Takeoff Operations Research Articles

Assessment of sound propagation for the urban air mobility

The noise generated by vertical takeoff and landing vehicles (VTOL) operating in urban environnement is a determinant factor for the community acceptance. The ray-tracing method used for predicting road and raylway noise in urban areas can also be applied to the Urban Air Mobility context. In densely populated urban area, the multipath of sound wave occurs due to numerous reflections on the buildings walls. Such a configuration generates both constructive and destructive interferences, given rise to a complex shape of the spectra, that can be difficult to explain. To assess ray codes dedicated to road noise for this kind of configurations, simple test cases such as a corner and a canyon based on image sources are proposed. The prediction is performed in octave bands in the frequency range 63 Hz to 8000 Hz, including acoustical source at high altitudes to account for the VTOL flight. A good agreement is found between the reference solution derived from the image-source and the ray tracing technique. In particular close to the corner a significant increase of about 9 dB can be found. When both the source and the microphone are in the canyon, an inscrease up to 14dB can be found.

Development of Deceleration-Based Friction Prediction Models and Methods on Semiprepared Runway Surfaces

Both civilian and military airfield managers require the safe operation of aircraft on runway surfaces. This includes the operation of ground traffic on airfield operating surfaces as well as connecting road infrastructure. Often times in austere environments, this road infrastructure is unpaved and consists mostly of either semiprepared or unbound soils. It has been shown in numerous research efforts that surface friction is an excellent indicator of safe operating conditions. Although a great deal of work has been done to quantify safe surface conditions for landing and takeoff operations on rigid and flexible pavement structures, limited research exists to extend such efforts to soil-based or semiprepared surfaces. The objective of this research was to develop deceleration-based surface friction prediction models on unpaved surfaces with varied moisture conditions and soil types. Surface friction, in this study, was quantified using the Findlay Irvine Mk2-D GripTester. Deceleration was measured using four smartphone inertial measurement units (IMUs), one Bowmonk IMU, and one Xsens IMU. Tests were conducted in three ground vehicles: a high-mobility multipurpose wheeled vehicle, a civilian ½-ton pickup truck, and a civilian full-size sport utility vehicle. The various deceleration-based devices tested here adequately correlated (coefficient of determination >0.6) with Mk2-D GripTester measurements collected on unpaved soil runways. The models and measurement methods detailed here are of considerable use to both semiprepared runway and ground vehicle operations managers around the world needing to measure safe surface conditions following inclement weather.

Thermodynamics, environmental damage cost, exergoeconomic, life cycle, and exergoenvironmental analyses of a JP-8 fueled turbodiesel aviation engine at take-off phase

The objective of this study is to evaluate the energetic, exergetic, sustainability, economic and environmental performances of a 4-cylinder turbodiesel aviation engine (TdAE) used on unmanned aerial vehicles for the take-off operation mode to assess the system with large aspects. Energy efficiency of the system is found as 43.158%, while exergy efficiency 40.655%. Thermoeconomic analysis gives information about the costs of the inlet and outlet energy and exergy flows of the engine. Hourly levelized total cost flow of the TdAE is found as 21.036 $/h, when the hourly fuel cost flow of the engine is found as 30.328 $/h. The waste exergy cost parameter is determined as 0.0144 MJ/h/$ from exergy cost-energy-mass (EXCEM) analysis, while it is estimated as 14.043 MJ/$ from modified-EXCEM analysis. Environmental damage cost analysis evaluates the cost formation of the exhaust emissions. The total environmental damage cost of the TdAE is computed as 12.895 $/h whilst specific environmental damage cost is determined as 0.054 $/MJ for 494.145 MJ/h TdAE power production. It is assessed that the main contributors to the environmental impact rate of the TdAE are the fuel consumption and the formation pollutants of combustion reaction.

