1,720,974 research outputs found
Improving structural weight estimation of novel aircraft configurations to enhance flying quality analysis
No full textStructural weight estimation of novel aircraft configurations, such as a box-wing aircraft, in the conceptual and preliminary design phase is a challenge due to a lack of statistical data. Most of the aircraft performance and handling qualities parameters are strongly influenced by the aircraft weight and inertia. Therefore an accurate weight estimation method is required. The application of existing (statistical) weight estimation methods provides a rather inaccurate and weak estimation for this novel configuration. An alternative is the use of higher fidelity weight estimation methods, which use more physics based calculations and less statistical estimations. A novel design framework with various disciplines is developed. In this framework, a parametric aircraft model, a weight estimation method, aerodynamic analysis and flight mechanics analysis are coupled to perform a fully automated design process. The various modules of this design framework create a decision making system so that the aerodynamic and weight estimations for handling quality measurements can take place with high fidelity for different aircraft category during the preliminary and conceptual design process. It is demonstrated that the design parameters of the PrP300 are closely coupled and a delicate balance has to be found between the design parameters in order to have adequate handling qualities throughout the flight envelope. Such a tradeoff is most likely very difficult, if not impossible to conduct by hand. The proposed framework is therefore a powerful tool to support the aircraft design activities and to investigate the handling qualities of an (unconventional) aircraft already in the early design stages. This can lead to a less error design and consequently decrease the cost due to additional design work and extra wind tunnel and flight testing
Feasibility study of a novel load alleviation system on the UH-60A Blackhawk helicopter
No full textFlight Performance and PropulsionAerospace Design, Integration & OperationsAerospace Engineerin
Application of Thrust Vectoring to Reduce Vertical Tail Size
No full textThe vertical tail size of a multi-engine aircraft is typically driven by the directional control requirement during one-engine-inoperative flight. This results in the vertical tail being over-sized for most regularly occurring flight conditions. By adding thrust vectoring technology to an aircraft, the vertical tail can be designed to cope with regularly occurring flight conditions rather than the one-engine-inoperative flight condition. A modern aircraft was redesigned such that it would have thrust vectoring capabilities and an unconventionally small vertical tail. The redesigned vertical tails had areas which were 85\%, 70\%, 60\%, and 50\% of the original vertical tail area, which corresponded to reductions in the vertical tail area of 15\%, 30\%, 40\%, and 50\%, respectively. By reducing the vertical tail area, an aircraft's parasite drag may be reduced, and a reduction in parasite drag would allow for a reduction in the aircraft's fuel consumption. Analyses showed that the redesigned vertical tail and change in aircraft inertia due to the addition of thrust vectoring technology had a negligible impact of the aircraft's roll mode dynamics. It was also shown that the reduction in vertical tail area resulted in a degradation of the aircraft's spiral mode flight qualities. With regards to the Dutch roll motion, a reduction in vertical tail area resulted in a reduction of Dutch roll damping coefficient and Dutch roll frequency. Based on the analysis of the Dutch roll mode, it has been recommended that a compromise between the 85\% and 70\% vertical tail area would likely produce an acceptable compromise between the reduced vertical tail area and Dutch roll flight characteristics; however, the aircraft design would required a yaw damper. It is predicted that trimmed flight with one-engine-inoperative can be achieved by simultaneously using thrust vectoring technology and an unconventionally small vertical tail. Through the use of directional thrust vectoring, an aircraft's rudder deflection angle, aileron deflection angle, and bank angle may reduced during the one-engine-inoperative flight condition. Analysis of the one-engine-inoperative and crosswind flight condition shows that using thrust vectoring for directional control may allow for a reduction in trim drag; however, additional analysis of this flight condition should be completed. A vertical tail mass estimation was completed, and it has been shown that the reduction in vertical tail mass resulting from a reduction in vertical tail area is of the same magnitude when compared to the engine mass increase due to the addition of thrust vectoring technologies. Lastly, it has been shown that an aircraft's mission fuel consumption can be reduced if the aircraft's vertical tail area is reduced and thrust vectoring flight control is implemented into the aircraft design. Reductions in mission fuel consumption greater than 1\% are unlikely; however, there are feasible reductions in mission fuel mass for the proposed thrust vectoring aircraft design.Aerospace EngineeringFlight Performance and Propulsio
Unsteady Aerodynamics in the Gust and Manoeuvre Response of Flexible Aircraft
