Large Civil Aircraft Research Articles

Optimization of aircraft remote power distribution unit placement using linear programming to decrease the wire weight

The modern large civil aircraft has the trend to utilize the remote distribution network. This paper presents an optimization concept for this distribution network to optimize remote power distribution unit placement in aircraft to decrease the wire weight. A model formulation has been created to minimize the total wire weight. The length of wire was calculated approximately by the different longitinal axis of center of gravity of wire ends. To solve the wiring weight reduction problem, the loads are selected to connect to specific remote power distribution unit which position is close, then model formulation has been transformed to the linear programming algorithm. In order to validate the concept a simulation model and different calculation case have been built. The calculation results show the method can decrease wires weight in remote power distribution system and has shown high benefits.

Dynamic simulation of complex multi-hinge space flap mechanism

Dynamics simulation of large civil aircraft complex multi-hinge space flap mechanism was studied, and a set of dynamics simulation modeling method of complex multi-hinge space flap mechanism based on Motionview was proposed. Firstly, a moving digital prototype of the complex multi-hinge space mechanism was constructed. The multi-point constraint RBE3 element was used to associate the intersection points of the rigid multi-hinge mechanism to the body of the flap surface considering flexibility, and the rigid-flexible coupling dynamic model of the flap mechanism was formed. The dynamics simulation of the mechanism was carried out under the aerodynamic load conditions of cruise, take-off and landing, the driving torque and hinge point load dynamics indexes of the complex multi-hinge space flap mechanism were obtained. The simulation results show that the driving arm of the inner mechanism bears most of the lateral load from the flap wing surface, the radial direction of the joints bearing at each hinge bears the aerodynamic pulling force from the flap wing surface. And the inner mechanism of the flap is the main bearing part, the load capacity of the inner rocker arm is almost four times that of the outer rocker arm. The dynamic simulation research can provide a certain reference for the design and improvement of the complex multi-hinge space flap mechanism.

Synthesis analysis of electric propulsion implement in large civil aircraft

Abstract With more and more concerns of carbon emission reduction in civil aviation, this article aims to illustrate the current development and product of electric propulsion in civil aviation, also to investigate the feasibility and benefit of electric propulsion implement on large civil aircraft. In order to achieve this objective, a single aisle passenger airliner concept with electric propulsion was designed and trade-studied. There are both advantages and disadvantages of different energy architecture such as Turbine generator, APU generator, Lithium battery and Hydrogen fuel cell system. As the practical energy density of lithium battery is much lower than needed, considering the current situation and development potential, fuel cell with liquid hydrogen are most possibly used as the main power source in future large civil aircraft.

A human hybrid tracking and localization method for mixed reality simulation of complex system

In order to obtain stable and high-precision motion tracking in mixed reality (MR) simulation of the complex system, an optical-inertial hybrid tracking method is proposed, which combines the accuracy of optical motion capture equipment and the robustness of inertial motion capture equipment, and can reduce the occlusion problem of entity scene on the premise of ensuring the localization accuracy. The method has been applied to the ergonomic evaluation of large civil aircraft development processes, and the effectiveness and usability of the method have been verified.

Initial airworthiness requirements for aircraft electric propulsion

PurposeThe purpose of this paper is to analyze the electric propulsion use in civil aviation and propose a framework for certification of electric propulsion subsystems. Although electric propulsion architectures are discussed as key technology for the future of aviation, the industry standards as well as regulations fail to cover the application in full extent, specifically for commercial large airplanes. This paper proposes an approach for the analyses of reliability and certification of the new-generation propulsion system by pointing out the “common structure” among the possible architectures.Design/methodology/approachThe research process used in this paper consists of following steps: the challenges of the hybrid-electric propulsion is listed, the architectures of the hybrid-electric applications in the literature are identified, the differences of the hybrid architectures from the present applications by means of application and standardization are discovered, the architectures are analyzed and the two main subsystems are defined – the present combustion system and the common unit, which is a similar structure used in all-electric aircraft. For this purpose, the standards used for design basis and certification of the present propulsion system and their relationship with the subsystems of the architectures have been analyzed. The procedure for the reliability assessment of the system is given, a framework for the safety assessment and the certification of the propulsion systems is proposed to make it easier and without sacrificing the already accumulated experience. This study shows that by using the common unit, the present certification framework can be used, by focusing on the reliability of the common unit and its integration with the rest of the architecture.FindingsA specific definition of common unit is proposed, to point out the difference in certification efforts of hybrid-electric propulsion architectures. Yet, there is no data available for propulsion-level airborne battery and electrical systems to assess the reliability. Thus, dividing the propulsion system into two main systems and providing a model for certification of the common unit sub-system would be beneficial for easy deployment of the hybrid architectures both for design and for certification. In this paper, it is proposed that by using this common unit, the present certification framework can be used as it is, by focusing on the reliability of the common unit and its integration with the rest of the architecture.Practical implicationsThe aircraft certification regulations act in two ways: they provide a starting point for new design projects, and they are a basis for certification of the final system. This study aims to draw focus on certification issues on the new-generation hybrid-electric propulsion systems. With the introduction of hybrid-electric propulsion for large aircraft, the present standards (CS-25, CS-E, CS-P, CS-Battery and CS-APU) create an obstacle for further progress as their borders get into each other. Instead of developing a new set of standard(s), this paper proposes a new approach by dividing the propulsion system into two subsystems.Originality/valueThis research proposes a definition of “common unit” for simplification of the hybrid-electric propulsion architectures for large civil aircraft. The common unit consists of both battery and electrical components and their reliability shall be considered for hybrid-electric propulsion.