Overcome uncertainties of vertical take-off and landing aircraft based on optimal sliding mode control

<span>This study aims to design a robust and optimal controller to overcome the problems related to the existence of disturbances and uncertainties during takeoff and landing operations of vertical take-off and landing (VTOL) aircraft. The dynamics are decomposed into two phase’s parts which are the minimum phase and the non-minimum phase. These two-part are controlled by proposing a robust nonlinear controller represented by sliding mode control (SMC). Also, the chattering effect due to the fast-switching surface in SMC is eliminated by utilizing a proposed sigmoid function which acts as the sigmoid function. The controller's main parameters are tuned optimally based on the particle swarm optimization (PSO) algorithm. In addition, the controller guaranteed the system stability based on the Lyapunov and Routh theories. The main output parameter responses represented by the positioning of the centre of mass and angle of rolling are determined with bounded control inputs. The performance of the proposed controller is tested by tracking VTOL parameters to the desired trajectories. The simulated results not only showed a significant tracking trajectory but also system stability guaranteed. In addition, the results showed an improved rate of 72% and 84% compared with those results obtained from the literature.</span>

Optimization of High-Crosswind-Tolerant Airplane Based on Double-Hinged-Wing and No-Vertical-Tail Configuration

Crosswind gusts can easily disturb the attitude of a small fixed-wing aircraft, potentially causing a serious accident during landing or take-off operations. An airplane with a high tolerance to crosswind gusts owing to quite small Clβ and Cnβ values, called a Quasi-Neutral Dihedral-effect and Directional-stability (QNDD) airplane, was previously proposed. Although the design of a QNDD airplane is more practical than that of a Neutral Dihedral-effect and Directional-stability (NDD) airplane, a QNDD airplane’s robustness to errors in Clβ and Cnβ should be comparatively higher. In the present study, the QNDD airplane’s robustness is optimized using Sequential Least-Squares Quadratic Programming (SLSQP). The optimized QNDD airplane has a unique configuration: a highly deflected swept-forward main wing. It is confirmed that the optimized design is much more robust than the original. To evaluate the performance of the optimized QNDD airplane, airplane plunging into a discrete crosswind gust is numerically simulated, and the results confirm that the airplane’s change in attitude is still quite small compared with that of a conventional airplane.

MODERN MATERIALS FOR REPAIRING AIRFIELD SURFACES

The existing network of airfields is largely represented by hard airfield surfaces. The main advantage of this design of coatings is sufficient load-bearing capacity, which allows to ensure the operation of any type of aircraft and a significant resource, which is 20 years before overhaul. Given that most airfields have been in operation for more than 20 years, the issue of maintaining the technical condition of artificial surfaces becomes urgent. In difficult economic conditions, only ongoing repair work remains the only way to maintain the necessary level of technical condition of airfield surfaces, capable of ensuring the safe performance of take-off and landing operations, taxiing and maintenance of aircraft. This determines the need to improve the methods of their operational and technical maintenance. In addition, timely and high-quality performance of current repair work allows to extend the service life of the coating between repairs.

The effects of COVID-19 pandemic on the performance of airport renovation projects: the case of Pulkovo Airport

This paper explores the effects of the COVID-19 pandemic on the performance of airport renovation projects. The research examines the case of the renovation project of the Saint Petersburg's Pulkovo Airport in Russia, which started in 2010 within the concession agreement of the Northern Capital Gateway and the Government of Saint Petersburg until 2040, and raises the question of how this pandemic influenced the performance of Pulkovo airport renovation project. A Cost-benefit analysis and its sensitivity analysis were used to determine how restrictive measures against the spread of COVID-19 affected the profitability and social indicators generated by Pulkovo Airport. The social effect of infrastructure renewal was determined in accordance with the Efficient Time Allocation and Generalized Cost of Travel theories. The study reveals a decrease in the Net Present Value (NPV) of the renovation project due to changes in the trends of passenger traffic and the number of take-off and landing operations, a decrease in the growth rate of airport revenue and a partial reduction in operating costs. The expected Social NPV of the project decreased by 94.32 percent, and the benefit-cost ratio drastically reduced to 1.33, from a 4.06, had the pandemic not developed. The sensitivity analysis suggests a shift in the key variables that affect the performance of the analysed infrastructure project.

