Aircraft Mass Research Articles

Design of a Human Muscle-Powered Flying Machine

This study explores the design and development of a human-powered aircraft (HPA), leveraging modern engineering techniques, materials science, and advanced CAD/CAM tools. The project addresses key aspects of aircraft design, including the geometry of wings and tail, control and power transmission mechanisms, propeller selection, and material identification to achieve ultra-lightweight construction. The 3DExperience platform facilitated comprehensive model creation, simulation, and production process development, while XFLR5 was employed for aerodynamic profile analysis using the vortex lattice and panel methods. JavaProp aided in evaluating propeller thrust and power requirements. Computational fluid dynamics (CFD) simulations using the SST k-ω turbulence model provided critical insights into flow behavior. The design was found to be theoretically capable of flight, although challenges arose in selecting appropriate software for aerodynamic analysis, leading to the use of XFLR5 for early-stage design and the more advanced 3DExperience platform for final evaluations. Although structural strength analyses were not performed due to the complexity of composite materials, future work in this area could enhance the precision of component selection and aircraft mass estimation.

Uncertainties in the Estimated Methane Emissions in Oil and Gas Production Regions Based on Aircraft Mass Balance Flights

Uncertainties in the Estimated Methane Emissions in Oil and Gas Production Regions Based on Aircraft Mass Balance Flights

Influence of structural elasticity on the aerodynamic characteristics of the common research model with deflected control surfaces

Numerical aerodynamic and aeroelastic investigations are conducted for the Common Research Model (CRM) configuration with deployable aileron control surfaces and a trimmable horizontal stabilizer at cruise and off-cruise conditions. The numerical methodology which is implemented in the multi-disciplinary simulation environment SimServer is based on CFD and coupled CFD-CSM simulations. The DLR Tau Code is applied in order to solve the Reynolds-Averaged-Navier-Stokes (RANS) equations. The Spalart-Allmaras turbulence model with Edwards modification is used for the closure modeling of the three-dimensional RANS equations. A linear modal solver is utilized to calculate structural displacements and rotations of control surfaces are modeled by a Chimera approach. A grid independence study is conducted by using the rigid aerodynamic model of the CRM. The main focus of the analysis lies on the evaluation of the stationary CFD-CSM simulations addressing the influence of structural deformation on aileron effectiveness. Influences of various flow conditions and different fuel tank filling levels on the resulting local and global aerodynamic properties of the CRM are investigated. The reduction of aileron effectiveness as well as the difference in horizontal trim deflection angle if structural elastic effects are considered is investigated for the considered Mach number range and aircraft mass configurations.

Investigating the impact of control strategies on the sulfur dioxide emissions of South Korean industrial facilities using an aircraft mass balance approach

We present top-down SO2 emission estimates from four large point sources, including two power plants, a steel mill, and a petrochemical industrial facility in Taean, South Korea. The airborne observations were conducted over two years, with three intensive observations in Fall 2019, Fall 2020, and Spring 2021. During this period, an active policy implementation to reduce air pollutant emissions from large industrial point sources in the region had been exercised, in addition to activity disruptions from the global COVID-19 pandemic. We quantify the observed SO2 emission reduction over the time period resulting from the policy implementation. The Continuous Emission Monitoring System (CEMS) datasets from the coal power plants were 1) validated by comparing them with emissions calculated using a top-down airborne mass balance method and 2) compared with the annual bottom-up national SO2 emission inventory. The comparisons illustrate that the policy implementation resulted in a 35% reduction in SO2 emissions from increased implementation of SO2 reduction technologies such as scrubbers. Finally, the COVID-19 pandemic did not cause a meaningful disruption in SO2 emissions from industrial sectors, such as steel mills and petrochemical manufacturing facilities.

