Dynamic Navigation System Integration
A high-frequency interface for flight simulation allows dynamic integration of navigation systems, further extending TechSAT’s test system technology platform
The integration of avionics navigation systems in commercial aircraft is a highly sophisticated engineering task. A broad spectrum of knowledge from navigation to electronics and high frequency technology is required to master the complexity of navigation system integration.
Around the world, several vendors provide measurement and test solutions for navigation aids such as instrument landing systems (ILS), distance measurement equipment (DME), VHF omnidirectional radio range (VOA), or radar altimeter (RA).They focus on dedicated applications at equipment level, such as transceiver testing, high frequency signal analysis, calibration or field tests.
Aircraft integrators use test systems for integration tasks at system or aircraft level as a matter of course. These test systems usually provide interfaces for the aerospace buses such as A664, A429, A825, or MIL1553B, and other discrete and analog I/0. HIL test systems additionally provide suitable aircraft, environment and flight simulations, allowing closed-loop operation of the system under test. An HIL test system for dynamic integration of navigation systems has to provide high- frequency interfaces for the different aeronautical radio navigation signals.
The challenge is to provide a high frequency interface for flight simulations that does not increase the complexity of the test system with regard to the high-frequency technology and all details of navigation.
The best approach is to build an HF simulator as a black box system for each navigation aid. The different HF simulators encapsulate the technological complexity and only provide the necessary interfaces for the flight simulation and the HF signals to the real navigation equipment. In this way, the HF simulator can be used for navigation subsystems or synchronized to a single simulation environment for the entire navigation system. TechSAT’s HF simulators for navigation are available for global navigation satellite systems (GNSS), ILS, DME, VOA, RA, and the automatic direction finder (ADF). The GNSS solution currently supports GPS, GLONASS and the satellite-based augmentation system. BeiDou and Galileo are available on request.
All of the HF simulators except the ADF simulator are based upon widespread COTS test equipment that forms the high-frequency component. The ADF simulator is the only one that has to transmit modulated and synchronized HF signals on three HF lines.
Therefore, a new product has been realized for the HF component of this application to keep complexity and cost down.
In the figure below, the principle architecture of all simulators and their integration in the Avionics Development System 2nd Generation (ADS2) test system is shown – in this example, the ADF simulator.
The high-frequency component of the ADF simulator is connected to the real ADF antenna input by cable and used to generate the HF signals. It is integrated into the test system by standard Ethernet.
The ADF simulator software component is used to control the HF component and make it dynamic for the closed-loop operation in the HIL test system. The software gets all data of the flight and environment simulation that is relevant for the dedicated application. It also computes all navigation algorithms to command the proper HF generation that is required for a particular flight phase.
All information relative to the actual aircraft situation is generated in the flight and environment simulation and exchanged with the ADF simulator software.
Any 6DOF flight simulation with world scenery data (flight gear, for example) providing a fitting dynamic data interface can be connected to the HF simulators. In a closed-loop scenario, the HF signals received by the ADF are converted and transferred via the ADF data interface to the rest of the navigation system, or directly to the test system.
When comparing the information simulated over the HF signal lines with that received on the data interfaces of the system under test, the dynamic functionality of the entire navigation system is verified.
TechSAT’s high-frequency simulators for navigation are fully integrated into the ADS2 real-time environment. Once they are connected to the system under test and integrated into the flight and environment simulation, they operate transparently.
Using a dedicated graphical user interface, they are controlled in the same way as the entire ADS2 technology platform. Therefore the test team and operational staff require no additional training.
The modular design of the HF simulator allows for the future extension of navigation aids such as ground-based augmentation systems or traffic alert and collision avoidance systems. The design of HF simulators for communication systems (VHF, satcom) will allow integration of future air navigation system features in HIL test systems.
Versions of the existing HF simulator for integration into other test environments are available upon request.