India’s reported plan to test the indigenous Kaveri engine on the Sukhoi Su-30MKI reflects both ambition and desperation in closing the long-standing gap in developing a sustainable, reliable and adaptive domestic fighter jet engine.

The Kaveri program, initiated in the 1980s, was originally designed to power the Light Combat Aircraft (LCA) TEJAS, but persistent shortfalls in thrust and reliability led to its repurposing primarily for the Ghatak UAV.

According to Republic World, the current initiative draws inspiration from the United States’ F-22 development effort, where experimental engines were validated extensively before combat integration, though under very different technical and logistical conditions.

The Kaveri GTX-35VS produces between 49–51 kN of dry thrust, significantly lower than the 88–90 kN generated by the Saturn AL-31FP, the twin-engine powerplant of the Su-30MKI. This mismatch poses inherent structural and performance constraints.

The Kaveri’s thrust class is closer to the General Electric F404 engine used on early TEJAS fighters, rather than on heavyweight platforms like the Su-30MKI. Attempting integration on the latter risks severe compromises in flight safety and manoeuvring envelope.

Testing an underpowered engine on such a large and heavy airframe may appear illogical, but the Su-30MKI provides a robust and readily available test bed. The airframe’s excess thrust from one functional AL-31FP allows for asymmetric power testing, acting as a safeguard if the developmental Kaveri fails mid-flight.

Unlike TEJAS, which has only a single engine, the Su-30’s twin-engine design reduces the operational risk of catastrophic failure during airborne tests. This makes it a more practical, if technically mismatched, platform.

During the F-22 Raptor’s development, Pratt & Whitney’s F119 engine was not tested directly on the fighter initially. Instead, a specially modified Boeing 747SP served as a flying test bed, allowing engineers to validate the engine in a controlled environment before high-performance experimentation. 

India lacks such large dedicated test aircraft, making it dependent on existing military fighters for integration trials. This fundamental difference highlights the technological constraints under which India’s program operates.

Several hurdles accompany this choice. Integration will require adapting mounts, ducts, and control systems of the Su-30 to handle a completely different powerplant geometry and performance profile. 

Electronic engine controls and digital-analogue interfaces must be reworked extensively. Furthermore, stress tests will need to confirm whether vibration, airflow, and temperature parameters of the Kaveri are compatible with the Su-30’s systems. Even if safe integration is achieved, the thrust deficit means the engine cannot operationally replace the AL-31FP.

India’s desire to conduct this test is also politically symbolic. With persistent maintenance and spare parts issues due to Russian sanctions, New Delhi is accelerating the search for an indigenous alternative. The Kaveri, though underpowered, represents an important learning platform for GTRE and HAL in understanding real-world flight performance beyond laboratory simulations. Even failure would yield valuable data in combustion stability, material tolerances, and high-altitude handling.

While GTRE’s logic for using the Su-30MKI centres on safety through twin engines, experts argue that retrofitting the TEJAS or a smaller indigenous test bed better mirrors the Kaveri’s intended thrust class. 

The reliance on the Su-30 might accelerate learning but adds unnecessary complexity, as the Su-30 has higher aerodynamic loads and design requirements. Developing or leasing a dedicated flying test bed, similar to the U.S. or French approaches, would be a more sustainable long-term plan.

The proposed flight tests will not make the Kaveri suitable for operational fighter deployment, particularly not on heavy platforms like the Su-30MKI.

However, they mark an important experimental stage in India’s slow march toward self-reliance in jet engine technology. If managed carefully, even partial success will feed directly into derivative programs such as Kaveri-Snecma co-development for AMCA and the Ghatak engine for unmanned systems. The risks remain steep, but the knowledge gained from real airborne testing could finally help India overcome a decades-long technological bottleneck.

Comparison table of the Kaveri, AL-31FP, GE F404, and Pratt & Whitney F119 turbofan engines:

EngineThrust (Dry)Thrust (Wet)Weight (Approx)ApplicationsNotes
GTX-35VS Kaveri49–51 kN~81–86 kN (Targeted, not fully realised)~1,050 kgIntended for TEJAS (never operationalised); now being considered for Ghatak UCAVUnderpowered, still in experimental stage
Saturn AL-31FP76–80 kN122–130 kN~1,520 kgSu-27, Su-30, Su-33, Su-34, Su-30MKIThrust vectoring version used in Su-30MKI
GE F404-GE-IN2048–50 kN~80–85 kN~1,040 kgTEJAS MK-1, F/A-18 Hornet (early versions)Close in class to Kaveri; proven and reliable
Pratt & Whitney F119~116 kN~156 kN~1,770 kgF-22 RaptorAdvanced 5th-gen stealth engine with supercruise capability

IDN (With Agency Inputs)