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Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Civil and military convergence?
Civil and military convergence?
Keywords: Avionics, Conferences
The 1999 ERA Avionics Conference and Exhibition with this theme addressed a variety of issues which embraced upgrades, technology demonstrator aircraft, developments and maintainability in the eight sessions. The first of these entitled Projects began with lessons learned fron F-22 software development. Given by Raytheon Systems, the paper describes how the F-22 processing system software architecture evolved by reviewing the problems encountered and how some of the more significant ones were solved.
The Common Integrated Processor (CIP) provides the facilities needed by the various subsystems and consists of a collection of processing elements that can be of different types depending on the need. The design had many challenging requirements. It soon became obvious that the list of Operating System requirements would have to be condensed to reflect a balance between the OS development effort required and the minimally acceptable features needed. After considerable searching, the required OS was developed from earlier versions produced for real-time avionics application.
Software systems designed for modern air combat systems have undergone significant changes due to increased performance requirements, etc., and the needs on the CIP included integration, multi-level security, open architecture, performance, size, schedule and cost.
A paper from Canadian Marconi dealt with the KLM 747-200/300 cockpit upgrade programme. It outlines the challenges associated with the system design, integration, certification and entry into service of, particularly, these wide-bodied aircraft. The original cockpit configuration included electro-mechanical flight instruments, etc., and the upgrade comprised the triple MCDU installation with 5-ATI EFIS and engine instrument displays, as well as involving some relocation of equipment.
There had to be no re-certification of Category III autoland functions and all control and display functions had to be integrated into the MCDU as well as the addition of FANS-111 equivalent datalink and RNAV capabilities. The system architecture is illustrated in a simplified form (Figure 1 ). Various integrations had to be performed. One concerns the LTN-92 Inertial Navigation System which in this architecture, functions as an inertial reference system. In this particular layout also, vertical navigation, performance optimisation, and autopilot pitch channel and autothrottle interfaces remain resident in the Performance Management System (PMS). Also integrated are the Autopilot/Flight Director System, the EFIS using ARINC 429 interfaces, and ACARS, ACMS and SATCOM. It is notable that the Smiths Industries EFIS and engine display systems are prominent in this upgrade as well as the Canadian Marconi GPS/FMS with embedded GPS receivers. Extensive certification testing and crew training have been undertaken and, with the fleet now in service, a series of preplanned software enhancements will be incorporated, including functions such as ADS.
The Lynx helicopter cockpit modernisation was dealt with by Smiths Industries. The areas discussed include engine instrumentation, flight instrumentation, and the mission system displays. Active Matrix Liquid Crystal Display (AMLCD) technology was selected to provide the Lynx glass cockpit displays. For flight displays the presentation of graphics representing primary flight and navigation information is best carried on either a square or portrait aspect 4:3 rectangular glass. Two engine displays are required, one to show primary engine data and one to display ancillary data such as temperatures and pressures. The Lynx glass cockpit is also required to present video data from radar and FLIR sensors. The Cockpit Display System (CDS) interfaces primarily with the Mission and Aircraft Management subsystems via ARINC 429 and RS-422 digital datalinks and analogue video inputs.
Figure 1Top level system block diagram
A key feature of the CDS design is the ability to reconfigure the system, either in normal operation to reduce crew workload, or as a result of a failure in order to maintain mission effectiveness. The display formats for the Lynx CDS are derived from those developed and certificated for the EH101 EFIS. Some design constraints had to be observed to be compatible in a military rotary wing airborne environment. The Integrated Display Unit (IDU) design makes extensive use of Commercial Off The Shelf (COTS) elements and the Electronic Power Systems Instrument (EPSI) for the Super Lynx 300 is a derivative of the civil 5-ATI display unit developed for the KLM B 747-200/300 cockpit upgrade.
Architecture and geography
From various authors in the USA came a contribution on the implications of federated and integrated architecture. It is true that most modern avionic systems are and will continue to be hybrids of federated and integrated means and in the future we must move to an evolutionary acquisition management of new or modified aircraft and reduce total operating costs while maintaining a responsive industry base for the future.
