Large Aircraft Research Articles

Experimental Study on Wave Motion Response Characteristics of Large Amphibious Aircraft

To master the motion response of an amphibious aircraft under regular waves of drifting and anchoring, a 1:8.5 scaled model test of an amphibious aircraft under regular waves was carried out, and the test device and acquisition method were designed. Through experiments, the wave response characteristics of the drifting and anchoring states were obtained, which provided technical support for the design of the IRS initial alignment algorithm for large amphibious aircraft.

Differences in large aircraft design between military and civil perspectives

Military transport aircrafts and civil aircrafts are important parts of the aviation field. With the development of aviation technology and the specificity of aircraft functions, the design of military transport aircraft and civil aircraft gradually differs according to application scenarios. However, in the aircraft design, military transport aircrafts and civil aircrafts still have a lot of mutual references. Analyzing the differences between them and the reasons for the differences may contribute to the design and development of military transport aircraft and civil aircraft in the future, and provide reference suggestions for the design of civil aircraft in the context of the civil-military integration. In this article, the application scenarios and functions of military transport aircraft and civil aircraft are analyzed, as well as the special situation of civil aircraft research and development. This article may offer a reference for the future research and development of military transport aircraft and civil aircraft.

Structural design and experimental study on the axial compression behavior of large-span carbon-fiber-reinforced polymer truss structures

Herein – with the optimization goals of a lightweight, large-span structure; modularization; and heavy loading – a tapered-section truss module and standard truss module are integrated and assembled, yielding a new design for an all-carbon-fiber-reinforced polymer (CFRP) truss structure. The design structure fully considers the mechanical characteristics of the truss and the requirements of standardized production efficiency, integrating the “fish keel” structural design method to give it a hollow structure style. By fabricating two 1:1 truss structures (A-Truss and B-Truss) with a length of 20.4 m, the conceptual design, modular design method, and integrated assembly technology of the truss structure were effectively verified; further, experimental research on the strength performance of the mold-clave-forming plate-type joint and the axial compression behavior of large-span full CFRP truss structure is carried out. The failure position of the truss structure is determined, and an enhancement measure for the key connection joint between the truss modules is proposed. Based on specific application scenarios, it is clear that the truss meets the design requirements in terms of bearing capacity and deformation, and can be used as the main bearing structure of large aircraft and aerospace assembly platforms.

Analysis of the Application and Benefits of Aircraft Electric Wheel Systems during Taxi and Take-Off

An electric wheel hybrid power system is designed for driving a large single-aisle passenger aircraft during the take-off and ground taxi phases, which consists of an APU, an energy storage system, and a motor. In the taxi phase, the electric wheel hybrid power system works alone, and the turbofan engine does not work, reducing fuel consumption and pollution emissions. During the take-off rolling phase, the electric wheel hybrid power system and turbofan engine work together to reduce the thrust requirement of the turbofan engine. This article establishes an aircraft kinematic model, hybrid power system model, and a mechanical wheel model. The feasibility of the collaborative work of the electric wheels and the turbofan engines is verified by simulations. By utilizing the established hybrid system of electric motor wheels, the fuel consumption can be reduced, and the emissions of CO, HC, and NOX can also be diminished to varying degrees. The input of motor power leads to lower turbine inlet temperature, thereby enhancing the turbofan engine’s service life by approximately 4.3% and saving operational costs.

Design of a large-scale model for wind tunnel test of a multiadaptive flap concept