Influence of geometric constraints on aircraft design

The paper considers the requirements to helicopter operating conditions, forming geometrical constraints at the design stages and their influence on the geometrical appearance of the helicopter as a whole, structural design and layout of individual components and assemblies of helicopters. The methodology of forming the system of geometrical constraints is based on the generalised requirements to ensure the operational and technical characteristics of the helicopter: ensuring the basing and production of take-off and landing operations on marine vessels, ensuring transportability, ease of access to the cockpit, ease of access to the units during maintenance, reducing the labour intensity of individual helicopter maintenance operations.

Aerodynamic Study and Design of Fixed Wing and Multi-copter Combination

This project aims to design a hybrid drone with fixed wing for the stable cruising as well as multi-copters for the vertical take-off and landing (VTOL) operations. Drones are utilized for number of applications leading from transportation to the surveillance purposes. Some drones are popular for their stable operation, while other for optimum landing and takeoff. Therefore, numerical analysis was performed on propeller, landing gear as well as on whole structure of the drone. The observed result from CFD analysis show that the velocity distribution had maximum velocity of 40 m/s at the mid span of the drone. In addition, the maximum stress obtained was on the landing gear with approximate value of 185 MPa which is due to the weigh and payload of the drone. The final model was built after the analytical and numerical analysis in order to achieve sustainable and reliable prototype.

Study of the static and endurance strength of reinforced concrete specimens loaded with the account of the characteristics arising in the process of aircraft takeoff and landing operations on airfield pavements

The article shows that the impact of aircraft with multi-wheel bearings on airfield pavements is a cyclical pattern, as a result, constant sign and alternating stresses arise in the material. The results of cyclic loading parameters calculations of coatings under the influence of aircraft with multi-wheeled bearings (load cycle asymmetry coefficient, values of the maximum and minimum stresses of the loading cycle), performed using the SCAD software-computer complex, which implements the finite element method in the form of the displacement method, are presented. The necessity of carrying out tests to determine the endurance strength of reinforced concrete under various loading conditions for more complete consideration in determining the operating modes of airfield pavements is shown, and the loading parameters of reinforced concrete specimens during their endurance tests are determined. A general view and a layout diagram of an experimental setup for determining the static and endurance strength of large-sized cement concrete samples are presented. A technique for determining the static strength of reinforced concrete samples is presented, including the determination of the criterion for their destruction (appearance of fluidity in the reinforcement of the sample), the applied strain-measuring, ultrasonic and acoustic methods for determining the stresses magnitude and strains in cement concrete and structural reinforcement, the dynamics of changes in the measured parameters on one of the samples is shown. The results of the reinforced concrete samples fatigue tests with dimensions of 1500x400x200 mm under various loading conditions are presented, with reference to which regression equations were obtained to determine the number of loading cycles to failure, and endurance coefficients were obtained based on 106 loading cycles. Based on the carried out studies, conclusions are drawn, and the need to develop practical recommendations for taking into account the cyclic nature of the load impact from aircraft and the fatigue strength of cement concrete when assigning operating modes for airfield pavements is indicated.

Aviation, energy, exergy, sustainability, exergoenvironmental and thermoeconomic analyses of a turbojet engine fueled with jet fuel and biofuel used on a pilot trainer aircraft

In this study, J69 military turbojet aero engine of Cessna T-37B/C pilot trainer aircraft fueled by jet fuel and %100-biofuel is assessed with aviation, energy, exergy, sustainability, exergoenvironment and thermoeconomic perspectives to show the reliability of the biofuel in terms of various aspects. The methyl-oleate (C19H36O2) is selected as a model substance for biodiesel for this study, because it is similar to the C:H:O ratio of the commercial biodiesel. J69 turbojet engine's exergy efficiency increases from 17.058% to 17.103% by using biofuel instead of jet fuel. J69 engine's environmental effect factor rises from 5.261 to 5.299 by the utilization of biofuel. Sustainability index reduces 1.463% for the combustion chamber component, 1.201% for the gas turbine component and 0.735% for the overall J69 engine by using biofuel instead of jet fuel. Fuel cost rates of the jet fuel mode is found as 533.355 $/h, while this cost of the biofuel mode is determined to be 846.058 $/h for take-off operation mode. Thereby, fuel cost of biofuel is higher than jet fuel. Specific exergy cost of jet fuel is determined as 20.14 $/GJ, while it is found as 31.667 $/GJ for biofuel. Results of the biofuel and jet fuel modes are close to each other. Thus, biofuel can be considered as a sustainable aviation fuel for J69 military turbojet engine used on the Cessna T-37B/C pilot trainer aircraft.

