Avionics 2000

Citation

(2001), "Avionics 2000", Aircraft Engineering and Aerospace Technology, Vol. 73 No. 2. https://doi.org/10.1108/aeat.2001.12773bac.001

Avionics 2000

Avionics 2000

The 14th Annual ERA Technology Conference in association with the Royal Aeronautical Society was held at Heathrow and focused on the theme of real-world avionics – meeting the customer's needs. It was divided into eight sessions over two days, the first session being concerned with The Operational Environment – Air Traffic.

After the keynote address, the initial paper came from Eurocontrol and dealt with issues and needs. Some details of Eurocontrol's background and core business were given. It was shown that the delays in 1999 had been somewhat worse than in the preceding year, 40 per cent of all flight delays being due to air traffic flow management (ATFM). It is noted that traffic growth in 1999 at 6 per cent is above the forecast 4.7 per cent and is set to be double that of 1997 by 2015.

Eurocontrol's ATM 2000 strategy therefore includes the priorities to improve capacity, accelerate integration, and realise the full concept. These will be implemented in three steps; up to 2005, from 2005 to 2010, and 2010 to 2015 and beyond. The programmes managed by Eurocontrol within the framework of EATMP have been established to fulfil the ATM 2000 objectives. They are as follows.

Route network development based on BRNAV capability of aircraft is illustrated by the fact that basic area navigation (BRNAV) was implemented on 23 April with an exemption period out to 31 July 1998, with a number of lessons having been learned from the implementation, such as the development of RNAV standards.

Another activity involved 8.33kHz channel spacing. A programme was set up to reduce channel spacing in the VHF frequencies in order to accommodate demand. The implementation occurred on 7 October 1989 after significant delay.

ACAS II in Europe will be required after 31 March 2001 (TCAS II Version 7). RVSM is also an important EATMP programme already having a considerable impact. It is being implemented in stages and will go live on 24 January 2002. A monitoring capability is being put in place based on ground and aircraft equipment.

The Free Route Airspace Concept aims to achieve implementation of a limited "free route" airspace in Germany, Benelux and Scandinavia by early 2003. Air Ground Co-operative Air Traffic Services being introduced employing improved equipment will also play a large part in in the introduction of delegated separarations between aircraft, as well as other communications activities.

Although many aircraft have been equipped with GNSS (global navigation satellite system), there will be a gradual integration of developing technologies. Through these programmes the agency has a much better idea of the impact that its work has on airlines and the costs involved.

From the UK CAA came a paper on "Certification for CNS/ATM: the role of JAA". Certification means the legal recognition by a certification authority of a product, service, organisation or person shown to comply with applicable requirements. CNS/ATM (communications navigation surveillance/ air traffic management) applications have their own certification difficulties due to the air/ground infrastructure being closely coupled with complex and highly integrated systems. The EATMP (European Air Traffic Management Programme) identifies 22 projects for enhancement of operations in European airspace. In addition to those closely connected with Eurocontrol, these include SSR Mode S, Automatic Dependent Surveillance (ADS), and Terrain Awareness Warning System (TAWS). To meet the needs of operators, various programmes are in place to provide a more efficient and safe European airspace operating environment.

The concluding paper in this section was presented by Boeing and concerned RNP RNAV, a tool for improvement in airspace design, flight operations, and operational efficiency. In 1993 the US Air Transport Association made a request to industry to develop systems criteria that would enable benefits to be derived from existing RNAV systems as well as establish a standard for future applications based upon the concept of RNP (required navigation performance). The RNP was made non-specific for equipment. The RNAV systems may provide information such as path deviation and speed commands, data interfaces for guidance cues such as flight director commands, and graphical map displays to enable the flight crew or system to follow and track the RNAV flight path. Further automation such as coupling of the RNAV system with an autoflight and autothrottle system to facilitate flight path tracking and performance is also very common.

