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For actuation of high lift surfaces in modern airplanes, complex mechanical shaft transmission systems powered by central drive units are deployed. The design of mechanical actuation systems, which have a major share in the weight of secondary flight controls, is a complex and challenging engineering task. Especially for specification of essential component and system design parameters within the preliminary design phase, engineering skill and experience are of significant importance owing to many uncertainties in component data and boundary conditions. Extensive trade-offs, as well as an evaluation of the system requirements and constraints lead to an iterative and time-consuming design process. Utilizing an integrated design assistance tool, mathematical functions and constraints can be modeled on system and component level and formalized as a constraint satisfaction problem (CSP). Thus, automated consistency checking and pruning of the solution space can be achieved.

This paper focuses on the virtual integration and test approach used for the evaluation of an automation system developed for the multifunctional operation of fuel cells in commercial aircraft. In order to accomplish the virtual integration a model of the overall automation system is linked with a dynamic model of the complete fuel cell system. For this purpose a modeling approach for complex physical systems is described in this paper. During virtual testing various simulation runs are executed based on automatically generated test cases, which cover a complete flight mission. For this reason a flight mission is modeled as a Statechart that includes next to time- based flight phases also potential events and malfunctions (e.g. engine flame-out, cargo fire). An algorithm is described, which can find all possible state combinations including parallel event sequences.

Simulation of avionics equipment is essential due to the complex nature of its development and integration process. Throughout the development process, executable component models are used to demonstrate the feasibility and the compliance of the system design with respect to its functional requirements. In later development phases, there is the need for system integration tests where a mix of real and simulated equipment is used to verify the overall system behavior. Since Boeing 777 and Airbus A380 programs, IMA1 technology has entered several civil aircraft systems. In recent programs like Boeing 787 and Airbus A350 the number of IMA components has significantly increased. In this paper we present a simulation model for a new IMA component - the common Remote Data Concentrator (CRDC)2, which is developed by Thales-Diehl for the Airbus A350 XWB. Building simulation models of IMA components is in general a challenging task due to their complexity on both software and hardware level.

This paper presents a methodology to develop, optimize and evaluate fuel cell system architectures. The main focus is placed on the sizing and optimization process which uses the simulation tool Matlab/Simscape. A model library is introduced which contains parametric behavior models. The benefit of this is that the size of the components is not fixed by the parameters. The size of the components is driven by the energy and mass flows of each component. Thus the implicit sizing and optimization process is easy to handle and numerically robust. Illustrative results are shown for a fuel cell system.

This paper presents a model-based design and verification approach, which is used to develop a complex state-based fuel cell control system. The architecture of the control system is organized in a hierarchical manner with one supervisory controller and several system controllers. The used development approach considers the systematic design of this hierarchical concept and enables the integration of requirements. The single modules of the control system are modeled as Statecharts. During the design process a method based on Petri Nets is used to analyze and verify the state-based structure of the supervisory controller. The verification of the control system functionalities is finally realized by a black box test approach. The required test sequences are systematically specified on the basis of the state transition graph of the supervisory controller.

The integration of fuel cell systems as an independent energy source (Auxiliary Power Unit, APU) requires enhanced aircraft cooling architectures. New environmental control systems and systems with an increased cooling demand are investigated in various research projects. Cooling system architectures can be designed which benefit from similar requirements, e.g. by using the same cooling loops. Additionally, an increased cooling demand makes the investigation of alternative heat sinks necessary. For detailed system investigations simulation studies are used. A model library has been created in Dymola/Modelica containing the necessary component models to simulate cooling systems. The used modeling approaches and main model information are presented in this article. In order to understand the basic system behavior a Design of Experiment (DOE) is useful. If only two or three parameters are considered, simulation studies can be performed for each possible parameter combination.

This paper presents a model-based approach for the multi-objective design of optimized diagnosis functions for high lift actuation systems. These systems are used to augment lift at low speed during takeoff and landing, and are safety critical. This demands requirements to the detection of failures and the isolation of root causes in order to provide a high availability at low risk. Dedicated functions cover the determination of features, the detection of symptoms and the isolation of root causes by means of inference and resolution. The aim of the design approach is to provide these functions in an optimal manner with respect to multiple objectives. In order to be clear and traceable the approach consists of separate consecutive steps. These are arranged by using systems engineering principles. With respect to requirements, models of different levels of detail are developed and used to design stepwise all required functions.

This paper describes the conceptual design of a variable-speed fixed-displacement electric motor pump for aircraft hydraulic systems. In contrast to today's approaches, the pump controls the constant system pressure by adapting the motor speed rather than the pump displacement or both. This concept might increase the pump's part load efficiency significantly. The paper starts with introducing and analyzing the dynamic requirements of aircraft hydraulic pumps and evaluating different pump concepts. The concept of an internal gear pump driven by a permanent magnet synchronous motor is selected. For this concept an experimental prototype is developed. The electric motor pump is modeled and a pressure controller is designed. The prototype is set up and tested on an experimental test bench regarding dynamics, efficiencies and noise emissions. The overall concept is evaluated regarding secondary power demand, system heat load, wear, reliability, noise, and mass.