No full textAircraft wings are becoming more flexible, making it important to take this flexibility into account from the start of the design process. With flexible wings, unsteady (time-varying) aerodynamics becomes important. For this reason, an unsteady aerodynamics model was constructed and coupled to an aeroelastic flight mechanics tool. This allows for investigating the response of the aircraft after gusts or control inputs. It was found that for wings of relatively high stiffness, unsteady aerodynamics is not important to take into account during gust response modelling. The difference between unsteady and steady aerodynamics was found to not be more that 5%. The short period motion is influenced significantly by the unsteady aerodynamics, with a change in period of 18%. Results have also indicated that unsteady aerodynamics is more important for more flexible wings. The current work allows for simulating these more flexible wings, in both longitudinal and lateral situations.Aerospace EngineeringAerodynamics, Wind Energy & Propulsio
Multibody Dynamics Modeling of Flexible Aircraft Flight Dynamics
No full textBecause of the focus on weight minimization, aircraft are becoming more and more flexible. Therefore, the frequency separation between flight mechanics motion and structural vibration decreases. This calls for a flight mechanics model that includes aeroelasticity. The development of such a model was the subject of the current research. This model can be used for gust and maneuver load prediction in the preliminary design phase. With accurate load prediction, structural integrity can be ensured and unstable flight conditions can be avoided. Moreover, the model may be used to design active load alleviation systems to increase passenger comfort, reduce fatigue, and decrease loads on the wing structure. A modal structural model and a quasi-steady aerodynamics model are integrated in a partitioned manner to form an aeroelastic wing model. This aeroelastic wing model is implemented in a multibody dynamics environment, in order to model flight dynamics and the effect of aeroelasticity thereon. An A320-like aircraft was analyzed in the current research. The effect of aeroelasticity on flight mechanics was investigated. Inclusion of flexibility substantially affected the trim control variables, but had an almost negligible effect on the flight mechanics modes and stability derivatives. When flexibility increases, these parameters are affected. Aeroelasticity has a non-negligible effect on the (peak) wing loads after maneuvers or disturbances. Especially for maneuvers or disturbances that increase lift, and therefore wing deformation, the peak loads are affected. Moreover, wing loads are particularly affected by disturbances that have a direct effect on the wing, such as aileron deflection. The objective of the current research was to improve on an existing aeroelastic flight mechanics model, based on the lumped-parameter approach. The modal model created in the current research proved to have a computational effort that is several times lower than the lumped-parameter model. In addition, the accuracy of the modal model can be increased beyond that of the lumped-parameter model at only a small additional computational cost. Because of the reduced computational cost, and the potentially increased accuracy, the modal model performs better than the lumped-parameter model. Due to the qualitative nature of these conclusions, it is probable that they can be extended to other conventional, low aspect-ratio aircraft in the subsonic flight regime. Definitive, quantitative conclusions could not be formulated, because of the absence of complete validation data.Flight Performance and PropulsionFlight Performance and PropulsionAerospace Engineerin
Rapid Design and Virtual Testing of UAV Within the DEE Framework
No full textSEADAerospace Engineerin
Comparing and improving steering forces in a race car and race simulator to increase simulator fidelity
No full textAs circuit testing days are expensive and limited by regulations, racing teams are more and more dependent on simulation tools. Van Amersfoort Racing built their own racing simulator to train drivers in an fully controlled environment. This environment is based on commercially available simulation software rFactor. However, no research on the accuracy of the physics of this software is available. Since level of fidelity of race simulators is important for the perception of racing drivers, force feedback steering forces are analyzed. Information of the real Formula 3 car is used to upgrade the vehicle model used in rFactor and to develop a Multibody Dynamic vehicle model of the same car. Steering metrics are used to make qualitative comparisons between steering force measurement in the real car, the simulator and the Multibody Dynamic model. It is shown that the baseline simulator vehicle model is less sensitive to steering input compared to the real car. Furthermore the simulator driver theoretically senses higher steering torques for a given lateral acceleration discarding electric power limitations of the force feedback motor. As a desire to improve simulator fidelity, a Pacejka tyre model of the Hankook Formula 3 tyre is converted to an rFactor model together with an improved suspension model using the exact suspension geometry as provided by car manufacturer Dallara. Simultaneously, the Multibody Dynamic vehicle model is constructed from these submodels, which purely focusses on lateral dynamics. In order to use the lateral based Multibody Dynamic model as a tool