The design and application of morphing systems are ongoing issues compelling the aviation industry. The Clean Sky - program represents the most significant aeronautical research ever launched in Europe on advanced technologies for greening next-generation aircraft. The primary purpose of the program is to develop new concepts aimed at decreasing the effects of aviation on the environment, increasing reliability, and promoting eco-friendly mobility. These ambitions are pursued through research on enabling technologies fostering noise and gas emissions reduction, mainly by improving aircraft aerodynamic performances. Within the Clean Sky framework, a multimodal morphing flap device was designed based on tight industrial requirements and tailored for large civil aircraft applications. The flap is deployed in one unique setting, and its cross section is morphed differently in take-off and landing to get the necessary extra lift for the specific flight phase. Moreover, during the cruise, the tip of the flap is deflected for load control and induced drag reduction. Before manufacturing the first flap prototype, a high-speed (Ma = 0.3), large-scale test campaign (geometric scale factor 1:3) was deemed necessary to validate the performance improvements brought by this novel system at the aircraft level. On the other hand, the geometrical scaling of the flap prototype was considered impracticable due to the unscalability of the embedded mechanisms and actuators for shape transition. Therefore, a new architecture was conceived for the flap model to comply with the scaled dimensions requirements, withstand the relevant loads expected during the wind tunnel tests and emulate the shape transition capabilities of the true-scale flap. Simplified strategies were developed to effectively morph the model during wind tunnel tests while ensuring the robustness of each morphed configuration and maintaining adequate stiffness levels to prevent undesirable deviations from the intended aerodynamic shapes. Additionally, a simplified design was conceived for the flap-wing interface, allowing for quick adjustments of the flap setting and enabling load transmission paths like those arising between the full-scale flap and the wing. The design process followed for the definition of this challenging wind tunnel model has been addressed in this work, covering the definition of the conceptual layout, the numerical evaluation of the most severe loads expected during the test, and the verification of the structural layout by means of advanced finite element analyses.

Investigating the potential of parallel hybrid-electric retrofit of narrow-body airliner for emission reduction

Due to the high power and energy demands of large aircraft and low energy density of batteries, parallel hybrid-electric propulsion (HEP) is an in-between solution to reduce carbon emissions instead of full-electric propulsion. Considering the long in-service time, parallel HEP retrofit of existing large commercial or transport aircraft is favorable for technical risks and economic values. To enhance the reliability of the analysis, a comprehensive parallel HEP retrofit study of a narrow-body airliner is carried out in this paper. At first, efficient and accurate aerodynamic and engine deck surrogate models are built to include multidisciplinary impacts. To capture the off-design performance, a detailed flight mission is modeled based on exact flight dynamic equations, which is solved in a time-stepping manner. Then, the hybridization levels and battery usage strategy are thoroughly investigated. Besides, fuel burn, carbon emissions, and total energy consumption performance is studied for fixed take-off weight and selected flight range scenarios. The results show that the total energy in flight can be reduced by 7.9% and fuel combustion and carbon emissions can be reduced by 13.2% for the 2000 km flight distance case compared to the reference case. The greenhouse gas (GHG) emission reductions are 3059.8 kg CO2, 1220.0 kg H2O, 0.1937 kg SO4, and 0.0387 kg soot. As our methods have incorporated reliable multidisciplinary data and off-design features, the results and conclusions on the parallel HEP retrofit of large aircraft for carbon emission reductions and sustainable aviation goals are more relevant.

Noise reduction for high-lift devices on a swept wing model by droop nose

The noise of slat in the high-lift device of large aircraft is one of the main noise sources of large aircraft during take-off and landing. This paper investigates a noise reduction measure which consists in droop nose for high-lift device of three-dimensional sweep wing instead of leading-edge slat. The unsteady flow field and the far-field noise are predicted by a hybrid SA-IDDES method coupled with the integration of the Ffowcs Williams–Hawkings equation (FW-H). Based on the optimal droop nose configuration from 2D airfoil, the results of the 3D swept wing model with the droop nose on the leading edge of the inner wing are given. Numerical results show that the droop nose configuration can reduce the overall sound pressure level (OASPL) of the intermediate frequency noise, and the peak noise can be reduced by 15 dB, and the sound pressure level of the broadband noise at low and high frequencies is also partially suppressed. The maximum lift-to-drag ratio of the droop nose configuration increased by 2.7 %. In addition, the noise reduction mechanism of leading-edge droop is analyzed by combining the vortex sound theory and the generation and evolution process of the vortex structure. The leading-edge droop nose configuration fundamentally not only eliminates the vortex structure of the slat cove of the leading-edge slat configuration, but also avoids the interaction between the slat slot flow and the upper surface of the main wing. These directly lead to a thinner boundary layer vortex near the top of the main wing, and the wall pressure pulsation is smaller than that of the leading-edge slat high-lift device, thereby reducing noise. The reduction of the BEF distribution on the upper surface boundary shows again that the droop nose inhibits the vortex on the upper surface of the main wing. The change of the Lamb vector divergence reveals the noise reduction mechanism of the drooping leading edge configuration directly from the sound source.