The main conclusions are that Government should resist using "Requirements" to dictate a detailed technical architecture; also, that industry needs to implement a compatible business and technical architecture with suppliers to mitigate both risk and total operating cost. In addition, a balanced business and technical stategy is critical as we exploit the advantages of digital based architecture and strive to retain a competitive electronic supplier industrial base. Increasing dependence will be placed on integrated "on board" and "off board" systems. Among "Lessons Learned" may be quoted the "Pave Pillar" design concept which was thought to be cost-effective at the time. However, as technology progressed and because of funding constraints, the programme could not alter course. Flexibility must be retained together with alternative strategies.
An overview of the ReACH programme was provided by DERA and MES, UK. Future military rotary wing platforms will need to support a wider range of roles over a longer service life than their current counterparts. Inregrated Modular Avionics (IMA) is an approach to meeting these objectives. The ReACH programme is investigating the benefits of applying a common IMA system across maritime and battlefield platforms with special emphasis on Merlin maritime derivatives.
The ReACH (Realisable integrated modular Avionics Common across Helicopters) is a collaborative venture between DERA, GWHL and DERA and seeks to use the requirements formulated to specify a common IMA solution that supports the diverse platform functionalities. To date the programme has captured the avionics requirements for specific helicopter platforms, and further work will be conducted to finalise the system analysis activity and enable the definition of work document to be generated. It is proposed that the current phase of ReACH will provide the technical foundation for a structured technology demonstrator programme.
British Aerospace described NEVADA, a three-year project supported by the EU. Issues not addressed in depth in previous programmes are considered. The NEVADA project is built of a number of workpackages, grouped as five tasks. Progress has been good and the review is grouped in four sections. The organisational aspect has generally been good. As far as external factors are concerned, mid way through the definition phase, Avionics Full Doppler Switched Ethernet (AFDX) emerged as a strong contender for bus applications and the programme has been replanned to suit. Technically at the current stage, there have been few problems. In processing, by performing tasks responsible for avionics technical development concurrently with those developing processes, some useful read-across has been possible.
The Global Grid Architectural concept was outlined by the US Mitre Corporation, in which, to facilitate the migration of the current communications architecture with the current USAF to a more "Global Grid"-like capability, an architecture framework is being developed. The principles for this Grid can be summarised as follows: employ a common network infrastructure; transport any traffic type; seamlessly integrate various transport media; adapt to change; and provide assurance of service. In summary, the aircraft environment provides some difficult challenges for accommodating the Global Grid architectural principles and an amount of work remains to ensure that the airborne modes of the Grid are as capable as the ground segment.
A Common Geographic Data Architecture was described by DERA, which dealt with a requirement for avionics systems. The principal objectives are to improve effectiveness and efficiency by providing a single, consistent source of geographically related information for avionic applications in a simple, open format capable of supporting real-time applications. Three specific applications are mentioned; Generic Mission Planning system (GMP); Hybrid vector/Raster Map Display (VRMD); and Sensor Augmented Display with Image Enhancement (SADIE).This endorses the premiss of convergence between civil and military avionics, through a particular area of defence research.
From Boeing came a paper on real time information mining from the cockpit: an open architecture demonstration project. The company together with the Air Force Research laboratory have defined a demonstration project that will provide a strike aircraft operator with Internet-access to off-board information in support of an en route mission update. The foundation for the capability is derived from Boeing's open systems architecture work in both the fighter and airborne command and control (AWACS) domains.
The project will employ the F-15E1 Technology Demonstrator as well as certain functions being performed by the 737 Avionics Flying Laboratory. There are three phases defined: demonstration planning; design of critical software elements; and demonstration execution. The flight demonstration will be conducted in the summer of 2001.
Technology developed for the military in the civil sector and similar interchanges were outlined by Marconi Electronic Systems. This company is the largest supplier of Head Up Displays (HUDs) in the world and more recently has produced HUDs which are dual mode, in that they are capable of displaying superimposed HUD stroke symbology in the flyback period of a raster image. The raster source sensor for these HUDs has in the main been infra red-based, since the main purpose of the systems was to afford good night vision for low flying and targeting applications. Interest in the civil sector increased in the 1990s, althouth there are essential differences in the two situations.