Multi-objective aerodynamic optimization design of variable camber leading and trailing edge of airfoil

Variable camber is an effective method for improving the flight efficiency of large aircraft, and has attracted the attention of researchers. This work focused on the optimization of a variable camber airfoil. First, the influences of the variable camber of the leading and trailing edges on the airfoil aerodynamic performance were investigated using a computational fluid dynamics numerical simulation. An initial database was established for a deep neural network. Second, an iterative algorithm was constructed to optimize the variable camber airfoil in terms of the rotation angle of the leading edge, deflection position of the leading edge, rotation angle of the trailing edge, and deflection position of the trailing edge. A genetic algorithm was used in each iteration to maximize the lift coefficient and lift-to-drag ratio, as predicted using a deep neural network (DNN). The optimal results were validated using Fluent. If the DNN result approximated the Fluent results, the iterative process was stopped. Otherwise, the Fluent results were inserted into the database to update the DNN prediction model. The optimization results showed that the lift-to-drag ratio of the 2D airfoil could be increased by more than 14 when the angle of attack was less than 8° relative to the original airfoil. Furthermore, to validate the 2D optimal results, the optimized 2D airfoil was stretched into 3D, and it was discovered that the aerodynamic performance trend of the 3D airfoil with respect to the angle of attack was basically the same as that of the 2D airfoil. In addition, the corresponding 3D airfoil improved the aerodynamic performance and reduced the noise at a high frequency (by approximately 16 dB). In contrast, the noise in the low and medium frequencies remained unchanged. Therefore, the optimization method and results can provide a reference for the aerodynamic design and acoustic design of large civil aircraft wings.

Motion synchronization for the SHA/EMA hybrid actuation system by using an optimization algorithm

The current research develops a mathematical model and control strategies to address two major problems force fighting and precise position tracking for a hybrid actuation system composed of servo-hydraulic actuator and electro-mechanical actuator (SHA/EMA). The force fighting and desired position tracking are two essential problems of the SHA/EMA actuation system for a large civil aircraft. The trajectory-based fractional order proportional integral derivative (FOPID) control for the SHA/EMA actuation system is proposed, tuned with the help of the particle swarm optimization (PSO) technique and implemented with the support of the FOMCON toolbox in Matlab. The experiments are performed under different external aerodynamic loads that the aircraft usually experiences during flight operations. The results show that the proposed method shows better results for tracking performance, force fighting and load rejection ability.

Making Sense of the Arbitrator's Ruling in DS 316, EC and Certain Member States – Measures Affecting Trade in Large Civil Aircraft (Article 22.6-EC): A Jigsaw Puzzle with (at Least) a Couple Missing Pieces

Abstract‘The US won a $7.5 Billion award from the World Trade Organization against the European Union, who has for many years treated the USA very badly on Trade due to Tariffs, Trade Barriers, and more. This case going on for years, a nice victory’, tweeted President Trump on 3 October 2019. The United States (US) won not only the highest amount of retaliation ever adjudicated in the history of the WTO but also an ongoing right to retaliate on an annual basis until such time as the EU had complied by either removing the subsidies it granted Airbus or somehow neutralizing their adverse effects on Boeing. In light of the facts of the case, this ruling has two major shortcomings. First, in sharp contrast with the statutory language and practice until now, the Arbitrator effectively introduced a permanent liability rule into the WTO system through the backdoor. Second, given the way the decision and the associated award has been written, it is simply impossible for the EU to comply because (a) the contested subsidies are no longer in existence and (b) no guidance has been provided on how the EU might go about removing their adverse effects on Boeing if it sought to achieve compliance. Thus, in all likelihood, the EU is saddled with a ruling that obligates it to cough up an annual sum of $7.5 billion USD for an indefinite time period.