for simulation and assessment, its response is tested given the same input as the real Formula 3 car experienced during a particular test. Three cases are considered: weaving on a straight, a low speed corner and a high speed corner. Longitudinal load transfer is inherent in low speed corners, which, due to its limitation in the Multibody Dynamic model, leaves the model adjustments inconclusive. Furthermore, tyre relaxation plays an important role in low speed corners following each other up in a short period of time, which affect low speed steering metrics. The Multibody Dynamic model showed close correlation of steering metrics with real car measurements for the high speed corner. The updated rFactor model improved steering torque feedback despite higher required steering angles.Flight Performance & PropulsionAerospace Engineerin
Investigation into the effect of relaxed static stability on a business jet's preliminary design
No full textAerospace EngineeringFlight Performance and Propulsio
Parametric modelling for determining aircraft stability & control derivatives
No full textThis thesis is part of a project that focuses on developing an optimisation framework for dynamically scaled flight testing. The optimisation framework must design the scale model and the flight test such that the performance of the scale model is representative to the full-scale aircraft. The similarity in the performances between the scale model and the full-scale aircraft is achieved by altering the geometry, the mass distribution and the structure of the model, which are related to the aerodynamic, flight dynamic and structures disciplines respectively. This thesis contributes to the aerodynamics optimisation framework by focusing on the development of a parametric model that is capable of deriving the stability and control derivatives. The research goals of the thesis are mostly related to the construction of a parametric aircraft model for the aerodynamic solvers that are based on a first order panel method like VSAERO. The most important goal is how to model the trailing edge moveables for a first order panel method for deriving the control derivatives. This thesis will investigate three options for creating the moveables. The first option (’normal rotation’) is a mathematical operation in VSAERO that rotates the normal vectors of the body panels that represents the moveable. The second option (’transition surface’) is a wing with a moveable model that has transition surfaces between the wing and the moveable in the spanwise direction. The third option (’gap’) is the same model as method two, but instead of transition surfaces, there is a gap between the wing and the moveable. The second research goal is to compute the stability & control derivatives of the parametric model and investigate the accuracy of these derivatives. Out of the three modelling options, the wing with a moveable model that has a gap between the sides of the moveable and the wing was useless in VSAERO. The model was unstable due to the presence of the gap. The gap creates a very low pressure locally, which accelerates the surrounding airflow to a ridiculously high value. The difference between the ’normal rotation’ and the ’transition surface’ models is the location of the moveable suction peak. The suction peak of the ’normal rotation’ model is located on the wing in front of the start of the moveable, while the suction peak of the ’transition surface’ is located at the start or slightly behind the start of the moveable. The effect of different locations of the suction peaks is that a suction peak on the wing will generate less induced drag than a suction peak located on the deflected moveable. The results of stability & control derivatives for the ’normal rotation’ and the ’transition surface’ modelling options were quite acceptable with the static derivatives as the most accurate derivatives with an average error of seven percent. The control derivatives, on the other hand, was the least accurate with a mean error of 40 percent. The overall performance of the two moveable modelling options is that they were performing equally well when only the accuracy of the derivatives was observed. The ’transition surface’ modelling option was more accurate in the prediction of lateral stability derivatives and the longitudinal control derivatives than the ’normal rotation’ option, while the ’normal rotation’ option was more accurate in predicting the longitudinal stability derivatives and the lateral control derivatives. But the deflection of the rudder produces side force, yaw moment and roll moment coefficients that are less accurate for the ’normal rotation’ option then for the ’transition surface’ option. The ’transition surface’ modelling option is the better option for modelling the moveable because it produced more accurate aerodynamic results than the ’normal rotation’ modelling option. Both moveable modelling options have its strengths and weakness when concerning the prediction of the stability and control derivatives, and neither of the two was considerably better. Thus based on the accuracy of the aerodynamic characteristics, the ’transition surface’ modelling option is the best option for modelling the moveables of a first order panel method solvers like VSAERO.Aerospace EngineeringAerodynamics, Wind Energy & Propulsio
Flight performance and propulsion; the introduction of a new master track
No full textAerospace Engineerin
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