A former HAL engine division engineer has cautioned that replacing the General Electric F404-IN20 engine in the Tejas Mk1A would be a highly complex undertaking rather than a simple upgrade. The aerospace veteran, speaking on condition of anonymity, stated that adopting an alternative powerplant such as the Safran M88 or a future operational version of the Kaveri engine would necessitate major airframe and systems modifications, effectively resulting in a substantially new aircraft configuration.
In modern fly-by-wire fighters, the engine influences nearly every aspect of aircraft design, from structural integrity and weight distribution to airflow management, thermal performance, avionics integration, and flight-control logic. Because the Tejas Mk1A was engineered around the F404-IN20, replacing it would trigger a cascade of redesign requirements throughout the aircraft.
One major area affected would be the intake system. The current intake design has been optimized to provide the airflow characteristics demanded by the F404 engine. Any alternative engine with different mass-flow requirements could require a redesigned intake arrangement to maintain efficiency and prevent airflow-related performance issues. Structural changes would also be necessary, including new engine mounts capable of handling different vibration patterns, loads, and installation requirements.
The aircraft’s FADEC architecture and associated software would need extensive rewriting and validation to ensure proper interaction with the Tejas’ mission systems and digital flight controls. At the same time, modifications to the rear fuselage would likely be required to accommodate differences in nozzle size, exhaust temperatures, and thrust output, along with updated thermal protection and structural reinforcement.
Other subsystems, including fuel delivery and cooling systems, would also require recalibration. The former engineer estimated that the engineering effort would begin with 12–18 months of aerodynamic, structural, and thermal analysis using CFD and FEA tools, followed by another 12–18 months of laboratory and ground testing.
Flight testing would represent the longest phase of the programme. A re-engined Tejas variant would likely need 300–500 flight hours covering diverse operational conditions, including high-speed maneuvers, weapons carriage, altitude performance, and environmental evaluations. The overall development and certification cycle could extend between five and seven years before the aircraft achieves IOC status.
Beyond propulsion testing, engineers would need to conduct vibration studies, thermal assessments, and extensive integration trials to ensure airworthiness and performance. Every weapon integrated onto the platform would also require renewed certification, as engine-related changes can affect airflow patterns and weapon-release characteristics.
The former HAL official noted that proposals to equip the Tejas Mk1A with alternative engines often underestimate these challenges. Although the M88 has proven capabilities in the Rafale, integrating it into the Tejas would likely require extensive redesign due to differences in dimensions and system architecture. Likewise, while the indigenous Kaveri engine remains a key long-term strategic programme, it is currently being matured primarily for future unmanned combat aircraft and has not yet achieved the certification standards, reliability levels, or logistical support framework expected for frontline fighter operations.
