SOURCE: AFI

The Indian Air Force’s indigenous fighter jet projects, the Tejas MkII and the Advanced Medium Combat Aircraft (AMCA), showcase India’s ambition to become self-reliant in military aviation. A notable distinction between these two aircraft is the use of Diverterless Supersonic Inlet (DSI) technology. While the AMCA adopts this modern design feature, the Tejas MkII does not. Here’s an analysis of the reasons behind this difference in design philosophy.
DSI intakes are a modern innovation in aircraft design, particularly for fighters, where they replace traditional intake systems with diverter plates. They offer benefits like reduced radar cross-section due to fewer moving parts, less drag, and potentially better airflow management. This technology is particularly advantageous for stealth aircraft, where minimizing radar visibility is crucial .
The Tejas MkII, or Medium Weight Fighter (MWF), is an evolutionary upgrade from the Tejas Mk1 and Mk1A. It retains much of the original airframe design to minimize development time and costs while enhancing performance. The existing intake design was part of this inherited architecture, which was optimized for the less stringent stealth requirements of a 4.5 generation fighter .
The primary focus for the Tejas MkII was enhancing maneuverability, payload, and avionics. Retrofitting with DSI would have required significant redesign, potentially leading to delays and increased costs. The Tejas MkII’s development aimed at balancing performance with the practicalities of budget and timeline constraints .
While the Tejas MkII includes some stealth enhancements, it was not designed with the same level of stealth priority as the AMCA. The MkII’s operational profile doesn’t necessitate the stealth advantages DSI offers to the extent that a 5th generation fighter like the AMCA does.
AMCA is designed to be India’s first true 5th generation fighter, with stealth as a core design parameter. DSIs significantly contribute to reducing the radar cross-section by eliminating the need for external moving parts like the traditional intake bypass doors, thus reducing radar reflectivity .
Unlike the Tejas, which evolved from an existing platform, the AMCA started from a clean slate, allowing designers to incorporate advanced technologies from the outset. This included adopting DSIs to align with the aircraft’s stealth objectives .
The decision to not include DSI on the Tejas MkII could be seen as a strategic move to get the aircraft into service faster, whereas the AMCA’s timeline allowed for the integration of such advanced technologies without the same rush to deployment.