Safety and efficiency for fly-by-wire systems in aviation

Aircraft Engineering and Aerospace Technology

ISSN: 0002-2667

Article publication date: 1 June 2004



(2004), "Safety and efficiency for fly-by-wire systems in aviation", Aircraft Engineering and Aerospace Technology, Vol. 76 No. 3.



Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited

Safety and efficiency for fly-by-wire systems in aviation

Safety and efficiency for fly-by-wire systems in aviation

Keywords: Safety, Software, Aircraft industry

At this year's international “Aerospace Testing” exhibition, ROSE Informatik GmbH of Heidenheim, Germany, demonstrated how efficient engineering and system quality can be economically optimized and technically automated in the development and maintenance of complex architectures. In the forefront are the new “Optimizer” and “Reliability” modules of the risk analysis and diagnostic software solution RODON, for automatically optimizing architectures critical to safety, such as fly-by-wire systems, with respect to weight, material or costs, while at the same time analysing failure probabilities and minimal cut sets and monitoring compliance. These technologies have been successfully applied in a project jointly conducted with the aviation company Airbus. On the other hand, the software specialists will be displaying new RODON developments in on-board diagnosis. By means of a new type of diagnostic engine that can be run on a flight computer, RODON identifies in a few dozen milliseconds concrete causes of system failures and malfunctions during the flight. By comparison with the conventional built in test equipment (BITE) feature of flight computers, this innovation allows significant improvement in diagnostic performance and fault correction. In addition, ROSE will demonstrate the functional scope of RODON for systematic monitoring and fault diagnostic procedures in the case of fly-by-wire flight control and a typical application from cabin electrical and electronic systems.

In the development of safety-critical systems, the road to the optimal architecture is often long and rocky. Time and staffing budgets are frequently overextended, and often the lists of technical requirements are over-fulfilled, to rule out any safety risks and functional weaknesses. Enormous system expenditures are the result. In the interest of accelerating the development process and avoiding unintentional system redundancy or overdesign, ROSE demonstrates the computation and maintenance of all failure probabilities and minimal cut sets for the system design of a new airfoil architecture in the case of a practically tested fly-by-wire system, with weight and cost-optimized architectural versions being simultaneously computed.

Besides the displayed optimization, the weight, material expenditure and costs can also serve as the objective functions. RODON's modeling language also allows the formulation of objective functions from other arbitrary system quantities.

For the fault diagnosis during the flight, the new diagnostic engine operates on the processor of an FCU, whereas a 16 bit processor is already sufficient. On the basis of compressed diagnostic knowledge, it identifies the possible causes of occurring malfunctions within a few dozen milliseconds. The service technician can then employ this information for correcting the fault significantly faster. The new on-board diagnostic application continually listens to the messages from the data bus, filters out the relevant information, prepares this information and then performs the particular diagnosis. In this way, the diagnostic engine can also identify multiple faults. This significant improvement in diagnostic performance is due to the incorporation of functional concepts from RODON's model-based diagnosis into the engine.

Another theme of the exhibition illustrated the model-based diagnostic functionality of RODON in the cases of a fly-by-wire function and the cabin electrical and electronic systems of airliners. A practical example shows how RODON can be used to monitor the fully electrical flight control feature with the operating unit, actuators, wiring and control units. By means of measured and observed symptoms, the diagnostic engine detects possible single or multiple causes, graphically highlights them and lists the located candidates for faults by name according to their probabilities of failure. This technology can also be used for cabin systems as illustrated by a comfort seat procedure compared with the customary self-diagnostic methods available on the market for flight computers.

Details available from: ROSE Informatik GmbH. Tel: +49 7321 959310; Fax: +49 7321 959317; E-mail:; Web site: