This concept paper focuses on integrating the Hydraulic Infinite Linear Actuator - Multi Rod (HILA-MR) technology into Variable Camber Continuous Trailing Edge Flap (VCCTEF) systems for Blended Wing Body (BWB) aircraft. HILA-MR is a novel actuator design enabling precise control of multiple flap segments in a VCCTEF via shared pistons. The HILA-MR/VCCTEF system demonstrates significantly lower power requirements compared to traditional simple flap systems and promotes a more optimal use of force and speed potential of hydraulic actuation throughout the flight envelope, reducing power requirements and contributing to overall efficiency and lower fuel burn. The system offers potential for drag reduction, improved efficiency, and reduced weight and volume for actuation and secondary power components in BWB aircraft. The aim of this paper is to give a comprehensive presentation of the HILA-MR system in a VCCTEF application, evaluate different aspects, design issues and benchmark the technology against present solutions.   

Purpose While computational methods are prevalent in aircraft conceptual design, recent advances in mechatronics and manufacturing are lowering the cost of practical experiments. Focussing on a relatively simple property, the lift curve, this study aims to increase understanding of how basic aerodynamic characteristics of a complex stealth configuration can be estimated experimentally using low-cost equipment, rapid prototyping methods and remotely piloted aircraft. Design/methodology/approach Lift curve estimates are obtained from a wind tunnel test of a three-dimensional-printed, 3.8%-scale model of a generic fighter and from flight testing a 14%-scale demonstrator using both a simple and a more advanced identification technique based on neural networks. These results are compared to a computational fluid dynamics study, a panel method and a straightforward, theoretical approach based on radical geometry simplifications. Findings Besides a good agreement in the linear region, discrepancies at high angles of attack reveal the shortcomings of each method. The remotely piloted model manages to provide consistent results beyond the physical limitations of the wind tunnel although it seems limited by instrumentation capabilities and unmodelled thrust effects. Practical implications Physical models can, even though low-cost experiments, expand the capabilities of other aerodynamic tools and contribute to reducing uncertainty when other estimations diverge. Originality/value This study highlights the limitations of commonly used aerodynamic methods and shows how low-cost prototyping and testing can complement or validate other estimations in the early study of a complex configuration.

Testing of untethered subscale models, often referred to as subscale flight testing, has traditionally had a relatively minor, yet relevant use in aeronautical research and development. As recent advances in electronics, rapid prototyping and unmanned-vehicle technologies expand its capabilities and lower its cost, this experimental method is seeing growing interest across academia and the industry. However, subscale models cannot meet all similarity conditions required for simulating full-scale flight. This leads to a variety of approaches to scaling and to other alternative applications. Through a literature review and analysis of different scaling strategies, this study presents an overall picture of how subscale flight testing has been used in recent years and synthesises its main issues and practical limitations. Results show that, while the estimation of full-scale characteristics is still an interesting application within certain flight conditions, subscale models are progressively taking a broader role as low-cost technology-testing platforms with relaxed similarity constraints. Different approaches to tackle the identified practical challenges, implemented both by the authors and by other organisations, are discussed and evaluated through flight experiments.

Remotely piloted scaled models not only serve as convenient low-risk flying test-beds but also can provide useful data and increase confidence in an eventual full-scale design. Nevertheless, performing advanced flight tests in a safe and cost-effective manner is often a challenge for organizations with limited resources. A typical scenario is testing within visual line-of-sight at very low altitude, a type of operation that offers major cost advantages at the expense of a reduced available airspace. This paper describes some of the authors' work towards efficient performance evaluation and system identification of fixed-wing, remotely piloted aircraft under these challenging conditions. Results show that certain techniques, manoeuvre automation, and platform-optimised multisine input signals can improve the flight test efficiency and the modelling process. It is also probable that some of the benefits observed here could be extrapolated to flight testing beyond visual line-of-sight or even to full-scale flight testing.

This paper reports the current status of a joint Swedish-Brazilian research project aiming at exploring sub scale flight testing. A 13% scale fighter aircraft is used as a test bench for developing methods and procedures for data acquisition. This paper will present an aerodynamic database as a partial result of the collaborative project.

Thispaper presents various techniques and procedures that aim to simplify flighttesting of fixed-wing, remotely-piloted aircraft with the purposes ofperformance evaluation and system identification. These methods have beenspecifically developed for flight within visual line-of-sight, a type ofoperation that limits the available airspace severely but offers major costadvantages considering the current regulations for unmanned flight in mostWestern countries.

The presented work considers designing, building and flight testing a solar poweraircraft as a student project. The goal is to allow student to participate in an aircraft projectfrom design to flight test in order to acquire aircraft design knowledge from theoretical andpractical means. A first theoretical part consists of creating a sizing program for studyingdifferent concepts. Then the gathered knowledge will result in the realization of a flyingdemonstrator. This was realized during a student project over a 5 month period

This dissertation concerns how design automation as well as rapid prototyping and testing of subscale prototypes can support aircraft design. A framework for design automation has been developed and is applied specifically to Micro Air Vehicles (MAV). MAVs are an interesting area for design automation as they are an application where the entire design, from requirements to manufacturing, can indeed be automated. From a complexity point of view it can be considered to be similar to conceptual design of manned aircraft.

The created design optimization framework interfaces several software systems to generate MAVs to optimally fulfil specific mission requirements. The goal has been to find a method for MAV design and optimization from a holistic viewpoint, i.e. not a method for optimizing single subsystems, such as motor or propeller, but a method that embraces all disciplines of MAV design. Key drivers have been the use of off-the-shelf components wherever possible and to optimize the geometric shape not just from an aerodynamic perspective, but also to consider internal component placement and stability criteria. The optimization technique chosen is a multi-objective genetic algorithm. Finally, a novel method for direct digital manufacturing of MAVs is proposed.

