Aircraft electromagnetic compatibility

Illustrated are aircraft architecture, electromagnetic interference environments, electromagnetic compatibility protection techniques, program specifications, tasks, and verification and validation procedures. The environment of 400 Hz power, electrical transients, and radio frequency fields are portrayed and related to thresholds of avionics electronics. Five layers of protection for avionics are defined. Recognition is given to some present day electromagnetic compatibility weaknesses and issues which serve to reemphasize the importance of EMC verification of equipment and parts, and their ultimate EMC validation on the aircraft. Proven standards of grounding, bonding, shielding, wiring, and packaging are laid out to help provide a foundation for a comprehensive approach to successful future aircraft design and an understanding of cost effective EMC in an aircraft setting

Component-led integrative optimisation methodology for avionic thermal management

The modern military aircraft can be defined as a System of Systems (SoS); several distinct systems operating simultaneously across boundary interfaces. As the on-board subsystems have become more complex and diverse, the development process has become more isolated. When considering thermal management of distributed heat loads, the aircraft has become a collection of individually optimised components and subsystems, rather than the implementation of a single system to perform a given task. Avionic thermal management is quickly becoming a limiting factor of aircraft performance, reliability and effectiveness. The challenge of avionic thermal management is growing with the increasing complexity and power density of avionic packages. The aircraft relies on a heat rejection growth capacity to accommodate the additional through-life avionic heat loads. Growth capacity is defined as an allowable thermal loading growth designed into the system by the underutilisation of spatial and cooling supply at aircraft introduction; however, this is a limited resource and aircraft subsystem cooling capability is reaching a critical point. The depleted growth capacity coupled with increased avionic power demands has led to component thermal failure. However, due to the poor resolution of existing data acquisition, experimental facilities or thermodynamic modeling, the exact inflight-operating conditions remain relatively unknown. The knowledge gap identified in this work is the lack of definitive methodology to generate high fidelity data of in-flight thermal conditions of fast-jet subsystems and provide evidence towards effective future thermal management technologies. It is shown that, through the development of a new methodology, the knowledge gap can be reduced and as an output of this approach the unknown system behaviour can be defined. A multidisciplinary approach to the replication, analysis and optimisation of a fast-jet TMS is detailed. The development of a new Ground Test Facility (GTF) allows previously unidentified system thermal behaviour to be evaluated at component, subsystem and system level. The development of new data to characterise current thermal performance of a fast jet TMS allows recommendations of several new technologies to be implemented through a component led integrative system optimisation. This approach is to consider the TMS as a single system to achieve a single goal of component thermal management. Three technologies are implemented to optimise avionic conditions through the minimisation of bleed air consumption, improve avionic reliability through increased avionic component isothermalisation and increase growth capacity through improved avionic heat exchanger fin utilisation. These component level technologies improved system level performance. A reduction in TMS bleed air consumption from 1225kg to 510kg was found to complete a typical flight profile. A peak predicted aircraft specific fuel consumption saving of 1.23% is seen at a cruise flight condition because of this approach to avionic thermal management

Avionics and controls research and technology

The workshop provided a forum for industry and universities to discuss the state-of-the-art, identify the technology needs and opportunities, and describe the role of NASA in avionics and controls research

Design and integrity of deterministic system architectures.

Architectures represented by system construction 'building block' components and interrelationships provide the structural form. This thesis addresses processes, procedures and methods that support system design synthesis and specifically the determination of the integrity of candidate architectural structures. Particular emphasis is given to the structural representation of system architectures, their consistency and functional quantification. It is a design imperative that a hierarchically decomposed structure maintains compatibility and consistency between the functional and realisation solutions. Complex systems are normally simplified by the use of hierarchical decomposition so that lower level components are precisely defined and simpler than higher-level components. To enable such systems to be reconstructed from their components, the hierarchical construction must provide vertical intra-relationship consistency, horizontal interrelationship consistency, and inter-component functional consistency. Firstly, a modified process design model is proposed that incorporates the generic structural representation of system architectures. Secondly, a system architecture design knowledge domain is proposed that enables viewpoint evaluations to be aggregated into a coherent set of domains that are both necessary and sufficient to determine the integrity of system architectures. Thirdly, four methods of structural analysis are proposed to assure the integrity of the architecture. The first enables the structural compatibility between the 'building blocks' that provide the emergent functional properties and implementation solution properties to be determined. The second enables the compatibility of the functional causality structure and the implementation causality structure to be determined. The third method provides a graphical representation of architectural structures. The fourth method uses the graphical form of structural representation to provide a technique that enables quantitative estimation of performance estimates of emergent properties for large scale or complex architectural structures. These methods have been combined into a procedure of formal design. This is a design process that, if rigorously executed, meets the requirements for reconstructability

Assessment of vapour chamber heat spreader implementation for avionic module thermal management

