Derby - Israel’s BVRAAM Solution

The Israeli missile and munitions giant, Rafael Advanced Defence Systems, has unveiled the I-Derby ER, the extended range (100+ km) version of its Derby Active Radar Homing (ARH) Beyond Visual Range Air-to-Air Missile (BVRAAM) currently completing development. It is an evolutionary version of the I-Derby BVRAAM shown earlier this year at Aero India 2015. The Derby entered service in the mid-1990s and is fielded with six customers worldwide.

The Israeli Defence Force- Air Force ( IDF- AF) realised the value and operational flexibility of BVRAAM long back as it was repeatedly frustrated by high-altitude over flights by the MiG-25R Foxbat-B reconnaissance aircraft of the Soviet Expeditionary Force between October 1971 and March 1972. Soviet MiG-25Rs based at Cairo covered the Israeli-held coastline from 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 feet they successfully evaded formidable Israeli defences including F-4 Phantoms, thus gathering valuable real time intelligence, and transmitting this 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 the F-15/AIM-7 Sparrow BVRAAM combination, emphasising the growing maturity of BVR tactics and procedures of the IDF-AF pilots. For the first time the formidable high-altitude MiG-25, hitherto regarded as ‘untouchable’, was shot down. The Raytheon AIM-120 AMRAAM succeeded the AIM-7 Sparrow in IDF-AF inventory in course of time and holds the distinction of being the first operational ARH ‘fire-and-forget’ BVRAAM.

However, the Derby BVRAAM, developed by Rafael Missile Division, was born from an Israeli desire to retain full control of BVRAAM technology especially in relation to Electronic Counter Counter Measures (ECCM) modes. The 3.62 metre long, 118 kg ARH BVRAAM shares design commonality with the Israeli Python 4 missile (including warhead and proximity fuse and even the same launcher), with the addition of midbody 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' MBT Division. Derby has look-down/shoot-down capability and advanced programmable and adaptable ECCM to operate under dense electronic warfare environments while remaining reconfigurable upon the emergence of new threats. For BVR engagements a Lock-On After Launch (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 distances to home in on the target with substantial kinematic performance allowing 'end game' manoeuvrability thanks to a 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 the baseline Derby (now no longer in production) has a launch range in excess of 63 km if launched at Mach 0.9 at 25,000 feet against a head-on target, although its maximum range and its effective seeker range remain highly classified. Derby also has a very low minimum range and an option for LockOn 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 shortrange engagements Derby's capabilities are regarded similar to Python 3 close-combat missile, trapping enemy aircraft in ‘killing fields’ out to 60 km.

In the present I-Derby ER 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 ‘second kick,’ thereby increasing the range of the I-Derby ER 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 a ‘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 I-Derby ER BVRAAM will be compatible with aircraft currently cleared to carry the Derby. Rafael claims it is superior to the AIM-120C7 AMRAAM variant and will be able to deliver 80 per cent of the MBDA Meteor’s performance at a third of its cost. The missile is already cleared on F-16I (Block 50/52), F-5E, Kfir and Indian Navy Sea Harrier. I-Derby ER integration tests are currently under way on India's Tejas LCA.