The technology and function are similar, however. The format of the HUD display (Figure 2) follows as closely as possible that of the standard head down instrumentation, so as to provide maximum synergy between the two. Two forms of imaging sensors originally developed for military applications have been extensively investigated for civil applications to date; Infra-red and Millimetre Wave Radar, each having advantages and disadvantages. These and other developments are essential steps towards the realisation of true "Free Flight".
Figure 2HUD display on the runway - Ground Roll mode
British Aerospace commented on situational awareness and the crew awareness rating scale (CARS). A model is presented in the paper which describes SA as consisting of a person's mental construction of the present status and dynamics of a task situation based upon their understanding of available data. This involves five interacting functions: perception; comprehension; projection; intention; and metacognition, each consisting of identifiable processes and each providing specific knowledge content.
Experiments have been conducted and results have satisfactorily demonstrated the developed CARS tool's utility, reliability and sensitivity.
From Marconi Avionics came a contribution on helmets which showed that helmet mounted displays place additional constraints on the helmet whose primary function is to protect the pilot. The helmet visor is often used as the display surface rather than eyepieces in front of the pilot's eyes. Helmet Mounted Displays are essential elements within a head coupled system which embrace several avionics functions. The HMD can also provide the pilot with means of command and control in addition instrumentation, etc. Pilot-protection is most important. The helmet must protect the user throughout the ejection sequence at speeds of up to 600 knots (KEAS), providing blast protection and minimising aerodynamic lift effects, which could result in neck injury. The helmet visor is a critical item and has a number of requirements arising from the contradictory functions of protection and display (Figure 3).
Figure 3Visor projected optical system
A recent development is the Marconi Striker HMD family which exploits the two part concept for fast jet applications. The Striker comprises a Life Support Inner, driven by the needs of the aircrew; and a Mission Outer, driven by the needs of the platform or application. This concept has already been implemented in a design for the Eurofighter Typhoon. The demanding requirements fulfilled by the two-part design ensure both current and future interest in the concept.
The CAA gave a paper on assessing system design for vulnerability to user error. Good human factors aspects are a requirement in the design of avionic equipment. It seems, however, that there is little guidance to suggest how compliance should be demonstrated with such requirements, or how the engineering community should discriminate between designs that are or are not acceptable in this respect.
The UK CAA has been active in seeking ways to ensure that aircraft designs are not unacceptably vulnerable to human error, the "effects of error" having attracted the most interest. A particular method is being developed for the purpose of systematically identifying system features that are vulnerable to error, and using it to demonstrate compliance when the "countermeasures" have been implemented.
There are three general approaches to error in the approval or evaluation of system safety: ignore it; probability method; and structured qualitative assessment. The probability numbers may have some broad application but, for the purpose of a thorough system evaluation, they may be seen as a somewhat unreliable and impractical method that can only address part of the problem. The alternative approach is structured analysis. The Human Hazard Analysis (HHA) method has been formulated. Illustrated is the HHA in its simplest form (Table I). The most difficult aspect of such a method may be the determining of the boundaries of the task. Clearly, HHA is not the answer to all of the "human user" problems, though it is thought better to aim for a structured approach that might resolve at least some of the problems, and encourage "human factors" thinking.
Table IThe HHA in its simplest form
White box safety was analysed by Praxis Critical Systems. This is so called since it makes use of detailed design information to guide the processes. As an example of the increase in the complexity of systems in the last decade, Integrated Modular Avionics (IMA) presents safety certification authorities with new challenges. The approach here requires a more detailed classification of safety requirements than has typically been used.
This is believed to be more cost-effective to use a more detailed approach in which integrity levels are assigned to specific functions, and safety requirements are separated from general functional requirements. The approach utilises the refined risk assessment to derive safety requirements that can be used to direct the choice of the most appropriate design, development and verification techniques. It also provides structured safety arguments that can be shown to be complete, correct and comprehensible.
