Re-engining the Tejas Mk1A: Why an engine swap won't work for India's Tejas

Significant delivery delays of the General Electric (GE) F404-IN20 engines from the United States have bottlenecked the Indian Air Force's Light Combat Aircraft (LCA) Tejas Mk1A fleet, prompting public calls for an alternative powerplant. However, an analysis by defence.in reveals that swapping the aircraft’s core propulsion system is far from a simple plug-and-play solution. 

An experienced former engineer from Hindustan Aeronautics Limited (HAL) told defence.in that integrating a new engine would demand extensive airframe redesigns. The aerospace expert warned that such an overhaul would essentially create a completely new variant, consuming five to seven years in engineering, manufacturing, and rigorous flight testing. 

In modern military aviation, an engine dictates a fighter’s aerodynamic profile, internal structural architecture, and safety margins. For an advanced fly-by-wire platform like the Tejas Mk1A, the physical structure is custom-tailored around the dimensions and performance parameters of the GE F404-IN20. Choosing a different powerplant would trigger a cascading chain of modifications across multiple vital systems: 

• Air Intakes: The jet's intakes are sculpted for the exact volume and pressure required by the GE engine. A replacement engine would draw air at different rates, forcing engineers to redesign and manufacture new intake channels to prevent engine stalls. 
• Structural Architecture: Internal mounts must be entirely rebuilt to absorb unique vibrations, weight distribution, and thrust forces. The rear fuselage would require new heat shields and strengthened structural frames to accommodate variations in nozzle sizes and exhaust temperatures. 
• Systems Integration: The Full Authority Digital Engine Control (FADEC) would require a complete software rewrite to communicate with the Tejas's main mission computers. Internal fuel delivery lines and cooling systems would also need adjustments to manage distinct operational profiles. 

This massive engineering overhaul would initiate a long, demanding certification journey. The veteran HAL engineer estimated that the initial computer-based design and simulation phase would take up to 18 months, followed by another year and a half of ground tests to eliminate dangerous aeroelastic vibrations or structural compatibility issues. 

The final phase is flight testing. A re-engined Tejas would need to log 300 to 500 hours in the air under extreme conditions, evaluating high-altitude performance, high-speed maneuvering, and center-of-gravity stability. Crucially, because a new engine alters the airflow over the wings and fuselage, every weapon integrated onto the Tejas — including the Astra missile and precision-guided bombs — would require fresh certifications to guarantee safe weapon separation. 

While alternative powerplants like the French Safran M88 are highly capable, placing them inside the Tejas would still require massive modifications to the aircraft's physical body due to different dimensions and technical architecture.

Meanwhile, India's indigenous Kaveri engine remains on a separate development path aimed at powering unmanned systems like the Ghatak UCAV, with certification milestones targeted around 2026. The Kaveri has not yet achieved the strict reliability metrics required for a frontline manned fighter jet, ruling it out as an immediate replacement.