How much of the Tejas is manufactured in-house?
If anyone knows. Because our JF-17 doesn't have our own radar, engine, etc either and it's only assembled in-house. It's better we be honest with ourselves, India struggled a bit but focused on building an indigenous ecosystem - we are now playing catch-up
Dassault was the consultant and over 500 HAL engineers were trained at Dassault facilities since Dassault's CATIA was selected as the design tool in the 1980s when it was almost brand new.
The PD phase was over in 1990 after which Dassault's role largely ended. Dassault offered the Mirage-2000's FBW FCS (3 channel digital with analog backup) for the Tejas but it was rejected by DRDO and ADA since they wanted state of the art quadruplex FCS with no analog backup. Dassault refused to share it saying that they themselves were developing it for the Rafale.
DRDO/ADA selected the US offer and went to CALSPAN/Marietta for the FCS related work and also had BAe as consultants but in a much smaller role. The ADA/DRDO guys were working on the FCS in the US when the nuclear tests happened and all were kicked out of the US and their computers and data was seized. That basically meant they had to re-do all their work from scratch after coming back to India.
Radar was supposed to be developed with Ericsson's PS-05A as the baseline. Ericsson refused to share ToT and they departed soon after and the Indian LRDE lab took up the MMR radar on it's own. Eventually they developed the antenna, actuators, back end signal processing, etc. but it failed to meet the mark. Finally the MMR's antenna was used, but the signal processing back end was taken from the Israeli Elta 2032.
As of today, India has an indigenous AESA flying on the Netra AEW&C successfully since several years. It has led to the Uttam AESA fire control radar which has cleared trials and is slated to be used on the Tejas Mk1A from the 40th fighter onwards.
Engine was the Kaveri that eventually was tested on a Il-78 in Russia but did not meet the afterburning thrust goal. It was able to meet the required dry thrust. Metallurgy is a science and an art and that is where tremendous amounts of money is required to be invested, which unfortunately was never done in the case of the Kaveri. The total money invested in the Kaveri is a fraction of what GE/Safran/RR spend on a new engine development program, despite the fact that they have all the facilities.
Composites was a big success and is almost entirely indigenous with even the carbon fiber pre-preg sourced in India now.
Basically the Tejas program laid the foundation for every single area of combat fighter development in India, from lightning test facilities, to iron rigs, to wind tunnels, to CFD solvers, to manufacturing to RCS measurement facilities..you name it, it has been done for the Tejas program, which is why the Tejas Mk2, TEDBF and AMCA can even be taken on.