Normal Flight Operations Research Articles

A Nonlinear Beam Finite Element with Bending–Torsion Coupling Formulation for Dynamic Analysis with Geometric Nonlinearities

Vibration analysis of wing-box structures is a crucial aspect of the aeronautic design to avoid aeroelastic effects during normal flight operations. The deformation of a wing structure can induce nonlinear couplings, causing a different dynamic behavior from the linear counterpart, and nonlinear effects should be considered for more realistic simulations. Moreover, composite materials and aeroelastic tailoring require new simulation tools to include bending–torsion coupling effects. In this research, a beam finite element with bending–torsion coupling formulation is used to investigate the effects of the deflection of beam structures with different aspect ratios. The nonlinear effects are included in the finite element formulation. The geometrical effect is considered, applying a deformation dependent transformation matrix. Stiffness effects are introduced in the stiffness matrix with Hamilton’s Principle and a perturbation approach. The results obtained with the beam finite element model are compared with numerical and experimental evidence.

Multisensor Avionics Architecture for BVLOS Drone Services

This ADACORSA demonstrator focuses on the implementation of a fail-operational avionics architecture combining Commercial Off-The-Shelf (COTS) elements from the automotive, the aerospace and the artificial intelligence world. A collaborative sensor setup (Time-of-Flight camera and FMCW RADAR from Infineon Technologies, stereo camera, LiDAR, IMU and GPS) allows to test heterogeneous sensor fusion solutions. A Tricore Architecture on AURIX™ Microcontroller supports the execution of safety supervision tasks as well as data fusion. A powerful embedded computer platform (NVIDIA Jetson Nano) accelerates AI algorithms performance and data processing. Furthermore, an FPGA enables power optimization of Artificial Neural Networks. Finally, a Pixhawk open-source flight controller ensures stabilization during normal flight operation and provides computer vision software modules allowing further processing of the captured, filtered and optimized environmental data. This paper shows various hardware and software implementations highlighting their emerging application within BVLOS drone services.

Using machine learning methods and EEG to discriminate aircraft pilot cognitive workload during flight

Pilots of aircraft face varying degrees of cognitive workload even during normal flight operations. Periods of low cognitive workload may be followed by periods of high cognitive workload and vice versa. During such changing demands, there exists potential for increased error on behalf of the pilots due to periods of boredom or excessive cognitive task demand. To further understand cognitive workload in aviation, the present study involved collection of electroencephalogram (EEG) data from ten (10) collegiate aviation students in a live-flight environment in a single-engine aircraft. Each pilot possessed a Federal Aviation Administration (FAA) commercial pilot certificate and either FAA class I or class II medical certificate. Each pilot flew a standardized flight profile representing an average instrument flight training sequence. For data analysis, we used four main sub-bands of the recorded EEG signals: delta, theta, alpha, and beta. Power spectral density (PSD) and log energy entropy of each sub-band across 20 electrodes were computed and subjected to two feature selection algorithms (recursive feature elimination (RFE) and lasso cross-validation (LassoCV), and a stacking ensemble machine learning algorithm composed of support vector machine, random forest, and logistic regression. Also, hyperparameter optimization and tenfold cross-validation were used to improve the model performance, reliability, and generalization. The feature selection step resulted in 15 features that can be considered an indicator of pilots' cognitive workload states. Then these features were applied to the stacking ensemble algorithm, and the highest results were achieved using the selected features by the RFE algorithm with an accuracy of 91.67% (± 0.11), a precision of 93.89% (± 0.09), recall of 91.67% (± 0.11), F-score of 91.22% (± 0.12), and the mean ROC-AUC of 0.93 (± 0.06). The achieved results indicated that the combination of PSD and log energy entropy, along with well-designed machine learning algorithms, suggest the potential for the use of EEG to discriminate periods of the low, medium, and high workload to augment aircraft system design, including flight automation features to improve aviation safety.

Influence of Aviation Meteorological Service on Flight Operation and Improvement Measures

Aviation meteorological services (AMS) are essential steps of civil aviation transportation, which play an important role in normal flight operations. In this study, the AMS are firstly briefly summarized. Then, the influence of AMS on normal flight operations is analyzed. Finally, some measures to improve AMS are proposed, so as to provide some reference for relevant departments.

