Fighter Generational Definitions & Implications  

Russian publications consistently refer to the Su-35 as a “4++ or 4.75 generation” fighter, rather than a 4+ generation fighter like the Su-30SM, to underscore the additional fifth generation qualities of the Su-35.[1] This assertion is largely reflective of Russia’s divergent conceptualization of fifth generation qualities when compared to the U.S. The U.S. has largely de-emphasized superior maneuverability performance above the fourth generation series as a core component of fifth generation aircraft. The two central qualities which define fifth generation capabilities in the U.S. context are low observability and enhanced situational awareness (SA).[2] In contrast, Sukhoi patent documents detailing the PAK FA’s design trade-offs indicate the Russian Aerospace Forces–the Russian Air Force was reorganized as of August 2015 and is abbreviated as the VKS for Vozdushno-Kosmicheskiye Sily–considers superior maneuverability above the fourth generation series as the dominant fifth generation trait with low observability being an important, but secondary, objective influencing the design.[i] 

Image 2: Fighter generations. Image Credit: USAF General Hawk Carlisle.[3]

This conceptual divergence with the U.S. regarding fifth generation fighter characteristics likely reflects the limitations of the Russian defense industrial base as well as historical-institutional preferences among the Russian defense establishment. While the PAK FA and the Su-35 are distinct designs, the Su-35 mirrors the PAK FA in that they both share the same design philosophy of maximizing maneuverability performance. While the Su-35 incorporates a host of additional improvements detailed below, the divergent Russian design philosophy will substantially influence how Russian pilots conceptualize engagements and create new techniques, tactics, and procedures (TTP).  


The Su-35 originated from the rivalry between the Irkutsk and Komsomolsk-on-Amur production plants during the 1990s. Sukhoi’s component companies struggled to survive in the absence of exorbitant Soviet-era defense expenditures and heavily relied upon foreign exports to sustain their industrial base and fund new research and development projects. The leadership of the Komsomolsk-on-Amur Plant decided it needed a design to compete with Irkutsk’s Su-30MKI in the international fighter market; the Russian Ministry of Defense (MOD) did not play an active role in the development of the Su-35.[4]

The Komsomolsk-on-Amur plant largely failed in its bid to compete with Irkutsk among foreign customers; the Su-30MKI and its derivatives became the most widely exported Russian fighter in the post-Soviet period.[ii] In August 2009, the Russian Air Force ordered an initial batch of 48 Su-35S aircraft for $2.51 billion (the deal also included 12 Su-27SM, 4 Su-30M2 aircraft, spares, maintenance, and $100 million for additional investments in the Su-35’s development); the S denotes the domestic Russian variant of the Su-35.[5] Two factors led to the adoption of the Su-35: (1) the Russian Air Force urgently needed new airframes to replace its aging Soviet-era equipment and (2) the fifth generation PAK FA faced significant technical and financial difficulties. In December 2015, the VKS placed a follow-on order for 50 Su-35S aircraft worth at least $778 million; deliveries of all aircraft are scheduled to be completed by 2020.[6] While the Su-35S was intended to serve as a gap filler and lower-end complement to the PAK FA–which is also produced by the Komsomolsk-on-Amur Plant–Russia’s ongoing financial difficulties and continued PAK FA program delays ensure the Su-35S will remain the VKS’ high-end air superiority fighter in the short to medium term.

The current version of the State Armaments Program or GPV-2020 plans for the procurement of 52 PAK FA aircraft by 2020.[7] However, in April 2015, Russian Deputy Defense Minister Yuri Borisov announced the MOD was considering curtailing PAK FA procurement to a single squadron of 12 production aircraft between 2016 and 2020. After the 12 aircraft are inducted into service, the MOD may consider pausing further production of the PAK FA until “until such time as the initial batch of aircraft prove their advertised performance during operational trials”; orders of the Su-35S would be increased between 2016 and 2020.[8][9] Delayed PAK FA production is highly likely as Russia’s defense budget is expected to fall 12% in nominal terms between 2016 and 2018; the actual cut is even larger given the current 6.4% inflation rate in Russia.[10] The Su-35S will be complemented the more numerous multi-role Su-30M2 and Su-30SM which will serve as the air-to-air backbone for both the VKS and Russian Navy into the 2020s and 2030s.[11]

Airframe Design

The Su-27’s robust and adaptable airframe provided the basis for development of the Su-35 which features minor airframe modifications such as: thorough use of composite materials to reduce radar cross section (RCS) and weight, inclusion of an electroconductive canopy for further RCS reductions, greater reliance on titanium rather than aluminum alloys compared to the Su-27 (to strengthen the fuselage), removal of the dorsal speedbrake (braking is achieved through differential actuation of the rudders), and improved flight control surfaces.[12][13][14] The use of composite materials, radar absorbent material (RAM) coatings, and an electroconductive canopy reduce the Su-35’s frontal RCS to between 1m^2 and 3m^2 in a clean configuration compared to the Su-27’s 15m^2.[15][16] Aside from the airframe, the most notable distinguishing traits of the Su-35 compared to other Flanker derivatives are its thoroughly modernized avionics and electronic warfare (EW) suite as well as its 3D thrust vectoring NPO Saturn 117S (AL-41F1S) turbofan engines.


