A modern avionics system consists of various components and subsystems, comprising digital computers. Avionics system is basically a distributed computer system with hardware peripherals containing embedded information and executive devices of various types – radar, IRST (infrared search and track) system, navigation system, SIGINT (signal intelligence) system, active jammer, weapon control system, countermeasures dispensers, automatic control system, cockpit instrumentation, cockpit controls and various systems of general onboard equipment, etc. The total number of avionics system components varies from10 to 20 or more depending on aircraft type.
Avionics components are connected by analog and digital communication links. Over 1000 parameters can be transmitted over digital communication link at a rate of up to 100 Hz. Each avionics system component uses computer module software to perform its functions. Since each computer module software is usually developed by different teams of programmers, and ADC (Airborne Digital Computer) software must function as a whole this brings the challenge of avionics components integration. The integration is implemented at hardware, functional and software levels. It is implemented in several steps.
In the first stage the integration is performed at functional and software levels. It is performed in virtual prototyping simulation facilities, where real avionics components are presented in the form of mathematical models. The dynamic test set is given. In the process of testing avionics functions are checked for compliance with system requirements specifications, including data exchange protocols and system operation logic. In this stage in addition to search for software errors the correction of system requirements themselves is performed. In other words, the dynamic tests provide feedback between functions and system requirements. The first stage of integration is particularly important in the process of avionics system development, when a system being developed does not have close analogues. That is avionics system structure and functions are essentially modified as compared to previous generation systems.
In the second stage the integration is performed at functional, software and hardware levels. It is performed in hardware-in-the loop simulation facilities, comprising real onboard equipment and target simulators, operating in different frequency bands. The integration is performed with the use of dynamic tests. In other words avionics hardware-in-the-loop simulation similar to full-scale experiments is performed. In the process of integration the compliance of functions, implemented in avionics system components and avionics system as a whole, with system requirements is assessed, airborne digital computer software errors are searched for, and avionics system hardware operation is checked. In this stage system requirements correction can be also performed.
In the third stage software system components are integrated during flight tests. Here the purposes and tasks are the same as in the second stage. Full-scale testing terminates the complete cycle of avionics system components integration, because a set of avionics system functions can be verified only during flight tests.
Avionics and weapon systems integration is performed in a similar way. It is also performed in three steps and is no less labor consuming if it is remembered that modern aircraft carry over a dozen of weapons of various types, and missile guidance systems comprise airborne digital computers similar to aircraft computers.
