Electronic/electric technology benefits study

The benefits and payoffs of advanced electronic/electric technologies were investigated for three types of aircraft. The technologies, evaluated in each of the three airplanes, included advanced flight controls, advanced secondary power, advanced avionic complements, new cockpit displays, and advanced air traffic control techniques. For the advanced flight controls, the near term considered relaxed static stability (RSS) with mechanical backup. The far term considered an advanced fly by wire system for a longitudinally unstable airplane. In the case of the secondary power systems, trades were made in two steps: in the near term, engine bleed was eliminated; in the far term bleed air, air plus hydraulics were eliminated. Using three commercial aircraft, in the 150, 350, and 700 passenger range, the technology value and pay-offs were quantified, with emphasis on the fiscal benefits. Weight reductions deriving from fuel saving and other system improvements were identified and the weight savings were cycled for their impact on TOGW (takeoff gross weight) and upon the performance of the airframes/engines. Maintenance, reliability, and logistic support were the other criteria

Advanced flight control system study

The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed

Integrated Application of Active Controls (IAAC) technology to an advanced subsonic transport project: Test act system description

The engineering and fabrication of the test ACT system, produced in the third program element of the IAAC Project is documented. The system incorporates pitch-augmented stability and wing-load alleviation, plus full authority fly-by-wire control of the elevators. The pitch-augmented stability is designed to have reliability sufficient to allow flight with neutral or negative inherent longitudinal stability

DISTRIBUTED ELECTRO-MECHANICAL ACTUATION AND SENSING SYSTEM DESIGN FOR MORPHING STRUCTURES

Smart structures, able to sense changes of their own state or variations of the environment they’re in, and capable of intervening in order to improve their performance, find themselves in an ever-increasing use among numerous technology fields, opening new frontiers within advanced structural engineering and materials science. Smart structures represent of course a current challenge for the application on the aircrafts. A morphing structure can be considered as the result of the synergic integration of three main systems: the structural system, based on reliable kinematic mechanisms or on compliant elements enabling the shape modification, the actuation and control systems, characterized by embedded actuators and robust control strategies, and the sensing system, usually involving a network of sensors distributed along the structure to monitor its state parameters. Technologies with ever increasing maturity level are adopted to assure the consolidation of products in line with the aeronautical industry standards and fully compliant with the applicable airworthiness requirements. Until few years ago, morphing wing technology appeared an utopic solution. In the aeronautical field, airworthiness authorities demand a huge process of qualification, standardization, and verification. Essential components of an intelligent structure are sensors and actuators. The actual technological challenge, envisaged in the industrial scenario of “more electric aircraft”, will be to replace the heavy conventional hydraulic actuators with a distributed strategy comprising smaller electro-mechanical actuators. This will bring several benefit at the aircraft level: firstly, fuel savings. Additionally, a full electrical system reduces classical drawbacks of hydraulic systems and overall complexity, yielding also weight and maintenance benefits. At the same time, a morphing structure needs a real-time strain monitoring system: a nano-engineered polymer capable of densely distributed strain sensing can be a suitable solution for this kind of flying systems. Piezoresistive carbon nanotubes can be integrated as thin films coated and integrated with composite to form deformable self-sensing materials. The materials actually become sensors themselves without using external devices, embedded or attached. This doctoral thesis proposes a multi-disciplinary investigation of the most modern actuation and sensing technologies for variable-shaped devices mainly intended for large commercial aircraft. The personal involvement in several research projects with numerous international partners - during the last three years - allowed for exploiting engineering outcomes in view of potential certification and industrialization of the studied solutions. Moving from a conceptual survey of the smart systems that introduces the idea of adaptive aerodynamic surfaces and main research challenges, the thesis presents (Chapter 1) the current worldwide status of morphing technologies as well as industrial development expectations. The Ph.D. programme falls within the design of some of the most promising and potentially flyable solutions for performance improvement of green regional aircrafts. A camber-morphing aileron and a multi-modal flap are herein analysed and assessed as subcomponents involved for the realization of a morphing wing. An innovative camber-morphing aileron was proposed in CRIAQ MD0-505, a joint Canadian and Italian research project. Relying upon the experimental evidence within the present research, the issue appeared concerns the critical importance of considering the dynamic modelling of the actuators in the design phase of a smart device. The higher number of actuators involved makes de facto the morphing structure much more complex. In this context (Chapter 2), the action of the actuators has been modelled within the numerical model of the aileron: the comparison between the modal characteristics of numerical predictions and testing activities has shown a high level of correlation. Morphing structures are characterized by many more degrees of freedom and increased modal density, introducing new paradigms about modelling strategies and aeroelastic approaches. These aspects affect and modify many aspects of the traditional aeronautical engineering process, like simulation activity, design criteria assessment, and interpretation of the dynamic response (Chapter 3). With respect the aforementioned aileron, sensitivity studies were carried out in compliance with EASA airworthiness requirements to evaluate the aero-servo-elastic stability of global system with respect to single and combined failures of the actuators enabling morphing. Moreover, the jamming event, which is one of the main drawbacks associated with the use of electro-mechanical actuators, has been duly analyzed to observe any dynamic criticalities. Fault & Hazard Analysis (FHA) have been therefore performed as the basis for application of these devices to real aircraft. Nevertheless, the implementation of an electro-mechanical system implies several challenges related to the integration at aircraft system level: the practical need for real-time monitoring of morphing devices, power absorption levels and dynamic performance under aircraft operating conditions, suggest the use of a ground-based engineering tool, i.e. “iron bird”, for the physical integration of systems. Looking in this perspective, the Chapter 4 deals with the description of an innovative multi-modal flap idealized in the Clean Sky - Joint Technology Initiative research scenario. A distributed gear-drive electro-mechanical actuation has been fully studied and validated by an experimental campaign. Relying upon the experience gained, the encouraging outcomes led to the second stage of the project, Clean Sky 2 - Airgreen 2, encompassing the development of a more robotized flap for next regional aircraft. Numerical and experimental activities have been carried out to support the health management process in order to check the EMAs compatibility with other electrical systems too. A smart structure as a morphing wing needs an embedded sensing system in order to measure the actual deformation state as well as to “monitor” the structural conditions. A new possible approach in order to have a distributed light-weight system consists in the development of polymer-based materials filled with conductive smart fillers such as carbon nanotubes (CNTs). The thesis ends with a feasibility study about the incorporation of carbon nanomaterials into flexible coatings for composite structures (Chapter 5). Coupons made of MWCNTs embedded in typical aeronautic epoxy formulation were prepared and tested under different conditions in order to better characterize their sensing performance. Strain sensing properties were compared to commercially available strain gages and fiber optics. The results were obtained in the last training year following the involvement of the author in research activities at the University of Salerno and Materials and Structures Centre - University of Bath. One of the issues for the next developments is to consolidate these novel technologies in the current and future European projects where the smart structures topic is considered as one of the priorities for the new generation aircrafts. It is remarkable that scientists and aeronautical engineers community does not stop trying to create an intelligent machine that is increasingly inspired by nature. The spirit of research, the desire to overcome limits and a little bit of imagination are surely the elements that can guide in achieving such an ambitious goal