The RNP RNAV solution recognised that certain weaknesses had to be mitigated, which resulted in a more deterministic and higher integrity means for RNAV based flexibility in airspace operations and procedure design that had not existed previously. These requirements are viewed as an extension of the existing navigation criteria applied for RNAV in an RNP environment that is designated RNP-(x) RNAV. The difference between RNP and RNAV is illustrated in an example in Figure 1. Path definition error, path steering error, and position estimation error, must all be accounted for, and the ranges in possible performance are quite different from and improve over the current established defaults used for procedure and airspace design.

Figure 1 Comparison of RNP and RNAV

RNP operations developments are very rapid and numerous, including general approach, approach affected by terrain and weather; lower minima, converging approach (example); improved departure; and stabilized descent. The conclusion is that RNP RNAV is an underutilized tool whose performance and capability will provide for significant improvements in operations and cost benefits.

Upgrades I

In this session, the first paper was given by Smiths Industries and concerned avionics upgrades for military fast jets. It describes some of the initiatives being progressed by Smiths Industries to enhance operational effectiveness through an open systems architecture mission computer upgrade programme.

There is a major opportunity for retrofit using the latest advantages in Commercial Off The Shelf (COTS) memory and processing technology to provide enhanced performance at lower cost. Summarising the functionality required are the following details.

HUD symbology generation, Bus control, Sensor processing, Data entry, Head down display (smart v. dumb), Video switching, Mode control (system/display), Multi-sensor slant ranging, and Reversionary features. For Navigation, Waypoint storage/flight plan, Threat zones, and Digital map generation facilities are required. Various weapon aiming aids also have to be included.

To meet the requirements for both simple and complex retrofit solutions a low cost, flexible mission computer is required. This OSAMC (Open Systems Architecture Mission Computer) allows other suppliers' COTS modules to be integrated. This approach does give significant benefits, although some care has to be taken to ensure all the issues are addressed.

A particular military upgrade, the Hawk Lift for the SAAF, was described, illustrating the BAE Systems' Hawk requirements for a different avionics suite than say, 20 to 30 years ago. The avionics suite selected by the SAAF (South African Air Force) makes best use of current technologies as well as innovative design approaches.

The front cockpit features three colour LCD MFDs as well as a wide-angle head-up display. The HUD will form the flight instrument mostly used by the pilot and will be capable of overlaying a FLIR image on the normal HUD symbology. The rear cockpit is a duplication of the front cockpit with the exception that the centre MFD serves as a HUD repeater. The core avionics consists of two identical mission computers.

A navigation function, ground attack function, and air defence function are integrated, together with a communication and identification system, the latter consisting primarily of three identical V/UHF transceivers as well as an IFF transponder. The electronic warfare requirement is optimised to meet the training requirement, and a Health and Usage Monitoring System (HUMS) is also included.

From Boeing came a contribution on "Upgrading legacy avionics software using 'wrapper' technology". The company together with the Air Force Laboratory, have conducted a programme focused on affordable modernization for military avionics software using this approach. The foundation of this incremental upgrade approach is the use of software wrappers to encapsulate the legacy software components.

Wrappers are generally applied at the application domain level. One example is a general wrapper structure for an OFP on a single processor. The legacy application interfaces with other applications and other layers only through the wrapper. The three wrapper approaches are rehost; hybrid; and emulate, and demonstrations of two of these on F-15 and C-17 aircraft were undertaken as part of the programme.

The operational environment – system

An open system approach to free flight was given by Rockwell Collins which set out to show that the emerging FANS system will automate most of the routine voice communication of the current system with data links that will provide communication between the aircraft and the air traffic control controllers/computers. In the cockpit, aircrews will be required to assume an increased level of responsibility for safely maintaining separation assurance from ground and airborne hazards and obstacles. The Eurocontrol vision set out in the EATMS Operational Concept is described, the three distinct types of airspace being unmanaged, managed, and free flight airspace. Implementation of the future concepts will require that users equip their aircraft with a number of new or additional enabling technologies to retain unrestricted access to all airspace types.