Recent trends towards lighter and more efficient commercial aircraft have motivated airframers to consider the use of electromechanical actuators EMA as the primary means of power for aircraft flight control systems. The transition from state-of-the-art hydraulic actuation to new electromechanical technologies poses a great challenge to both airframers and system suppliers for the correct and complete definition of new requirements. Transient effects such as electric motor overheating and inertial loads, previously not present or irrelevant for hydraulic actuators, now have to be taken into account. A knowledge-based environment containing design drivers for electromechanical components is combined with a validation method in order to aid the systems engineer to accomplish such task. This approach offers the potential to guarantee that all requirements are covered by a new technology, and that they are complete and consistent.

This paper proposes an extension to curved surfaces of a design method of piezoelectric ice protection systems established for planar surfaces. The method is based on a finite element analysis which enables the fast computation of the resonant modes of interest to de-ice surfaces as leading edges. The performance of the modes of interest is assessed according to their deicing capacity estimated from the electro-mechanical coupling between the electric charge of the piezoelectric actuators and the strain energy in the structure. The method is illustrated on a NACA 0024 airfoil. Several experimental tests are conducted in an icing wind tunnel to verify the numerical predictions of the ice shedding and the operation of the system.

Due to a shift of the major aviation concerns to focus on enhancements of the successful programs instead of pushing their successors, the need for new methodologies for aircraft system architecture design emerges. Challenging the existing requirements and reconsidering the functions and their allocation could help to dissolve the system specific development paradigm and lead to beneficial architecture concepts. To help understand the mechanisms and boundary conditions of developing fault-tolerant systems, the first part of the paper gives an overview of the successive process of architecture design. The significant architectural design decisions and the concurrent safety assessment process are discussed. One crucial step in the design space exploration of future aircraft system architectures is the allocation of the consumers to the available power sources. Within the paper a methodology for the optimization of the power allocation for flight control systems is proposed.

The continuous need for improved high lift performance motivates the evaluation of innovative high lift systems. Single flap drive systems are possible solutions to implement novel functionalities for aerodynamic performance optimization. The previously mechanical coupling needs to be replaced by approved equivalent means. This directly results in high demands on control and monitoring of the multiple single drive systems in order to preserve a safe operation. In the context of the national German research project SysTAvio, strategies for a new concept of a multifunctional high lift system are investigated and presented in this paper. The conceptual system comprises four single flap surfaces, each driven by a local transmission system and powered by a local power control unit. This architecture requires an innovative control strategy for a safe operation of a single drive system as well as synchronous movement of multiple systems.

For the shift to more-electric aircraft systems, the system specific design paradigm has to be dissolved and the allocation of functions has to be reconsidered. Including more degrees of freedom within the architecture design process for aircraft systems could lead to beneficial architecture concepts. However, new methods for conceptual systems design are required, to cope with the significantly increasing number of potential architecture variations to be evaluated. Within this paper, the GENESYS methodology enabling the design and evaluation of numerous architecture variations will proposed. The methodology consists of several modules, each dedicated to a specific process step of conceptual aircraft system design. Initially, a method for the design-independent analysis of the aircraft level functions and the identification of requirements for the aircraft systems will be illustrated.

Fuel cell technology will play a decisive role in the process of achieving the ambitious ecological goals of the aviation industry. However, apart from its obvious environmental advantages, the integration of fuel cell technology into commercial aircraft represents a challenging task in terms of operational and economical aspects. Since fuel cell systems are currently exposed to an intense competition with well-established power sources onboard an aircraft, engineers are in pursuit of highly efficient and particularly lightweight fuel cell systems. Supported by model-based design in conjunction with elaborate optimization techniques this pursuit has led to highly specialized systems. These systems tend to use their components to full capacity, which typically implies marginal system robustness. In consequence, preliminary design studies propose fuel cell systems that are sensitive to partial faults, or even to the slightest deviation, or degradation of their components' behavior.

The All-Electric-Engine with only electrical power offtake is a main goal in aircraft system development. The use of electric-motor pumps instead of engine-driven pumps for powering the central hydraulic systems could be a part of this objective. Additionally, the concept would meet the incremental development strategy performed by the aerospace industry today and saves costs by using state-of-the-art hydraulic actuation technology. This paper describes a process for optimizing such systems regarding their architecture and design parameters. For this task a methodology for the hydraulic consumer allocation called OPAL is used and extended by an automatic power system sizing. Feasible allocations, called permutations, are determined on the basis of preliminary system safety assessments regarding multiple top failure events. In the next step an automated sizing of the permutations is performed based on simplified hydraulic load analyses.

Ice adhesion characterization relies heavily on experimental data, especially when dealing with fracture parameters. In this paper, a complementary framework encompassing experimental testing with the numerical treatment of the fracture variables is proposed to provide a physical description of adhesive fracture propagation at the interface of an iced structure. The tests are based on a quasi-static flexural testing setup composed of a displacement-driven actuator and an iced plate. The measured crack length and plate deflection provide the data to be analyzed by the Virtual Crack Closure Technique in order to approximate the critical energy release rate required to study adhesive fracture propagation. The critical energy release rate in mode II is under-predicted and its value is approximated using its counterpart in mode I.

The aviation industry is facing major challenges due to increased environmental requirements that are driven by economic constraints. For this reason, guidelines like "Flightpath 2050", the official guide of European aviation, call for significant reductions in pollutant emissions. The concept of the More Electric Aircraft offers promising perspectives to meet these demands. A key-enabler for this concept is the integration of new technologies on board of the next generation of civil transportation aircraft. Examples are electro-mechanical actuators for primary and secondary flight controls or the fuel cell technology as innovative electrical energy supply system. Due to the high complexity and interdisciplinarity, the development of such systems is an equally challenging and time-consuming process.