Article 21.5 DSU Appellate Body Report United States – Measures Affecting Trade in Large Civil Aircraft (Second Complaint): Spillovers from Defense R&D Add to the Tug-of-War between Panels and the WTO Appellate Body

AbstractThe March 2019 release of the Appellate Body's compliance report in United States – Measures Affecting Trade in Large Civil Aircraft (Second Complaint) marks yet another chapter in the ongoing Boeing–Airbus dispute. While raising numerous new and old subsidy issues, this paper focuses on one specific aspect, the evaluation of the financial contributions and benefits associated with the Department of Defense (DOD) R&D procurement contracts. The paper describes the differing views taken by the panels compared to the Appellate Body. It highlights two issues that led to an extremely lengthy proceeding: (1) the black or white nature of the decision regarding the characterization of contracts which have features of both purchases of services and joint ventures; and (2) the difficulty in demonstrating a financial contribution flowing from payments for R&D for military systems to Boeing's civil aircraft production. It concludes that this case represents a failure of the WTO dispute settlement system and underscores flaws in the ASCM in that after fifteen years of litigation, no determination was made as to whether or not the DOD R&D contracts examined here constituted impermissible subsidies.

Structural health monitoring of aerospace sandwich structures via strain measurements along zero-strain trajectories

This paper investigates a strain-based structural health monitoring (SHM) method for damage detection and localization in composite sandwich structures. As case example, an idealized aircraft spoiler of a large civil aircraft is considered. Critical failure modes of such sandwich structures composed of fiber reinforced polymer (FRP) face layers and a honeycomb core are, e.g., face layer delamination and debonding from the core. The latter challenges today’s non-destructive testing methods, and thus, shall be addressed in the present work. The presented research compromises an idealized spoiler model of the real spoiler structure in the scale 1:2. The model is composed of glass fiber reinforce polymer (GFRP) face layers and a honeycomb core. The damage identification is investigated based on static strain measurements along so-called zero-strain trajectories (ZST) at the loaded structure. A zero-strain direction exists for every plane strain state with major strain directions with opposite signs (tensile and compression). Connecting zero-strain direction vectors at various points of a structure yields a ZST. Strains along ZST are most sensitive to changes of the load path due to, e.g., damage. This work investigates the use of strain measurements along ZST for damage detection at the edge of the considered sandwich structure by means of numerical and experimental analysis. A real wind-load condition of a large civil aircraft spoiler is considered as load case. An in-depth numerical and experimental investigation is performed to calculate the ZST for the pristine structure. The experimental validation of the Finite element (FE) model is realized by deformation measurements via a digital image correlation system (DIC). Moreover, strain measurements via strain gauge (SG) rosettes were performed to evaluate the correct calculation of the zero-strain directions. Finally, the application of strain measurements along a ZST for debonding detection and localization is demonstrated and its potential and issues for real online monitoring is discussed.

Research on mission characteristics-based evaluation model of flight test workload

As a product of modern industrial cutting-edge technology, a large civil aircraft needs to undergo rigorous flight test before entering the aviation market, which fully ensures the safety of aircraft and its system. This makes the aircraft meet the airworthiness standards and requirements. The flight test of civil aircraft is a complex system project, which the top-level planning throughout the flight test period has an important influence on progress control and flight test efficiency of a new type aircraft. The core content of the top-level plan is the evaluation of flight test workload with consideration of test aircraft quantity. This paper proposes a flight test workload analysis and evaluation model based on the types of test missions through the analysis of the characteristics of civil aircraft flight test mission, which provides a feasible method for quantitative evaluation of flight test workload.

Using shock control bumps to improve engine intake performance and operability

AbstractShock control bumps can be used to control and weaken the shock waves that form on engine intakes at high angles of attack. In this paper, it is demonstrated how shock control bumps applied to an engine intake can reduce or eliminate shock-induced separation at high incidence, and also increase the incidence at which critical separation occurs. Three-dimensional Reynolds-average Navier–Stokes (RANS) simulations are used to model the flow through a large civil aircraft engine intake at high incidence. The variation in shock strength and separation with incidence is first studied, along with the flow distribution around the nacelle. An optimisation process is then employed to design shock control bumps that reduce shock strength and separation at a fixed high incidence condition. The bump geometry is allowed to vary in shape, size, streamwise position and circumferential direction around the nacelle. This is shown to be key to the success of the shock control geometry. A further step is then taken, using the optimisation methodology to design bumps that can increase the incidence at which critical separation occurs. It is shown that, by using this approach, the operating range of the engine intake can be increased by at least three degrees.