Image 3: Detection range of N135 in peak power mode against select aircraft. The detection range is significantly reduced when operating in the search mode which would detect an F-35 at 15.6 nautical miles (29 km) and an F-22 at 10 nm (18 km). Image Credit: Colin Throm, AW&ST.

The Su-35S features the most powerful passive electronically scanned array (PESA) radar of any Flanker variant in service, the N135 Irbis radar (Irbis-E is the export version).[17] The N135 in an evolution of the N011M Bars and features a greater search azimuth of +/-125°, higher resolution, wider variety of frequencies, and greater resistance to jamming.[18] The N135 can detect an approaching 3m^2 target at 199 to 216 nm (350 to 400 km) or a tail aspect target at 108 nm (200 km) while operating in its peak power mode. However, operating in peak power mode would focus radar energy on a single narrow point in space thereby diminishing the radar’s search capabilities. Furthermore, the use of peak power mode would betray the N135’s position to emission locator systems. In effect, using peak power mode to generate target quality track data against a low RCS target at maximum range requires queuing from other sensors or platforms to narrow the N135’s search area. Without input from other sensors or platforms, Su-35S pilots are likely to operate their radars in either the search or track-while-scan modes; the search mode provides detection against 3m^2 approaching targets at 108 nm or 200 km.[19] The OLS-35 infrared search and track (IRST) system could potentially act as the queuing source to narrow the N135’s search radius to gain target quality track information on low RCS targets.

Image 4: Sukhoi clearly markets the OLS-35 as a means to defeat stealth aircraft, note the YF-22 (instead of F-22) graphic. Image Credit: Sukhoi. 

The OLS-35 is mounted near the canopy and provides IRST, target designation, and laser rangefinding capabilities. The OLS-35’s can track up to four targets simultaneously across +/-90° azimuth and -15/+60° elevation; the detection range against of tail aspect aircraft is at 30 nm (56 km) and is 19 nm (35 km) against forward aspect aircraft.[20] It is highly like the OLS-35 possesses a mode in which it is slaved to the N135 radar to improve detection against stealthy targets similar to the Su-27’s OLS-27.[21] While the OLS-35 provides greater flexibility to Russian pilots when engaging low observable aircraft, the OLS-35 does not represent a panacea solution against stealth aircraft. Like all IRST systems, the OLS-35 does not provide target quality track data for weapons employment. For example, if a Russian pilot detected an approaching forward aspect F-35 at 15 nm, the Russian pilot could not directly utilize the IRST data to direct semi-active, active, or passive homing missiles; laser illumination capabilities are generally a means to guide air-to-ground munitions rather than air-to-air missiles.[iii] Therefore, the main benefit the OLS-35 provides is enhanced SA at short to intermediate ranges.

Image 5: The Su-35 cockpit features two 15 inch multi-functional displays.

Despite possessing powerful sensors, the extent in which the Su-35’s sensor inputs are fused to provide SA is unclear. The Su-35S’ development process was reportedly delayed as a result of difficulties integrating the Su-35’s avionics.[22] This would be consistent with ongoing difficulties with the PAK FA program which has also struggled to fuse the aircraft’s multiple sensor inputs to generate a coherent view of the battlespace.[23] As with the F-35, modern fighter aircraft provide enormous quantities of raw data, but pilots need actionable information. That is, pilots need to be able to quickly discern information such that they can build a mental picture of the environment which informs there decision making. The faster an avionics suite is able to assist the pilot in building a mental image of the battlespace, the quicker the pilot’s decision making cycle. The software involved in facilitating SA is among the most difficult aspects of designing a fifth generation aircraft. English open source literature on the Su-35’s SA and software is very limited as is literature describing Russian military datalinks.

Threat Analysis: Su-35 Part II - Armament R-27 & R-73

Author’s Note: Part II will cover the Su-35’s electronic warfare and countermeasures suite, engines, armament, and potential TTP Russian pilots will use to best maximize the comparative strengths of the Su-35.

 Works Cited 

My sincerest apologies on the formatting, the blogger template is terrible for formatting citations. 

