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Raghavendra Prasad Asked: China is developing PL-15 Beyond Visual Range Air-to-Air Missile (BVRAAM) with a 300 to 400 km long range. How safe and effective will Sukhoi and Rafale jets be against it?

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  • Kishore Kumar Khera replies: Air-to-Air Missiles (AAM) have three basic attributes that define their effectiveness: Sensors, Energy, and Structure.

    The initial trajectory of any medium or long-range AAM is based on an initial fix about the target obtained from the mother aircraft or an Airborne Warning and Control System (AWACS) or a ground-based electronic sensor. Navigation towards the intended target is based on an Inertial Navigation System or a Satellite Based System or a combination of the two. As the intended target is an aircraft moving at high speed in three-dimensional space, a data link is normally used for mid-course update about the target position. Terminal guidance to the target is by a radar fitted on board the missile. This radar switches on only in the final attack phase at a range of 20-30 km from the target. This in certain cases may be supported by additional sensors like Imaging Infra-Red (IIR). While the missile aims to hit the target, it may not be always possible because of continuous manoeuvring of the missile and the target. To obviate a complete miss, normally AAMs are equipped with proximity sensors to activate its fuses for an explosion in the close vicinity of the target. Larger aircraft with low manoeuvrability have a greater probability of being hit or damaged.

    Being launched from an aircraft, AAMs have high initial potential and kinetic energy. But for a long-range AAM, a large amount of fuel/propellant is a necessity. This allows it to cover the distance from the mother aircraft to the intended target at high speed. Fuel and power plant stowage makes long-range AAMs bulky and imposes structural limitations on their manoeuvrability. While a short and medium range AAM is designed to take a structural load of over 30g, the same cannot be achieved in a long range AAM. Although no fighter aircraft manoeuvres with more than 9g, such a high limit for intercepting a fighter class of aircraft is required as the missile reacts to actions of the intended target. This gets further accentuated because of very high approach speed of the missile to catch up with the intended target. Therefore structurally, long-range AAMs are not optimal to engage fighter class of aircraft.

    The Radar Warning Receivers (RWR) and/or Missile Approach Warning Systems (MAWS) are a standard fit on all military aircraft. These warn the aircrew about a missile threat when the aircraft is tracked by the ground-based/airborne radar for the launch of a missile. An additional warning is provided when the radar on board the missile starts transmitting in the terminal phase of its attack. The targeted aircraft can counter by utilising Electronic Counter Measures (ECM) or manoeuvres or a combination of these two to deceive the missile.

    The distance at which an aircraft can be detected and tracked is based on its Radar Cross Section (RCS). Fighter aircraft with relatively low RCS have low detection and tracking range as compared to wide-bodied aircraft like AWACS, Flight Refuelling Aircraft (FRA) and Maritime Patrol Aircraft (MPA). Additionally, greater manoeuvrability of fighter aircraft reduces the Single Shot Kill Probability (SSKP) of a long-range AAM against them.

    All factors considered, a long-range AAM like PL15 is primarily designed to target large RCS, low manoeuvrability but high-value targets like AWACS, FRA and MPA. Although it can be launched against a fighter aircraft but will have a low probability of success.

    Posted on May 10, 2018