F-16 VISTA was used as a testbed to test the initial version of the Tejas LCA’s fly-by-wire system.
Development of a FBW flight control system requires extensive knowledge of flight control laws and the expensive writing of a considerable amount of software code for the flight control computers, as well as its integration with the avionics and other electronic systems.
When the LCA programme was launched, FBW was a state-of-the-art technology and such a sensitive one that India could find no nation willing to export it.
Therefore, in 1992 the LCA National Control Law (CLAW) team was set up by the National Aeronautics Laboratory to develop India’s own version of FBW.
The CLAW team’s scientists and mathematicians were successful in developing their control laws, but could not test them since India did not possess advanced real-time ground simulators at that time.
Accordingly to British Aerospace (BAE) and Lockheed Martin were brought in to help in 1993, but the effort required for the Aeronautical Development Establishment to code the control laws into the FCS software proved a much larger job than originally anticipated.
Specific control law problems were tested on BAE’s simulators (and on HAL’s, once theirs became available). As it was being developed, progressive elements of the coding were checked out on the “Minibird” and “Ironbird” test rigs at the ADE and HAL, respectively.
A second series of inflight simulation tests of the integrated flight control software were conducted on the F-16 VISTA (Variable In-flight Stability Test Aircraft) simulator in the U.S. in July 1996, with 33 test flights being carried out. However, Lockheed Martin’s involvement was terminated in 1998 as part of an embargo enacted by the U.S. in response to India’s second nuclear tests in May of that year.
The NAL’s CLAW team eventually managed to successfully complete integration of the flight control laws indigenously, with the FCS software performing flawlessly for over 50 hours of pilot testing on TD-1, resulting in the aircraft being cleared for flight in early 2001.
The LCA’s maiden flight was made by TD-1 from National Flight Test Centre (NFTC), near Bangalore, on 4 January 2001, and its first successful supersonic flight followed on 1 August 2003. TD-2 made its first flight on 6 June 2002.
The automatic flight control system (AFCS) of the Tejas has been highly praised by all of its test pilots, one of whom said that he found it easier to take off with the LCA than in a Mirage 2000.
Tejas FBW was considered to be such that even the F-16 VISTA that flew with LCA FBW software actually performed better with it in some flight regimes, than with the F-16’s own FBW, a comment that irked many in America.