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A number of challenges in the development and application of flying qualities criteria for modern aircraft are addressed in this dissertation. The history of flying qualities is traced from its origins to modern day techniques as applied to piloted aircraft. Included in this historical review is the case that was made for the development of flying qualities criteria in the 1940's and 1950's when piloted aircraft became prevalent in the United States military. It is then argued that UAVs today are in the same context historically as piloted aircraft when flying qualities criteria were first developed. To aid in development of a flying qualities criterion for UAVs, a relevant classification system for UAVs. Two longitudinal flying qualities criteria are developed for application to autonomous UAVs. These criteria center on mission performance of the integrated aircraft and sensor system. The first criterion is based on a sensor platform's ability to reject aircraft disturbances in pitch attitude. The second criterion makes use of energy methods to create a metric to quantify the transmission of turbulence to the sensor platform. These criteria are evaluated with airframe models of different classes of air vehicles using the CASTLE 6 DOF simulation. Another topic in flying qualities is the evaluation of nonlinear control systems in piloted aircraft. A L1 adaptive controller was implemented and tested in a motion based, piloted flight simulator. This is the first time that the L1 controller has been evaluated for piloted handling qualities. Results showed that the adaptive controller was able to recover good flying qualities from a degraded aircraft. The final topic addresses a less direct, but extremely important challenge for flying qualities research and education: a capstone course in flight mechanics teaching flight test techniques and featuring a motion based flight simulator was implemented and evaluated. The course used a mixture of problem based learning and role based learning to create an environment where students could explore key flight mechanics concepts. Evaluation of the course's effectiveness to promote the understanding of key flight mechanics concepts is presented. / Ph. D.

During planetary entry, a vehicle uses drag generated from flight through the planetary atmosphere to decelerate from hyperbolic or orbital velocity. To date, all guided entry systems have utilized lift-modulation trajectory control. Deployable aerodynamic devices enable drag-modulation trajectory control, where a vehicle controls its energy and range during entry by varying drag area. Implementation of conventional lift-modulation systems is challenging for deployable systems. In contrast, drag-modulation trajectory control may be simpler and lower-cost than current state-of-the-art lift-modulation systems. In this investigation, a survey of analytical methods for computing planetary entry trajectories is presented and the approximate analytical solution to the entry equations of motion originally developed by Allen and Eggers is extended to enable flight performance evaluation of drag-modulation trajectory control systems. Results indicate that significant range control authority is available for vehicles with modestly sized decelerators. The extended Allen-Eggers solution is closed-form and enables rapid evaluation of nonlifting entry trajectories. The solution is utilized to develop analytical relationships for discrete-event drag-modulation systems. These relationships have direct application to onboard guidance and targeting systems. Numerical techniques were used to evaluate drag-modulation trajectory control for precision landing and planetary aerocapture missions, including development of prototype real-time guidance and targeting algorithms. Results show that simple, discrete-event drag-modulation trajectory control systems can provide landed accuracies competitive with the current state of the art and a more benign aerothermal environment during entry for robotic-scale exploration missions. For aerocapture, drag-modulation trajectory control is shown to be feasible for missions to Mars and Titan and the required delta-V for periapsis raise is insensitive to the particular method of drag modulation. Overall, results indicate that drag-modulation trajectory control is feasible for a subset of planetary entry and aerocapture missions. To facilitate intelligent system selection, a method is proposed for comparing lift and drag-modulation trajectory control schemes. This method applies nonlinear variational techniques to closed-form analytical solutions of the equations of motion, generating closed-form expressions for variations of arbitrary order. This comparative method is quantitative, performance-based, addresses robustness, and applicable early in the design process. This method is applied to steep planetary entry trajectories and shows that, in general, lift and drag-modulation systems exhibit similar responses to perturbations in environmental and initial state perturbations. However, significant differences are present for aerodynamic perturbations and results demonstrate that drag systems may be more robust to uncertainty in aerodynamic parameters. Finally, the results of these contributions are combined to build a set of guidelines for selecting lift or drag-modulation for a Mars Science Laboratory-class planetary entry mission.

This report summarizes the task of conceptually designing an UAV suited for agricultural observation of Swedish farmland. The design of the UAV was divided into two parts. This report focuses on the flight mechanics, performance analysis, and cost analysis of the UAV, whereas the other part centers around the aerodynamic performance. Therefore, some elements, such as the wing selection, will not be subject to discussion in this report. A set of different requirements were posed, such as having a flight time longer than two hours, being able to between 5-10 m/s, able to perform vertical take-off and landing, fly at a maximum of 100 meters, and weighing less than 5 kg. By using different sources of literature, reasonable assumptions, and Matlab analytics, a UAV was designed that met all constraints demanded. The cost analysis yielded a result that was reasonable, which overall makes this conceptual UAV a realistic product that could be manufactured using the project design.