[1] Suhkoi Products: Su-35 multi-role fighter, last access October 2016.
[2] Matt, “The Benefits of Stealth and Situational Awareness”, November 2013.
[3] General Hawk Carlisle, “5th Generation Fighters”, February 2012.
[4] Piotr Butowski, “The Flanker Family Part Two: Upgrades, Su-33 and Su-35”, Combat Aircraft September 2016 Issue, pgs. 61-66.
[5] Defense Industry Daily, “Russia’s Su-35 Super-Flanker: Mystery Fighter No More”, last updated October 2016.
[6] Nikolai Novichkov, “Russia orders 50 Su-35S multirole fighters”, January 2016.
[7] Vladimir Karnozov, “Russia May Slow T-50 Production for Economic Reasons”, March 2015. 
[8] Ibid.
[9] Julian Cooper, “Russia’s state armament programme to 2020: a quantitative assessment of implementation 2011–2015”, March 2016.   
[10] Craig Caffrey, “Russian Defense Budget Set to Drop 12%”, October 2016.
[11] Piotr Butowski, “The Flanker Family Part One: The Multi-role Su-30”, Combat Aircraft October 2016 Issue, pp. 67.
[12]Global Security, “Su-35BM (Bolshaya Modernizatsiya - Big Modernization)”, last updated July 2011.
[13]Carlo Kopp, “Sukhoi/KnAAPO Su-35BM/Su-35-1/Su-35S Flanker”, last updated 2012.
[14] AWIN Program Profiles, Sukhoi Su-27/30/32/34/35, Aviation Week, last accessed October 2016.
[15] Dan Katz, “Raptor Revisited”, Aviation Week Space and Technology July 4-17, pgs, 75-76.  
[16] Sukhoi, Su-35: Multifunctional Supermaneuverable Fighter, last accessed October 2016.
[17] Russia’s Warplanes: Volume I, pgs. 87-91, Houston: Harpia Publishing L.L.C. & Moran Publishing, 2015,
[18] Ibid.
[19] Ibid.
[20] Ibid.
[22] Piotr Butowski, “The Flanker Family Part Two: Upgrades, Su-33 and Su-35”, Combat Aircraft September 2016 Issue, pgs. 61-66.
[23]Reuben F Johnson, “Singapore Airshow 2016: Analysis - PAK-FA's Asian export hopes stymied by lack of 'fifth-generation' qualities”, February 2016.

Works Consulted

J. Thomas Anderson, "How Supersonic Inlets Work: Details of the Geometry and Operation of the SR-71 Mixed Compression Inlet", August 2013. 

Advisory Group For Research and Development - North Atlantic Treaty Organization, "Precision Terminal Guidance for Munitions", 1997.

Tyler Rogoway, "Infrared Search And Track Systems And The Future Of The US Fighter Force", March 2015. 


[i] For example, Sukhoi considered incorporating S-shaped inlets in PAK FA to reduce its frontal radar cross section (RCS), but ultimately decided the weight and length penalties associated with S-shaped inlets were too great. The current inlet design is a compromise which includes radial blockers and RAM as well as a variable throat section, spill doors on the inboard, outboard, and lower surfaces of the ducts. The combined effect of these features optimizes airflow at supersonic speeds while reducing the frontal RCS. However, even with radial blockers and RAM treatments, inlets are responsible for roughly 60% of the PAK FA’s frontal RCS; the patent document states the design goal was a frontal RCS between 1.0-0.1m^2 which is, at its smallest, roughly 77 times larger than the F-35 or 500 times larger than the F-22A [Source: Aviation Week Intelligence Network (AWIN) Program Profiles, T-50, last accessed October 2016].

[ii] As Piotr Butowski explains, the Su-30 family is broadly divided between those manufactured by the Irkutsk and Komsomolsk-on-Amur plants in Russia’s Warplanes: Volume I. The Irkutsk line consists of the Su-30MKI, Su-30MKM, and Su-30SM which are generally more capable than the Su-30MKK, Su-30MK2, Su-30MK2V, and Su-30M2 produced by the Komsomolsk-on-Amur plant. Visually, each line of Su-30s can be distinguished as the Irkutsk line includes canards and the Komsomolsk-on-Amur does not.

[iii] Several short range surface to air missile systems such as the U.S. Army’s Avenger system utilize a laser rangefinder to provide data for the fire control system. Airborne systems such as the ATFLIR pod produced by Raytheon for the F/A-18E are only discussed as providing laser designation against ground targets. 

Thursday, October 20, 2016

Article Announcement: F-22A vs Su-35

Image 1: Su-35S. Image Credit: Mikhail Voskresenskiy 

By next week I  will publish an article detailing a hypothetical engagement between a dozen F-22As and 48 Su-35s around 2020. The purpose of the article is to identify the challenges future Raptor pilots are going to face and how those challenges should inform potential mid-life upgrades of the F-22. Going forward, I will try to include additional analysis on Russian systems on this blog. I will be sure to list all of my assumptions and methodology in the endnotes as trying to predict an accurate engagement with only open source data is extremely difficult.

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