Flight Control and Software and Other Avionics
The LCA uses advanced digital fly-by-wire technology which essentially employs computers to optimise the aircraft's performance. Foreign companies were consulted. Infact, LCA avionics were first flight tested on a US F-16XL.
Witout the automatic flight control, the LCA will not be flyable, due to the Delta wing's inherent instability. As more and more flights are conducted, the software is updated to allow the aircraft to do more complex maneuvours.
To combat the threat of obsolescence in the LCA Programme, a concerted effort has been made to introduce an Open-architecture Avionics system which permits hardware scalability and upgradability to state-of-the-art technology levels with reusability of the software.
LCA Avionics architecture is configured around a three bus system (MIL-STD-1553B) in a distributed environment. The heart of the system is a 32-bit Mission Computer (MC) which performs mission oriented computations, flight management, reconfiguration / redundancy management and in-flight system self-tests. In compliance with MIL-STD-1521 and 2167A standards, Ada language has been adopted for mission computer software.Accurate navigation and guidance is realised through RLG based Inertial Navigation System (INS) with provision for INS / Global Positioning System (GPS) integration. Jam resistant radio commumication system with advanced Electronic Warfare (EW) environment. In the EW suite, Electromagnetic and Electroptic receivers and jammers provide the necessary "soft-kill" capability.
DFCS Computer
The digital FBW system of the LCA is built around a quadruplex redundant architecture to give it a fail op-fail op-fail safe capability. It employs a powerful Digital Flight Control Computer (DFCC) comprising four computing channels, each powered by an independent power supply and all housed in a single line replaceable unit (LRU). The system is designed to meet a probability of loss of control of better than 1x10-7 per flight hour. The DFCC channels are built around 32-bit microprocessors and use a safe subset of Ada language for the implementation of software. 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.
For maintenance the aircraft has more than five hundred Line Replaceable Units (LRUs), each tested for performance and capability to meet the severe operational conditions to be encountered.
* Mission Computer(MC): MC performs the central processing functions apart from performing as Bus Controller and is the central core of the Avionics system. The hardware architecture is based on a dual 80386 based computer with dual port RAM for interprocessor communication. There are three dual redundant communication channels meeting with MIL-STD-1553B data bus specifications. The hardware unit development was done by ASIEO, Bangalore and Software Design & Development by ADA.
* Control & Coding Unit (CCU): In the normal mode, CCU provides real time I/O access which are essentially pilot's controls and power on controls for certain equipment. In the reversionary mode, when MC fails, CCU performs the central processing functions of MC. The CCU also generates voice warning signals. The main processor is Intel 80386 microprocessor. The hardware is developed by RCI, Hyderabad and software by ADA.
* Display Processors (DP): DP is one of the mission critical software intensive LRUs of LCA. The DP drives two types of display surfaces viz. a monochrome Head Up display (HUD) and two colour multifunction displays (MFDs). The equipment is based on four Intel 80960 microprocessors. There are two DPs provided (one normal and one backup) in LCA. These units are developed by ADE, Bangalore
* Mission Preparation & Data Retrieval Unit (MPRU): MPRU is a data entry and retrieval unit of LCA Avionics architecture. The unit performs mission preparation and data retrieval functions. In the preparation mode, it transfers mission data prepared on Data Preparation Cartridge (DPC) with the help of ground compliment, to various Avionics equipment. In the second function, the MPRU receives data from various equipment during the Operational Flight Program (OFP) and stores data on Resident Cartridge Card (RCC). This unit is developed by LRDE, Bangalore.
* USMS Electronic Units: The following processor based digital Electronics Units (EU) are used for control and monitoring, data logging for fault diagnosis and maintenance.
o Environment Control System Controller (ECSC)
o Engine and Electrical Monitoring System Electronics Unit (EEMS-EU)
o Digital Fuel Monitoring System Electronics Unit (DFM-EU)
o Digital Hydraulics and Brake Management System Electronics Unit (DH-EU)
* V/UHF Equipment: V/UHF equipment is a secure jam resisant airborne radio communication set which provides simplex two way voice and data communication in the VHF and UHF frequency bands. This unit is developed by HAL, Hyderabad.
* Multi Function Keyboard (MFK): MFK is an interfce for pilot dialogue concerning certain selected equipment of Avionics system. It comprises LCD panel, alphanumeric keys, push buttions for power ON / OFF and LEDs indicating power ON / OFF status of certain Avionics equipment. This unit is developed by BEL, Bangalore.
* Head Up Display (HUD): HUD is of conventional type with a Total Field of View (TFOV) of 24 degrees circular. A Change Coupled Device (CCD) based camera is mounted on the HUD for recording purposes. HUD dsplays various navigation and weapon related data. This unit is developed by CSIO, Chandigarh.
* Colour Multi Function Displays (MFDs): LCD based colour MFDs hava a useful screen area of 125 mm x 125 mm. They have soft keys around their periphery for interaction with the systems. This display provides various aircraft system pages and navigation pages in addition to RADAR & FLIR display.
Digital fly-by-wire Flight Control System is another advanced feature of LCA. 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 synthesises inputs from pilot's stick and rudder pedals with flight parameters from inertial and airdata measurements to generate commands to the actuators that move various control surfaces. The design of the control law is evaluated susing real-time flight simulator for acceptable flight handling qualities. The IFCS ensures stability, agility, manoeuvrability and carefree handling over the entire operating envelope of LCA. The Digital Flight Control Computer (DFCC) is the heart of IFCS, and uses a quadruplex redundant system to achieve high reliability and safety.
Independent Verification and Validation (IV&V) activity is an integral part of the Software development process. From requirement specification to final testing, IV&V ensures correctness, consistency, completeness and adherence to MIL standards of the software.
The flight control system along with all the associated software is tested and validated at the iron-bird rig.
http://www.geocities.com/spacetransport/aircraft-lca.html
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