The Indian Air Force (IAF) is all set to arm its Sukhoi Su-30MKI multirole air superiority fighters with Rafael Advanced Defense Systems Derby Mk3 Beyond Visual Range Air-to-Air Missile (BVRAAM). Rafael Advanced Defense System, the Israeli missiles & munitions giant, at Paris Air Show 2015 unveiled the missile, then known as I-Derby ER, the extended range (100-km+) version of its Derby Active Radar Homing (ARH) Beyond Visual Range Air-to-Air Missile (BVRAAM). It is an evolutionary version of the I-Derby BVRAAM unveiled earlier at Aero India 2015. The Derby entered service in the mid-1990s and is fielded with multiple customers worldwide. The Israeli Defence Force-Air Force (IDF-AF) realised the value and operational flexibility of BVRAAM long ago as it was repeatedly frustrated by high-altitude over flights by the MiG-25 Foxbat-B reconnaissance models of the Soviet Expeditionary Force between October 1971 and March 1972. Soviet MiG-25Rs based at Cairo covered the Israeliheld coastline Haifa to Port Said and flew the length of Sinai Peninsula involving 500 km penetration of the Israeli airspace. With a speed of Mach 2.5 to 2.8 at a cruising altitude of 80,000 ft they successfully evaded the formidable Israeli defences including F-4 Phantoms thus gathering valuable “real time” intelligence and transmitting them to ground-stations through secure data-links for further analysis. Appropriate IDF-AF BVR tactics underwent development and during June 1982 two Syrian MiG- 25 Foxbat-A were destroyed by the IDF-AF with carefully planned and executed “snap up” attack by F-15 fighter/AIM-7 Sparrow BVRAAM combination emphasising the growing maturity of the BVR tactics and procedures of the IDF-AF pilots. For the first time the formidable highaltitude MiG-25 interceptor, hitherto regarded as “untouchable” was shot down. United States Raytheon AIM- 120 AMRAAM succeeded AIM-7 ‘Sparrow’ in IDF-AF inventory in course of time and holds the distinction of being the first operational ARH “fire-andforget” BVRAAM.
However Derby BVRAAM, developed by Rafael Missile Division, was born from an Israeli desire to retain full control of the BVRAAM technology especially in relation to Electronic Counter Counter Measures (ECCM) modes. The 3.62 metre long 118 kg weight active-radar homing BVRAAM shares design commonality with Python 4 (including warhead and proximity fuse and even sharing same launcher); with the addition of mid-body wings while its own ‹no escape zone› overlaps that of the Python 4. The Derby is fitted with an ARH seeker with a compact gimballed antenna, developed by Israeli Aerospace Industries (IAI) MBT Division. Derby has Look- Down/Shoot-Down capability and advanced programmable and adaptable ECCM to operate under dense electronic warfare environments while reconfigurable upon the emergence of new threats. For BVR engagements a LOAL mode is adopted in which the missile initially fired using cues from the launch aircraft›s fire control radar, or perhaps an Infra-Red Search & Track (IRST) system employing inertial guidance immediately after launch until the ARH seeker is activated at appropriate distance to home in on the target with substantial kinematics performance allowing ‹end game› manoeuvrability thanks to slightly enhanced rocket motor.
For greater accuracy over extended ranges, the ‹Derby Uplink› capability allows targeting data to be transmitted from the launch aircraft to provide accurate mid-course guidance while dealing with fast-moving or manoeuvring targets. The missile also has the ability to receive data-link updates from other platforms besides the launch aircraft thereby permitting ‹stealthy› engagements. According to Rafael even ‘baseline’ “multi-shot capable” Derby has a launch-range in excess of 63 km if launched at Mach 0.9 at 25,000 ft against a head-on target, although its maximum range, or its effective seeker range, remain highly classified. During Aero India 2007 on being suggested so by this Vayu correspondent on aspects of Derby’s maximum range, top Rafael officials along with their aides burst into laughter and intended to retain the veil of secrecy by reaffirming it as “mystery”. Now very much apparent, Rafael was contemplating an extended ranged version for over a decade. Derby also has a very low minimum range and an option for Lock-On Before Launch (LOBL) mode thus also capable of being employed for short-range engagements with Derby’s seeker slaved to the aircraft›s radar or the pilot›s helmet mounted cueing system. During short range engagements Derby’s capabilities are regarded similar to Python 3 close-combat missile trapping enemy aircraft in “killing fields” 60 km inwards. In the present Derby Mk3 evolution, the BVRAAM appears to have reached its inherent optimum potential. The latest variant is equipped with a new seeker that employs an advanced solid-state Software Defined Radar (SDR) technology, based on combat proven technology derived from the Tamir interceptor used in Rafael’s Iron Dome system. The new lighter and more compact seeker has cleared valuable space which has been used by the missile designers to augment the propulsion system by adding a dual pulse rocket motor for “second kick” mode, thereby increasing the range of the Derby Mk3 beyond 100 km against “straight line” targets, and more importantly specifically to accelerate the missile at the critical terminal phase of the flight prior intercept of manoeuvring targets by increasing the BVRAAM kinematic envelope, and trapping the target in “no escape zone”. The “second kick” operates independently of the primary rocket propulsion and can be activated at any time during the fight, by the BVRAAM Flight Control System (FCS). The use of SDR technology means the missile seeker can be reprogrammed with software upgrades including new waveforms, duty cycles and processing techniques, addressing new threats, countermeasures and techniques that may evolve in foreseeable future. Smooth integration is a plus point as Derby Mk3 BVRAAM will be compatible with aircraft currently cleared to carry Derby. The missile is already cleared on F-16I (Block50/ 52), F-5E and Kfir. I-Derby ER integration tests are currently under way on the IAF Tejas Light Combat Aircraft.
Sayan Majumdar