Jet Aircraft Research Articles

Evaluation of flyover auralisations of today's and future long-range aircraft concepts

The European research project ARTEM (Aircraft noise Reduction Technologies and related Environmental iMpact) develops innovative aircraft noise reduction technologies such as advanced engine fan lining, metamaterials and low-noise high-lift systems applied to a vehicle with enhanced shielding of the engine noise, namely, a blended wing body. Using aircraft flyover auralisation in laboratory listening experiments, such future technologies can be evaluated with respect to human sound perception. To assess the reliability of such perception-based evaluations, the simulation chain should be validated with existing aircraft flyovers. This contribution presents a systematic and rigorous hierarchical validation of auralisations of current jet aircraft using field recordings. Uncertainty in the source modelling is considered by using two different prediction tools for partial sound sources. In addition to comparing computed noise indicators, a psychoacoustic validation is done in laboratory listening experiments with a 3D loudspeaker array. The validation comprises three levels: (i) direct comparison of auralisations with recordings to study the identifiability of auralisations, (ii) ranking of auralisations and recordings regarding plausibility, and (iii) subjective annoyance ratings to test whether auralisations and recordings differ with respect to noise effects. Further, first results on the comparison of a future concept with a current aircraft are presented.

Viewing the changes in community annoyance due to aircraft noise over the times

More than 60 years have passed since the introduction of jet aircraft to civil aviation, and technological innovations have made aircraft much quieter. Nevertheless, people still complain that they experience serious suffering from aircraft noise. This paper overviews and considers the changes over the times both in the aircraft sound exposure level and in the community annoyance caused by aircraft noise. It will also discuss the issue of recent noise complaints associated with the introduction of performance-based flight navigation as well as view the impact of pandemics over the past two years.

Study on the ground attenuation of engine run-up and APU noise for developing the airport noise model in Japan

The correction for ground effect around airports is modeled based on the results of numerical analysis in order to make it possible to estimate the propagation of noise caused by ground operations in airports such as engine run-ups and APU to the vicinity of airports. The excess attenuation due to ground effects on sound caused by engine run-ups and APU is calculated using a PE method for typical jet aircraft and propeller aircraft, respectively. On the assumption that the ground around an airport consists of asphalt-paved surface and grass-covered surface in a certain ratio, the excess attenuation for the mixed impedance ground is calculated with the Fresnel-zone method using the results of PE calculation. The composition ratio of ground surface is assumed based on the composition ratio of asphalt-paved surface and grass-covered surface along the propagation path from the engine run-up spot to the airport site boundary of six major airports in Japan. In this paper, we introduce the excess attenuation calculated with the PE method and the correction model for ground effects on noise of engine run-ups and APU is discussed to implement it in the airport noise prediction model used in Japan.

Effects of FAME Biofuel and Jet A-1 Aviation Kerosene Blends on the Operating Characteristics of Aircraft Jet Engines

The article investigates the possibilities for the miscibility and practical use of different concentrations of biofuel rapeseed fatty acid methyl ester (FAME) with aviation kerosene Jet A-1 (or aviation kerosene PL-7 used in the Air Force of the Slovak Republic) in aircraft jet engines. The main objective of this research was the experimental verification of the technical possibilities of reliable operation of the experimental engine SJE-20 in a special laboratory of small jet engines using different concentrations of the mixture of aviation kerosene Jet A-1 and biofuel FAME and their influence on the selected operating parameters of the experimental engine. The motivation for this research is the desire to replace conventional aviation fuels with fuels that can be obtained from renewable sources. Investigation of the possibilities of powering the experimental SJE-20 engine with a mixture of traditional aviation kerosene Jet A-1 (PL-7) and rapeseed fatty acid methyl ester FAME was the subject of the internal project BIOFUEL (Biofuel for Aviation).