Thermal management of aircraft heat loads is quickly becoming a limiting factor of vehicle performance and reliability. This paper details improvements in forced-convection cooled avionic module heat removal efficiency with the implementation of two-phase high thermal conductivity Vapour Chamber Heat Spreaders (VCHS). A bespoke test rig provides experimental thermal comparisons of an aluminium and embedded VCHS avionic heat exchanger. The experimental results validate a numerical thermal resistance network, which is utilised to simulate more representative avionic chassis geometries. The VCHS dramatically reduces thermal variation in circuit card and avionic heat exchanger exhaust temperatures. Increased isothermalisation of the heat exchanger greatly increases effective heat transfer area in comparison to a traditional aluminium chassis. The VCHS acts as a very effective thermal buffer between the avionic circuit cards and coolant airflow, allowing a more predictable avionic thermal behaviour irrespective of circuit card architecture. The improved heat rejection capability allows either a substantial increase in avionic growth capacity (increased power output for a fixed exhaust temperature) or a substantial reduction in mass flow rate (reduced demand on vehicle thermal management system). An avionic growth capacity of up to 58% is achieved with representative thermal loading conditions

Assessment team report on flight-critical systems research at NASA Langley Research Center

The quality, coverage, and distribution of effort of the flight-critical systems research program at NASA Langley Research Center was assessed. Within the scope of the Assessment Team's review, the research program was found to be very sound. All tasks under the current research program were at least partially addressing the industry needs. General recommendations made were to expand the program resources to provide additional coverage of high priority industry needs, including operations and maintenance, and to focus the program on an actual hardware and software system that is under development

Innovative Model Based Systems Engineering approach for the design of hypersonic transportation systems

L'abstract è presente nell'allegato / the abstract is in the attachmen

Aeronautical engineering: A continuing bibliography with indexes, supplement 100

This bibliography lists 295 reports, articles, and other documents introduced into the NASA Scientific and Technical Information System in August 1978

Mixed-Criticality Systems on Commercial-Off-the-Shelf Multi-Processor Systems-on-Chip

Avionics and space industries are struggling with the adoption of technologies like multi-processor system-on-chips (MPSoCs) due to strict safety requirements. This thesis propose a new reference architecture for MPSoC-based mixed-criticality systems (MCS) - i.e., systems integrating applications with different level of criticality - which are a common use case for aforementioned industries. This thesis proposes a system architecture capable of granting partitioning - which is, for short, the property of fault containment. It is based on the detection of spatial and temporal interference, and has been named the online detection of interference (ODIn) architecture. Spatial partitioning requires that an application is not able to corrupt resources used by a different application. In the architecture proposed in this thesis, spatial partitioning is implemented using type-1 hypervisors, which allow definition of resource partitions. An application running in a partition can only access resources granted to that partition, therefore it cannot corrupt resources used by applications running in other partitions. Temporal partitioning requires that an application is not able to unexpectedly change the execution time of other applications. In the proposed architecture, temporal partitioning has been solved using a bounded interference approach, composed of an offline analysis phase and an online safety net. The offline phase is based on a statistical profiling of a metric sensitive to temporal interference’s, performed in nominal conditions, which allows definition of a set of three thresholds: 1. the detection threshold TD; 2. the warning threshold TW ; 3. the α threshold. Two rules of detection are defined using such thresholds: Alarm rule When the value of the metric is above TD. Warning rule When the value of the metric is in the warning region [TW ;TD] for more than α consecutive times. ODIn’s online safety-net exploits performance counters, available in many MPSoC architectures; such counters are configured at bootstrap to monitor the selected metric(s), and to raise an interrupt request (IRQ) in case the metric value goes above TD, implementing the alarm rule. The warning rule is implemented in a software detection module, which reads the value of performance counters when the monitored task yields control to the scheduler and reset them if there is no detection. ODIn also uses two additional detection mechanisms: 1. a control flow check technique, based on compile-time defined block signatures, is implemented through a set of watchdog processors, each monitoring one partition. 2. a timeout is implemented through a system watchdog timer (SWDT), which is able to send an external signal when the timeout is violated. The recovery actions implemented in ODIn are: • graceful degradation, to react to IRQs of WDPs monitoring non-critical applications or to warning rule violations; it temporarily stops non-critical applications to grant resources to the critical application; • hard recovery, to react to the SWDT, to the WDP of the critical application, or to alarm rule violations; it causes a switch to a hot stand-by spare computer. Experimental validation of ODIn was performed on two hardware platforms: the ZedBoard - dual-core - and the Inventami board - quad-core. A space benchmark and an avionic benchmark were implemented on both platforms, composed by different modules as showed in Table 1 Each version of the final application was evaluated through fault injection (FI) campaigns, performed using a specifically designed FI system. There were three types of FI campaigns: 1. HW FI, to emulate single event effects; 2. SW FI, to emulate bugs in non-critical applications; 3. artificial bug FI, to emulate a bug in non-critical applications introducing unexpected interference on the critical application. Experimental results show that ODIn is resilient to all considered types of faul