On the conditions for absolute minimum fuel burn for turbofan powered, civil transport aircraft and a simple model for wave drag

Abstract In a recent series of papers, Poll and Schumann have been developing a simple model for estimating fuel burn for turbofan powered, civil transport aircraft for a given mass, Mach number and flight level and in a specified ambient temperature profile for all phases of flight. This paper focuses upon the combination of Mach number and flight level at which an aircraft cruises with the absolute minimum fuel burn. For a given aircraft type, the information necessary to determine these conditions must be specified and this poses a challenge. An initial attempt to obtain these data has been described previously by the first author. In this paper, the optimum conditions are found using a completely different approach. Starting from first principles and using established theory, the equations governing the situation where engine overall efficiency and airframe lift-to-drag ratio both have local maxima at the same flight condition are developed. This special case is termed the “design optimum” condition and, for a specified aircraft mass and a specified atmospheric temperature versus pressure profile, it gives the lowest possible fuel burn for any aircraft and engine combination. The design optimum occurs at a particular Mach number and Reynolds number, and it is a fixed characteristic of the aircraft. The analysis reveals the significance of Reynolds number variations, wave drag, including its derivatives with respect to both lift coefficient and Mach number, and the atmospheric properties. Whilst wave drag is notoriously difficult to determine accurately, it is found that solutions to the equations are not particularly sensitive to the accuracy of this quantity. Consequently, a simple, physically realistic model can give good results. An appropriate model is developed and a complete, approximate solution is obtained. Taking the International Standard Atmosphere as the design atmosphere, results are presented for the 53 aircraft types previously considered by Poll and Schumann. Relative to the design optimum conditions, when Reynolds number is constant and wave drag is zero, compressibility alone reduces L/D by about 5%, reduces lift coefficient by about 1.5% and increases drag coefficient by about 3.5%. Reynolds number variation has little effect upon L/D, but it reduces lift coefficient and drag coefficient by a further 7% and 8% respectively. The reduction in lift coefficient has a significant impact on the optimum cruise flight level. In general, an aircraft’s operating optimum will not coincide with its design optimum, but deviations are expected to be small. Therefore, using the design optimum solution as a reference point, an improved version of the operating optimum estimation method described by Poll and Schumann in previous work is developed. This allows the estimation of the conditions for absolute minimum fuel burn for an aircraft of given mass flying thorough any atmosphere. Updated coefficients for the 53 aircraft types are given.

Exploration of optimal control based surrogate modeling as a basis for fuel efficient 4D aircraft routing on graphs

AbstractFuel efficient coordination of aircraft operations in the Terminal Maneuvering Area of large airports can contribute to the reduction of the environmental impact of air traffic. To exploit the full potential of the air traffic system, coordinated routing in the Terminal Maneuvering Area, runway assignment and scheduling need to be optimized considering detailed models of the aircraft dynamics and performance. Due to the inhomogeneous nature and level of detail of these combined discrete and continuous decision problems, the optimization of the overall operations poses significant challenges. As part of an integrated approach to the solution of this hybrid problem, this work explores the generation of surrogate models for the fuel consumption of individual aircraft using optimal control methods to exploit the physical capability of the aircraft within an operationally permissible envelope. The surrogate models approximate the predicted fuel consumption of a given point-mass aircraft model on short generic trajectory segments. The trade-off between flight duration and fuel consumption on such segments is analyzed, focusing on the influences of initial aircraft mass, altitude, distance, mean climb angle, along-track wind velocity and linear wind shear. An extensive description of the optimal control-based data generation and surrogate modeling methodology is followed by a discussion of the effects of parameter variation. Based on an illustrative case study, the applicability of the approach is critically analyzed.

Analysis of the relationship between mass, speed and cost of an unmanned aircraft

Analysis of the relationship between mass, speed and cost of an unmanned aircraft

