Aeroelastic Stability Assessment Of a CS-25 Category Aircraft Equipped With Multi-Modal Wing Morphing Devices

Morphing wing structures have the greatest ambition to dramatically im-prove aircraft aerodynamic performance (less fuel consumption) and reduce aerodynamic noise. Several studies in the literature have shown their potential for increased aerodynamic efficiency across nearly all flight conditions, en-hanced aircraft maneuverability and control effectiveness, decreased take-off/landing length, reduced airframe noise, etc. However, despite a long herit-age of research, morphing wing technology has yet to be approved by the Euro-pean Aviation Safety Authority (EASA) for use in commercial aviation. Models and approaches capable to predict the aeroelastic impact of a morphing wing still need to be matured to safely alter design and operation of future genera-tions of aircraft. Additionally, a number of practical challenges remain to be addressed in the suitable materials, systems reliability, safety and maintenance. Due to the reduced stiffness, increased mass and increased Degree Of Freedom (DOF) with respect to conventional wings, these mechanical systems can cause significant reduction of aircraft flutter margins. This aspect requires dedicated aeroelastic assessments since the early stages of the design process of such an innovative wing. Flutter boundaries predictions need sensitivity anal-yses to evaluate bending/torsional stiffness and inertial distribution variability ranges of the aircraft wing equipped with the morphing wing devices. In such a way, aeroelastic assessments become fundamental to drive a balance between weight and stiffness of the investigated adaptive systems. Furthermore, in pseu-do rigid-body mechanisms-based morphing structures, the inner kinematics is so important that its faults may compromise the general aircraft-level functions. Similarly to the demonstration means of safety compliance, commonly applied to aircraft control surfaces, the novel functions resulting from the integration of adaptive devices into flying aircraft thus impose a detailed examination of the associated risks. In the framework of Clean Sky 2 Airgreen 2 project, the author provides advanced aeroelastic assessments of two adaptive devices enabling the camber morphing of winglets and flaps, conceived for regional aircraft integration (EASA CS-25 category). Segmented ribs architectures ensure the transition from the baseline (or un-morphed) shape to the morphed ones, driven by em-bedded electromechanical actuators. Some of the advantages resulting from the combination of the two aforementioned morphing systems are wing load con-trol, lift-over-drag ratio increase and root bending moment alleviation. The aircraft aeroelastic model was generated by means of the proprietary code SANDY 3.0. Then, the same code was adopted to solve the aeroelastic stability equa-tions through theoretical modes association in frequency domain. To carry out multi-parametric flutter analyses (P-K continuation method), the actuation lines stiffness and winglet/flap tabs inertial parameters were considered in combina-tion each other. Nominal operative conditions as well as systems malfunction-ing or failures were examined as analyses cases of the investigated morphing devices, together with actuators free-play conditions. Proper design solutions were suggested to guarantee flutter clearance in accordance with aircraft stabil-ity robustness with respect to morphing systems integration, evaluated through a combination of “worst cases” simulating the mutual interaction among the adaptive systems. The safety-driven design of the morphing wing devices required also a thorough examination of the potential hazards resulting from operational faults involving either the actuation chain, such as jamming, or the external interfaces, such as loss of power supplies and control lanes, and both. The main goal was to verify whether the morphing flap and winglet systems could comply with the standard civil flight safety regulations and airworthiness requirements (EASA CS25). More in detail, a comprehensive study of systems functions was firstly qualitatively performed at both subsystem and aircraft levels to identify poten-tial design faults, maintenance and crew faults, as well as external environment risks. The severity of the hazard effects was thus determined and then ranked in specific classes, indicative of the maximum tolerable probability of occurrence for a specific event, resulting in safety design objectives. Fault trees were final-ly produced to assess the compliance of the system architectures to the quanti-tative safety requirements resulting from the FHAs

Case report: Ponatinib as a bridge to CAR-T cells and subsequent maintenance in a patient with relapsed/refractory Philadelphia-like acute lymphoblastic leukemia

