Here’s Why Indian Air Force Declined Russia’s Offer to Buy 117S Engine and Irbis-E Radar?

India's Su-30MKI fighter aircraft is seating idle under hanger due to lack of spare parts and working engines. Photo by Indian Air Force

The Su-30MKI is powered by two Lyulka-Saturn AL-31FP turbofans, each rated at 12,500 kgf (27,550 lbf) of full afterburning thrust, which enable speeds of up to Mach 2 in horizontal flight and a rate of climb of 230 m/s.

According to Sputnik news, the Russian Aerospace Forces recently revealed that from 2021, all 36 Su-30SM fighters delivered to the Russian Aerospace Forces will be upgraded to the latest standards and equipped with “Irbis E” passive phased array.

The Su-35’s AL-41F-1S (117S) thrust vector engine is yet to reach maturity phases. Russian manufacturer has rushed the trial phase and delivered Su-35 with 117S engines to the Russian, Egyptian and Chinese Air Force, reported Russian website topwar.

Russian Phased Array

Early Russian electronically scanned radars for fighters such as the V Tikhomirov Scientific-Research Institute of Instrument Design (NIIP) N007 ZASLON PESA radar for the MiG-31 FOXHOUND used PESA technology. Experience gained from the development of the ZASLON allowed the organisation to use a PESA array for the N011M Bars adapted for India’s Su-30MKI. The first Russian radar to use an AESA antenna was probably the Phazotron Zhuk-AE first displayed in 2005, but without a production version.

Russia’s AESA radar is the Sh-121, still under development by NIIP for the Sukhoi Su-57 PAK FA fighter. The main forward-looking array is the N038 X-band antenna based on gallium arsenide T/R modules. Flank-mounted secondary arrays are used to extend the angular coverage in the azimuth plane. In contrast, at least one more array provides rearward coverage that may allow ‘over-the-shoulder’ missile engagements. The function of L-band arrays built into the wing leading edges of the aircraft remains unclear. They may have an IFF function but have no capability against low-observable aircraft.

Russia’s counterpart to the E-3 SENTRY is the BERIEV A-50 AEW aircraft. This uses a pulse-Doppler SHMEL radar operating in S-band. The antenna is housed in a dorsally-mounted rotodome and uses mechanical scanning in azimuth and electronic scanning in elevation. An upgraded SHMEL-M was subsequently developed as part of the A-50U upgrade. A SHMEL-2 version developed for a second-generation A-50 variant is reported to be underperformed than the US APY-1/2 radar system. A new AESA-based version of the SHMEL radar is under development for the Ilyushin A-100, an AEW variant of the PS-90 engined II-476 transport aircraft.

117S engine problems

Russia has updated an old engine, 117S engine gets its thrust ratios pretty much similar to legacy engines and their modern derivatives.

The AL-31F-M3 is confirmed as 3LP; 6HP; 1HPT; 1LPT, by the then Managing Director of MMPP Salyut, Yuri Elisiev said without proper confirmation it’s pure speculation how advanced or not, the 117 is relative to the FM-3.

AL-31F engine

It is also noteworthy that although the FM-3 is described as ‘from the same family as’ the AL-31F-M1. Similar analogies have been made about the 117/117S. The 117 and 117S are basically the same engines, but 117S is heavier than 117 hence the Indian Air Force and Chinese Air force declined to procure the 117S engine.

HAL removed engines from Su-30MKI for maintenance.

The higher the Bypass ratio is, the higher the achievable thrust augmentation from afterburner is – for example, the GE F404 or F-110-GE-129 have more than 1.6 ratio. In that regard, the F135 is a new-generation engine. It has the highest bypass ratio, perhaps indicating that the engine is the best among all other engines.

HAL engineers are trying to regenerate a Su-30MKI.

India declined Su-30SM standard

Affected by this batch of Su-30SM, Russia has proposed to India many times before that more than 200 Su-30MKIs in active service should be upgraded to the latest batch of Su-30SM, Irbis-E radar and 117S engine. This project is called the “Super Sukhoi” project by India. The number of Su-30MKIs covered by it reaches 272 at most. If the two sides can negotiate, it will be a huge order worth billions of dollars.

Su-30MKI was dismantled for not having enough spare parts.

However, as far as the latest information is known, the Indian Air Force still has reservations about the so-called “Super Sukhoi” program. The replacement of a Irbis-E radar is still one of its core items, but the option of replacing the 117S engine seems to be shelved. Indians feel that the existing AL-31FP engine on the Su-30MKI can still meet the main demand, and they do not think that the 117S is qualitatively improved compared to the AL-31FP, so temporarily press the table.

Su-30MKI without radar.

It is interesting to say that the 117S engine actually has a deep relationship with China, Russia and India. The engine is derived from the AL-31F, and the AL-31F is the standard power for the Chinese Air Force’s active J-10 and J-11 series fighters. Before the domestic WS-10 series engine matures, the AL-31 has been the best or even the only turbofan engine of this level that we can rely on for a long time.

Su-30MKI fighter jets are catabolized for spare parts.

However, in fact, the thrust vectoring nozzle technology of AL-31FP is immature, and the thrust loss is extremely large when used, which will seriously interfere with the normal tactical operation of pilots. Therefore, Indian pilots rarely use its thrust vector nozzle when flying Su-30MKI. In addition, this engine has always had reliability and maintenance problems, and Russians use the same trick to promote the 117S, and it is not surprising that Indians do not catch a cold.

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