Development of an Active Wingtip for Aeroelastic Control

This paper presents the design of an innovative wingtip device actively actuated to control the aeroelastic loads, with a focus on the gust load alleviation. It summarizes the work carried out in the Clean Sky 2 AIRGREEN2 project, where the device was developed from scratch and reached a relevant technology readiness level with the full-scale prototype manufacturing and testing, compulsory to obtain the permit to fly. This paper describes the overall design of the devices, covering the structure, the aero-servo-elasticity characteristics of the whole aircraft, the actuation system design, the scaled wind tunnel testing, and the full-scale structural qualification tests. The paper proves how the development of a new item involves several disciplines simultaneously, remarking on the importance of an integrated approach to the new generation aircraft design

Magnetorheological Fluids and Applications to Adaptive Landing Gear for a Lightweight Helicopter

During hard landing or crash events of a helicopter there are impact loads that can be injurious to crew and other occupants as well as damaging to the helicopter structure. Landing gear systems are the first in line to protect crew and passengers from detrimental crash loads. The main focus of this research is to improve landing gear systems of a lightweight helicopter. Magnetorheological fluids (MRFs) provide potential solutions to several engineering challenges in a broad range of applications. One application that has been considered recently is the use of magnetorheological (MR) dampers in helicopter landing gear systems. In such application, the adaptive landing gear systems have to continuously adjust their stroking load in response to various operating conditions. In order to support this rotorcraft application, there is a necessity to validate that MRFs are qualified for landing gear applications. First, MRF composites, synthesized utilizing three hydraulic oils certified for use in landing gear systems, two average diameters of spherical magnetic particles, and a lecithin surfactant, are formulated to investigate their performance for potential use in a helicopter landing gear. The magnetorheology of these MR fluids is characterized through a range of tests, including (a) magnetorheology (yield stress and viscosity) as a function of magnetic field, (b) sedimentation analysis using an inductance-based sensor, (c) cycling of a small-scale MR damper undergoing sinusoidal excitations (at 2.5 and 5 Hz), and (d) impact testing of an MR damper for a range of magnetic field strengths and velocities using a free-flight drop tower facility. The performance of these MR fluids was analyzed, and their behavior was compared to standard commercial MR fluids. Based on this range of tests used to characterize the MR fluids synthesized, it was shown that it is feasible to utilize certified landing gear hydraulic oils as the carrier fluids to make suitable MR fluids. Another objective of this research is to satisfy the requirement of a helicopter landing gear damper to enable adaptive shock mitigation performance over a desired sink rate range. It was intended to maintain a constant stroking force of 17 793 N (4000 lbf) over a sink rate range of 1.8-7.9 m/s (6-26 ft/s), which is a substantial increase of the high-end of the sink rate range from 3.7 m/s (12 ft/s), in prior related work, to 7.9 m/s (26 ft/s). To achieve this increase in the high-end of the sink rate range, a spiral wave spring-assisted passive valve MR landing gear damper was developed. Drop tests were first conducted using a single MR landing gear damper. In order to maintain the peak stroking load constant over the desired sink rate range, a bang-bang current control algorithm was formulated using a force feedback signal. The controlled stroking loads were experimentally evaluated using a single drop damper test setup. To emulate the landing gear system of a lightweight helicopter, an iron bird drop test apparatus with four spiral wave spring-assisted relief valves MR landing gear dampers, was fabricated and successfully tested. The effectiveness of the proposed adaptive MR landing gear damper was theoretically and experimentally verified. The bang-bang current control algorithm successfully regulated the stroking load at 4000 lbf over a sink rate range of 6-22 ft/s in the iron bird tests, which significantly exceeds the sink rate range of the previous study (6-12 ft/s). The effectiveness of the proposed adaptive MR landing gear damper with a spiral wave spring-assisted passive valve is theoretically and experimentally verified

