Craig Lawson

Environmental Impact Assessment, on the Operation of Conventional and More Electric Large Commercial Aircraft

Global aviation is growing exponentially and there is a great emphasis on trajectory optimization to reduce the overall environmental impact caused by aircraft. Many optimization techniques exist and are being studied for this purpose. The CLEAN SKY Joint Technology Initiative for aeronautics and Air transport, a European research activity run under the Seventh Framework program, is a collaborative initiative involving industry, research organizations and academia to introduce novel technologies to improve the environmental impact of aviation. As part of the overall research activities, “green” aircraft trajectories are addressed in the Systems for Green Operations (SGO) Integrated Technology Demonstrator. This paper studies the impact of large commercial aircraft trajectories optimized for different objectives applied to the on board systems. It establishes integrated systems models for both conventional and more electric secondary power systems and studies the impact of fuel, noise, time and emissions optimized trajectories on each configuration. It shows the significant change in the fuel burn due to systems operation and builds up the case as to why a detailed aircraft systems model is required within the optimization loop. Typically, the objective in trajectory optimization is to improve the mission performance of an aircraft or reduce the environmental impact. Hence parameters such as time, fuel burn, emissions and noise are key optimization objectives. In most instances, trajectory optimization is achieved by using models that represent such parameters. For example aircraft dynamics models to describe the flight performance, engine models to calculate the fuel burn, emissions and noise impact, etc. Such techniques have proved to achieve the necessary level of accuracy in trajectory optimization. This research enhances previous techniques by adding in the effect of systems power in the optimization process. A comparison is also made between conventional power systems and more electric architectures. In the conventional architecture, the environmental control system and the ice protection system are powered by engine bleed air while actuators and electrics are powered by engine shaft power off-takes. In the more electric architecture, bleed off take is eliminated and the environmental control system and ice protection system are also powered electrically through engine shaft power off takes.

Electrical load-sizing methodology to aid conceptual and preliminary design of large commercial aircraft

The importance of the more electric aircraft has been highlighted in many publications, projects and industrial presentations. By definition, the more electric aircraft concept achieves the majority of the required system functionality by using electrically powered sub-systems and components. This manifests itself in much higher electrical power demands on-board aircraft, compared to conventional architectures. This presents many challenges in the design process. To alleviate the risk and choose the optimum architectures for the systems on the aircraft, it is essential to incorporate the characteristics and possible configurations of the electrical network in the conceptual and preliminary design stages. Hence the current practice of performing an electrical load analysis at the detailed design stage is not adequate. To address this gap, this paper presents a viable and robust methodology to define requirements, size components and systems and calculates the electric power requirements at the preliminary design stages. The methodology uses the conventional aircraft, systems and components as the baseline and uses mathematical techniques and logical sequences of component operation, developed through the research, to size electrical load profiles for conventional aircraft. It then adapts this result to the more electric aircraft concept by adding key components that would account for the difference between a conventional system and a more electric system. The methodology presented here makes the design process more robust and aids the choice of the optimum design for the aircraft.

Multidisciplinary Optimisation Framework for Minimum Rotorcraft Fuel and Air Pollutants at Mission Level

Helicopters play a unique role in modern aviation providing a varied range of benefits to society and satisfying the need for fast mobility. However, environmental concerns associated with the operation of rotorcraft have increased due to envisaged growth of helicopter operations. New rotorcraft designs, innovative aero engines and all-electrical systems, which may take decades to be in service, are being developed in order to diminish rotorcraft footprint on environment. However, since there is a large number of polluting rotorcraft that are in use and will only gradually be replaced, in the nearterm, improvements to minimise air quality degradation may also be possible from better use of existing rotorcraft by focusing on mission profile management. A multidisciplinary framework, intended to generate outputs for estimating rotorcraft block fuel burn and emissions, was developed. Outcomes generated with this tool were, subsequently, the basis to carry out a parametric study for assessment of light single-engine rotorcraft environmental impact, in terms of fuel burn and emissions. Single and multi-objective optimisation for minimum fuel consumption and air pollutant emissions was part of this research as well. Case studies were carried out varying flight parameters at every segment of a baseline mission profile. Single and multi-objective optimisation proved that favourable reductions in fuel burn of about 2% may be attainable at the expense of a slight increase in NOX emissions during the entire mission. If reductions of more than 3% in block fuel burn are to be achievable in the short term for a single helicopter, savings for air transport companies are expected to be significant if mission profile management is considered for a whole fleet of helicopters.

Compressor Blade Tip Timing Using Capacitance Tip Clearance Probes

Turbomachinery blade vibrations of sufficient amplitude cause High Cycle Fatigue, which reduces blade life. In order to observe this vibration a non-intrusive monitoring system is sought. The vibration can be detected by measuring blade tip timing since in the presence of vibration the blade timing will differ slightly from the passing time calculated from rotor speed. This paper provides new insights into the ability of a commercially available capacitance probe tip clearance measurement system for application as a non-intrusive turbomachinery blade tip timing measurement device. Initial experimental investigations are reported where a compressor blade with mounted strain gauges is used in a low-speed compressor. Capacitance probe results are correlated with simultaneously measured strain gauge results. Finite Element simulations are also used. The performance of the capacitance system in measuring blade vibration is analysed. Measurements were facilitated by the commissioning of a new instrument dedicated compressor test facility and this test facility is described.Copyright

Application of an automated aircraft architecture generation and analysis tool to unmanned aerial vehicle subsystem design

The work presents the application of a new computational framework, addressing future preliminary design needs for aircraft subsystems. The ability to investigate multiple candidate technologies forming subsystem architectures is enabled with the provision of automated architecture generation, analysis and optimisation. The core aspects involve a functional decomposition, coupled with a synergistic mission performance analysis on the aircraft, architecture and component level. This may be followed by a complete enumeration of architectures combined with a user-defined technology filtering and concept ranking procedure. In addition, a novel hybrid heuristic optimiser, based on ant colony optimisation and a genetic algorithm, is employed to produce optimal architectures in both component composition and design parameters. The framework is applied to the design of a regenerative energy system for a long endurance high altitude unmanned aerial vehicle, considering various emerging technologies. A comparison with the traditional design processes and certification requirements is made as well as technology trends summarised and substantiated.

