The unstable configuration of LCA demands a highly efficient Integrated Flight Control System (IFCS) to fly the aircraft. Control law resident in the flight control computer synthesizes inputs from pilot's stick and rudder pedals with flight parameters from inertial and air-data measurements to generate commands to the actuators that move various control surfaces. The design of the control law is evaluated using real-time flight simulator for acceptable flight handling qualities. The IFCS ensures stability, agility, maneuverability and carefree handling over the entire operating envelope of LCA. The Digital Flight Control Computer (DFCC) is the heart of IFCS. It hosts 4 computing channels each powered by an independent 28V DC power input from the aircraft. The four channels are identical and each has one digital module which is the main computing unit for control law and redundancy management, three analog boards and one power supply board, all housing in a single LRU. A high speed serial link connects the four channels under the control of redundancy control software performing system failure detection and control reconfiguration. The digital modules also provide MIL-STD-1533B and RS -422 interfaces to various sub systems including the air data transducers, flight test panel, crash data records and so on. The DFCS features extensive built in test, recording and extensive built in test, recording and extensive signal monitoring.
The DFCC receives signals from quad rate, acceleration sensors, pilot control stick, rudder pedal, triplex air data system, dual air flow angle sensors, etc. The DFCC channels excite and control the elevon, rudder and leading edge slat hydraulic actuators. The computer interfaces with pilot display elements like multifunction displays through MIL-STD-1553B avionics bus and RS 422 serial link. The complete air-data system is triplex redundant while rate sensor and accelerometer assemblies are quadruplex redundant.
A solid state crash data recorder (SSCDR) records the aircrafts analog and discrete flight parameters along with the voice and audio transactions.
The quadruplex redundant architecture without mechanical backup has evolved to meet the fail operate fail-safe requirement. The Tejas digital FBW FCS also uses quad redundant electrical power supply dual redundant hydraulic power supply and meets the stringent PLOC requirement of 0.1 failures in million flights.
Provisions for the growth of hardware and software in the avionics and flight control system, available in LCA, ensure to maintain its effectiveness and advantages as a frontline fighter throughout its service life. For maintenance the aircraft has more than five hundred Line Replaceable Units (LRSs), each tested for performance and capability to meet the severe operational conditions to be encountered.
) have seen the CoI findings and it would be foolish to ascribe causes.
