It appears that India’s Tejas fighter is not meeting performance specs. It’s take off thrust and low speed performance with the US F-404 engine is lacking.

This is surprising, since the F-404 is a very known quantity, it’s been flying for 25 years, and one must assume that this is an issue of problems of engine integration/inlet design.

The F-404 was intended as an interim engine, but:

The failure has been attributed to insufficient available thrust from the aircraft’s General Electric F404 engine, and underlines India’s need to replace the US design with the Kaveri powerplant now under development by its Gas Turbine Research Establishment. In common with the wider Tejas programme, the Kaveri project has been dogged by development delays and cost escalations, which have forced New Delhi to order additional F404s to power its initial production batch of lightweight fighters.

It sounds like the Arjun all over again.

What’s more, it now appears that they are having problems with the radar:

New Delhi in mid-August announced a co-operative agreement under which its defence industry will develop the aircraft’s multi-mode radar with Israel Aerospace Industries’ Elta Systems subsidiary.

….

The initiative will replace previous work conducted by the Bangalore-based Electronics and Radar Development Establishment, with technical hitches having prevented a radar design from being integrated with a prototype Tejas.

Antony says the new fire-control radar is needed to support demonstration flights of the fully developed and armed fighter from 2010, and Israeli sources reveal that the sensor will be a further development of Elta’s EL/M-2052 active electronically scanned array.

So, they have just dumped an indigenous system for a largely developed system.