Design manufacturing integration and flight testing of a health monitoring system for a prototype unmanned airborne vehicle

This article describes the design, development, build and flight testing of a health monitoring system for the landing gear and the electrical power system on board the Demon prototype unmanned airborne vehicle. Demon is a flying technology demonstrator which successfully flew in September 2010. The Demon can achieve pitch and roll control without the use of hinged control surfaces, by instead using fluidic devices based on the Coanda effect, attaining low-maintenance, high-manoeuvrability operations. A vehicle health monitoring system was added on board between the first and the second flight test campaigns. The integration of the health monitoring system into the vehicle is discussed as a whole. The key health monitoring sub-systems include data logging and real-time measurement of several parameters. This includes systems to measure Voltage and current from the main batteries, landing gear stress, suspension travel, wheel hub acceleration and shock absorber pressure. Wherever possible, the use of commercially available components was maximised to minimise development time and cost. Some example results of system health monitoring during flight trials are presented.

Tip fin inclination effect on structural design of a box-wing aircraft

Computational studies were performed at conceptual design level to investigate the structural implications of changing only the tip fin inclinations on a medium-range box wing aircraft. Tip fin inclination refers to the angle the tip fin makes to the vertical body axis of the aircraft. This study is mainly addressed to conceptual designers. For different tip fin inclinations, flight loads were generated using a vortex lattice tool. These flight loads were then input into finite element simulations allowing the preliminary structural elements to be sized. For the category of aircraft considered, no significant variations in wing structural design drivers as a function of tip fin inclination were observed.

Simulating actuator energy consumption for trajectory optimisation

This work aims to construct a high-speed simulation tool which is used to quantify the dynamic actuator power consumption of an aircraft in flight, for use within trajectory optimisation packages. The purpose is to evaluate the energy penalties of the flight control actuation system as an aircraft manoeuvre along any arbitrary trajectory. The advantage is that the approximations include major transient properties which previous steady state techniques could not capture. The output can be used to provide feedback to a trajectory optimisation process to help it compute the aircraft level optimality of any given flight path. The tool features a six degree of freedom dynamic model of an aircraft which is combined with low frequency functional electro-mechanical actuator models in order to estimate the major transient power demands. The actuator models interact with the aircraft using an aerodynamic load estimator which generates load forces on the actuators that vary as a function of flight condition and control surface demands. A total energy control system is applied for longitudinal control and a total heading control system is implemented to manage the lateral motion. The outer loop is closed using a simple waypoint following guidance system with turn anticipation and variable turn radius control. To test the model, a simple trajectory analysis is undertaken which quantifies a heading change executed with four different turn rates. The tool shows that the actuation system requires 12.8 times more electrical energy when performing a 90° turn with a radius of 400 m compared to 1000 m. A second test is performed to verify the model’s ability to track a longer trajectory under windy conditions.

Analytical investigation into the effects of nitrogen enriched air bubbles to improve aircraft fuel system water management

In the aircraft fuel system, water–ice contamination within fuel tanks has been one of the most serious challenges. This issue was highlighted in 2008 by an accident triggered by restricted fuel flow due to the ice formation within the system. The on-board inert gas generation system, which is already installed on some aircraft to prevent the outbreak of fire in the fuel tank, is a potentially feasible method to improve the water management. This paper focuses on the impact of bubbles from the on-board inert gas generation system system on water in the fuel tank. In order to explore the bubble effect, the relationship between orifice configuration and bubble parameter was investigated by means of mathematical models and existing experimental data. Moreover, by combining a MATLAB code and the introduced bubble model, the effect of bubble size and rising speed on the water contamination in the fuel tank was observed. For the water absorption process, a new model was introduced using a mass transfer coefficient. Finally, this article concludes that the amount of accumulated water is dependent on the bubble size and rising speed, and an optimal bubble size or speed is predictable once the coefficient has been obtained.

Development of an automated aircraft subsystem architecture generation and analysis tool

Purpose – The purpose of this paper is to present a new computational framework to address future preliminary design needs for aircraft subsystems. The ability to investigate multiple candidate technologies forming subsystem architectures is enabled with the provision of automated architecture generation, analysis and optimization. Main focus lies with a demonstration of the frameworks workings, as well as the optimizers performance with a typical form of application problem. Design/methodology/approach – The core aspects involve a functional decomposition, coupled with a synergistic mission performance analysis on the aircraft, architecture and component levels. This may be followed by a complete enumeration of architectures, combined with a user defined technology filtering and concept ranking procedure. In addition, a hybrid heuristic optimizer, based on ant systems optimization and a genetic algorithm, is employed to produce optimal architectures in both component composition and design parameters. Th...