Philadelphia (Ph)-like acute lymphoblastic leukemia (ALL) constitutes a heterogeneous subset of ALL with a uniformly unfavorable prognosis. The identification of mutations amenable to treatment with tyrosine kinase-inhibitors (TKIs) represents a promising field of investigation. We report the case of a young patient affected by relapsed/refractory Ph-like ALL treated with chimeric antigen receptor T (CAR-T) cells after successful bridging with compassionate-use ponatinib and low-dose prednisone. We restarted low-dose ponatinib maintenance three months later. Twenty months later, measurable residual disease negativity and B-cell aplasia persist. To the best of our knowledge, this is the first case reporting the use of ponatinib in Ph-like ALL as a bridge to and maintenance after CAR-T cell therapy

Description of Position Control Laws for Functionality Test of a Bi-modal Morphing Flap

Modern aerospace research programs are increasingly focusing on structural design strategies based on the adaptive wing philosophy. Morphing wing technologies are being studied because they can be used to maximize the aerodynamic efficiency, maneuverability, and load control effectiveness under different flight conditions. As one of the most important research projects in Europe, the JTI Green Regional Aircraft (GRA) focused on the design and demonstration of a true-scale morphing flap applicable to the natural laminar flow (NLF) wing of a 130-seat EASA CS25 category reference aircraft. The authors worked on developing an appropriate actuation and control system to enable flap bi-modal operational modes. In the deployed configuration, the overall camber morphs during take-off and landing for high-lift performances. In the stowed configuration, the flap trailing edge (nearly 10% of the local chord) is deflected upwards and downwards to improve the wing aerodynamic efficiency during cruising. Tailored control units were programmed according to a proper digital logic control law based on LTI DriveManager® software. Flap functionality tests showed that the obtained morphed shapes had an excellent correlation with the design target geometries

Structural design of a multifunctional morphing fowler flap for a twin-prop regional aircraft

In the framework of Clean Sky 2 Airgreen 2 (REG-IADP) European research project, a novel multifunctional morphing flap technology was investigated to improve the aerodynamic performances of the next Turboprop regional aircraft (90 passengers) along its flight mission. The proposed true-scale device (5 meters span with a mean chord of 0.6 meters) is conceived to replace and enhance conventional Fowler flap with new functionalities. Three different functions were enabled: overall airfoil camber morphing up to +30° (mode 1), +10°/-10° (upwards/downwards) deflections of the flap tip segment (mode 2), flap tip “segmented” twist of ±5° along the outer flap span (mode 3). Morphing mode 1 is supposed to be activated during take-off and landing only to enhance aircraft high-lift performances and steeper initial climb and descent. Thanks to this function, more airfoil shapes are available at each flap setting and therefore a dramatic simplification of the flap deployment system may be implemented. Morphing modes 2 and 3 are enabled in cruise and off-design flight conditions to improve wing aerodynamic efficiency. The novel structural concept of the three-modal morphing Fowler flap (3MMF) was designed according to the challenges posed by real wing installation issues. The proposed concept consists of a multi-box arrangement activated by segmented ribs with embedded inner mechanisms to realize the transition from the baseline configuration to different target aero-shapes while withstanding the aerodynamic loads. Lightweight and compact actuating leverages driven by electromechanical motors were properly synthesized to comply with stringent requirements for real aircraft implementation: minimum actuating torque, minimum number of motors, reduced weight, and available design space. The methodology for the kinematic design of the inner mechanisms is based on a building block approach where the instant center analysis tool is used to preliminary select the locations of the hinges’ leverages. The final geometry of the inner mechanisms is optimized to maximize the mechanical advantage as well as to provide the kinematic performances required by the three different morphing modes. The load-path was evaluated, and the cross-sectional size of leverages was subsequently optimized. Finally, actuating torques predicted by instant center analysis were compared to the calculated values from finite element analysis. The structural sizing process of the multi-box arrangement was carried out considering elementary methods, and results were compared with finite element simulations

Actuation and control of a novel wing flap architecture with bi-modal camber morphing capabilities

