Aircraft Flying Research Articles

Stress Analysis of Ice Layers on Fan Rotor Blades in Aeroengines

Fan rotor blades are critical components of aeroengines. When an aircraft flies in icing conditions, ice accumulation on the fan surface may lead to periodic shedding. Severe ice shedding can cause mechanical damage to the engine, posing significant safety risks. This study investigates ice accretion on the surface of ROTOR 67 rotor blades and their stress distribution. This paper presents an in-depth analysis of the internal stress distribution of ice layers on the surface of rotating blades under different icing times and rotational speeds, especially the stress concentration of the areas at the contact surface between the ice layer and the blade. This study predicts the stress distribution of ice layers under different working conditions more accurately, which helps to identify potential ice layer fracture risks in advance. Moreover, it integrates the icing process, stress distribution, and shedding mechanism for analysis, providing a comprehensive perspective. It considers the interaction of various environmental factors and operating conditions, offering an in-depth understanding of ice layer behavior under complex working conditions.

Research on supersonic film cooling of hypersonic optical window under different nozzle pressure ratios

When optical imaging-guided aircraft flies at hypersonic speeds in the atmosphere, the optical window withstands severe aerodynamic heating. Conducting the thin film resistance thermometer measurements in a hypersonic gun wind tunnel with a Mach number of 7.1 and total temperature of 670 K, the study investigates the effect of nozzle pressure ratio (NPR = film exit static pressure/nearby mainstream static pressure) on supersonic (Mach 2.43) film cooling for the hypersonic optical window. By combining the flow information near the window obtained using the three-dimensional compressible Reynolds-averaged Navier–Stokes method, the study reveals the mechanism of the effect of NPR on film cooling. The results indicate that increasing NPR can enhance the momentum of the unit volume film and improve the film's ability to resist mainstream mixing. Moreover, the film with a large NPR can better maintain its own momentum, leading to an increase in the film effective cooling length and film cooling effectiveness. The film effective cooling length corresponding to the unit mass flow rate of the cooling gas increases with the increase in NPR. It verifies the nonlinear relationship between the film cooling performance and the coolant mass flow rate, indicating the additional benefits of increasing NPR on the film cooling performance. Through research, it is found that increasing NPR can increase the film thickness, thereby enhancing its ability to isolate the mainstream. Moreover, as NPR increases, the cooling film expands, objectively leading to the widening of the film flow channel, allowing the Mach number of the supersonic film to increase continually. This further reduces the static temperature of the film in the flow field, thereby enhancing its cooling capability for the mainstream.

Research on ice shedding experiment for large civil aircraft to exit ice protection mode

While aircraft flying, once the icing detector finds the icing environment, the stall protection system will turn on the icing stall protection mode. After aircraft leaves the icing environment, due to the lack of effective means to determine whether there is still ice on the unprotected surface of the aircraft, it is impossible to exit the icing stall protection mode, which can lead to issues such as high approach speed of the aircraft, affecting landing safety and passenger comfort. To solve this problem, this paper conducts experimental research on ice shedding time under different temperature conditions, simulating the phenomenon of ice shedding during aircraft fight. This work helps formulate the logic of aircraft exiting icing protection mode, and lays a basis for future work of aircraft performance optimization.

A prediction method for aircraft icing severity forecast based on probability model and meteorological observation data

Aircraft flight performance and safety are inevitably affected by adverse meteorological conditions, one such weather is icing. Aircraft icing can cause severe aerodynamic and flight mechanical effects, thus threatens aircraft flight safety. This study presents an aircraft icing severity prediction method with probabilistic model, in which meteorological observation data are described as random variables and the airplane icing severity level is defined as fuzzy variables with membership function. When the information of aircraft flying cloud type, altitude, speed, temperature, pressure and dew point temperature is known, the probability of aircraft icing severity during aircraft fly can be effectively predicted by a weighted icing forecasting method. Using the proposed method into two aircraft icing cases, the analysis results show that the proposed method is accurate and valid. It can provide technical support for aircraft icing forecasting.

