Air Power Australia
APA Updated - Flanker Analysis Radars
The first of these is its massive radar bay, capable of fitting a 1 metre class X-band phased array antenna. In the long range BVR combat game, radar range is a key factor and for any given radar technology, the larger the aperture the better. While the current N011M/ME BARS (Panther) and Pero (Plume) upgrades use passive array technology which delivers less peak power than competing active arrays (AESA) it is only a matter of time before NIIP and Phazotron adapt commercial GaAs MMIC technology (98% of the total GaAs chip market) to build an AESA variant competitive against the AESAs in the latest Western evolved 3rd Gen fighters.
With similar TR (Transmit-Receive) module performance, the fighter with the largest aperture size wins in this game - for instance the N011M has around twice the aperture size of the JSF AESA and F/A-18E/F's APG-79 and even with inferior TR module technology will be highly competitive. It is worth noting that India is only the fourth nation worldwide to field a phased array equipped aigile air combat fighter, after France, the US and Russia.
Electrical power and liquid cooling have been issues for the integration of AESAs in Western fighters, especially so with smaller types like the F/A-18E/F, F-16E/F and Joint Strike Fighter. This is not an issue given the sheer size of the Flanker.
While the existing N011M has limitations in its older technology back end processing, the future is the path India has followed, retrofitting third party hardware with better performance than the Russian processor hardware. With widely available commodity processor chips in the 1 to 2 GHz class, we can expect to see many other Sukhoi users emulate the Indians in coming years, be it in MLUs or new build aircraft.
The baseline N011M radar uses a vertically polarised 0.9 metre diameter aperture hybrid phased array, with individual per element receive path low noise amplifiers delivering a noise figure cited at 3 dB, similar to an AESA. Three receiver channels are used, one presumably for sidelobe blanking and ECCM. The EGSP-6A transmitter uses a single Chelnok Travelling Wave Tube, available in variants with peak power ratings between 4 and 7 kiloWatts, and CW illumination at 1 kW. Cited detection range for a closing target (High PRF) is up to 76 NMI, for a receding target up to 50 NMI. The phased array can electronically steer the mainlobe through +/-70 degrees in azimuth and +/-40 degrees in elevation. The whole array can be further steered mechanically. Polarisation can be switched by 90 degrees for surface search modes.
The follow on to the BARS is the new Irbis-E (Snow Leopard) hybrid phased array, in development since 2004 and planned for the Su-35 block upgrade, and as a block upgrade or new build radar for other Flanker variants. The Irbis-E is an evolution of the BARS design, but significantly more powerful. While the hybrid phased array antenna is retained, the noise figure is slightly worse at 3.5 dB, but the receiver has four rather than three discrete channels. The biggest change is in the EGSP-27 transmitter, where the single 7 kiloWatt peak power rated Chelnok TWT is replaced with a pair of 10 kiloWatt peak power rated Chelnok tubes, ganged to provide a total peak power rating of 20 kiloWatts. The radar is cited at an average power rating of 5 kiloWatts, with 2 kiloWatts CW rating for illumination. NIIP claim twice the bandwidth and improved frequency agility over the BARS, and better ECCM capability. The Irbis-E has new Solo-35.01 digital signal processor hardware and Solo-35.02 data processor, but retains receiver hardware, the master oscillator and exciter of the BARS. A prototype has been in flight test since late 2005.
The performance increase in the Irbis-E is commensurate with the increased transmitter rating, and NIIP claim a detection range for a closing 3 square metre coaltitude target of 190 - 215 NMI (350-400 km), and the ability to detect a closing 0.01 square metre target at ~50 NMI (90 km). In Track While Scan (TWS) mode the radar can handle 30 targets simultaneously, and provide guidance for two simultaneous shots using a semi-active missile like the R-27 series, or eight simultaneous shots using an active missile like the RVV-AE/R-77 or ramjet RVV-AE-PD/R-77M. The Irbis-E was clearly designed to support the ramjet RVV-AE-PD/R-77M missile in BVR combat against reduced signature Western fighters like the Block II Super Hornet or Eurofighter Typhoon. Curiously, NIIP do not claim superiority over the F-22A's APG-77 AESA, yet their cited performance figures exceed the public (and no doubt heavily sanitised) range figures for the APG-77.
The existing N011M series lacks a Low Probability of Intercept capability, in part due to antenna bandwidth limits and in part due to processor limitations. This is likely to change over the coming decade, with the Irbis-E, as customers demand an ability to defeat or degrade Western ESM equipment and the technology to do this becomes more accessible.
The N012 tail warning radar has been reported to be part of the Su-30MKI suite and is offered as a retrofit to other models.
In terms of block upgrades, of the two competing radar houses in Russia, NIIP (http://www.niip.ru/) and Phazotron, the former has been the most active of recent. A block upgrade package, designated 'Panda' was recently developed for the baseline N-001-01 radar carried by Su-27S/SK. The first stage is the N-001V back end upgrade using C/C++ COTS software and a Ts-100 processor.
Of more interest however is a low cost phased array block upgrade package designated Pero ('Plume'), designed jointly with Ryazan GRPZ. This lightweight design avoids the cost and complexity of the backplane fed BARS (N-011M) phased array, instead using a space (optical) feed scheme, and reflective rather than transmissive phase elements, a technique used with the 64N6E Big Bird SAM system radar. The design incorporates the phase element array, and a strut supported boom which mounts the X-band waveguide and radiating horn. Cost is comparable to the existing Su-27S/SK Cassegrain antenna, weight is lower. The launch customer is the RuAF, but reports indicate one of the two prototypes was sent to China for evaluation. The Pero will provide the beam steering agility of modern Western AESAs, but with lower cost and transmit power ratings, and is likely to appear in regional MLUs later this decade. An open question is whether a future Pero based block upgrade would include the 20 kiloWatt Irbis-E transmitter, as engineering the space feed for a 20 kiloWatt rated transmitter is neither difficult nor expensive. While a 20 kiloWatt Pero system would have inferior receiver sensitivity due to the space feed loss, compared to the BARS hybrid array, it would be significantly cheaper to build and deploy en masse.
In summary, near term we can expect to see the Irbis-E and Pero appear in new build and upgrade packages, in the longer term an AESA is an inevitability.
Dr Carlo Kopp, MIEEE, SMAIAA, PEng
Defence Analyst and Consulting Engineer
Editor: Air Power Australia @ http://www.ausairpower.net