Three sets of requirements, communications, navigation, and safety/surveillance, will have to be satisfied. In communications, channel spacing and digital voice capability is crucial, as well as CPDLC, first introduced on the South Pacific air routes. One method of achieving the needed gains in efficiency is by RVSM, with reduction of the minimum horizontal separation to come in the future. The Required Navigation Performance (RNP) concept is important in this regard. The emerging functional requirements for improved safety and surveillance capabilities are reflected in advisory systems such as TCAS II/ACAS II and TAWS. ADS-B is also an important capability. A number of data link technologies are being assessed within the European Community.

A simplified reference model for a CNS/TMA avionics architecture is illustrated in Figure 2. This can be realised with any number of federated, integrated, or hybrid systems architecture. New applications developed in support of the free flight concept will require higher levels of integration at both the avionics sub-system and airspace infrastructure levels.

Figure 2 A simplified reference model for a CNS/TMA avionics architecture

"Air traffic management solutions" came from BAE Systems and looked at some of the issues to be tackled from an airborne perspective, and how they can be addressed and what the benefits can be expected to be. Areas particularly identified for change include taxi management; improving safety on the ground; improvements to take-off and approach phases to maximise throughput without compromising safety; providing en route flight re-planning to enable efficient route changes with all parties in agreement: and improved cockpit display of traffic information and airborne separation assurance for increased safety.

The proposed solutions include a cockpit display of traffic information (CDTI) for increased situational awareness; graphical information, perhaps on the navigation display as well as other means, to assist airborne separation assurance; additional equipment that enables the pilot to tell exactly how far he is behind another aircraft; several areas in taxi management including runway capacity, taxi route guidance, and the use of data link clearances. En route flight planning also needs to be addressed.

New projects

The first paper in this section concerned the challenges for procurement of future weapon systems, also from BAE Systems, and emphasised that affordability is fundamental to the successful continuation of the Future Offensive Air System (FOAS) programme. The Smart Procurement Initiative (SPI) addresses this and is concerned with the maturation of critical technology, exploration of the trades between system capability and cost, as well as scope.

Some of the techniques developed to produce a cost effective solution include the convergence of many options for smart procurement. Critical to the success of the FOAS assessment phase are: knowledge based management; programme structure; environmental pressure; challenges for capability management, affordability, and technology development, as well as implications. In response to many of these issues there is a requirement to understand and control the information set from the start of a project. There is a requirement for an information model, the core of which consists of a relational database which is concerned primarily with defining and controlling items in exact terms.

A contribution from Bombardier described the automated avionics simplicity of the Global Express. The basic concepts of increased safety, increased passenger comfort, and reduced operating cost, have been applied to the Honeywell 2000 XP automated avionics suite of this aircraft. This avionics suite is built around the central display system. Aircraft data are transmitted to four dual-channel data acquisition units (DAU), through the avionics standard communication bus (ASCB), to three integrated avionics computers (IAC), to the six display units (DU). The ASCB is the principal communications network and each IAC performs several functions.

Aural and visual warnings include EICAS, EGPWS, Weather radar, TCAS, altitude alert portion of the air data computer (ADC), and stick shaker portion of the stall protection system (SPS).

The systems on the Global Express use software control to provide automatic operation while still providing full flight crew awareness of system operation and manual override capability. System controls are located in the overhead panel. Two bleed management controllers (BMC) control the bleed air system during all phases of operation. Hydraulic power is provided by three independent systems operating at a nominal pressure of 3,000 psi. The aircraft electrical system consists of four 40 KVA engine-driven variable frequency generators (two on each engine) and one constant frequency 40/45 KVA APU generator. The automatic flight control system (AFCS), flight management system (FMS), and autothrottle system architecture and system functions are typical for transport category aircraft. The head up display (HUD) is fully integrated with the AFCS.

Rockwell Collins detailed the 3D map concept, which originated from an idea to provide the pilot with a complete set of graphical information on an electronic map that described the FMS lateral flight plan, vertical flight plan, and performance predicted flight trajectory. A dual 3D map is representative of the actual aircraft installation, the first product application being based on an avionics upgrade to an existing fielded system.