Research on Improvement Methods for Driven System of Bio-Inspired Aircraft to Increase Flight Speed

The flapping-wing ornithopter is an aircraft that imitates the flight of birds in nature. It has significant potential and value in various fields such as surveying, search and rescue, military reconnaissance, and unmanned warfare, due to its biomimetic stealth and high efficiency in low Reynolds number flight. However, the cruising speed of current flapping-wing ornithopters is generally lower than that of birds of the same size, which seriously affects biomimicry, mission capability, and wind resistance. Increasing the cruising speed can make the aircraft fly more like a bird, improve the efficiency of reconnaissance missions and wind resistance per unit time, and has important research significance. However, the methods to increase the cruising speed of flapping-wing ornithopters are currently lacking. Firstly, this paper presents improvements to the propulsion system based on the team’s “Dove” aircraft to meet the speed requirements. The actual flapping frequency and rocking arm end torque of the “Dove” aircraft under different voltages are tested. To select and match the motor and gearbox in the propulsion system, a method for matching and selection among the motor, gearbox, and load is proposed. Finally, wind tunnel experiments and flight validations are conducted on the improved flight prototype. The wind tunnel experiments show that the increase in flapping frequency has a significant impact on thrust. The trimmed states at different speeds are obtained. The flight validation demonstrates the sustained high-speed flight capability of the aircraft. At a flapping frequency of approximately 15 Hz, the average flight speed of the aircraft is 13.3 m/s within a 15 min duration, which is close to the actual flight speed of pigeons. The duration of high-speed flight is tripled compared to the initial duration. The speed improvement successfully enhances the biomimicry and efficiency of reconnaissance missions per unit time for the aircraft.

Thrust Rebalance to Extend Engine Time On-Wing With Consideration of Engine Degradation and Creep Life Consumption

Abstract Over the years, airlines have consistently attempted to lower their operational costs and improve aircraft availability by applying various technologies. Engine maintenance expenses are one of the most substantial costs for aircraft operations, accounting for around 30% of overall aircraft operational costs. So, maximizing aircraft time between overhaul (TBO) is crucial to lowering the costs. The engine time on-wing is often limited due to the expiration of Life Limiting Parts, performance deterioration, etc. This paper presents a novel method of rebalancing the thrust of engines of an aircraft to maximize the time between overhaul of the aircraft considering the performance degradation and creep life consumption of the engines. The method is applied to a model aircraft fitted with two model engines similar to GE90-115B to test the feasibility of the method with one engine degraded and the other engine undergraded. The obtained results demonstrate that for the aircraft flying between London and Toronto with 5000 nominal flight cycles given to the engines, the time on-wing of the degraded engine could drop from 5000 to 2460 flight days due to its high-pressure (HP) turbine degradation (1% efficiency degradation and 3% flow capacity degradation), causing the same level of drop of time between overhaul of the aircraft. The time on-wing of the degraded engine could increase from 2460 flight days without thrust rebalance to 3410 flight days with thrust rebalance, i. e. around 38.6% potential improvement for the time between overhaul of the aircraft at the expenses of increased creep life consumption rate of the clean engine. The proposed method could be applied to other aircraft and engines.

Steady-State Transonic Flowfield Prediction via Deep-Learning Framework

This paper focuses on the development of a deep-learning framework for predicting distributed quantities around aircraft flying in the transonic regime. These quantities play a crucial role in determining aerodynamic loads and conducting aeroelastic analysis. Angle of attack and Mach number are chosen as the two independent parameters for the reduced-order models. A comparative assessment is conducted between the proposed deep-learning framework and the proper orthogonal decomposition approach to identify the strengths and weaknesses of each method. The accuracy of the data-driven machine-learning method in modeling steady-state transonic aerodynamics is assessed against three benchmark cases of three-dimensional test cases: Benchmark Super Critical Wing and ONERA M6 wings, and the wing–body Common Research Model configuration. Despite the challenges of the analyzed scenarios, promising results are obtained for each test case, showing the effectiveness of the model implemented. Furthermore, the paper demonstrates the application of the method for aeroelastic analysis and uncertainty quantification. This quantifies the robustness and versatility of the implemented model.