Development of an anisokinetic particle sampling probe for use in a gas turbine engine compressor

Sand and dust particle ingestion is an inevitability for aircraft operating in arid environments. For conventional takeoff and landing aircraft, significant dust can be ingested into the gas turbine powerplant. Helicopters and vertical takeoff and landing (VTOL) aircraft are at especially high risk due to their tendency to blow significant debris into the air during takeoff and landing operations. The present study highlights the development of an anisokinetic particle sampling probe for use in aircraft engines to obtain real-time measurement of ingested particles often present in these harsh environments. Offtake of particles during engine operation in dusty conditions will provide researchers with an improved understanding of particle breakage tendency and component erosion susceptibility. Three foundational studies were conducted to establish a baseline understanding of probe performance: an aerodynamic study, a particle tracking study, and a particle sampling study. These studies were performed using the Free Jet rig at the Advanced Propulsion and Power Laboratory at Virginia Tech. Particles as large as 1.3 mm were sampled at Mach numbers where M = (0.25, 0.70) and yaw angles ranging from 0° to 45° relative to freestream, conditions not previously investigated. Results indicate that the probe operates sub-isokinetically throughout the full range of test conditions and that probe aerodynamic capture efficiency is inversely proportional to both Mach number and yaw angle. However, this efficiency limitation does not notably influence the sampling probe’s ability to capture the test dust of interest. While the presence of the probe in the flow does result in an airflow velocity reduction of up to 55%, due to their relatively large Stokes numbers the particles of interest only experience a decrease of roughly 5%. These results indicate that this probe is capable of providing researchers with valuable particle size and shape information through effective particle sampling at particle sizes (100 μm ≤ dp ≤ 1,300 μm) and speeds (M ≥ 0.25) not previously investigated.

A Lagrangian Description of Buoyancy Effects on Aircraft Wake Vortices from Wing Tips near a Heated Ground Plane

The present paper introduces the key ideas of a purely Lagrangian temperature particle method, which includes preheating effects on fluid flow nearest a heated wall. The numerical approach is then applied for the study of mixed heat transfer on aircraft wake vortices from wing tips in the vicinity of a heated ground plane, a situation commonly found during landing or takeoff operations at airports around the world. It was found in the literature experimental results of an investigation without the effects of heat transfer and crosswind, which were useful for a comparison with some present numerical results. Other numerical results are also discussed, focusing on the physics of the effects of mixed convection heat transfer and crosswind. As a contribution, the Richardson number is defined in terms of both aircraft wingspan and constant ground plane temperature, being the most important dimensionless group to capture the effects of laminar ascending mixed convection flow. The present methodology presents potentialities for predicting the transport and decay of primary vortical structures (under buoyancy forces), including their interaction with secondary vortical structures generated from a ground plane.

Airports as Sensitive Areas to Mitigate Air Pollution: Evidence from a Case Study in Rome

The environmental concerns are behind urban and regional mobility plans, with one of the goals being to manage surface traffic to reduce emissions. Yet, in sensitive areas such as those around airports, the contribution to the emissions generated by air traffic are commonly not considered. The research goal of this paper is to quantify and compare the magnitude of the emissions generated by both air and surface traffic, taking the second airport in Rome as an example, in the awareness that a proper knowledge of the emission phenomena might help steer local transport policies towards more appropriate and sustainable solutions. The paper describes the case study’s regulatory and land use frameworks both affecting the current traffic patterns around the airport and the emission generation, along with the methodology adopted to quantify the emission magnitude of both air and surface modes; as a result, air traffic emissions are not even comparable in magnitude to those from surface modes. In light of that, implications for surface transport policies are presented, leading to a revision of current mobility plans, and solutions to minimize emissions during land and take-off operations suggested, although problems for their implementations are acknowledged in the conclusions. All within the additional goal to advance the research further afield.