A modified Arinc 702 map bus protocol is used for communication between the FMC and MFD. Data in the form of latitude, longitude and altitude, which represents the FMS lateral flight plan, vertical flight plan and aircraft performance predicted flight path (all described in three dimensions) are computed in the FMC. The content of the map bus data transmitted to the MFD is a function of the selected map range and map centre, which is similar to current FMS designs. Map range control is provided by the display control panel (DCP) via an Arinc 429 bus.

Although distributed controls were used on the first 3D map project application, in future, applications are anticipated to use an integrated set of controls. The 3D map actually has three different display formats. The plan view format is displayed for a vertical viewing angle of 0°, the side view format for a vertical viewing angle of 90°, and the 3D view format for vertical viewing angles between 0° and 90°. The first applications of the 3D map are for commercial flight operations, but interest in military applications is expected to increase.

Upgrades II

The UK Defence Procurement Agency gave a paper on MoD Helicopter Health and Usage Monitoring Systems (HUMS) and noted that work on these systems has been continuing since the late 1970s and early 1980s. The lessons learnt included the protracted time taken and reflect quite accurately the well-documented shortfalls with the military procurement process, and changes have been implemented.

The difficulties experienced during the Chinook programme are relevant to these lessons. One involved the aircraft Interface Control Document (ICD) and it is necessary to make the HUMS contractor and the relevant Aircraft Design Authority (ADA) jointly responsible for the ICD for future programmes. Incidents involving the nose optical blade tracker, three channel LVDT, and ground station technology were also notable and resulted in measures being taken to avoid future difficulties.

On introduction the HUMS will not modify any of the existing aircraft maintenance practices, as it has always been the policy to have a progressive introduction of functionality to ensure confidence in the systems and validation of the function with the MoD operational structure. The MoD has every faith and confidence in the capability and integrity of the HUMS it has procured, with the true testimony coming from its use in service.

From the Swedish Defence Material Administration came a paper on "Introducing liquid colour display in JA37 Viggen". It describes the mid-life upgrades performed on the aircraft through its service life. Software upgrades have been done since the aircraft was delivered, either in the symbology computer, central computer or the radar computer. A dynamic programe check is then undertaken in the system simulator at Saab, Linkoping, and after that, a flight security check takes place where pilots from FMV Test Directorate and personnel from Saab and FMV are represented.

A retrofit featuring, among others, a large colour display has been developed and will be introduced in the Swedish Air force during 2001 to some JA 37 aircraft. This colour display will replace a monochrome one. The size of the display surface is 6.2in x 8.3in and the brightness of AMLCDs has now reached the required minimum level of 700Cd/m² for white. All software for the embedded computer graphics generator and the map databases can be downloaded via the ML-STD-1553 interface. Numerous flight tests have been conducted and reports and criticisms incorporated in production.

"Civil modes on military aircraft" were described by GKN Westland Helicopters, in which the incorporation of Mode S for use within the IFF (identification friend or foe) was detailed. With two new platforms under contract for the UK MoD, the company performed a rigorous selection and contract process to integrate the recently developed APX-100 with Mode S IFF.

This is an example of where civilian and military requirements diverge but where the final solution will be a compromise and firmly controlled via the civil authorities. Decisions had to be made, including the expansion for TCAS when required. Obviously, the earlier a definite requirement is known, the easier and cheaper its implementation will be with the necessary interfaces incorporated.

The MoD has accepted the early Mode S implementation onto the EHIO1 Merlin MkIII and WAH-64 Apache as a precursor to SIFF (Successor IFF) and that the relevant civil aspects have been incorporated. Lessons learnt were IPTs (integrated product teams) must start from the conception of the programme or as soon as possible thereafter; the programmme must be managed openly and directly; all contributions should be valued; new technology should be tested fully, both on the bench and in a real environment; successes and failures and their causes should be reviewed; and, the team once established can provide a very strong foundation for future projects and therefore should be positively considered during future selection activities.