Research on Aircraft/Engine Integrated Method of Civil Aircraft Products Development Oriented to System Engineering

This research proposes an aircraft/engine integrated design system construction method for civil aircraft based on system engineering oriented to large civil aircraft airworthiness certification. The aircraft/engine integrated design system of civil aircraft based on the “mapping model” highlights the logical completeness of the development evidence. This research contains two types of core design evidence: 1) design data of aircraft/engine integrated system; 2) aircraft/engine integrated system confirming and verifying data. The mapping model corresponds to the constraints of airworthiness regulations on the aircraft/engine integrated system design in three aspects: requirements analysis and confirmation, functional design, and design execution and verification, which promotes design data and airworthiness compliance evidence build in parallel.

Stable Inversion Based Fault-tolerant Trajectory Tracking Control of Civil Aircrafts Autolanding

This paper deals with aircraft autoland control in the presence of wind disturbances and actuator faults. To solve this problem, a fault-tolerant trajectory tracking controller is presented to autoland a commercial aircraft. Firstly, the dynamics models of the aircraft with faults and winds are built. Secondly, the stable inversion based fault-tolerant autolanding control architecture is proposed. The stable inversion control is used to improve output tracking precision. The H_∞ control is applied for robust stability against uncertainties caused by wind disturbances and the faults. Compare with common fault-tolerant autolanding control, the stable inversion based fault-tolerant autolanding control has more robust capability including stabilizing the non-minimum phase system. Finally, two scenario simulations are carried out for automatic landing control of a large civil aircraft under winds and elevator failures. The results indicate that the proposed stable inversion based fault-tolerant autolanding controller has better tracking performances than those of the stable inversion control and fault-tolerant autolanding control, even in control surface faults and large winds.

Research on Variable Sweepback Angle of Winglet Driven by Shape Memory Alloy

Because of its shape memory effect, shape memory alloy (SMA), as a driver, provides more possibilities for the design and optimization of winglets of variable sweepback angle. In view of three different flight states of a large civil aircraft, i.e. take-off, cruise and landing, the effects of different winglets of variable sweepback angle on the aerodynamic performance of the aircraft are analyzed by computational fluid dynamics (CFD), and then the optimal sweepback angles are 35°, 45° and 50° respectively. Based on the change of the sweepback angle of winglets in different flight states, a variable sweepback winglet structure based on SMA wire is designed. Combined with SMA constitutive relation, SMA driving mechanism is designed by the coupling method of force, heat and strain. The mechanism can automatically adjust the swept angle of winglets according to different flight conditions, so as to improve the lift drag ratio of wings.

Morphing wing flaps for large civil aircraft: Evolution of a smart technology across the Clean Sky program

Morphing wing structures are widely considered among the most promising technologies for the improvement of aerodynamic performances in large civil aircraft. The controlled adaptation of the wing shape to external operative conditions naturally enables the maximization of aircraft aerodynamic efficiency, with positive fallouts on the amount of fuel burned and pollutant emissions. The benefits brought by morphing wings at aircraft level are accompanied by the criticalities of the enabling technologies, mainly involving weight penalties, overconsumption of electrical power, and safety issues. The attempt to solve such criticalities passes through the development of novel design approaches, ensuring the consolidation of reliable structural solutions that are adequately mature for certification and in-flight operations. In this work, the development phases of a multimodal camber morphing wing flap, tailored for large civil aircraft applications, are outlined with specific reference to the activities addressed by the author in the framework of the Clean Sky program.The flap is morphed according to target shapes depending on aircraft flight conditions and defined to enhance high-lift performances during takeoff and landing, as well as wing aerodynamic efficiency during cruise. An innovative system based on finger-like robotic ribs driven by electromechanical actuators is proposed as morphing-enabling technology; the maturation process of the device is then traced from the proof of concept to the consolidation of a true-scale demonstrator for pre-flight ground validation tests. A step-by-step approach involving the design and testing of intermediate demonstrators is then carried out to show the compliance of the adaptive system with industrial standards and safety requirements. The technical issues encountered during the development of each intermediate demonstrator are critically analyzed, and justifications are provided for all the adopted engineering solutions. Finally, the layout of the true-scale demonstrator is presented, with emphasis on the architectural strengths, enabling the forthcoming validation in real operative conditions.