Risk-bounded and fairness-aware path planning for urban air mobility operations under uncertainty

Collision avoidance is an important issue in the field of the autonomous operations of aerial vehicles in dynamic and uncertain urban environments. This paper introduces a risk-bounded and fairness-aware path planning algorithm for multiple electrical vertical take-off and landing (eVTOL) aircraft operating in such environments. This algorithm advances the sampling-based path planning with the risk domain formulation to generate stochastically safety assured collision-free paths that are robust to both vehicle and environmental obstacle uncertainties for multiple eVTOL aircraft. To address the concern of flight fairness between different eVTOLs in the free flight airspace, the strategy of permit assignment is introduced. By incorporating the risk domain formulation into the sampling-based path planning with the strategy of permit assignment, the algorithm proposed in this paper not only inherits the computational advantage of the sampling-based methods, but also guarantees a stochastically feasible flying zone at every time step. Simulation studies demonstrate the promising performance of the proposed algorithm.

DETERMINATION OF THE IMPACT OF DISRUPTIONS IN GROUND HANDLING ON AIRCRAFT FUEL CONSUMPTION

The authors of the paper distinguished two basic problems that occur during the ground handling of aircraft. The first one concerns the identification of disruptions during ground handling that have an impact on the scheduled completion of ground handling. The second problem is determining how these disturbances affect the environment by estimating the increased fuel consumption of the aircraft. In the first step, a catalog of disruptions in the ground handling process of the aircraft, which delays the performance of subsequent aircraft operations, was developed. Simio software was used to analyze the impact of disturbances on the performance of ground service, in which random disturbances were simulated. The simulation was run for several variants, taking into account the sample aircraft and various airlines. The developed model allows for the analysis of the impact of disturbances on the punctual performance of the ground service of the aircraft for various variants with given probability values. In the next step, simulations were performed to determine the impact of the disturbances on the increase in fuel consumption by the aircraft. Research has shown that even minor disruptions increase an aircraft’s fuel consumption over a 200-km flight path. The analyzes carried out in this work are of great importance for sales agents and airlines who strive to minimize the duration of elementary activities and eliminate threats during ground handling. Additionally, it is important from the point of view of environmental protection. As research has shown, even small disturbances can substantially increase fuel consumption, which is not beneficial for airlines. Past research has focused on the analysis of fuel consumption by aircraft and emissions during takeoff and landing operations and taxiing aircraft. There is a large correlation between the disturbances occurring at the parking place and increased fuel consumption, which is important from an economic and environmental point of view.

Construction Progress and Aviation Flight Test of BDSBAS

As an important part of the BeiDou global navigation satellite system (BDS-3), the BeiDou satellite-based augmentation system (BDSBAS) aims to provide a high-integrity navigation service for users in China and its surrounding areas. At present, BDSBAS has completed the preliminary construction of the system and formed the single frequency (SF) augmentation service. The paper introduces the composition and working process of BDSBAS, and expounds the solution and performance evaluation methods of the BDSBAS SF service. Tests based on a general aviation aircraft were carried out at Caihu Airport in Shenyang, China, which simulated the aircraft’s take-off and landing operation during the approach phase and the transition flight operation during the en-route phase. On this basis, the BDSBAS SF service performance was analyzed and evaluated. The horizontal positioning errors of the three flight tests are 1.62, 1.27, and 1.49 m, respectively, and the vertical positioning errors are 4.38, 4.30, and 4.04 m, respectively. In the first two tests, the APV-I availability and continuity of the service reach 100%. In the last test, a receiver false alarm event occurred, resulting in an APV-I availability and continuity of 99.993% and 99.989%, respectively. The event was confirmed to be caused by some aviation environmental factors and was not related to the system service. No integrity events occurred during the tests. The test results show that the positioning accuracy, availability, and integrity of the BDSBAS SF service meet the APV-I level requirements of the ICAO standards, which preliminarily illustrates the ability of BDSBAS to be used in the field of civil aviation.