At the Beginnings of Turbojet Aviation

The article is devoted to the history of invention of turbojet engine that later became the main type of power plant in aviation. It describes the motivations for the inception of these works, the role of private business in their development, the history of the tests of the first jet aircrafts, and the influence of WWII on the emergence of jet aviation. The sources used in the preparation of this article include the memoirs of the pioneers in jet engine development Hans von Ohain, Frank Whittle, and Arkhip Lyulka, aircraft designer Ernst Heinkel, and test pilots Erich Warsitz and John Grirson. The analysis of relevant Russian archival documents allowed explaining the causes of turbojet aviation lagging behind in the USSR.

Robust Preview Feedforward Compensation for LIDAR-based Gust Alleviation

This paper deals with the preview gust alleviation control system of an aircraft, which mitigates dangerous vertical acceleration due to wind gust using the forward wind velocity measured by the LIDAR (LIght Detection And Ranging). Although the vertical acceleration can be alleviated by preview control, the preview feedforward part tends to be sensitive to measurement errors. In order to maintain consistently high acceleration alleviation performance, the preview feedforward needs to be robust to errors. This paper presents a design method for preview feedforward gains that can reduce the effect of measurement errors. Nonlinear simulation results of a small jet aircraft are provided to show that the designed preview control gain can both alleviate vertical acceleration and be robust against random and bias errors.

A Macro- and Microscopic Inspection of the Safety Critical Components

In many cases related to critical infrastructures, we find equipment that is extremely important from a safety point of view and key safety-critical components in them. Such parts are turbine blades, engine elements of jet aircraft, as well as high-pressure steam lines of power plants and pressure equipment for liquid gases. In the case of safety critical components, non-destructive and the destructive tests are indispensable. The damage to these components can cause catastrophic failures that need to be avoided. During the inspection of the components, microscopy tests give information about macrostructure and microstructure. Carrying out the tests consists of several steps, during which it is necessary to follow the relevant standards. During the examination of macrostructure, conditions that may lead to premature failure and breakage of the component can be detected. Getting to know the microstructure can provide information about manufacturing, welding, or microstructural defects, which can be a key issue from the point of view of safe operation.

The Design of Advanced Very Light Jet Aircraft

The current state of the art in aircraft design has shown that in order to be economically viable and competitive it is necessary to investigate technology, which may give an improvement in performance and operational flexibility goal, but must be shown to be cost-effective. The current competitive environment forces the potential customers to buy advanced technology aircraft and requires manufacturers to provide more operational flexibility, without drastic performance penalties. This is a challenging task, which might be solved by the use of new technologies. It is believed that the application of an advanced high-lift capability, high cruise Mach number and lower moment turbulent airfoils derived from MS (1)-0317 and MS (1)-0313 to a wing would assist in achieving such a task. This paper describes an investigation aimed to examine the suitability of an aerodynamic wing design, allowing for the use of an advanced turbulent wing section concept for advanced medium-speed Very Light Jet (VLJ) aircraft. The paper describes the phenomenon of configuration design and outlines the wing design process. Description is then given of the aerodynamic design of a wing incorporated with an advanced turbulent wing section technology, tail design and aircraft performances. It concludes with a discussion of the results and recommendations for future work.

Development of an Adaptive Aero-Propulsive Performance Model in Cruise Flight – Application to the Cessna Citation X

To accurately predict the amount of fuel needed by an aircraft for a given flight, a performance model must account for engine and airframe degradation. This paper presents a methodology to identify an aero-propulsive model to predict the fuel flow of an aircraft in cruise, while considering initial modeling uncertainties and performance variation over time due to degradation. Starting from performance data obtained from a Research Aircraft Flight Simulator, an initial aero-propulsive model was identified using different estimation methods. The estimation methods studied in this paper were polynomial interpolation, thin-plate splines, and neural networks. The aero-propulsive model was then structured using two lookup tables: one lookup table reflecting the aerodynamic performance, and another table reflecting the propulsive performance. Subsequently, an adaptative technique was developed to locally and then globally, adapt the lookup tables defining the aero-propulsive model using flight data. The methodology was applied to the Cessna Citation X business jet aircraft, for which a highly qualified level D research aircraft flight simulator was available. The results demonstrated that by using the proposed aero-propulsive performance model, it was possible to predict the aerodynamic performance with an average relative error of 0.99%, and the propulsive performance with an average relative error of 3.38%. These results were obtained using the neural network estimation method.