Recent Progress in Some Aircraft Technologies

The book describes the recent progress in some engine technologies and active flow control and morphing technologies and in topics related to aeroacoustics and aircraft controllers. Both the researchers and students should find the material useful in their work

Full Scale Servo-Actuated Morphing Aileron for Wind Tunnel Tests

Typically, aircraft roll control is accomplished by simultaneously moving ailerons together and in opposite angular direction. Nevertheless, throughout the flying range, more particularly in cruise conditions, it is highly desirable to increase aircraft aerodynamic performance by a differential control of the lift distribution over the wing span. Recent European design studies concerning morphing devices, such as the Clean Sky multifunctional flap or the SARISTU trailing edge device, have largely proved the potential of novel aircraft structural systems, aiming at adaptively modify the wing structural shape to reduce the induced drag penalty associated with off-design flight conditions. In particular, wing camber variation was achieved through adaptive wing trailing edges because of the highly associated L/D ratio enhancements. Such projects proved also the aileron region to be the one where higher cruise benefits could be achieved by local camber variations. Following the enthusiastic results, achieved with the Adaptive trailing edge device, a new challenge has been faced up. The former configuration did in fact refer to the standard position of the flap, leaving apart the aileron region. There are several reasons to leave that part unchanged. The most relevant may be associated to the fact that the aileron has a critical function in the aircraft flight and its collapse could lead to dramatic failures. The investigated configuration would have lied over an extended region of the aileron instead than a limited part, as in the case of a flap, characterised by a large chord. As a direct consequence, the available volumes are reduced and the installation of integrated actuators could have been a problem. Finally, the aeroelastic response of the device is critical as well and its strong modification should have been deeply studied. On the other hand, the studies on the ATED showed as the region, farer from the root, gave a more significant contribution to the aerodynamic behaviour. So, it was really interesting to investigate the possibility to extend the adaptive trailing edge technology to the aileron region. The occasion was given by a joint Italian/Canadian research activity fostered by the Consortium de Recherche et d’Innovation en Aerospatiale au Quebec (CRIAQ). The activity aimed at realising a full-scale demonstrator of a wing section in the tip region for investigating the capability of wing box and trailing edge morphing device, to ensure a certain level of flow control and aerodynamic performance variations, respectively. The first issue was in charge of the Canadian team (ETS, NRC, Thales Aerospace, Bombardier AS), while the Italian group (University of Naples and CIRA) aimed at realising a device for the aileron camber control. The enlisted problems were all evident at the very first approach. Volume limitation forced the designers to follow a different strategy. Instead of having a couple of actuators acting on each rib, the architectural layout was specialised per each single bay. At the aileron root this possibility was maintained, while the more external two bays were commanded by a single actuator. In other words, the last two segments were made of two slave and a master ribs, driven by a single actuator. Calculation showed as this configuration was able to maintain the specified loads. Aeroelastic studies confirmed the reliability of the device, in sense that the selected architecture was demonstrated to be safe in the design flight conditions. The adaptive aileron finally maintained the original capability while ensuring morphing characteristic. This target was accomplished by realising a device with two separate motor system. The first, acting on the main aileron shaft, to preserve its characteristic dynamic response for flight control. The second, acting on the rib, implemented the searched camber variations to follow the aerodynamic necessities related to fuel consumption. Another relevant point concerns the skin. In order to check the possibility of skipping the need of implementing a compliant solution, a heavy and sophisticated element, the single hinged blocks were properly shaped to slide one into the other like a meniscus. This solution was however strongly correlated to manufacture tolerances and the assembly precision, because small deviation could have had a significant impact on the kinematic performance. As usual, vantages and disadvantages try to compensate each other. The innovative device can be considered as a system with augmented capabilities aimed at working in cruise, by means of symmetric deflection, to obtain a near optimum wing geometry enabling optimal aerodynamic performance. The approach, including underlying concepts and analytical formulations, combines design methodologies and tools required to develop such an innovative control surface. A major difficulty in the development of morphing devices is to reach an adequate compromise between high load-carrying capacity to withstand aerodynamic loads and sufficient flexibility to achieve the target shapes. These targets