CORDIS

ADFCS is a follow-up project which set out to develop an architecture and design methodology that would reduce the cost of ownership (development, acquisition, operation, and maintenance) of fly-by-wire (FBW) technology and make it affordable to small commercial aircraft applications. The goal of the second phase was to provide; a mix of new tools; new methodologies; clear design requirements; and new system architectures to provide a cost-effective platform for the designs. Digital FBW technology has become state-of-the-art for all modern large commercial aircraft. The additional initial cost of acquisition has been proven to be cost effective in terms of airframe design and manufacture costs, through life maintenance costs, and increased reliability resulting in an overall reduction in the through life cost of ownership. As the aircraft size is reduced, the digital flight control system (DFCS) technology component remains substantially unchanged whilst the airframe related component costs reduce with aircraft scale. The DFCS therefore becomes an increasing proportion of the total cost until there is no longer a supportable reduction in the through life cost of ownership. At this stage DFCS becomes a cost penalty despite its proven operational and safety benefits. The objective of this project was to investigate and review current techniques and technologies, architectures, and processes with a view to identifying cost effective solutions that would make DFCS technology more affordable, and within the budget of smaller commercial aircraft. - The flight control law (FCLAW) design process was identified as of low efficiency with no clear design requirements or goals, and little inherent knowledge transfer between projects due to the long temporal separation between major aircraft programmes. This area was addressed through the creation of a general purpose simulation tool and the generation of a set of design targets that were demonstrated as providing good handling qualities for small aircraft applications. - Fault tolerance, to satisfy the airworthiness safety and integrity requirements for commercial aircraft, is currently provided by independence, replication, and cross-comparison and selection processes. Whilst this is simple and easy to validate it is not necessarily the most cost efficient use of resources and new technologies may prove to provide greater fault coverage at a lower overall cost. Hence, the inclusion of a sensor management plane to provide synergistic fault tolerance was investigated. - Integrated modular electronics/avionics (IME/IMA) is an emerging technology aimed at standardising and separating the application hardware and host support environment from the application function. The potential benefit includes hardware cost reduction through volume production and reuse of standard hardware modules containing certificated operating system features to support drop-in applications. This project developed a high-integrity processing module complete with integral fault identification and board support utilities as a demonstrator. This module was used to support the actuator development and demonstration phases. - Continued safe operation following the loss of aircraft services, hydraulic and electrical, place significant demands on DFCS actuation architectures that must remain effective following the loss of all engine generated power. Large aircraft generally rely on the inclusion of a ram air turbine to provide engine-independent power, however the cost of these systems can be prohibitive for small aircraft. Alternative hybrid actuation architectures based on primary hydraulic and back-up electrical actuators were studied. This included the design of low-voltage electric actuators that could operate from reserve battery power or from other fuel-cell technology. - An actuator test-bench, with a set of hydraulic and electric actuators and associated actuator control electronics, were developed to demonstrate the operation and power requirements of the candidate architectures. The project achieved most of its objectives, as summarised in the final technical report, and supported by detailed technical reports on individual topics. - Design tools and processes were identified to help and increase the efficiency of the FCLAW design process. A flight simulator assessment activity identified an initial set of performance goals pertinent to this class of aircraft. Avionics knowledge and engineering experience allowed the pilot ranking and assessments to be extrapolated into full coverage, although more simulator assessment work is required to verify the extrapolated extreme boundaries. The MathWorks MATLAB/Simulink based design tools and simulation package brought a significant improvement to the design process allowing a free interchange of material developed in separate partner organisations. - The goal of an integrated sensor management plane in the DFCS was less successful although a number of improved fault detection and identification (FDI) techniques were identified. This topic was primarily the domain of the universities and the problem appeared to relate to an inherent background of research competition and rivalry between educational establishments rather than the role of collaboration necessary to select between and integrate the resulting component technologies. - The IMA technologies were successfully built and proven. The concept of multiple processors with inherent cross-monitoring and FDI inherent at the board level was demonstrated in a dual environment. Expansion to a triplex-dissimilar production standard computing element was considered to be a low-risk development. Similarly the concept of 'drop-in' applications was proven during the actuator test bench assessment where application changes were created, installed, and quickly validated. - The backup electric actuator was designed and proven. A significant problem with the electric actuator in the prototype set-up was the level of noise at the electromechanical actuator (EMA) drive switching frequency (20 kHz). This emphasised the need to provide good earth isolation and signal screening between the control electronics and the power drive electronics. - The assessment validated the feasibility of using battery powered electric actuators as a back-up means of control since the power requirements were shown to be within the capabilities of conventional aircraft 28 V battery packs.