Modern aerospace research programs are increasingly oriented towards adaptive wing structures for greening the air transport in the near future. New structural concepts implementing and integrating innovative technologies are mandatory for succeeding in this critical task. Among these, the so-called morphing structures are taken into account in aerospace applications, since they ensure the structural shape control in order to optimize the aerodynamic efficiency during the different flight phases. Among the most ambitious research projects launched in Europe, the JTI - Green Regional Aircraft (GRA) is placed in foreground for the design and the demonstration of a true-scale morphing flap applicable to the Natural Laminar Flow (NLF) wing of a 130-seats reference aircraft belonging to EASA CS25 category. In this framework, the authors intensively worked on the definition of a specific actuation and control system layout properly enabling two flap operational modes: overall camber morphing in deployed configuration, during take-off and landing, to enhance high lift performances; upwards and downwards deflection of the flap trailing edge (nearly the 10% of the local chord) in stowed configuration, to improve wing aerodynamic efficiency in cruise. For this purpose, a digital logic control law was opportunely implemented into controller devices by using LTI DriveManager® software. Obtained results have been presented in terms of controlled morphed shapes, showing an excellent correlation with respect to the target geometries imposed by design requirements

Preliminary failure analysis of an innovative morphing flap tailored for large civil aircraft applications

Aircraft wings are usually optimized for a specific mission design point. However, since they operate in a wide variety of flight conditions, some of these have conflicting impacts on aircraft design process, as a single configuration may be efficient in one instance but perform poorly in others. A shape-shifting surface, or usually referred as 'morphing', potentially enables transport aircraft to reach maximum performance in any flight conditions. Within the framework of the Joint Technology Initiative Clean Sky (JTI-CS) project, and during the first phase of the Green Regional Aircraft Integrated Technological Demonstration (GRA-ITD), the authors focused on the design and technological demonstration of an innovative bi-modal morphing outer wing flap to be installed on the next generation open rotor green regional aircraft. A novel active rib layout was designed to enable the articulation of the entire flap structure by means of multi-box arrangement. In order to prove structural load-carrying capabilities with the reference to a relevant environment, the full-scale morphing flap was properly analyzed by means of detailed finite element model analysis. To the authors' knowledge, there is no morphing concept in literature based on a similar architecture based on distributed servo-mechanical actuators. Hence, a rational review of the potential problems associated with actuators off-design conditions has been conducted to investigate the maturity of the concept and safety issues concerning the flap ground static test. In addition, useful insights have been provided to effectively detect potential failure conditions in service

Preliminary assessment of morphing winglet and flap tabs influence on the aeroelastic stability of next-generation regional aircraft

Future aircraft wing technology is rapidly moving toward flexible and morphing wing concepts capable to enhance aircraft wing performance in off-design conditions and to reduce operative maneuver and gust loads. However, dealing with reduced stiffness, increased mass, and increased degree of freedom (DOF), this kind of mechanical systems typically require dedicated aeroelastic assessments since the early design phases; this to mitigate the impact at aircraft level of any unconventional arrangement adopted for the conceptual design of the morphing mechanisms especially when they are installed in sensible regions such as the winglets and the wing trailing edge. Speaking about the latter, preliminary investigations have shown that the combined use with adaptive flap tabs allows a global improvement of aerodynamic performance of regional aircraft wings in climb and cruise conditions by the order of 3%. Additionally, by adapting span-wise lift distributions to reduce gust solicitations and to alleviate wing root bending moment at critical flight conditions, significant weight savings can also be achieved during aircraft wing design. Within the scope of Clean Sky 2 Airgreen 2 project, flutter and divergence characteristics of a morphing wing design are discussed, with specific reference to a configuration involving adaptive winglets and flap tabs. Multi-parametric flutter analyses are carried out in compliance with CS-25 airworthiness requirements (paragraph 25.629, parts (a), (b), (c) and (d)) to investigate static and dynamic aeroelastic stability behavior of the aircraft. The proposed kinematic systems are characterized by movable surfaces, each with its own domain authority, sustained by a structural skeleton and completely integrated with EMA-based actuation systems. For that purpose, a sensitivity analysis was performed taking into account variations of the stiffness and inertial properties of the referred architectures. Such layouts were reduced to a stick-equivalent model which properties were evaluated through MSC-NASTRAN-based computations. The proprietary code SANDY 4.0 was used to generate the aero-structural model and to solve the aeroelastic stability equations by means of theoretical modes association in frequency domain. Analyses showed the presence of critical modal coupling mechanisms in nominal operative conditions as well as in case of systems malfunctioning or failure. Design solutions to assure clearance form instabilities were then investigated. Trade-off flutter and divergence analyses were finally carried out to assess the robustness of the morphing architectures in terms of movable parts layout, mass balancing and actuators damping