Technology

BAE Systems described a method for the assessment of technology transparency, which is a key architecture property required for future avionic systems and upgrades to current systems since they will have to make provision for system and technology growth.

The proposed assessment method is in a series of steps; define the scope of the assessment; decompose the items within the scope into convenient fundamental blocks; assess growth or obsolescence; propose new strategies; and test for balanced solution. The assessment of growth or obsolescence consists of various activities. In short, the assessment appears to involve a lot of extra work but it is possible to share the burden between the suppliers, the system integrator and the customer. Various other conclusions include the fact that the method has an impact on the procurement process and that technology transparent interfaces alone do not guarantee technology transparency.

Also from this company was a contribution on Application Obsolescence Tolerance, which considers the issues encountered in producing such a system. Experience gained during a programme to investigate the functional integration of flight and propulsion control systems for advanced STOVL aircraft was detailed. In the final analysis and implications for future systems, the portion of application interface changes that require more investigation are those that emerged as a result of application assumptions on the behaviour of the underlying hardware. Considering future systems, this activity indicates that the main areas of change will be restricted to the hardware dependent software layers with the possibility of some minimal application interface changes.

A paper on IMA technology insertion was given by Smiths Industries Aerospace which began with an overview of IMA concepts. It was noted that IMA architectures are not just about "core" technology locked up in "common racks" but extend to include flexible interface management (e.g. through remote interface units), data gateways (e.g. to "open" networks for maintenance) and incorporation of dedicated equipments via the defined "common" infrastructure. IMA seeks to leverage the infrastrusture to support modularity (interchange and replacement) and technology independence (through standards). Key drivers are life-cycle costs, mission performance, and operational performance. Since IMA equipment in the Boeing 777, work has continued to develop and promote IMA standards for use in civil systems. ASAAC (Allied Standard Avionic Architecture Council) is an established European project (UK, France, Germany) defining and validating a set of open architecture standards for advanced avionics architecture applicable to new aircraft and upgrade programmes. There is a range of options available for implementing systems. It is clear that IMA is being inserted into JSF, and civil systems programmes, such as in the Boeing 777 and planned for the A3XX, support further technology insertion. A typical launch point for such a programme is that for the F-16, in which the insertion of IMA (via the mission computer) was launched through the rationalisation of a number of equipments into a common system. IMA principles are now becoming well understood and the application of open systems to solve real problems today has led to an understanding of how they are applied.

From Stewart Hughes (a Smiths Industries Aerospace company) came "SHIMA – small aircraft/helicopter integrated modular avionics", which described how these manufacturers address minimum size, weight and power problems, as well as reconfiguration of systems.

The SHIMA programme is supported by the UK Department of Trade & Industry, and features a real-time executive that will allow the different software functions to co-exist. A key issue is also the hardware upon which the software will operate. The objective of the software is to satisfy the requirement to develop an ARINC 653 compliant executive that can run on a single processor and offer a partitioning model such that several applications can run under the executive with guaranteed spatial and temporal partitioning. Figure 3 shows the IMA software structure as defined within ARINC 651 and ARINC 653. The term "executive" has been introduced as this more accurately describes what is being implemented.

Figure 3 IMA software structure as defined by ARINC 651 and ARINC 653

It is being developed in two layers. The system will be implemented using a commercially available Ada95 compiler with a Ravenscar-compliant RTS and appropriate board support pack (BSP) for the PowerPC architecture.

A certification strategy has been developed and once the demonstrator has been produced it is intended that it shall be installed at the Avionics and Simulation Development Center (ASDC) at Bell Helicopter Textron at Fort Worth Texas. The programme intends to use off-the-shelf hardware for the demonstrator.

The operational environment – safety

Raytheon Systems UK spoke of the provision of downlink aircraft parameters for older aircraft. The restrictions on the use of existing data were described, one example concerns altitude, which may be derived from several sources. Should this information be used for ACAS, several checks are required.