Study and analysis of lift to drag ratio performance of supercritical wing based on computational fluid dynamics method

As the main airfoil of large fixed-wing aircraft at present, the supercritical wing has better performance than the traditional airfoil, especially its aerodynamic performance. Therefore, it is necessary to calculate and experiment with the supercritical wing to optimize its structure. In this paper, computational fluid dynamics (CFD) technology is used to evaluate and compare the performance of a supercritical wing (half wingspan) and a flat wing (half wingspan) with similar size and the same boundary conditions. First, shrink modelling of the two airfoils is performed using the similarity principle. Then it was imported into the simulation environment to calculate the lift-drag ratio under different boundary conditions and draw a corresponding dot plot for comparison. The results show that the aerodynamic indexes of the supercritical wing are better than those of the flat wing of the same size at the cruise stage. Under the standard cruise condition (the angle of attack of the flow is 2°, the air density is 0.5259 kg/m3, and the incoming flow velocity is 800 km/h, for example), the lift-drag ratio of the supercritical wing is increased from 15.0855 to 28.1962 by 1.869 times.

A Civil Aviation Customer Service Ontology and Its Applications

ABSTRACT In the process of developing the C919 large aircraft customer service intelligence system, we find that heterogeneous and incomplete data cause the inefficient and inaccurate decision making. Thus, to solve this problem, we propose to introduce the idea of ontology modeling and reasoning into competitive intelligence system building in this paper. We first present the building principles and methods of the civil aviation customer service ontology. We then define the classes and properties to contribute a real-world civil aviation customer service ontology, which is published on the Web (http://www.openkg.cn/dataset/cacso). We finally design SWRL rules corresponding to different intelligence analysis targets to support reasoning in our designed competitive intelligence system.

Large long-haul aircraft entry, survival, and exit in China's air transport market: The Airbus 380 and Boeing 747-8I

This study explores the dynamics of entry, survival, and exit of large long-haul aircraft in China's burgeoning air transport market, focusing on the Airbus 380 and Boeing 747–8I as case studies. Utilizing rare events logistic regression and the time-dependent Cox regression model, the determinants of route entrance and survival for these aircraft from 2011 to 2021 were analyzed. The data is based on the flight plans of pertinent air routes and aircraft. Key findings include: (1) Both aircraft types favored entry into home-airfield-related, long-haul routes with a substantial existing flight volume. (2) Both aircraft exhibited prolonged survival on international long-haul routes, especially when airlines used them to bolster market share with consistent frequency. (3) Without the home-airfield advantage enjoyed by Air China, China Southern Airlines trialed the Airbus 380 on multiple occasions. Notably, if the Airbus 380 maintains operation on a route for at least 16 weeks, it demonstrates a lower likelihood of exit compared to the Boeing 747–8I.

Drones or uncrewed aircraft – acronyms, definitions, and gender equality

Unmanned aircraft/drones are increasingly present in everyday life, from flight demonstrations, event filming, mapping, and agricultural use to delivering goods or, in the future, transporting people. Uncrewed aircraft systems have also been deployed throughout the military services, from handheld micro-UA (Unmanned Aircraft) to medium-sized tactical systems and to large uncrewed aircraft. The multitude of terms used to identify a particular type of aircraft can be confusing and therefore clarification is needed on how to use them, while at the same time considering gender equality and fairness in language.

Structure design of variable camber wing trailing edge based on multi-block rotating mechanism

The variable camber trailing edge enables the aircraft to maintain the best aerodynamic performance throughout the flight envelope, so as to achieve the ultimate goal of reducing aircraft fuel consumption and air pollutant emissions. It is one of the important characteristics and development direction of the new generation civil aircraft. In order to solve the contradiction between the high load-bearing and the large deformation of the variable camber trailing edge of large aircraft, a structure scheme for variable camber trailing edge based on multi-block rotation was proposed. A parametric optimization method was established for smooth and continuous deformation of multi-block rotating mechanism. The multi-block rotating structure and driving system of variable camber trailing edge were designed, and the deformation function of the variable camber trailing edge demonstrator was preliminarily verified by ground test. The result shows that variable camber wing trailing edge designed by using the present optimization method of multi-block rotating mechanism can realize smooth and continuous morphing. The actual deformation range of the demonstration is 3.9 degrees up to 12.5 degrees down, and the error with the design target is 16.7%. It provides a design reference for solving the engineering application problem of variable camber structure for large aircraft.