Mobile Collaborative Robot with Obstacle Avoidance

This product has been designed to scan and inspect the flooring of a predefined space. Essentially, a camera at the tip of an arm mounted on a mobile base scans the environment as the robot moves. The robot’s components can be programmed to halt all motion upon noticing any discrepancies in its scanning, and to then take photographs of said discrepancies before continuing along its trajectory. The applications of such a device can range anywhere from a simple workplace janitorial overview to industrial aircraft jet fuel tanks’ safety inspections, wherein the robot can examine the tank for leaks, cracks, or corrosion

Assessing impact of near-ground meteorology on spectral variability in static jet aircraft noise measurements

ANSI/ASA standard S12.75 (2012) provides guidance on allowable meteorological conditions for acoustical measurements of installed high-performance jet engines. This paper investigates meteorological effects on acoustic data acquisition by analyzing recent measurements of a T-7A-installed GE F404 engine. During this measurement, the aircraft was run up six times at engine powers from idle to full afterburner, with test conditions following those prescribed by S12.75. However, far-field spectra show variability between runs, despite relatively uniform test conditions. Measurements of the vertical temperature gradient show a correlation between the gradient and spectral characteristics. This analysis suggests that local temperature profiles must be considered more carefully in future full-scale measurements. [Work supported by ONR Grant No. N00014-21-1-2069.]

Potential Benefit of Structural Health Monitoring System on Civil Jet Aircraft.

Structural health monitoring represents an interesting enabling technology towards increasing aviation safety and reducing operating costs by unlocking novel maintenance approaches and procedures. However, the benefits of such a technology are limited to maintenance costs reductions by cutting or even eliminating some maintenance scheduled checks. The key limitation to move a step further in exploiting structural health monitoring technology is represented by the regulation imposed in sizing aircraft composite structures. A safety margin of 2.0 is usually applied to estimate the ultimate loading that composite structures must withstand. This limitation is imposed since physical nondestructive inspection of composite structures is really challenging or even impossible in some cases. However, a structural health monitoring system represents a viable way for a real time check for the health status of a composite structure. Thus, the introduction of structural health monitoring should help into reducing the stringent safety margin imposed by aviation regulation for a safe design of composite structures. By assuming a safety margin reduction from 2.0 to 1.75 thanks to the installation of permanently attached sensors for structural health diagnostics, this paper assesses the potential fuel savings and direct operating costs through a multidisciplinary analysis on a A220-like aircraft. According to the foreseen level of technology, addressed through the number of sensors per square meter, a DOC saving from 2% up to 5% is achievable preserving, at the same time, all the key aircraft performance.

Intake System Performance Stability as a Function of Flow Throttling

This paper presents a numerical analysis of the stability of the flow parameters along the intake duct of an aircraft jet turbine engine. This problem has been investigated by many research teams and was included in the literature analysis. The unstable operation of a turbojet intake system can be the consequence of many adverse factors, including an intake vortex. The investigated intake system, due to its low location to the plane of the airport, is highly susceptible to the formation of an intake vortex. The phenomenon of an intake vortex can, in the worst-case scenario, result in the surging of the turbojet, and even engine stalling. This paper presents a developed model of the forward section of an aircraft, complete with its intake duct, and the method of its discretization. The intake-system model and numerical analysis were performed in Ansys Fluent. The flow parameters adopted for numerical simulations, under specific boundary conditions, corresponded to the operating conditions of the engine cooperating with the investigated intake system. The numerical calculations were performed assuming an air-pressure rise in the end section of the engine-intake system, reflecting the reduction in the pitch angle of the inlet stator blades of the fan. As a result, the pressure distributions in a significant cross section in the intake system were obtained. The results were analyzed with the quantitative distribution of the pressure fields by applying a dimensionless potential-pressure ratio. The pressure ratio enabled a comparative analysis of the nonuniformity of the total-pressure distribution in selected cross sections of the intake system. The results were revealing in terms of growing unstable flows in the flow duct. A major conclusion drawn from the results, by testing the dimensionless potential-pressure ratio, was that, within certain limits, it was possible to improve the flow uniformity by increasing the throttling pressure.