The omnidirectional runway with infinite heading as a futuristic runway concept for future free route airspace operations

PurposeThe purpose of this paper is to create and analyze the effectiveness of a new runway system, which is totally created for the future free route operations.Design/methodology/approachThis paper researches and analyses the new generated runway concept with the fast time simulation method. Fuel consumption and environmental effect of the new runway system are calculated based on simulation results.FindingsAccording to different traffic density analyses the Omnidirectional Runway with Infinite Heading (ORIH) reduced fuel consumption and CO2 emissions up to 46.97%. Also the total emissions of the ORIH concept, for the hydro carbon (HC), carbon monoxide (CO) and nitrogen oxides (NOx) pollutants were lower than the total emissions with the conventional runway up to 83.13, 74.36 and 51.49%, respectively.Practical implicationsFree route airspaces bring many advantages to air traffic management and airline operations. Direct routes become available from airport to airport thanks to free route airspace concept. However, conventional single runway structure does not allow aircraft operations for every direction. The landing and take-off operations of a conventional airport with a single runway must be executed with only two heading direction. This limitation brings a bottleneck direct approach and departure route usage as convenient with free route airspace concept. This paper suggests and analyzes the omnidirectional runway with infinite heading (ORIH) as a solution for free route airspace.Originality/valueThis paper suggests a new and futuristic runway design and operation for the free route operations. This paper has its originality from the suggested and newly created runway system.

A Computational Study on Rotor and Fuselage Configuration Effect on Rotorcraft Brownout

Rotorcraft brownout is an in-flight visibility restriction caused by clouds of sand and dust particles during landing, takeoff, and near-ground flight operations in arid desert terrain. This complex phenomenon is caused by the entrainment of dust, sand, and ground particles by rotor downwash and is compounded by fuselage geometry and its orientation with respect to the ground. Highly unsteady wind velocities are common in near-ground operations and play a significant role in the particulate cloud's behavior that creates the brownout condition. Experiments and flight tests to understand brownout are challenging, expensive, and risky. Alternatively, computational fluid dynamics (CFD) has been used extensively over the past few decades to study rotorcraft aerodynamics. However, there are additional computational challenges associated with modeling the dust particle transport in a brownout. In this work, a computationally efficient Eulerian-based framework has been developed to model rotorcraft brownout. The flowfield is modeled by Reynolds averaged Navier–Stokes (RANS) equation and is solved using the SIMPLER algorithm. Turbulence properties are modeled using Realizable κ – ε equations, while the rotor is modeled as a momentum source to focus on the global flowfield rather than the flow near the rotors. The Eulerian approach for both the flowfield and the dust transport allows computationally efficient and rapid analysis, taking an order of few hours in a single CPU to a fraction of an hour using GPU-based computation. In this work, results from two sets of experiments are presented. At first, a study on the fuselage's effect on brownout with respect to height for a single-rotor configuration in hover is demonstrated. Next, a study on the brownout characteristics of three rotor–fuselage configurations in hover, namely single-rotor, tandem-rotor, and quad-rotor, is presented. It has been observed that the ground friction velocity profile and flowfield vorticity around the rotorcraft play a significant role in dust cloud behavior. Additionally, the body forces and interference due to the fuselage plays a vital role in the formation of brownout dust clouds. The experiments showed that the quad-rotor is worst affected in terms of size and height of the dust clouds. However, the tandem-rotor has been found to be worst in the terms of average dust density.

EVTOL Certification in FAA and EASA Performance-Based Regulation Environments: A Bird Strike Study-Case

Considering the new generation of air mobility vehicle that has been developed, the electric vertical take-off and landing (eVTOL) aircraft operation will become a reality in the next years. This paper studies the main concerns that can be pointed out due to the different certification approaches that the Federal Aviation Administration (FAA) and European Union Aviation Safety Agency (EASA) have been applying for this kind of aerial vehicle. The paper explores the 14 CFR Part 23-64 and CS-23-5 reorganization to demonstrate how these changes into the requirement structure will be important and influence the eVTOL certification basis construction. Based on the high probability of bird strike events that an eVTOL may face due to its altitude operation, a study-case for a bird strike certification using the known FAA and EASA approaches is performed, considering the current regulation presented into Part 23/CS-23, Part 27/CS-27, Part 29/CS-29 and SC-VTOL-01. The main differences concluded in this evaluation and possible risks and difficulties that an applicant will face during the process are then explored. A final comparison between a bird strike certification process that may be required by FAA and EASA is presented, as well as a recommendation based on the study.