Control strategy of an electrically actuated morphing flap for the next generation green regional aircraft

The design and application of adaptive devices are currently ambitious targets in the field of aviation research addressed at new generation aircraft. The development of intelligent structures involves aspects of multidisciplinary nature: the combination of compact architectures, embedded electrical systems and smart materials, allows for developing a highly innovative device. The paper aims to present the control system design of an innovative morphing flap tailored for the next generation regional aircraft, within Clean Sky 2 – Airgreen 2 European Research Scenario. A distributed system of electromechanical actuators (EMAs) has been sized to enable up to three operating modes of a structure arranged in four blocks along the chord-wise direction:  overall camber-morphing;  upwards/downwards deflection and twisting of the final tip segment. A state-of-art feedback logic based on a decentralized control strategy for shape control is outlined, including the results of dynamic stability analysis based on the blocks rational schematization within Matlab/Simulink® environment. Such study has been performed implementing a state-space model, considering also design parameters as the torsional stiffness and damping of the actuation chain. The design process is flowing towards an increasingly “robotized” system, which can be externally controlled to perform certain operations. Future developments will be the control laws implementation as well as the functionality test on a real flap prototype

Stress analysis of a morphing system

Morphing structures have the greatest potential to dramatically improve aircraft aerodynamic performance. They are designed to accomplish with a single device what conventional mechanisms can do with major aerodynamic penalties. In doing so, such systems have to be flexible enough to deliver the desired motion while ensuring a certain structural response under operative loads.In this chapter, focus is given to the structural design of morphing structures. The objective is to develop a generalized scheme, spanning from stress analysis to material selection, to design morphing devices that can morph one shape to another with minimum error. After a brief introduction, general design guidelines and practical tips are provided to ensure satisfactory mechanical structural performance and durability, with an overview of subcomponents and systems validation, design loads and simulation constraints. The application of this approach is demonstrated through an adaptive trailing edge device design example, including FE modeling, simulations and results assessment

Modal stability assessment for a morphing aileron subjected to actuation system failures: Numerical analysis supported by test evidence

The meaningful growth process and the exponential development related to aircraft industry has currently introduced new requirements concerning the fuel burn reduction and the noise emitted. The awareness on meeting the comfort targets implied a significant evolution of the assessments in aircraft design, aimed at reducing the problems that have emerged in empirical investigations. The aircraft renewal process involves targeted technical choices both to careful observance of safety as to the market requirements. In the current 'low-noise' research scenario on a global scale, the morphing technology is playing a dominant role for the many benefits available in the greening of the next generation air transport. The research project CRIAQ-MDO505, born by an intense synergy among industries, research centers and universities has allowed for investigating morphing structures potentials through the design and manufacturing of a variable camber aileron tailored for CS-25 category aircraft applications. In this framework, the authors focused on the setup of an advanced finite element model (FEM) and on its validation through ground resonance tests performed on a true-scale prototype. A very good correlation between numerical and experimental modal parameters was proven thus showing the adequacy of the adopted modelling strategies as well as the reliability of the FEM. Relying upon the validated FEM, sensitivity modal analyses were carried out to evaluate the stability of results with respect to single and combined failures of the actuation line enabling morphing. Modal parameters pertinent to each failure scenario were arranged into a rational database for further studies on the aero-servo-elastic behavior of the morphing system