Development trends and future expectations of jet engine

Nowadays, nearly all large commercial aircraft are powered by gas turbine engines. Having been developed for about 80 years of engines applied on commercial aircraft, from low bypass ratio turbojet engines to high bypass ratio turbofan engines since the first turbojet engine was patented in 1930 by Frank Whittle, gas turbine engines still have a high potential to improve the performance. Currently, motor thermodynamic efficiency can still rise in the following decades; composite materials, for instance, gamma titanium aluminum and polymer matrix composites, are becoming widely used in airliner propulsion due to their lightweight and high-temperature capability. Accordingly, environmental issues related to gas emissions have also become vital due to the continued flourishing of commercial airliners. In this paper, the development of gas turbine engines applied on commercial airliners from low bypass ratio turbojet engine "Nene1" to high bypass ratio turbofan engine "GE9X," and the current advancement of jet engines applied will be discussed in order to gain possible improvement on the performance of jet engines. Current conditions and expectations of jet engines will be discussed with specific examples, focusing on efficiency, materials and manufacturing, and environmental issues. In the paper, the engines mentioned are all related to commercial aircraft.

Improving Cell-Level Specific Energy for All-Solid-State Lithium Sulfur Batteries

All-solid-state lithium-sulfur (Li-S) batteries are considered as one of the top choices toward 500 Wh/kg of specific energy, a key metric for an energy storage system that enables large regional electric aircrafts. Many obstacles remain, such as S utilization in the cathode, cyclability with regard to both cathode and anode as well as electrode-electrolyte interfaces, and effective means to increase the S content within the all-solid-state cell architecture. The latter is directly related to cell-level specific energy when considering the weights of all battery cell components. In this presentation, we discuss the efforts in both cathode optimization and cell-level improvement toward increasing the overall specific energy. Various strategies in improving S utilization and reducing the solid electrolyte layer thickness will be presented.

Performance sensitivity of subsonic liquid hydrogen long-range tube-wing aircraft to technology developments

Liquid hydrogen (LH2) may enable the decarbonisation of long-haul aviation. However, its low volumetric energy density and subsequent tank space and weight requirements could penalise an aircraft's specific energy consumption (SEC, MJ/tonne-km). We evaluate the impacts of developments in four technology areas – aerodynamics, structures, cryo-tank gravimetric index (η), and overall efficiency (ηo) – on the design-point performance of a large subsonic tube-wing LH2 aircraft. We characterise the critical value of η, which must be exceeded to enable a given design range. For a design range of 14,000 km, η must exceed 0.52 today but only 0.35 with expected 2030 airframe and engine efficiency improvements. Using the most optimistic technology development estimates we observe that SEC could reduce by ∼25% via improvements in ηo and aerodynamics and by 33% via improvements in all four areas. Developments in technologies to improve ηo and reduce drag are critical to enabling zero-carbon long-haul air travel.

Methodology for Electromagnetic Optimization of a Partially Superconducting 1.4 MW Electric Machine for Electrified Aircraft Propulsion

Large transport aircraft with electrified propulsion systems require MW-class electric machines that have higher efficiency and power-to-weight ratio than existing machines. Superconducting machines are being evaluated as potential solutions. This paper presents a method to optimize the electromagnetic design of a partially superconducting machine in terms of these metrics and the approximate fuel burn of the aircraft. The optimization is based on 2D electromagnetic finite element simulations, a prediction of the superconducting coils' critical current, and geometry relations that design the superconducting coils based on dependent variables while constraining the total cost of superconductor and ensuring adequate space for structure. The design process is completed by (1) a 3D electromagnetic finite element simulation to improve the prediction of torque and assess magnetic flux leakage, (2) refinement of the superconductor width for each individual racetrack coil, and (3) evaluating inverter-produced stator current harmonics on eddy current losses in the rotor.