Evaluation of Airspace Operation Safety Level based on PMS

The point merge (PM) flight procedure is a new type of flight procedure of performance -based navigation (PBN). The capacity of the point merge procedure is evaluated through the parameters of the point merge flight procedure. Through the parameters of the point merge flight procedure and the parameters of the aircraft flying in the point merge flight procedure, the collision risk between two aircraft in the merge area and the overall collision risk of the aircraft in the point merge procedure are calculated. The evaluation methods and calculation formulas of these three parameters are summarized, and a reasonable method of airspace operation safety level evaluation based on point merge system (PMS) is sought. The inferred method of airspace operation safety level evaluation based on PMS is to compare the operation capacity with the calculated theoretical capacity, and compare the collision risk between two aircraft in the fusion area calculated according to track data and radar data and the overall collision risk of aircraft in PMS with the target safety level specified by China’s air transportation industry.

Developments in Wingtip Vorticity Mitigation Techniques: A Comprehensive Review

Wingtip vortices generated from aircraft wingtips, as a result of the pressure differential at the wingtip, constitute a major component of the total drag force, especially during take-off and landing. In addition to the drag issue, these vortices also pose a significant hazard to smaller aircraft flying in the wake of the larger airplane. The wingtip vortices play a crucial role in aerodynamic efficiency, fuel consumption, flight range, and aircraft stability. This paper presents an overview of the volume of work conducted over the past six decades to encapsulate the phenomena and the techniques devised to mitigate the wingtip vortices. It is shown that the aerodynamic efficiency of the examined wingtip devices ranges from 1% to 15%, depending on the type of wingtips and the flight conditions. Furthermore, it is pointed out that the decrease in fuel consumption ranges from 3.4% to 10%, and the reduction in the induced drag ranges from 5% to 20%.

Safely Learn to Fly Aircraft From Human: An Offline–Online Reinforcement Learning Strategy and Its Application to Aircraft Stall Recovery

Safely Learn to Fly Aircraft From Human: An Offline–Online Reinforcement Learning Strategy and Its Application to Aircraft Stall Recovery

ON NUMERICAL BEAMFORMING FOR CORRELATED DIPOLE TYPE SOURCES

A numerical beamforming method for correlated dipole-type sources in the frequency domain is developed. The typical configuration of the location of acoustic field sources and microphones is considered to analyze the noise generated under an aircraft flying in turbulent flow regimes. Three problems of numerical beamforming are studied, allowing one to take into account a priori information about connections between the components of the dipole function at a point. They differ in the number of real functions to be found: six (no connection), four (components are in phase) and two (the direction of the dipole moment is known). The discretization parameters of source function grids and microphones are estimated to ensure stable matrix inversion in numerical beamforming algorithms. The issues of nonuniqueness of solutions for the tangent components of the dipole function in the first and second problems are identified and discussed; for the third problem such an issue does not arise.

Poster] Classification of Holdings in Flights Arriving at Dubai International Airport (DXB) in One Year

The purpose of this study was to use a machine-learning approach for the classification of holdings for all flights arriving at Dubai International Airport (IATA DXB) in a period of one year. The study used data from ADS-B for all flights arriving and departing DXB for the period 15 February 2018 and 15 February 2019. For all 189,999 arrivals analyzed, it was identified the Standard Terminal Arrival Route (STAR) flown, the occurrence of holdings, the aircraft flying (for the determination of wake turbulence category), the visibility, and data related to the interception of a circle centered around DXB with a radius of 50 NM (geographical position, number of aircraft entering the circle for several time windows, number of aircraft flying within this circle etc), along with the number of aircraft taking-off and landing during a given time period. These features were tested, in different combinations, to determine their impact on metrics used to evaluate the classifier output quality. After running classifiers designed with different algorithms and combinations of features, it was identified the one which, with the CatBoost algorithm, gave the best F1 (0.777), Precision (0.847) and Accuracy (0.912) for a period of 10 minutes after interception. The F1 increased to 0.85 when the altitude and the speed at the interception of the circle were included as features, but they were discarded as they introduced an undesirable bias in the final model.