Hybrid-electric power unit for an ultralight aircraft

High power-weight ratio, reliability and efficiency are the main design goals for the propulsion system of ultralight aircraft (mass up to 650 kg). For power outputs beyond 40 kW, 4-stroke multi-cylinder SI engines are the most widespread solution, while pure electric powertrains do not appear at the moment as a practical proposition. Four stroke diesel engines would also be very attractive, in particular for military applications, but their weight is significantly higher than their gasoline powered counterpart. The goal of the study presented in this article is to develop a hybrid-electric power unit for ultralights, running on heavy fuels (diesel, kerosene, jet fuels). Reference is made to Falco EVO, by Leonardo, originally equipped by the Rotax 912 ULS/S engine (peak power 73.5 kW, weight about 60 kg): the proposed power unit has the same cylinders layout, smaller overall dimensions and almost equivalent weight. The thermal engine is an innovative two-stroke unit, coupled in parallel to a permanent magnet electric motor. The design and optimization of the hybrid power unit has been supported by CAE tools, including CAD and CFD simulations.The results of the study show that the new hybrid system can save about 30% of fuel mass at the typical cruise conditions, and it can increase the peak power output up to 20%, compared to the reference Rotax engine. The reduction of fuel consumption can be translated into an equivalent increment of the operative range of the aircraft, or into an increase of payload (+30%, considering the Falco EVO aircraft). Finally, compared to the Rotax engine, the hybrid power unit exhibits significantly lower CO2 emissions (from -12% to -37%), thanks to the improvement of fuel efficiency.

Predicting the Remaining Useful Life of Light Aircraft Structural Parts: An Expert System Approach

This paper introduces an expert system approach for predicting the remaining useful life (RUL) of light aircraft structural components by analyzing operational and maintenance records. The expert system consists of four modules: knowledge acquisition, knowledge base, inference, and explanation. The knowledge acquisition module retrieves data from mandatory records, such as aircraft logbooks and mass and balance sheets. The knowledge base stores specific remaining useful lives (SRULs) for different load profiles that are determined using numerical strength analysis. The inference module utilizes the Palmgren-Miner rule to estimate the accumulated fatigue damage of the structural component based on the input data and the knowledge base. Lastly, the explanation module links the accumulated damage to the maintenance program and suggests the appropriate maintenance action. The Cessna 172R main landing gear leg is utilized as a case study, demonstrating the variance of RUL depending on the operating conditions. The objective of this approach is to enhance light aircraft maintenance decision making and advance operational safety.

Spatial attribution of aircraft mass balance experiment CO2 estimations for policy-relevant boundaries: New York City

To effectively address the unprecedented acceleration of climate change, cities across the United States are leading efforts to reduce greenhouse gas emissions. Coherent, aggressive, and lasting mitigation policies in controlling carbon emissions are beginning to be adopted to help strengthen climate resilience across different sectors. However, evaluating the effectiveness of current climate legislation requires careful monitoring of emissions through measurable and verifiable means to inform policy decisions. As a part of this effort, we developed a new method to spatially allocate aircraft-based mass balance carbon dioxide (CO2) emissions. In this work, we conducted 7 aircraft flights, performed downwind of New York City (NYC) to quantify CO2 emissions during the nongrowing seasons between 2018 and 2020. We used an ensemble of emission inventories and transport models to calculate the fraction of enhancements (Φ) produced by sources within the policy-relevant boundaries of the 5 NYC boroughs and then applied that to the bulk emissions calculated using the mass balance approach. We derived a campaign-averaged source-apportioned mass balance CO2 emission rate of (57 ± 24) (1σ) kmol/s for NYC. We evaluated the performance of this approach against other top-down methods for NYC including inventory scaling and inverse modeling, with our mean emissions estimate resulting in a 6.5% difference from the average emission rate reported by the 2 complementary approaches. By combining mass balance and transport model approaches, we improve upon traditional mass balance experiment methods to enable quantification of emissions in complex emission environments. We conducted an assessment using an ensemble of emission inventories and transport models to determine the sources of variability in the final calculated emission rates. Our findings indicate that the choice of inventory accounted for 2.0% of the variability in the emission estimates and that the atmospheric transport model contributed 3.9% at the campaign level. Additionally, on average, at the daily scale, the transport model contributed 7.6% and the inventory accounted for 14.1%. The daily flight-to-flight variability contributed a significant portion, at 42.1%. This approach provides a solution to the difficulty of interpreting aircraft-based mass balance results in complex emission environments.