Developments in the flight recorder industry were detailed by DRS Flight Safety and Communication of Canada. Although FDRs and CVRs have been in use for many years, changes in needs have resulted in a number of initiatives to revise the standards. The 1998 ICAO meeting made a number of recommendations on recorder changes that would need to be implemented over the next decade. These, along with others in place, are setting an evironment that will require aircraft operators to be upgrading or replacing their flight recorder systems.
An issue regarding Cockpit Voice Recorders (CVR) that has been raised as a consequence of the Swissair Flight 111 accident is the need for video recording of the cockpit interior. Apart from the possibility of the visibility of the instruments being obscured, there is also concern that with EFIS displays there is no certainty of what information was presented through analysing flight recorder information. The display could have been malfunctioning in some way which is not apparent from the data fed to it. Standards of video recording are being drafted and may eventually be adopted.
Trends in flight recorders include flash memory chip capacity increases, rapid obsolescence, and new recorder configurations. There is also the use of master data distribution computers and the use of fibre optics communications. One recommendation by ICAO is the use of two combined "dual combi" recorders including FDR and CVR capability for use on new aircraft in the "medium term". More data but at the same time, simpler recorders, will be required, and potentially a matching change in avionics architecture will result in a system built of smaller, more distributed components.
Obsolescence and maintainability
DY 4 systems of Canada presented a paper on COTS as a possible solution to obsolescence management. The benefit of COTS adoption has been widely aired in recent years. COTS or equipment which can be procured from a price list and a catalogue to commercial terms and conditions has been the subject of pressure to incorporate it into new systems to meet all the criteria.
Lessons have been learned through research work that COTS components, when properly applied, can be as reliable as, or even more so than, their military specific predecessors. Strategies have been developed to successfully apply and deploy COTS or Open System solutions to mitigate the effects of obsolescence and to offer the maximum economic benefit through the full life of a programme.
A portable code for avionic systems was introduced from British Aerospace Military Aircraft and the University of York. IMA aims to provide a highly flexible, reliable and integrated solution for affordable civil and military avionic systems. One of the key enabling technologies is portable code, which provides a method by which software can be developed once, but subsequently executed on many different platforms without change. Two main existing portable code solutions have been proposed: ANDF and Java. Since safety-critical systems are required to be predictable and analysable, the proposed portable code solution maintains the desired characteristics from source code to portable code and then from portable code to a variety of target computing platforms.
From a variety of companies and organisations, component obsolescence management for aerospace electronic equipment was described. The solutions proposed take into account the fact that new processes are required to be implemented by the equipment supplier, in the regulatory framework, and by the customer and end user to enable the continued manufacture and support of avionics equipment. The requirements for these processes are best expressed through industry standards or guides, implemented through equipment supplier specific operating procedures. One guide is the forthcoming ARINC 662 document. New procedures will be required, which may run counter to established custom and practice but must be considered rationally if the industry is to be able to continue to innovate and reduce costs.
From British Aerospace Airbus came "Designing for Maintenance Free Operating Period (MFOP)", which can apply to both civil and military aircraft and has been included as part of a proposal for a new military transport aircraft. The essential features of MFOP include a period of time during which there is no need for scheduled or unscheduled maintenance. It is not necessarily a fault-free period; systems element faults may happen but, as a result of the inherent design system, the aircraft continues its operation uninterrupted. The pilot and/or ground crew can be content in the knowledge that the aircraft is likely to complete its current MFOP without any rectification work required, and in all cases with the emphasis on safety.
The enabling techniques and technologies required to achieve a full MFOP will be many and include optimised MMEL, improved BITE, Integrated Modular Avionics, and HUMS for mechanical equipment. In addition to the systems aspect, aircraft structural and propulsion aspects will also be key drivers for the overall success of MFOP, the former including safe life and fail safe items and propulsion mainly divided into structural life limited items and propulsion systems. The maintenance recovery period and the failure-free operating period also play important parts. MFOP could reduce some of the uncertainty present in maintenance planning and, hence, in cost of ownership. The final implementation of MFOP will require the co-ordinated expertise of all aspects of the industry, including both civil and military aerospace sectors, in order to reach its full potential.