A Comparative Study between Paper and Paperless Aircraft Maintenance: A Case Study

The rapid growth of airlines over the last period has led to the development of the aviation industry, resulting in increased requirements for ancillary services. Nowadays, the demand for the use of paper-based documents is increasing day by day as airlines encourage passengers to use more ancillary products. One of the most important issues in the aviation industry is flight safety. The procedures and instructions required for all aviation operations are organized in accordance with the regulations and printed on paper in accordance with the demands. For this reason, since it is mandatory to keep all aircraft maintenance, repair, and operation records on printed paper and to keep them for a certain period of time, aircraft fly with almost their entire weight on paper. Considering the global hazards in the world, although the aviation sector is the least environmentally damaging of all transportation sectors, new solutions have been sought to make aviation operations less harmful to the environment, minimize errors and risks, allow for faster communication, and be safer and more sustainable. In order to meet the demands, studies on reducing the use of paper have been brought to the agenda. In this study, after a literature review, real data from a maintenance, repair, and overhaul organization are used to suggest digital conveniences that can save costs, increase productivity, save space, facilitate documentation and information sharing, keep personal information more secure, and help the environment through paperless living.

Experimental validation and tightly coupled numerical simulation of hot air anti-icing system based on an extended mass and heat transfer model

When an aircraft flies through a cloud containing supercooled liquid water droplets, ice accretion may deposit, posing a threat to flight safety. Hot air anti-icing is one of the most widely used anti-icing techniques. An extended mass and heat transfer model for runback water on a hot air anti-icing surface is developed. The model is based on the mass conservation and energy conservation of continuous water film and rivulet water film, considering the conditions under which continuous water film may break up into rivulet water film. Additionally, the effect of water vapor resulting from liquid water evaporation is also taken into account. Then, a three-dimensional tightly coupled numerical method for hot air anti-icing systems is constructed based on the developed model. The method includes modules for the calculation of external cold air flow, solid skin heat conduction and internal hot air flow, the calculation of water droplet impingement, and the calculation of anti-icing thermodynamics. The accuracy of the method is validated against experimental studies on an enhanced heat transfer piccolo tube anti-icing system in the icing wind tunnel of China Aerodynamics Research and Development Center (CARDC). The temperature results obtained from the three-dimensional numerical simulations showed good agreement with the experimental results, indicating that this method can be utilized in preliminary and detailed designs to evaluate the thermal performance of hot air anti-icing systems.

Lift and Drag Analysis of NACA 1412 Airfoil Using Unstructured Mesh

Abstract: This research paper gives insight to the analysis of NACA 1412 airfoil. The airfoil is the two-dimensional cross section of the aircraft’s wing. The aircraft flies due to generation of the lift, this lift is caused by the pressure difference on the upper and lower surface of the airfoil. The pressure on the lower surface is greater than the pressure on upper surface which provides a lift to the airfoil. We are going to see the airfoil’s behaviour in incompressible flow at different angles of attack with constant velocity. In this research, we are going to use the Ansys software to do the analysis. This research is based on the computational fluid dynamics concepts. At the end, we will see how the lift and drag changes at different angles of attack and some graphical results from the research.

Experimental investigation on supersonic film cooling of hypersonic optical dome under different nozzle pressure ratios

When an aircraft flies at hypersonic speeds in the atmosphere, its optical window is subjected to severe aerodynamic heating. To investigate the supersonic film cooling laws of hypersonic optical dome, three supersonic (Mach 2.35) film generation devices with different jet outlet heights (1 mm, 2 mm, 3 mm) were designed. The experiments were conducted in a hypersonic (Mach 7.1) gun wind tunnel. The NPR (nozzle pressure ratio = jet outlet static pressure/nearby mainstream static pressure) ranged from 0 to 2.3. The heat flux on the window surface was measured by the thin film resistance thermometer. Experimental results indicate that, under different jet outlet heights, the film cooling effectiveness increased gradually as the NPR increased, corresponding to an increase in effective cooling length. The existing similarity parameters for film cooling could effectively predict the effective cooling length of supersonic film when NPR = 1. However, the prediction effect deviated significantly when NPR ≠ 1. Moreover, the effective cooling length corresponding to the unit mass flow rate of the coolant first increased and then decreased with the increase of NPR, and there existed an optimal solution. Furthermore, with the same coolant mass flow rate, higher jet Mach number lead to better supersonic film cooling performance.