The utility of the framework has been demonstrated with several case studies on MAV design. The propulsion system is identified as most influential on MAV performance and thus is where it is most important to have accurate models. For this reason the models used in the framework are experimentally validated. The influence of atmospheric winds and turbulence on MAV performance is also experimentally investigated

The subscale testing efforts are aimed at reducing cost and increasing the usability of flight testing with subscale vehicles. Data acquisition system design is described and low-cost testing methods are presented, such as car top testing or in-flight flow visualization. Two subscale flight projects are also presented.

Den här avhandlingen handlar om hur konstruktionsprocessen av flygplan kan stödjas dels genom förbättrade analysverktyg, s.k.  konstruktionsautomation, och dels genom metoder för att snabbt och billigt kunna tillverka och testa nedskalade prototyper.

Konstruktion av flygplan är ett komplext område som innefattar många tätt sammanlänkade underdiscipliner. Ett lyckat flygplan är således en väl avvägd kompromiss mellan alla dessa discipliner. Dagens hårda konkurrens, krav på miljö, samt tekniska komplexitet ökar kraven på att framtidens flygplan måste vara bättre optimerade än idag. Traditionell flygplanskonstruktion kan ses som en sekventiell process där man stegvis förfinar konstruktionen en disciplin i taget. Med modern datorkraft och beräkningsprogram kan denna process delvis automatiseras varpå man på ett tidigare stadium kan ta hänsyn till fler discipliner. Många av de steg som tidigare genomförts sekventiellt kan nu göras parallellt. Det ökar möjligheten att nå en optimal konstruktion, samt minskar riskerna för att man tidigt bygger in fel i konstruktionen som är kostsamma att rätta till i ett senare skede. I den här avhandlingen beskrivs hur sådan konstruktionsautomation kan genomföras med hjälp av multidisciplinär optimering och en sammankoppling av ett flertal programvaror. Detta har speciellt applicerats på så kallade ”micro air vehicles” (MAV).

En MAV kan beskrivas som en luftfarkost av en sådan storlek att den enkelt kan bäras och skötas av en person. I princip ett flygplan i samma storleksklass som fåglar. I Sverige benämns dessa ofta som ”micro UAV”. Nyttan med MAVs är många sett både från ett militärt och civilt perspektiv. Typiska användningsområden är spaning/övervakning inom polis, militär och räddningsverksamhet, samt kartering, meterologi, gränsbevakning, jordbruksinventering etc. Den konstruktionsautomation som har utvecklats möjliggör att generera MAVs optimerade för givna prestandakrav och önskad nyttolast. I optimeringen så genereras den optimala skrovformen, val av framdrivningssystem, samt placering av interna komponenter. Slutligen så tillverkas den genererade farkosten genom en 3D skrivare. Avhandlingen lägger även vikt vid att experimentellt validera de beräkningar som ligger till grund för optimeringen.

Det andra spåret i avhandlingen behandlar ämnet konceptutvärdering genom nedskalade modeller. Att bygga och testa fysiska modeller är egentligen inget nytt inom flygkonstruktion. Avhandlingen visar dock hur man med modern teknik kan göra detta billigare än tidigare och samtidigt öka nyttan. Miniatyriseringen av elektronik gör att det idag går att utrusta radiostyrda demonstratorer med avancerade mätsystem varpå värdefull data kan insamlas. Vikten av att kunna testa fysiska prototyper ökar alltjämt som flygindustrin blir allt mer teoretisk. Tiden mellan olika flygplanskonstruktioner blir också längre, samt att behovet för nya radikala konstruktioner ökar för att möta de strama miljökraven. Att snabbt och billigt kunna utvärdera prototyper blir därför en allt viktigare del för att hålla kompetensen på en hög nivå. Avhandlingen behandlar skalning, konstruktionsmetoder, instrumentering och testning.

This paper presents the development of a design framework for the initial conceptual design phase. The focus in this project is on a flexible database in XML format, together with close integration of automated CAD, and other tools, which allows the developed geometry to be used directly in the subsequent preliminary design phase. The database and the geometry are also described and an overview is given of included tools like aerodynamic analysis and weight estimation.

Purpose - The purpose of this paper is to present the latest subscale demonstrator aircraft developed at Linkoping University. It has been built as part of a study initiated by the Swedish Material Board (FMV) on a Generic Future Fighter aircraft. The paper will cover different aspects of the performed work: from paper study realised by SAAB to the first flight of the scaled demonstrator. The intention of the paper is to describe what has been realised and explain how the work is may be used to fit within aircraft conceptual design. Design/methodology/approach - The approach has been to address the challenges proposed by the customer of the demonstrator, how to design, manufacture and operate a scaled demonstrator of an aircraft study in conceptual design within five months. Similar research projects have been reviewed in order to perform the current work. Findings - The results obtained so far have led to new questions. In particular, the project indicated that more research is needed within the area of subscale flight testing for usage in aircraft conceptual design, since a scaled demonstrator is likely to answer some questions but will probably open up new ones. Research limitations/implications - The current research is just in its infancy and does not bring any final conclusion but does, however, offer several guidelines for future works. Since the aircraft study was an early phase concept study, not much data are available for validation or comparison. Therefore, the paper is not presenting new methods or general conclusions. Practical implications - Results from a conceptual aircraft study and a realisation of a scaled prototype are presented, which show that scaled flight testing may be used with some restriction in conceptual design. Originality/value - The value of this paper is to show that universities can be involved in prototype development and can work in close collaboration with industries to address issues and solutions within aircraft conceptual design.