Nonlinear Dynamic Characteristics of Rotating Thick Ring on the Elastic Foundation Based on Plane Stress Theory

Radial tires are widely used in transportation machinery, such as large aircraft, new energy vehicles, and engineering vehicles. The ring on the elastic foundation (REF) model is often used for dynamic analysis of radial tires, but the influence of elastic boundary on the dynamic characteristics of radial tires is ignored in this model. In this paper, based on the absolute nodal coordinate formulation (ANCF) and plane stress theory, a rotating thick ring on the elastic foundation (RTREF) model is established to explore the influence of elastic boundary position and other factors on dynamic characteristics. Because existing rectangular and triangular elements in ANCF can’t accurately describe radial/circumferential mesh of a thick ring, a novel ANCF-annular-sector element (AASE) is proposed for the RTREF model. By analyzing the influences of elastic boundary position, thick wall, and rotational speed on the vibration characteristics and nonlinear forced transient response of the RTREF model, it is demonstrated that even if the ring wall is thin, the influence of elastic boundary positions on the dynamic characteristics of the model can’t be ignored.

Evaluation of aircraft random vibration under roughness excitation during taxiing

The assessment of runway smoothness or roughness is intimately tied to the vibrational response of aircraft during taxiing. In this study, employing the pseudo excitation method (PEM) based on random vibration analysis, we unearthed the relationship between the random vibrations of five distinct aircraft types and runway irregularities. Initially, we established two three-dimensional (3D) models of aircraft taxiing vibration and derived the response output under roughness excitation. Subsequently, we employed MATLAB to analyze the power spectral characteristics of the vibrational response in different parts of the aircraft. Lastly, we examined the effects of taxiing speed, aircraft type, runway roughness, and lift on the aircraft's vibration. Our findings indicate that the distribution of vibration power spectral density (PSD) exhibits multiple peaks, correlating with the degrees of freedom of the aircraft. We further note that the frequency that aligns most closely with the response peak should be the focus of investigation. High-frequency excitation impacts the pilot and nose landing gear more significantly than the passenger and main landing gear. Absent the consideration of lift, increased taxiing speed amplifies the impact of roughness excitation on aircraft taxiing safety. Larger aircrafts are more sensitive to long-wave roughness. With lift in consideration, all aircraft types exhibit a speed sensitivity to vibration, which should be the primary concern in runway roughness evaluations.

Antenna Directional Pattern Testing System Based on Multirotor Unmanned Aerial Vehicles

Obtaining azimuth data of antennas after installation on actual platforms (such as large aircraft, ships, etc.) is crucial for effectively analyzing the platform's impact on the antennas and facilitating optimization and improvement. Traditional testing methods are unable to accurately and efficiently acquire azimuth data due to significant differences between measurements in a dark room and the actual conditions. With the rapid development of drone technology, unmanned aerial platforms have been widely utilized in various engineering fields. Utilizing the flexibility of drones in three-dimensional space and their ability to be precisely controlled through RTK technology, it is possible to use drones equipped with test antennas to measure the azimuth pattern by receiving spectrum signals transmitted by antennas on real platforms. In order to achieve precise angle control, a gimbal system is designed to control the angle of the test antenna. The effectiveness of the entire testing system is verified through experimental results.

Does sunk‐cost affect prices? Evidence from the US airline industry

AbstractIn contrast to the extensive literature on behavior bias by individuals, studies on behavior bias by firms have been relatively scarce. We explore the possibility of the latter in the context of US airlines, where fuel hedging leads to lump sum gains or losses which may impact airlines' pricing decisions. Our results show that the (sunk) hedging gains or losses affect airlines' ticket prices. In particular, a 10% reduction in airlines' reported fuel costs (due to hedging gains) leads to a 2.2% reduction in ticket prices. Moving onto nonprice decisions, we find that hedging gains lead airlines to use larger aircraft and reduce the airtime of their flights, yet have no impact on the number of routes and flights which the airlines operate. Our results provide empirical evidence that fixed/sunk costs can affect firms' prices and nonprice decisions, establish a link between financial market and product market competition, and have important welfare/policy and managerial implications.