Lucas Aerospace outlined a systems approach to in-service rejection management at TRW Aeronautical Systems. The developed process optimises the monitoring and analysis of in-service unit rejections and comprises a number of discrete elements, the first, and arguably the most important, being the collection and validation of in-service data, removal investigation follows and then fault investigation. This is followed by fix investigation, fault isolation investigation, and fix implementation.
A reliable real time monitoring system is required to operate the process in a practical and effective way. There are two distinct types of output that can be generated while using the process; operational information and trend information, the latter providing an indication of realibility performance over time. The goal for the future is to integrate both the in-service and manufacturing data into the design process.
RF Modular Avionics was the subject of the Thomson-CSF paper which presented a point of view regarding future generations of RF and microwave airborne hardware. The key aspects of RF Modular Avionics are inputs; common modules definition; signals/local oscillators distribution and switches; and architecture consolidation and costs/performance effectiveness evaluation. Some work has been undertaken in a national context and other tasks are subject to international co-operation. Additional benefits will also probably be identified for other airborne and surface platforms.
Smiths Industries Aerospace, USA, contributed Solid State Power Control in which two generations of such a system were presented. One is the F22 power distribution centre (PDC) controlling all 28VDC and 270VDC loads on the aircraft, and the second is the solid state power control that is now being applied for the C130J electical circuit breaker unit (ECBU).
In 1993 Smiths Industries proposed solid state PDCs controlling secondary 28VDC and 270VDC power for the USAF F-22, whose systems have been developed and installed with flight test proceeding. In succeeding years, SI developed the electrical load management centre (ELMC) for the More Electric Aircraft programme. In 1999 SI won the contract to develop an enhanced version of the existing ECBU on the C130J aircraft. Comparison of the first generation power control, developed for the F-22, with an electromechanical solution shows that solid state power control in many ways is superior to power control by electromechanical means. It is also true to say that SI's second generation solid state power control represents significant advancement on the current control of this type.
Silicon carbide-aluminium composite technology for high reliability applications was described by AEA Technology and details the application of SiC-Al composites in two mainstream avionics electronics applications. These are cores for printed circuit cards and heatsinks for weight critical power electronics thermal management. The first concerns a collaborative programme between AEA Technology as a supplier and developer of HIVOLT SiC-Al metal matrix composite materials and TRW Aeronautical Systems Lucas Aerospace and Viasystems for development of advanced printed circuit boards for application in high reliability avionics environments. Substantial weight saving and increased functionality compared with conventional cores have been demonstrated.
The heatsinks development had reliability and weight management as key drivers in another collabortive effort involving the DTI, TRW Aeronautical Systems Lucas Aerospace, MITEL Semiconductor, AEA Technology, Loughborough University and British Aerospace Airbus. The aim is to develop and build a 20KVA aircraft variable to constant frequency power converter (VFCF) unit. This unit, alongside the variable frequency power supplies, will replace the mechanical variable speed gearbox systems currently used. It has been shown that the qualities of HIVOLT products in two typical applications will deliver improved performance and reduced weight and wider uses are expected.
A contribution on Fibre Channel - the solution to real time avionic networks was given by the Royal Air Force. Fundamental to Integrated Modular Avionics (IMA) architectures is the requirement for a reliable, high speed data network. It is thought to be the commercial market that will provide the foundations for a future avionics gigabit network.
Fibre Channel is the name for an integrated set of standards developed by American National Standards Institute (ANSI) T11 committee. FC offers a number of beneficial features for avionics including performance and reliability. This technology is already making advances. As in a telephone, FC makes use of unique addresses to connect processors to other processors or to peripherals. In the words of one engineer, "what the transistor was to the vacuum tube, Fibre Channel is to 1553". The range of standards available and design options is very large and evolution will continue for many years.
A number of supplementary papers were also presented and these will appear in a future issue of Aircraft Engineering and Aerospace Technology.