Browsing by Author "Portapas, Vilius"

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Handling qualities of high aspect ratio wing aircraft.
    (2018-07) Portapas, Vilius; Lone, Mudassir M.; Cooke, Alastair K.
    To reduce the environmental impact of the aviation industry aircraft designers invest much effort to develop new and improve existing technologies to create new aircraft configurations. New high aspect ratio wings allow to improve aerodynamic efficiency while reducing aircraft weight through the use of new lightweight materials. However, their slenderness tends to introduce significant interaction between flight dynamics and aeroelastics. These interactions need to be identified in order to allow future pilots to anticipate behaviour of those aircraft. The literature review revealed a gap in the knowledge of flying and handling qualities (HQs) of large transport highly flexible wing aircraft. Hence, this thesis presents a comparison between rigid and flexible aircraft configurations carried out by the means of the pilot-in-the-loop simulations of flight test manoeuvres. Firstly, the analysis of the extended equations of motion, which consider the structural flexibility, revealed significant flexibility impact on the lateral/directional dynamics of the aircraft. Then, the equations were integrated into the Simulation Framework for Flexible Aircraft (SFFA) that was developed by integrating the aeroservoelastic model CA² LM with the engineering flight simulator EFS500. The simulation campaign was performed using the SFFA for the HARTEN aircraft model, which exhibited an unusually aft neutra point position. The results of the simulation campaign revealed minor differences in the longitudinal dynamics between the rigid and flexible aircraft. However, the lateral/directional dynamics showed significant differences, especially in the change of the Dutch roll shape from horizontal to vertical and the spiral mode from unstable to neutrally stable. It also highlighted the ‘wing rocking’ phenomenon and the ‘wing ratcheting’ significantly decreased roll performance. Finally, a new slalom task proved its applicability to efficiently assess HQs and revealed a degradation of HQs for the flexible aircraft configuration. The SFFA was also assessed and limiting hardware issues were indicated to support the comparison of aircraft HQs. For the future it is recommended to identify a set of dynamic parameters that would allow to highlight deficiencies of flexible aircraft and to improve the SFFA allowing pilots to fully concentrate on the task.
  • Thumbnail Image
    ItemOpen Access
    Method to assess lateral handling qualities of aircraft with wingtip morphing
    (2018-01-13) Dussart, Gaétan X.; Yusuf, Sezsy Y.; Portapas, Vilius; Lopez Matos, Guillermo E.; Lone, Mohammad M.
    The impact of in- ight folding wingtip on roll characteristics of aircraft has been studied in the past. In this study, a handling qualities assessment carried out to de-risk further development of such a device. A specialised ight simulation campaign is prepared to evaluate the roll dynamics in di erent morphing con gurations. Various manoeuvres, including the O set Landing Manoeuvre and herein presented Slalom and Alignment Tracking task are used. Cooper Harper Rating scales and ight data analysis are used to collect pilot opinion and validate pilot-in-the-loop simulation results. This example is used to demonstrate the use of the slalom and Alignment Tracking manoeuvre for lateral dynamic assessment.
  • Thumbnail Image
    ItemOpen Access
    Modelling framework for flight dynamics of flexible aircraft
    (Vilnius Gediminas Technical University Press, 2016-12-20) Portapas, Vilius; Cooke, Alastair K.; Lone, Mudassir M.
    The flight dynamics and handling qualities of any flexible aircraft can be analysed within the Cranfield Aircraft Accelerated Loads Model (CA2LM) framework. The modelling techniques and methods used to develop the framework are presented. The aerodynamic surfaces were modelled using the Modified Strip Theory (MST) and a state-space representation to model unsteady aerodynamics. With a modal approach, the structural flexibility and each mode’s influence on the structure deflections are analysed. To supplement the general overview of the framework equations of motion, models of atmosphere, gravity, fuselage and engines are introduced. The AX-1 general transport aircraft model is analysed as an example of the CA2LM framework capabilities. The results showed that, according to the Gibson Dropback criterion, the aircraft with no control system lacks the stability and its longitudinal handling qualities are unsatisfactory. Finally, the steps for future developments of the CA2LM framework are listed within conclusions.
  • Thumbnail Image
    ItemOpen Access
    Pilot-in-the-loop flight simulation of flexible aircraft in Matlab / Simulink: Implementation and coding peculiarities
    (AIAA, 2018-01-13) Lopez Matos, Guillermo E.; Portapas, Vilius; Dussart, Gaétan X.; Lone, Mohammad M.; Coetzee, Etienne
    Integration of flight dynamic models, developed in the MATLAB R ⃝ /Simulink R ⃝ environment, with an engineering flight simulation platform allows rapid pilot-in-the-loop evaluation of new aircraft concepts at early stages of design. This paper aims to provide an overview of the integration activities needed to develop an engineering flight simulator capable of providing means to assess future concept aircraft, such as high aspect ratio wing configurations, where aeroelastic effects have a significant impact on rigid body flight dynamics. Details of the approach used to integrate an aeroelastic simulation framework with an engineering flight simulator are presented. The challenges of obtaining a real-time simulation capability and coding peculiarities of this approach are discussed. The paper expands on the discussion of integration and coding, and provides an example that demonstrates capabilities of such a framework for handling qualities assessment of a high aspect ratio wing aircraft.
  • Thumbnail Image
    ItemOpen Access
    Simulated pilot-in-the-loop testing of handling qualities of the flexible wing aircraft
    (Taylor and Francis, 2020-02-09) Portapas, Vilius; Cooke, Alastair
    This article aims to indicate the differences between rigid and flexible wing aircraft flying (FQ) and handling (HQ) qualities. The Simulation Framework for Flexible Aircraft was used to provide a generic cockpit environment and a piloted mathematical model of a bare airframe generic high aspect ratio wing aircraft (GA) model. Three highly qualified test pilots participated in the piloted simulation trials campaign and flew the GA model with both rigid and flexible wing configurations. The results showed a negligible difference for the longitudinal HQs between rigid and flexible wing aircraft. However, significant changes were indicated for the lateral/directional HQs of the flexible wing aircraft. A wing ratcheting phenomenon manifested itself during the roll mode tests, the spiral mode exhibited neutral stability and the Dutch roll mode shape changed from a horizontal to a vertical ellipse. The slalom task flight tests, performed to assess the FQs of the aircraft, revealed the degradation of both the longitudinal and lateral/directional FQs.
  • Thumbnail Image
    ItemOpen Access
    Verification of a low fidelity fast simulation framework through RANS simulations
    (Springer, 2019-07-22) Carrizales, Martin A.; Dussart, Gaétan; Portapas, Vilius; Pontillo, Alessandro; Lone, Mudassir
    Verification and validation of simulation models are critical steps in engineering. This paper aims at verifying the suitability of reduced order aerodynamic models used in an aeroservoelastic framework designed to analyze the flight dynamics of flexible aircraft, known as the Cranfield Accelerated Aircraft Loads Model. This framework is designed for rapid assessment of aircraft configurations at the conceptual design stage. Therefore, it utilizes or relies on methods that are of relatively low fidelity for high computational speeds, such as modified strip theory coupled with Leishmann–Beddoes unsteady aerodynamic model. Hence, verification against higher order methods is required. Although low fidelity models are widely used for conceptual design and loads assessments, the open literature still lacks a comparison against higher fidelity models. This work focuses on steady-trimmed flight conditions and investigates the effect of aerodynamic wing deformation under such loads on aerodynamic performance. Key limitations of the reduced order models used, namely fuselage and interference effects, are discussed. The reasons for the overall agreement between the two approaches are also outlined.