Methodology for determining the takeoff mass of all-electric aircraft at the early stages of design

Methodology for determining the takeoff mass of all-electric aircraft at the early stages of design

Intelligent feedforward gust alleviation based on neural network

This paper proposes a neural network-based intelligent feedforward gust alleviation framework, which includes a neural network identification model and a neural network controller. A neural network training dataset is formed by collecting flight data and the gust data encountered during the aircraft flight. A neural network identification model is first trained to accurately predict the aircraft’s output. Then, based on the output of the identification model and the collected flight data, the parameters of the time-delay neural network controller are obtained through a learning process. The simulation results show that the designed intelligent controller has good gust alleviation effects for both continuous turbulence excitation and discrete gust excitation. For example, when the aircraft is 40000 kg and the flight speed is 0.81Ma, the controller achieves a 67.82% reduction in wingtip acceleration and a 35.90% reduction in center of mass acceleration under continuous turbulence excitation. When considering the measurement uncertainties, such as noise existing in the collected data, the trained controller can still achieve an acceptable gust alleviation effect. Finally, considering a flight in which the aircraft mass is constantly changing, the intelligent controller, which continuously learns from new flight data, maintains a good gust alleviation effect throughout the flight.

Technical note: Isolating methane emissions from animal feeding operations in an interfering location

Abstract. Agricultural emissions, including those from concentrated animal feeding operations (CAFOs) for beef and dairy cattle, make up a large portion of the United States' total greenhouse gas (GHG) emissions. However, many CAFOs reside in areas where methane (CH4) from oil and natural gas (ONG) complicates the quantification of CAFO emissions. Traditional approaches to quantify emissions in such regions often relied on inventory subtraction of other known sources. We compare the results of two approaches to attribute the CAFO CH4 emission rate from the total CH4 emission rate derived from an aircraft mass balance technique. These methods make use of the mixing ratio data of CH4, ethane (C2H6), and ammonia (NH3) that were collected simultaneously in-flight downwind of CAFOs in northeastern Colorado. The first approach, the subtraction method (SM), is similar to inventory subtraction, except the amount to be removed is derived from the observed C2H6 to CH4 ratio rather than an inventory estimate. The results from this approach showed high uncertainty, primarily due to how error propagates through subtraction. Alternatively, multivariate regression (MVR) can be used to estimate CAFO CH4 emissions using the NH3 emission rate and an NH3 to CH4 ratio. These results showed significantly less uncertainty. We identified criteria to determine the best attribution method; these criteria can support attribution in other regions. The final emission estimates for the CAFOs presented here were 13 ± 3 g of CH4 per head per hour and 13 ± 2 g of NH3 per head per hour. These estimates are higher than the inventory of the US Environmental Protection Agency (EPA) and previous studies highlighting the need for more measurements of CH4 and NH3 emission rates.

Assessing the bias and uncertainties in the aircraft mass balance technique for the determination of carbon dioxide emission rates

Urban areas are the major sources of greenhouse gas emissions but also leaders in emission reduction efforts. Appropriate techniques to quantify emissions and any potential reductions over time are necessary to effectively inform these mitigation efforts. The aircraft mass balance experiment (MBE) is an established technique used for such a purpose. In this work, we use a series of 55 MBEs downwind of power plants to assess the technique’s bias and precision. In addition, we investigate what factors drive the absolute error, determined as the absolute difference between observed and reported emission rates, in individual experiments using multilinear regressions. Power plants are required to monitor their carbon dioxide emissions with an hourly resolution, and these publicly available reported emissions can be directly compared to the mass balance estimates as a pseudo-known release. To quantify the bias we calculated the mean error, which was 10 ± 240 Mg·h−1 (1σ), regressed mass balance emission rates against reported emission rates to yield a slope of 0.967 ± 0.062, and compared the sum across all mass balance emission rates, 31,000 ± 1,000 Mg·h−1, to the sum across all reported emissions, 30,660 ± 740 Mg·h−1. All three of these approaches suggest no systematic bias. Then to quantify the precision for individual determinations we calculated the slope of a regression between the standard deviation across repeated MBEs and the corresponding average emission rate, which is 30.7% ± 6.7%. The main drivers of the absolute error were sparse sampling of the plume, poor horizontal and vertical mixing of the plume, and smaller signal-to-noise ratios. Quantifying the capabilities of this technique provides context for previous analyses and allows stakeholders and researchers to make informed decisions when choosing quantification methods. Identifying the factors that drive the absolute error also allows us to adjust flight design to minimize it and potentially improve uncertainty estimates.