Numerical Simulation of Bird Strike on Jet Engine Considering Bird Ingestion Requirements

To mitigate the consequences of bird strikes, compliance with bird ingestion requirements must be substantiated by corresponding physical tests relying on a jet engine. However, current simulation models capturing soft-impact damage on the engine are mostly limited to part of the front of the engine, such as fan blades. In this paper, considering relationships and interactions among engine components under normal flight operations, the numerical model of a jet engine subjected to bird strike was developed to evaluate impact damage and the effect of fan rotor unbalancing on the jet engine. First, substitute bird models were established using the smoothed particle hydrodynamics method, and then validated with experimental and theoretical results. Second, to characterize the maximum impact damage, critical ingestion parameter was derived from simulations of the prescribed bird targeted at fan blades at the required bird ingestion conditions. Finally, considering single-bird-ingestion requirements, numerical analysis of a jet engine during impact was investigated. It is of great significance for engine manufacturers to incorporate a predictive modeling methodology of a turbine engine under bird strikes into crashworthiness of engine designs.

Modeling and Controlling the Dynamic Behavior of an Aerial Manipulator

Unmanned Aerial Vehicles (UAVs) installed with a gripper is an effective and robust way to grab the wanted object from inaccessible locations. In this study, we develop a novel control mechanism to regulate the nonlinear dynamics of the aerial manipulator. In this research, hex-rotor UAV is chosen in order to fulfill the mission requirement in terms of size and weight of the object. It is equipped with a manipulator and the gimbal-based camera that will help to see the desired object and then transport it. The aerial vehicle has six-degrees-of-freedom (6-DOF) and the installed manipulator has 4-DOF which in total makes the 10-DOF aerial manipulator vehicle. At the time of clutching the desired object to eliminate or reduce the external noise, and stabilize the dynamic behavior of the aerial manipulator, we need a robust and efficient controller. To solve the aforementioned problems, this study develops a hybrid control mechanism that tracks and controls the altitude and attitude of UAV after clutching the desired object. The main contribution of this study is to design a control mechanism that includes Model Reference Adaptive Control with an Integrator (MRACI) in conjunction with regulation, pole-placement and tracking (RST) control algorithm. On one hand, the simulation results using MATLAB demonstrate the efficiency of the proposed control mechanism. On the other hand, to cross verify the validity of the proposed control algorithm, we perform the experiment by clutching the desired object at hovering and normal flight operation.

Cabin air quality – Quantitative comparison of volatile air contaminants at different flight phases during 177 commercial flights

Quantitative assessment of human exposure to semi-volatile organic compounds (SVOC), such as tricresyl phosphates (TCP) that may originate from engine oil contamination of the cabin air, during air travel is challenging due to the technical complexity of the air supply in commercial jet aircraft. Normal flight operations involve reduced air exchange before and during takeoff, which results in increased concentrations of potential cabin air pollutants. During cruise, normal ventilation rates (>20 h− 1) are reestablished and thus lower pollutant concentrations are also reestablished. This relationship between changes in ventilation rate and associated changes in pollutant concentrations during the departure phase is first described in the present study, although this effect was found by previous studies that investigated distinct flight phases.The perception of so-called "smell events" in cabin air does not necessarily indicate the presence of harmful contaminants and TCP-containing oil mist must be clearly distinguished thereof. Thus, aldehydes, VOCs, and organophosphates such as TCP were investigated. In this paper, the occurrence of TCP contamination in a bleed air free Boeing 787 (B787) aircraft is reported for the first time. The results presented here show that there are TCP sources other than bleed air from leaky engines. Furthermore, exceptional release behavior of TCP suggests that a more detailed classification for engine oil-triggered cabin air contamination (CAC) events is necessary. This study evaluated measurement data from 177 flights that were either commissioned by the EASA or conducted as part of studies with the support of Lufthansa, Condor, and British Airways.

