Monday, June 20, 2011

An insight into “Darin-II” and “Project Tiger” fighter aircraft upgrade programmes in India

The Darin-II upgrade programme on Jaguar aircraft and the Project Tiger upgrade programme on Sea Harrier aircraft have been successfully accomplished and the Final Operational Clearance (FOC) has been issued for service use. Also on the anvil are the Jaguar Darin III upgrade, Jaguar re-engine and Mirage mid-life upgrade programmes. India has been operating these aircraft since 1980s and after years of service these aircraft are well understood. The strengths and weaknesses of these aircrafts are known and appropriate doctrines formed around them. The upgrades are being defined to target the deficiencies and bring these platforms to contemporary standards.

Jaguar DARIN-II Upgrade

A major avionics upgrade on the Jaguar direct supply aircraft, christened DARIN II, was undertaken in early 2000. The upgrade concentrated around improving the navigational capabilities, reducing pilot work-load, improving the attack capabilities and survivability in the electronic warfare. Introduction of core avionic systems like Ring-Laser Gyro-based (RLG) inertial navigation system along with an embedded GPS have improved the accuracy of navigation. The addition of an advanced mission computer, smart multi- function displays (MFDs), a digital map generator, a superior head-up display along with an improved pilot’s stick top, hand controller, instrument landing system and navigational aids (ILS/VOR/TACAN), autopilot have helped reduce pilot work-load. Advanced accessory systems like a secure communication system, electronic warfare suite with ECCM capability, laser designator system have improved the survivability and effectiveness of the Jaguar in a dense EM environment. Additions like a solid-state flight data recorder, etc have improved the reliability and ease of maintenance of the Jaguar. The upgrade programme has allowed the pilots to focus on their primary task of attacking. The twin Mil-Std-1553 bus architecture with a dual redundant mission computer and hot standby features are some of the other major highlights of the system.

Project Tiger- Sea Harrier aircraft

The limited upgrade of the Sea Harrier aircraft termed as Project Tiger is intended to restore a qualitative advantage to the fleet in air defence operations against ASM equipped strike aircraft. Additionally a parity in combat range of Beyond Visual Range (BVR) equipped supersonic fighters. Since the upgraded aircraft would still remain disadvantaged in maximum speeds and maneuverability, this had to be compensated through a combination of enhanced situational (ECCM) Electronic Counter Counter-Measures capability and a capability for co-operative engagement in conjunction with other Sea Harrier aircraft. The add-on systems identified included advanced avionics systems as replacements for obsolete systems on-board and additional systems to enhance mission capability. Similar to the objectives of the Darin upgrade, the Project Tiger also sought to make improvements in aircraft navigation, reduce the pilot’s work-load, improve the strike-capability of the Sea Harrier as well as reduce the effort spent in its maintenance. Like any bird of prey, the need to see far and accurately is vital to the Sea Harrier, which has been improved with the introduction of an advanced fire control radar allows better targeting which coupled with the newly added BVR missiles allow the Sea Harrier to fully exploit its longer range “vision”. The pilot can more accurately pin-point the position of the Sea Harrier thanks to the addition of a RLG-based inertial navigation and global positioning system. The use of new MFDs, a new hand controller and a better stick top has improved cockpit ergonomics and reduced pilot work-load. A combat maneuver monitor cum flight data recorder, a network centric data recorder help improve the situational awareness of the pilot, allowing him to have a better picture of the over-all situation so as to be able to deal with it in the most effective manner possible.

Challenges in certification

The original aircraft manufacturers were not associated in either the Jaguar or the Sea Harrier upgrade programmes. The Jaguar being a licence built aircraft meant that, a fair amount of aircraft design data was available to ensure proper integration and certification. The Sea Harrier on the other hand is a bought out aircraft for which no design details are available, consequently, extensive data collection and validation had to be taken up to facilitate design evaluation and certification. In a project of this nature it is essential to have complete end-to-end visibility on the approach to design and certification in the beginning of the programme.

Avionics upgrade

The mid-life upgrade (MLU) involved integration of newer, advanced avionics systems into the avionics architecture of the legacy system. One of the major challenges in an avionics upgrade process is the integration of an advanced system with the systems already onboard. The integration process is governed by the legacy avionics architecture of the aircraft. Analysis of the legacy system and advanced systems to identify the architecture and technological growth parameters is a major step in interface design clearance. Testing and validation of the interface design parameters for compatibility, functionality and performance is a critical step towards realising the avionics architecture with upgrade potential. Even in the case of complete replacement of the legacy avionics system by new design as in the case of Jaguar Darin-II upgrade, a great deal of effort is involved in interfacing with legacy sensors, weapon system, air data computer, etc and ensuring that there is no loss in the integrity of the data. In the case of Project Tiger on the Sea Harrier, the upgrade was more of a standalone system with minimum handshaking with legacy system. The functionality of legacy system was fully preserved while adding the functionality of advanced systems. Other challenges in integration clearance are the space constraints for equipment installation, weight and balance management (the addition of new components must still keep the CG of the aircraft within the original design limits), mechanical integration and load diffusion to existing airframe (each additional kilogram of that was added to any structure required the team to validate the structural integrity through the entire range of accelerations that the aircraft could undertake), power supply compatibility, electrical load and cooling system constraints under various phases of flight, electromagnetic compatibility, etc. These factors had to be addressed and resolved at the design review stage before commencing the detailed design.

In case of Jaguar Darin II upgrade, only the ‘Nav Attack’ system’s algorithms and software were updated. The updated system supports attack mode selection and weapon aiming computations for all cleared weapon configurations on the aircraft and provides accurate display of attack symbology. The release pulse generation and electromagnetic compatibility were assessed. Integrity of sensor data (aircraft altitude, speed etc) and accuracy of the computations were verified through field trials.

The BVR integration on Sea Harriers involved assessment of geometric capability; mechanical integrity of the installation; electrical load analysis; electromagnetic compatibility; aircraft handling and performance; missile plume and power plant compatibility; aero-elasticity; and hazard analysis.

Thus the Darin-II and Project Tiger programmes have not only provided the IAF and IN with more capable aircrafts, but it has also provided us with tremendous data and confidence in carrying out such activities in the future – the proposed Darin-III being one such example. As India moves on to strengthen in its defence capabilities, the experience gained by these projects would be invaluable in delivering more capable improvements in an effective manner.

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