The most important part of a fighter aircraft is engine, It is like the heart .this kind of huge project will have allways delays every one is aware of it. i am sure at the end we will sucseed because hundred of bae system egeneers are working together wit turkisch engeneers to design and to develop the tfx and more engeneers will come. except engine most subsystems like avionics Radars and weapons are either developed or are in development .
If you can make an engine you can make a fifth generation fighter .
Many BAE engineers are working together to develop the engine. My question is are they able to design and make the engine without ToT ?