In order to reduce these restrictions and maximise the flexibility to accept different signal formats, it is necessary to reduce the number of electrical interfaces to a minimum. A mechanism by which the use of Gillham encoded altitude is avoided is desirable since this could remove the need for altitude comparators. By using a solid state air data sensor and dedicated processor, a discrete air data module can be integrated into a small light package. This will allow the device to support ACAS and the RVSM environment. The task of acquiring ten aircraft parameters of very diverse formats on older aircraft for basic and enhanced surveillance is significantly simplified by the application of a dedicated air data module with overlaid data aquisition interfaces and data processing.

This results in an affordable and certifiable solution to the provision of downlink aircraft parameters required for future mode S air traffic control services.

The application of head up displays (HUD) to reduce controlled flight into terrain (CFIT) and approach and landing accidents through enhanced situational awareness was described by BAE Systems. The paper describes an enhanced visual guidance system (EVGS) which assists the safe operation of the aircraft by increasing the pilot's situational awareness during the critical phases of flight. Concerning the two major areas of risk mentioned, the most immediate benefit of a VGS is its direct visual connection with the outside world. The differences between head up and head down are considerable, the most immediate feature being scale. The field of regard of the head down in one example is about 5° x 5° – the Head Up is 30° x 25°. Perhaps more significant, and central to the head up display advantage is the conformity of the symbols.

The VGS is a particularly apt system for presenting terminal collision avoidance system warnings, providing the pilot with not only avoidance guidance but also potentially the provision of a "threat identifier box". In the case of unusual attitudes, the VGS system automatically switches to an "unusual attitudes recovery mode". BAE has been involved in enhanced vision systems for civil applications for some years, perhaps the most significant of these being trials of a holographic HUD on a Gulfstream GII. Autonomous landing guidance has also been demonstrated using a BAE Systems' Imaging HUD and Millimetre Wave Radar sensor. Synthetic vision images can also be of assistance to the pilot, requiring an accurate terrain database.

The passenger's needs

"IFE and coping with upgrades" was given by British Airways and looked at the typical IFE product offering of today, making no reference to any particular system. Today's IFE typically provides multiple video/audio channels delivered to individual seats, as well as provision for many other services. The initial installation of such a system can represent a huge undertaking. Many options will be on offer and a particular choice may differ, e.g. a screen of a particular size may not be suitable. The design and development programme may be long and the start of it might have first installation and initial functionality a full 12 months away, with completed functionality a considerable time after this. The integration activity takes place in parallel with the design activity, as also does much of the certification process.

Installation of a new IFE system together with new seating configurations etc. is a major activity. Importance to the passenger and complexity have increased, which has major implications for engineers and crew alike. Two measures of availability are made: despatch availability – at departure, this is a measure of maintenance performance; and system availability – this is the degradation of the system in the course of one sector and is the availability at arrival less despatch availability. Targets of the order of 99 per cent or better are typical.

Continual upgrades have to be planned, allowing for changing technology, and with programmes lasting four years, some obsolesce is inevitable. As far as upgrades are concerned, one must not forget that the upgrade is not confined to the aircraft and significant changes to the ground infrastructure could be required depending on the application. With future upgrades, changing technology must be understood.

Page Aerospace presented "In-seat power supplies" which noted that many airlines are finding that more of their customers want to operate passenger electronic devices (PEDs) and are fitting in-seat power supply systems (ISPSS) to help meet this demand. Basically the ISPSS requires a +15v DC supply at each seat, via a dedicated outlet. This requires a power unit to be fitted under each seat group. Fitting the unit to each seat requires an interconnection policy based on zones.

The ISPSS is made up of the following major components: a master control unit (MCU) that is connected at the head of the system; a number of in-seat power supplies (ISPSU) that are installed under each seat group; the outlet connectors, one for each passenger; and the interconnecting wiring that links the installation together. The ISPSUs are designed to operate as a system, and a fault on one will not affect others in that zone. Future growth potential is considerable, which must take account of the fact that the demand for communication is still growing.