United States – Measures Affecting Trade in Large Civil Aircraft – Second Complaint – Recourse to Article 21.5 of the DSU by the European Union (US – Large Civil Aircraft (2nd Complaint) (Article 21.5 – EU)), DS353

This compliance proceeding under Article 21.5 of the Dispute Settlement Understanding (DSU) concerned measures adopted by the United States to comply with the Dispute Settlement Body (DSB) recommendations and rulings in US–Large Civil Aircraft (2nd Complaint). The types of measures at issue that were found to have caused adverse effects to the European Union (EU, formerly European Communities) in the original Panel and Appellate Body proceedings were NASA aeronautics R&D instruments; United States Department of Defence (DOD) military research instruments (‘assistance instruments’); the business and occupancy (B&O) tax rate reduction in the State of Washington in relation to Boeing's production of the 787; property and sales tax abatements related to Industrial Revenue Bonds issued by the City of Wichita, Kansas; and the FSC/ETI subsidies.

Perturbation Analysis and Control of Mach Number 2.4-Meter Transonic Wind Tunnel

Because of the large domestic civil aircraft projects started in China a decade ago, there is a greater need to control the accuracy of the Mach number in aerodynamic tests, especially near the designed cruise point of large commercial aircraft. Nowadays the control accuracy of China Aerodynamics Research and Development Center 2.4-meter transonic wind tunnel Mach number is in the range of to when , which is far from the measurement accuracy of drag coefficient required for testing advanced aircraft. This value should result in a better-than-one drag count. As a consequence, it is imperative to improve the control accuracy of Mach number urgently. The nonlinearity, large time delays, and strong coupling of wind tunnel flowfield control, along with the variation of the model angle of attack, could cause the Mach number to deviate from the expected value. To solve these problems, a model predictive control method based on dynamic matrix control algorithm is proposed. This method builds a prediction model based on step response test. The accuracy of Mach number predictive control can be efficiently improved by performance optimization in the form of vector norms, rolling optimization, and feed-forward compensation. This control strategy has been successfully tested in the wind tunnel, and the control accuracy of Mach number has been remarkably enhanced, to the point where it can be controlled to within . This value satisfies the requirements of aerodynamic aircraft testing.

‘Flying High in a Plane’ Appellate Body Report, European Communities and Certain Member States – Measures Affecting Trade in Large Civil Aircraft

AbstractThis article reviews the Appellate Body decision in the implementation phase of the EC–Aircraft dispute. Focusing on some of the key findings, we assess whether they are legally and economically correct. We conclude that (a) though still unclear, the test for establishing de facto contingency on import substitution subsidies is probably too demanding; (b) though legitimate, the interpretation of the remedy of removal of the adverse effects for actionable subsidies is the weakest and most deferential possible; (c) the hesitation in confirming that quantitative methods are the key tool to define the relevant market is unwelcome; and (d) the Appellate Body correctly recognize the importance for Panels to consider, in the context of the serious prejudice analysis, whether the like product of the complainant has been subsidized. Most importantly, the analysis of this case, set within the broader jurisprudence and practice, has led us to conclude that WTO subsidy disciplines are not particularly strong. The review of the main economic theories justifying subsidy control (strategic trade policy, terms of trade, private information, commitment theory) has shown that no single theory is able to fully account for subsidies and the need to control them. The key question is the definition of what we want to achieve by controlling subsidies, which is the main message sent to the policy-makers and negotiators that are currently considering law reform.

LPV robust servo control of aircraft active side-sticks

PurposeThis paper aims to focus on the variable stick force-displacement (SFD) gradience in the active side stick (ASS) servo system for the civil aircraft.Design/methodology/approachThe problem of variable SFD gradience was introduced first, followed by the analysis of its impact on the ASS servo system. To solve this problem, a linear-parameter-varying (LPV) control approach was suggested to process the variable gradience of the SFD. A H∞ robust control method was proposed to deal with the external disturbance.FindingsTo validate the algorithm performance, a linear time-variant system was calculated to be used to worst cases and the SFD gradience was set to linear and non-linear variation to test the algorithm, and some typical examples of pitch angle and side-slip angle tracking control for a large civil aircraft were also used to verify the algorithm. The results showed that the LPV control method had less settling time and less steady tracking errors than H∞ control, even in the variable SFD case.Practical implicationsThis paper presented an ASS servo system using the LPV control method to solve the problem caused by the variable SFD gradience. The motor torque command was calculated by pressure and position feedback without additional hardware support. It was more useful for the electronic hydraulic servo actuator.Originality/valueThis was the research paper that analyzed the impact of the variable SFD gradience in the ASS servo system and presented an LPV control method to solve it. It was applicable for the SFD gradience changing in the linear and non-linear cases.