Aircraft Clean Air Requirements Using Bleed Air Systems

There are certification and airworthiness requirements relevant to the provision of clean breathing air in the crew and passenger compartments. There have been continuing reports and studies over the years regarding oil fumes in aircraft, including impaired crew performance. Oil fumes are viewed in varying ways ranging from rare seal bearing failures, to low level leakage in normal flight. A Masters of Science (MSc) research degree was undertaken to assess whether there is any gap between the certification requirements for the provision of clean air in crew and passenger compartments, and the theoretical and practical implementation of the requirements using the bleed air system. A comprehensive literature search reviewed applicable certification standards, documented and theoretical understanding of oil leakage. Two types of interviews were conducted to address the research questions. Key aviation regulators were questioned about the process by which they certify and ensure compliance with the clean air requirements. Aerospace engineers and sealing professionals were interviewed about their understanding of how oil may leak past compressor oil bearing seals, and into the air supply under various flight conditions. The outcome of the research showed that there is a gap between the clean air certification requirements, and the theoretical and practical implementation of the requirements using the bleed air system. Low level oil leakage into the aircraft cabin in normal flight operations is a function of the design of the engine lubricating system and bleed air systems, both utilising pressurised air. The use of the bleed air system to supply the regulatory required air quality standards is not being met or being enforced as required.

Sound power level and sound pressure level characterization of a small unmanned aircraft system during flight operations

Unmanned aerial vehicles, actually Federal Aviation Administration calls them unmanned aircraft systems, have aroused a great deal for many applications in the scientific, civil, and military sectors. The goal of this article is to evaluate the acoustic emissions of some small unmanned aircraft systems during normal flight operations (e.g. take off, landing, turning, and hovering) related to electric engines and propellers. This analysis will be useful for developing a system (unmanned aircraft systems Tracking and Reconnaissance System), which will be able to locate a small unmanned aircraft system using its sound power level, in a prefixed area. The investigation on sound power levels and sound pressure level is based on EN ISO 3745, which specifies measurement method. The acoustic measurements were carried out in an anechoic room, and the results of each unmanned aircraft system have been presented and discussed.

Sustainable bio kerosene: Process routes and industrial demonstration activities in aviation biofuels

Alternative fuels are expected to play a major role in EU in the coming years due European Directives on the promotion of renewable energies and reduction of greenhouse gas emissions in transports. However, while in road transports a variety of possible renewable fuels (mainly biofuels, but also electricity) can be considered, in aviation only high quality paraffinic biofuels can be adopted. This means that biomass must be converted through advanced processes into pure hydrocarbon fuels, fully compatible with the existing systems. The aviation sector is responsible for the 2% of the world anthropogenic CO2 emissions and the 10% of the fuel consumption: airlines’ costs for fuel reach 30% of operating costs. In addition, the aviation traffic is expected to double within 15years from 2012, while fuel consumption and CO2 emissions should double in 25years. Thus, more than 2 billion people and 40 Mt of good/cargo will have to be moved every year. In this context, the EU Flightpath set a target of 2Mt per year for aviation alternative fuel by 2020 (i.e. 4% of annual fuel consumption). New processes towards bio-hydrocarbons are being developed, demonstrated and soon industrialized.The present work explores the possible routes from biomass feedstock to sustainable paraffinic fuels, either through bio or thermo-chemical processes, as well as discusses those more mature, focusing on industrial demonstration initiatives. In fact, while the number of possible options towards paraffinic biofuel production is very large, and covers both thermochemical and biochemical routes, as well as hybrid one, only two pathways are today ready for testing a significant large scale: these are FT and Hydrotreating. Major industrial activities and testing experiences are thus reported in the present work.In this context, the ITAKA group is developing a full value-chain in Europe to produce sustainable drop-in Synthetic Paraffinic Kerosene (SPK) – called HEFA – in an economically, socially and environmentally sound manner, at large scale enough to allow testing its use in existing logistic systems and in normal flight operations in Europe. The generated knowledge will aim to identify and address barriers to innovation. Within ITAKA, possible pre-processing of used (waste) cooking oil (UCO) to make it compatible with current downstream hydroprocessing techniques are being investigated: this can includes esterification of waste oils, as well as catalytic thermal processing, which will be carried out in a pilot unit available at RE-CORD/CREAR. First samples of feedstock oils were collected and characterized, for further investigation towards their conversion into biokerosene through hydrotreatment.