Electric Aircraft Battery Performance: Examining Full Discharge Under Two Conditions

The understanding of battery performance, particularly over the full course of discharge and over battery life is critical to allow pilots to maintain safety in electric aviation. In this study, an electric aircraft powered by two Lithium-Ion battery packs is used as a test article. The objectives of the current study are to build on previous work by conducting two full tests discharging both battery packs from a 100% charge. This allows examination of the battery performance a) under a constant power output and b) with periodic tests of the maximum power available. In addition to state of charge (SOC), remaining flight time, battery temperature, and motor power, this study presents data on motor RPM, torque, voltage, current, battery internal resistance, and available energy. The data on motor power indicates that the available maximum power decreases with lower SOCs when the throttle settings are varied; however, at lower power settings, such as an optimum cruise at 27 kW, the motor power remains constant and as expected during discharge. Also, the constant power setting illustrates that there are inflection points in physical battery characteristics. These results confirm that electric aircraft performance changes during a flight are different than what a pilot expects from a gasoline-powered aircraft. The longer the aircraft flies at different throttle settings, the faster the batteries discharge; the discharge curve is nonlinear. Thus, a piston-trained pilot’s expectation for an aircraft’s performance later in a flight will not match an electric aircraft.

Augmenting Flight Training with AI to Efficiently Train Pilots

We propose an AI-based pilot trainer to help students learn how to fly aircraft. First, an AI agent uses behavioral cloning to learn flying maneuvers from qualified flight instructors. Later, the system uses the agent's decisions to detect errors made by students and provide feedback to help students correct their errors. This paper presents an instantiation of the pilot trainer. We focus on teaching straight and level flying maneuvers by automatically providing formative feedback to the human student.

Vertical Airborne Wind Energy Farms with High Power Density per Ground Area based on Multi-Aircraft Systems

This paper proposes and simulates vertical airborne wind energy (AWE) farms based on multi-aircraft systems with high power density (PD) per ground area. These farms consist of many independently ground located systems that are flying at the same inclination angle, but with different tether lengths, such that all aircraft fly in a large planar elliptical area that is vertical to the tethers. The individual systems are assigned non-overlapping flight cylinders depending on the wind direction. Detailed calculations that take into account Betz’ limit, assuming a cubically averaged wind power density of 7 m/s, give a potential yearly average PD of 43 MW/km2. A conventional wind farm with typical packing density would yield a PD of 2.4 MW/km2 in the same wind field. More refined simulations using optimal control result in a more modest PD of 6.5 MW/km2 for practically recommended flight trajectories. This PD can already be achieved with small-scale aircraft with a wing span of 5.5 m. The simulations additionally show that the achievable PD is more than an order of magnitude higher than for a single-aircraft AWE system with the same wing span.

Feasibility Study of Operation Volume Design Concept for Integration of Aircraft Flying Under Visual Flight Rules Based on Actual Flights

Segregation through operation volumes can enable safe and efficient low altitude airspace usage by various aircraft types, both manned and unmanned. Current traditional aircraft flying under visual flight rules (VFR) are not required to adhere to a strict flight plan and share their flight intentions, but their integration in high-density environment will require better strategic trajectory prediction. This paper proposes VFR trajectory modeling based on mission type and typical flight characteristics. The idea is illustrated with a reconnaissance mission mimicking landmark (highway) tracking to check for post-disaster damages. Results from a flight campaign with an experimental helicopter conducted in 2020 verify the assumptions posed at trajectory modeling and identify the degree of uncertainties necessary to determine the buffers around each trajectory and therefore design operation volumes. The same mission-based trajectory modeling and operation volume design approach can be applied to further missions and vehicles, which makes it transferable to the needs of advanced air mobility as well, especially addressing dense operations.