Phase stability of Ti-containing high-entropy alloys with a bcc or hcp structure

Solid-solution-strengthened alloys with a hexagonal close-packed (hcp) structure are used as high-temperature structural materials; for example, hcp and body-centered cubic (bcc) two phase Ti alloys are used in aircraft jet engines. The temperature limit of Ti alloys is ~873 K because of deterioration of their creep properties and oxidation resistance at higher temperatures. Greater solid-solution strengthening will be beneficial to improve the strength of Ti alloys at temperatures greater than 873 K. High-entropy alloys (HEAs) are expected to exhibit superior mechanical properties because of the sluggish diffusion of their constituent elements and their large lattice distortion. Hcp HEAs are expected to result in improved high-temperature mechanical properties. However, making the hcp structure stable in HEAs is difficult. To understand the phase stability of Ti-containing HEAs, the present study focuses on two alloys: Ti34Al33V33 and Ti34Zr33Hf33. Al and V are used in commercial Ti alloys. In Ti34Al33V33, a bcc structure is stable at high temperatures and a hcp phase precipitates during cooling. Hcp-structured Ru, Sc, Co, and Zr were selected as additional elements to investigate the change in phase stability of a bcc phase of TiAlV. In Ti34Zr33Hf33, a hcp structure is stable at room temperature. Ru with a hcp structure, Al with a face-centered cubic structure, and V with a bcc structure were selected as additional elements to investigate the phase stability of TiZrHf. Phase stability is discussed on the basis of binary phase diagrams, the formation energy of phases, and the valence electron concentration of the constituent elements.

The effect of helmet mass and aircraft acceleration on cervical spine loads during typical fast jet aircraft pilot head motions

ObjectivesGravitational Force (Gz), head motion, and helmet mass are associated with neck pain in high performance aircraft pilots. Few studies have quantified neck kinetics (intersegmental neck moments) during aerial combat manoeuvres. DesignCross-sectional. MethodsWe quantified net joint moments between the skull and C1, and C6–7 during typical flight related headchecks using the Musculoskeletal Model for the Analysis of Spinal Injuries (MASI). We measured the influence of pilot-specific helmets and Gz on joint moments. Nineteen fighter pilots performed four head checks (check6 left, check6 right, extension hold and extension scan) under two helmet conditions. Motion data were transferred to OpenSim where joint moments were calculated at 1G to 9G. Net joint moments were compared across helmet conditions, Gz and headchecks. ResultsThe Joint Helmet Mounted Cueing System (JHMCS) resulted in higher moments at each segment- by a factor of 1.25 per unit of Gz, at C1, and by a factor of 1.08 per unit of Gz for C7. ExtensionScan and Check6Left were associated with the highest peak (96.13 Nm and 92.56 Nm). ExtensionScan and ExtensionHold accrued the highest mean cumulative loads at C7 at 9Gz (607.35 Nm.sec/motion, 362.99 Nm.sec/motion respectively). Asymmetries were observed between the Left and Right Check6 motions. High variability was evident between and within pilots. ConclusionsThe MASI model has been successfully applied to quantify intersegmental neck joint moments for typical headchecks that are performed during combat flight manoeuvres. In future, data derived from this model may inform conditioning, rehabilitative and preventative interventions to reduce neck pain in fast jet pilots.