necessitate the use of innovative structural and actuation solutions. When dealing with adaptive structures for lifting surfaces, the level of complexity naturally increases as a consequence of the augmented functionality of the designed system. In specific, an adaptive structure ensures a controlled and fully reversible transition from a baseline shape to a set of different configurations, each one capable of withstanding the associated external loads. To this aim, a dedicated actuation system shall be designed. In addition, the adopted morphing structural kinematics shall demonstrate complete functionality under operative loads. Such a morphing device wants to augment the former device by adapting local wing camber shape and lift distribution through a quasi-static deflection, its excursion ranging into few unit of degrees, positive and negative. In a morphing aircraft design concept, the actuated system stiffness, load capacity and integral volumetric requirements drive flutter, strength and aerodynamic performance. Design studies concerning aircraft flight speed, manoeuvre load factor and actuator response provide sensitivities in structural weight, aeroelastic performance and actuator flight load distributions. Based on these considerations, actuation mechanism constitutes a very fundamental aspect for adaptive structures design because the main prerequisite is to accomplish variable shapes within the physical constraints established by the appropriate actuation arrangement. This thesis addresses the design of a morphing aileron with a specific focus on the structural actuation system sizing and integration while the structural sizing was under Unina responsibility. Particular focus is given to the numerical validation of the entire aileron integrated with the actuation leverage by means of FE model and experimental tests campaign. The aileron actuation system is driven by load bearing servo-electromechanic rotary actuator in a distributed and un-shafted arrangement which combine load carrying and actuation capacities. The use of electro-mechanical actuators is coherent with a “more electric approach” for next-generation aircraft design. Such an actuation architecture allows the control of the morphing structure by using a reduced mass, volume, force and consumed power with respect to conventional solutions. Benefits are obvious. No hydraulic supply buses (easier to maintain and store without hydraulics leaks), improved torque control, more efficiency without fluid losses and elimination of flammable fluids. In addition, it is potentially possible to move individual ribs either synchronously or independently to different angles (twist) in order to enhance aerodynamic benefits during flight. On the other side, actuators susceptibility to jamming may represent the most important drawback that can be tested and prevented by means of an iron bird facility. Finally, the realised system was assembled onto a wing model and tested in a wind tunnel at the National Research Council (NRC) facilities in Ottawa (CAN). On the same model, the adaptive wing box was also installed. The adaptive aileron device proved its functionality in real flow conditions and the main aerodynamic results are herein presented and widely described. The developed device has a lot of further potentialities, that will be object of further works and publications and that are currently explored by the authors: for instance, by giving it a large bandwidth, it could be used as an additional load alleviation device for the outer wing in order to reduce peak loads for gusts. Moreover it can be tailored for active load control distribution in order to modify spanwise lift distribution obtaining a reduced wing root bending moment; in such a manner a lightweight design can be assessed

Design and development of a structural mode control system

A program was conducted to compile and document some of the existing information about the conceptual design, development, and tests of the B-1 structural mode control system (SMCS) and its impact on ride quality. This report covers the following topics: (1) Rationale of selection of SMCS to meet ride quality criteria versus basic aircraft stiffening. (2) Key considerations in designing an SMCS, including vane geometry, rate and deflection requirements, power required, compensation network design, and fail-safe requirements. (3) Summary of key results of SMCS vane wind tunnel tests. (4) SMCS performance. (5) SMCS design details, including materials, bearings, and actuators. (6) Results of qualification testing of SMCS on the "Iron Bird" flight control simulator, and lab qualification testing of the actuators. (7) Impact of SMCS vanes on engine inlet characteristics from wind tunnel tests

Alternate avionics system study and phase B extension

Results of alternate avionics system studies for the space shuttle are presented that reduce the cost of vehicle avionics without incurring major off-setting costs on the ground. A comprehensive summary is provided of all configurations defined since the completion of the basic Phase B contract and a complete description of the optimized avionics baseline is given. In the new baseline, inflight redundancy management is performed onboard without ground support; utilization of off-the-shelf hardware reduces the cost figure substantially less than for the Phase B baseline. The only functional capability sacrificed in the new approach is automatic landing