The field of man portable UASs (Unmanned Aerial Systems) is currently a key area in improving the fielded warrior's capabilities. Pressurized aerostructures that can perform with similar results of solid structures can potentially change how this objective may be accomplished now and in the future. Construction with high density polymers and other composites is currently part of active inflatable vehicle research. Many shape forming techniques have also been adapted from the airship and balloon manufacturing industry. Additional research includes modeling techniques so that these vehicles may be included in simulation packages. A flight dynamics simulation with reduced-order aeroelastic effects derived with Lagrangian and Eulerian dynamics approaches were developed and optimized to predict the behavior of inflatable flexible structures in small UASs. The models are used to investigate the effects of significant structural deflections (warping) on aerodynamic surfaces. The model also includes compensation for large buoyancy ratios. Existing literature documents the similarity in structural dynamics of rigid beams and inflatable beams before wrinkling. Therefore, wing bending and torsional modes are approximated with the geometrically exact ntrinsic beam equations using NATASHA (Nonlinear Aeroelastic Trim And Stability for HALE Aircraft) code. An approach was also suggested for inclusion of unique phenomena such as wrinkling during flight. A simplified experimental setup will be designed to examine the most significant results observed from the simulation model. These methods may be suitable for specifying limits on flight maneuvers for inflatable UASs.

The only aeroballistic laboratory of Turkey is the Flight Mechanics Laboratory, FML of T&Uuml / BITAK - SAGE. In FML, flight profiles of projectiles are reconstructed using their tear marks on paper sheets, called yaw cards. Tear marks are created on yaw cards as projectiles pass through them. These yaw cards are tightly stretched to metal frames which are positioned normal to the direction of projectile flight path. The use of yaw cards for flight profile reconstruction is a low cost and reliable solution. However, the yaw card method requires a heavy workload for the analysis of tear marks. Yaw cards collected from the frames are fed through an optical scanner and converted to digital images. These digital images are then processed by operators to calculate the projectile&rsquo / s flight position and angles. To automate this manual process, an algorithm is developed by using histogram based segmentation techniques, custom search algorithms, and Radon transform. This algorithm identifies and locates the projectile marks and finds angle of attack, angle of side slip and roll angle at each frame station by conducting the necessary transformations. Using this automated algorithm, a considerable amount of improvement is accomplished in terms of both decreasing the analysis time and increasing the accuracy of flight profile reconstruction.

This thesis presents a tool for conceptual design of a traditional configuration aircraft by using a parametric six degrees of freedom (6DOF) flight mechanics model implemented in the Modelica Language using Wolfram System Modeler. Being first only able to model and simulate the uncontrolled flight of an aircraft with fixed mass and centre of gravity (CG), and requiring detailed aerodynamic parameters as an input, the 6DOF model is improved by developing new features to reduce the number of required inputs while also increasing the data output of the simulations. First, the propulsion submodel is added with models for alternative propulsions to the existing model of turbofan engines. The energy and fuel consumption is also modelled for all propulsion types, and thus the aircraft model has no longer fixed mass properties, except for aircraft with electric propulsion. To further evaluate the fuel consumption for pre-defined flight missions with given flight speed, altitude and track angles, autopilots for a few different aircraft types are developed. Additionally, the 6DOF model is improved by establishing algebraic and statistical relationships between the aircraft geometric input parameters, aerodynamic coefficients and moments of inertia such that the values for the two last mentioned can be estimated inside the 6DOF model based on the minimum amount of design variables, geometric input parameters and aerodynamic properties of the 2D airfoils used in the wings. Ultimately, the improved 6DOF model is evaluated and analysed in terms of its performance in initial weight estimation on aircraft conceptual design stage as well as in predicting the aerodynamic properties.

<p>Aerocapture has been envisioned as a potential orbit insertion technique for planetary destinations with an atmosphere. Despite not being flight proven technique, many studies found in the literature and recent mission proposals have employed aerocapture into their respective mission designs. The potential varying levels of trajectory dispersions experienced during atmospheric flight at each destination drives the need for robust and fuel-efficient guidance and control solutions. Existing guidance algorithms have relied on tracking precomputed reference trajectories, which are computed using significant simplifications to the flight mechanics, are not generally designed to be fuel-efficient, and require tedious performance gain tuning. When simulated with higher levels of uncertainty, the existing algorithms have been shown to produce large orbit insertion errors. Furthermore, existing flight control methodologies have been limited in scope to bank angle modulation. While some studies have introduced new methodologies, such as drag modulation and direct force control, they haven’t been tested at the same level of rigor as the existing methods. Advances in on-board computational power are allowing for modern guidance and control solutions, in the form of numerical predictor-corrector algorithms, to be realized. This dissertation presents an aerocapture guidance architecture based on a numerical predictor-corrector algorithm. Optimal control theory is utilized to formulate and numerically obtain fuel-minimizing flight control laws for lifting and ballistic vehicles. The unified control laws are integrated into a common guidance algorithm. The architecture is utilized to conduct Monte Carlo simulation studies of Discovery-class and SmallSat-class aerocapture missions at various planetary destinations.</p>