Techniques for adjusting qualities of aircraft structural models for more effective aeroelastic flutter analyses

To solve numerically the problem of aeroelastic flutter, two virtual components are required: a structural finite element model (FEM) and an aerodynamic model. MSC Software package containing Nastran with embedded flutter solution enables to perform calculations with the use of an integrated aeroelastic model. For data block including the model and the set of entry parameters, flutter equation is being solved. On the basis of postprocessed output data curves of run for resulting parameters can be plotted which gives information of flutter critical point.Numerical results may be subject to some uncertainty. Result deviation could occur as effects of various factors resulting from inaccurate geometry or poor structural qualities of mapped aircraft. Structural defects affecting mass or stiffness matrices of FEM are often hard to identify. Aspects important for effective flutter solutions are strictly connected with the coincidence of structural properties of the real aircraft and its model. In the paper, the method of numerical flutter analysis was presented with the use of techniques available in MSC Nastran. Three assessment methods were proposed to identify structural parameters usable for validating FEMs. The method of mass correction relies on adjustment of model mass values and tuning the location of the center of mass of the model to the coordinates of the location of the center of mass of the real aircraft. For adjusting stiffness of model parts, very useful are results obtained from strength test of the real airframe. The completely reliable but costly method is performing ground vibration tests (GVT) to measure precisely resonant frequencies and natural modes of free vibrations. The results obtained from experiments should be treated as the referenced, but tuning FEM to them requires both adjusting numerical eigenfrequencies and normal modes.

Simulation-Based Prediction of Departure Aircraft Performance from Surveillance-like Data Using Neural Networks

Estimating the environmental impact of aviation, in terms of noise and emissions, requires accurate knowledge of flight parameters such as departure/arrival procedure, aircraft mass, thrust and flap settings. However, these parameters are not available from radar/ADS-B data, which are the main sources of multiple flight-specific information including aircraft position over time. This paper introduces a novel approach to estimating these parameters from radar/ADS-B data using three neural network models trained on flight simulator data for the Boeing 747-400 airplane. The models are tested on 2204 simulated flights that are not used for training and that are transformed into radar/ADS-B data formats. The models are capable of predicting the unknown parameters for the ADS-B data format, with the weight prediction error being 2.63% of maximum takeoff weight, the average R2 score for the thrust profile prediction being 89.90% and the flap setting profile having an average R2 score of 84.68%, while for the radar-like data format, the values are 2.11%, 95.74% and 88.24%, respectively. The predicted parameters can be used to improve the environmental impact assessment of individual flights and to support policy-making and management decisions. This approach is a proof of concept based on simulation data that will need to be validated on real data before being applied in practice.

Conceptual assessment of the fuel efficiency of passenger aircraft with the transition to composite wings

One of the success indicators for any new aircraft is its fuel efficiency, influencing both range and cost-effectiveness, as fuel costs amount to 30% of direct operating costs. Based on the analysis of take-off mass response to design changes, a solution to the basic-type aircraft improvement in terms of fuel efficiency is considered. The feature of proposed redesigning is the use of a higher aspect- ratio of an airfoil allowing for fuel efficiency to be increased by reducing the induced drag. Two solutions are considered to substantiate this approach. The first one is the transition to composite wing structures, which will allow for a high aspect ratio of an airfoil without losing rigidity. The second one is the application (if necessary) of devices, reducing the wingspan, caused by the airport restrictions. The methodology for assessing the mass of composite wings based on the universal weight formula by V.A. Komarov which was specified by applying an integral factor considering the features of mass distribution in the structure, the structural adaptation of structure elements and their strength performance, has been proposed. To simplify the arrangement of aircraft with large-span wings in the available airport layout, the application of folding wingtips was considered. The principal analysis of the wingtip swiveling unit structure was performed. The assessment of the folding device effect upon the mass of a passenger aircraft was completed. The proposed approach was verified based on the Boeing company of B777 aircraft family. The numerical analysis of the composite wing application for the IL-96, Tu-214 and SSJ-100 was performed, and the winglet use effect on the MC-21 aircraft was studied.