Evolution of charged particles in jet combustion chamber

The combustion process in the combustion chamber of the engine will change the electrostatic field characteristics of the jet aircraft, thereby affecting the accuracy of the electrostatic field information obtained by the electrostatic detector. Based on the quantitative analysis of the evolution of charged particles in the combustion chamber, this study further analyses the effect of different surface materials in the combustion chamber on the charging process of combustion products. The combustion chamber is divided into burning zone, intermediate zone and dilution zone, and the evolution model of charged particles in the combustion chamber is constructed under the time constraint. Finally, the variation curve of the charged particle concentration when the surface materials in the combustion chamber are metal materials and non-metal materials are calculated by simulation, and the influence of the conductivity of the surface materials in the combustion chamber on the combustion charging process is analyzed. This study provides the analytical basis for the application of electrostatic detection technology in jet aircraft.

Navy aircraft sound monitoring study

The United States Department of the Navy (Navy), as directed by Congress, executed a real time sound monitoring study of jet aircraft at Naval Air Station (NAS) Whidbey Island and NAS Lemoore over the past year and compared the resulting measured data with modeled noise data. The Navy collected real-time aircraft sound level and operational data during four discrete seven-day monitoring periods in 2020 and 2021. The data collected each period included: (1) acoustic recordings by sound level meters deployed at sites around each airfield to capture sound levels during a range of flight operations across a range of seasonal weather conditions; and (2) detailed operations data. The collected acoustic data are compared to noise modeling done specifically for this study using the observed flight operations data. This presentation provides and overview of the measured data and the results of the comparison with modeled data.

Automatic Evaluation of the Robotic Production Process for an Aircraft Jet Engine Casing

This paper investigated the design of a system to monitor the status of the robotic welding process of thin-walled components for an aircraft jet engine. Opportunities to measure and log processing parameters, such as welding speed, current, and voltage, on the existing production cell were taken. The acquired data were processed using elements of descriptive statistics. Obtained indicators were matched with physical inspection results of the weld’s quality. The adopted methodology was used to identify an essential parameter determining the presence of defined weld defects. The developed solution was implemented in the production cell.

Modeling the impact of sustainable aviation fuel properties on end-use performance and emissions in aircraft jet engines

The present study supports the development and testing of alternative jet fuels by introducing a state-of-the-art mathematical model that enables for the first-time accurate estimations of the fuel consumption in jet engines via employing the collective impact of the most significant fuel properties. Based on literature data the matrix with fuel properties and end-use performances was constructed. The Best Multiple Linear Regression combined with quantitative analysis was employed in the modeling procedure. The developed Jet-model contains the effects of viscosity, density, and calorific content on fuel consumption, with p-values much below 1%. The coefficient of determination R-Square of 0,993 indicates a high accuracy, that in the validation procedure translated into the error of 0,21% against internal data and 0,68% in external data. The Jet-model was applied to simulate the end-use performance of commercial sustainable aviation fuels. The results show changes in fuel consumption relative to standard kerosene oscillating between −0,85% and +3,72% and reduction in carbon dioxide emissions that vary from −3,22% to +0,42% for selected fuels. The present study shows that Sustainable Aviation Fuels have the potential to outperform their fossil counterpart not only in terms of the environmental impact but also in fuel and energy consumption.

A comprehensive fracture research of an aircraft swash-plate pump

Aviation pumps are widely used to feed the actuators of the components such as the aileron, flap, slat, rudder, elevator, and landing gear of an aircraft. The swash-plate pumps are the most popular ones of the aviation pumps. This study analyses the failure of a jet aircraft’s swash-plate pump mounted on the inner wing and has the function of feeding the flap actuators. After the pump’s failure had been discovered and an investigation was performed. At first, the Foreign Object Damage (FOD) originated from a foreign particle carried by hydraulic flow attracted the doubts. But after further fractographic analysis, it was shown that a micro-crack on the slipper retainer holes had initiated the asymmetric loads and led to cross-section friction on the Swash-Plate surface. It was an Inner Object Damage (IOD). Some suggestions for preventing the lack of lubrication in the slipper retainer holes are given in this paper.