This report presents the first steps of development aiming towards making, the open-source aeroelastic code, GEBTAero flight dynamics capable. The implementation was done partly in the Fortran code and part in the GEBTAero Python API with the objective of reusing as much of the existing code as possible with as little substantial architecture modification. The added capacities include the widening of the purview of the software to take into account beam assembly arranged in a plane-like structure, a trim function for the steady level flight was also implemented and the twelve degree of freedom flight mechanics system of equations was introduced in the algorithm. In this short time, unfortunately, few tests were performed fully but important foundation work giving preliminary results was carried out. This includes the verification of the structural modes simulation as well as several bug and inacuracy fixes. / Den här rapporten presenterar de första utvecklingsstegen som syftar till att göra, öppen käll aeroelastisk koden, GEBTAero flygdynamik kapabel. Implementeringen gjordes dels i Fortran-koden och dels i GEBTAero Python API med målet att återanvända så mycket av den befintliga koden som möjligt med så lite väsentlig arkitekturändring. De tillagda kapaciteterna inkluderar utvidgningen av programvaransräckvidd för att ta hänsyn till strålmontering anordnad i en flygplansliknande struktur, en “trim” funktion för jämn nivåflygning implementerades också och de tolv frihetsgraderna flygmekanik system av ekvationer introducerades i algoritmen. Under denna korta tid utfördes tyvärr få tester helt men viktigt grundarbete med preliminära resultat utfördes. Detta inkluderar verifiering av strukturlägen simulering samt flera korrigeringar av fel och felaktigheter.

The primary objective of this thesis is to evaluate the prospect of machine learning methods being used to classify flying qualities based on simulator data (with the focus being on pitch maneuvers). If critical flying qualities could be identified earlier in the verification process, they can be further invested in and focused on with less cost for design changes of the flight control system. Information from manned simulations with given flying quality levels are used to create a replication of the performed pitch maneuver in a desktop simulator. The generated flight data is represented by different measures in the classification to separately train and test the machine learning models against the given flying quality level. The models used are Logistic Regression, Support Vector Machines with radial basis functions (RBF), linear and polynomial kernels along with Artificial Neural Networks.  The results show that the classifiers correctly identify at least 80% of cases with critical flying qualities. The classification shows that the statistical measures of the time signals and first order time derivatives of pitch, roll and yaw rates are enough for classification within the scope of this thesis. The different machine learning models show no significant difference in performance in the scope of this thesis. In conclusion, machine learning methods show good potential for classification of flying qualities, and could become an important tool for evaluating flying qualities of large amounts of simulations, in addition to manned simulations. / Huvuduppgiften med detta examensarbete är att utvärdera huruvida maskininlärning kan användas för att klassificera flygkvaliteter från simulatordata (där fokus ligger på att utvärdera tippmanövrar). Om kritiska flygkvaliteter kan identifieras tidigare i verifikationsprocessen, kan resurser fokuseras för att åtgärda problemet tidigt med mindre kostnader för ändringar av styrsystemet. Information från bemannade simuleringar där flygkvalitetsnivåer har angetts av pilot används för att återskapa tippmanövern i skrivbordssimulatorn. Den genererade flygdatan representeras av olika mått i klassificeringen för att separat träna och testa maskininlärningsmodellerna mot den givna flygkvalitetsnivån. De modeller som används i rapporten är logistisk regression, stödvektormaskiner med radiella basfunktioner (RBF), linjär och polynomisk kärna samt artificiella neurala nätverk. Resultaten visar att klassificerarna korrekt identifierar över 80% av fallen med kritiska flygkvaliteter. Klassificeringen visar att statistiska mått av tidssignalen och första ordningens tidsderivator i tipp, roll och gir är tillräckligt för klassificering inom gränserna av detta examensarbete. De olika maskininlärningsmodellerna visar inga signifikanta skillnader i prestanda med datan som används. Sammanfattningsvis kan maskininlärningsmodellerna anses ha god potential för klassificering av flygkvaliteter, och kan vara ett viktigt verktyg för att klassificera flygkvaliteter för stora mängder flygdata, som komplement till bemannade simuleringar.