An Efficient and Robust Sizing Method for eVTOL Aircraft Configurations in Conceptual Design

This paper presents the development of a robust sizing method to efficiently estimate and compare key performance parameters in the conceptual design stage for the two main classes of fully electric vertical take-off and landing (eVTOL) aircraft, the powered lift and wingless aircraft types. The paper investigates hybrids of classical root-finding methods: the bisection, fixed-point and Newton-Rapson methods for use in eVTOL aircraft sizing. The improved convergence efficiency of the hybrid methods is at least 70% faster than the standard methods. This improved efficiency is significant for complex sizing problems. The developed sizing method is used to investigate the comparative performance of the wingless and powered lift eVTOL aircraft types for varying mission lengths. For a generic air taxi mission with a payload of 400 kg, the powered lift type demonstrates its mass efficiency when sized for missions above 10 km in range. However, the simpler architecture of the wingless eVTOL aircraft type makes it preferable for missions below 10 km in range when considering energy efficiency. The results of the sizing study were compared against a selection of eVTOL aircraft data. The results showed a good agreement between the estimated aircraft mass using the proposed sizing method and published eVTOL aircraft data.

Predictive Energy Management for Hybrid Electric Aircraft Propulsion Systems

We present a model predictive control (MPC) algorithm for energy management in aircraft with hybrid electric propulsion systems consisting of gas turbine and electric motor components. Series and parallel configurations are considered. By combining a point-mass aircraft dynamical model with models of electrical losses and losses in the gas turbine, the fuel consumed over a given future flight path is minimized subject to constraints on the battery, electric motor, and gas turbine. The optimization is formulated as a convex problem under mild assumptions and its solution is used to define a predictive energy management control law that takes into account the variation in aircraft mass during flight. We investigate the performance of algorithms for solving this problem. An alternating direction method of multipliers (ADMM) algorithm is proposed and compared with a general purpose convex interior point solver. We also show that the ADMM implementation reduces the required computation time by orders of magnitude in comparison with a general purpose nonlinear programming solver, making it suitable for real-time supervisory energy management control.

Determination of main performance data of an aircraft threedimensional maneuver split-S with a permissible flight envelope limiter

Due to a steady extension of the flight envelope of modern agile combat aircraft, with the growing requirements for state tests, it is increasingly necessary to study the entire flight envelope and specifically, to determine the main performance data of individual maneuvers. Currently, state tests are based on a flight full-scale experiment, which is cost-ineffective in terms of cost, duration, and limit lines of the flight envelope. The accelerating trends to update state tests are semirealistic simulation and complex simulation modeling. The article presents the various techniques to determine main performance data of a three-dimensional maneuver split-S, which include the calculation method, semirealistic simulation, and simulation modeling. The calculation method is understood as calculation formulas expressed from the system of equations for motion of the aircraft mass center. Semirealistic simulation was carried out using a flight-simulation stand by operator pilots. Simulation modeling was conducted using a complex simulation model of an aircraft, consisting of a pilot’s control actions model based on fuzzy logic. The article provides the description, advantages and disadvantages, comparison of the results of each of the techniques. The calculation method, despite its efficiency, is the most inaccurate due to the complexity and inability to define the average flight parameters. Additionally, this method does not take into consideration such factors as the aircraft flight configuration, atmospheric disturbances, the pilot’s command profile, the logic of the permissible flight envelope limiter operation. The results of semirealistic simulation showed that this method is more accurate than the calculation one, but complex and time consuming in terms of the organization and execution of experiments. The analysis of the study illustrated that the most appropriate way to determine main performance data of split-S is simulation modeling on a complex simulation model of the aircraft, because the given method considerably saves financial and time resources used on state flight tests.