Static Stall Model in Aeroelastic Analysis of a Flexible Wing with Geometrical Nonlinearity

This paper presents the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with a nonlinear unsteady aerodynamic model. A high-aspect ratio and flexibility are the specific characteristics of this type of wing. Wing flexibility, coupled with a long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore, a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear flexible Euler-Bernoulli beam equations is used for the structural modeling. An unsteady nonlinear aerodynamic considering static stall based on the Wagner function is used for determination of aerodynamic loading of the wing. Combining these two types of formulations yields fully nonlinear integro/differential aeroelastic equations. Using Galerkin’s method, a mode summation technique, and a numerical method, the governing equations are solved to predict the nonlinear aeroelastic response of a wing in the stall region. The results obtained are compared with the results given in the literature. In addition, the effects of the static stall characteristics of some typical airfoils on the aeroelastic behavior of a flexible wing are investigated. The results indicate that in a range of static stall angles of attacks there is a specific angle of attack in which the limit cycle oscillation boundary speed has a maximum value.

Restricted sleep and negative affective states in commercial pilots during short haul operations

This study aims to investigate (1) the relationship between restricted sleep and Heightened Emotional Activity (HEA) during normal flight operations, and (2) whether sleep patterns influence the strength of the HEA as a response to threats. Accident investigation reports continue to highlight the relationship between restricted sleep and poor safety outcomes. However, to date we have a limited understanding of how sleep and HEA interact. A total of 302 sectors of normal airline flight operations were observed by trained observers, and instances of heightened emotional activity were recorded. During the cruise phase of each of these sectors, crew members were asked to calculate the amount of sleep they had obtained in previous 24 and 48 h. In the 302 sectors of normal flight operations, 535 instances of HEA were observed. Descriptive analyses of instances of HEA and sleep in the prior 24 and 48 h showed a significant relationship between the occurrence of HEA and recent sleep. The relationship between restricted sleep and HEA suggests that there may well be further implications with respect to operational safety.

An efficient method for nonlinear aeroelasticy of slender wings

This paper aims the nonlinear aeroelastic analysis of slender wings using a nonlinear structural model coupled with the linear unsteady aerodynamic model. High aspect ratio and flexibility are the specific characteristic of this type of wings. Wing flexibility, coupled with long wingspan can lead to large deflections during normal flight operation of an aircraft; therefore, a wing in vertical/forward-afterward/torsional motion using a third-order form of nonlinear general flexible Euler–Bernoulli beam equations is used for structural modeling. Unsteady linear aerodynamic strip theory based on the Wagner function is used for determination of aerodynamic loading on the wing. Combining these two types of formulation yields nonlinear integro-differentials aeroelastic equations. Using the Galerkin’s method and a mode summation technique, the governing equations will be solved by introducing a numerical method without the need to adding any aerodynamic state space variables and the corresponding equations related to these variables of the problem. The obtained equations are solved to predict the aeroelastic response of the problem. The obtained results for a test case are compared with those of some other works and show a good agreement between results.

Prior Sleep, Prior Wake, and Crew Performance During Normal Flight Operations

Industries that operate outside daytime hours are known to carry higher safety risks related to fatigue. While we are beginning to understand better the role of fatigue in increasing the risk of accidents in the workplace, relatively little is known about the manifestation of fatigue in the multicrew environment, where operational safety involves interaction between two or more crewmembers and a complex operating environment. Data were collected by trained expert observers during 302 normal flight operations of a commercial airline flying short-haul jet operations. Crewmembers were asked to provide an estimate of their total sleep in the prior 24 h, total sleep in the prior 48 h, and total wake time since their last sleep period at the commencement of cruise. Observers used the Threat and Error Management Model, developed as a standardized and highly structured method to collect operational performance data. Restricted sleep in both the 24-h and 48-h period prior to each sector were found to be associated with changes in crews' threat and error management performance. However, prior wake was not associated with any significant changes in crew performance. Restriction to less than 6 h sleep in the prior 24 h was associated with degraded operational performance and increased error rates. The findings of this study provide support to the notion that prior sleep is a critical fatigue-related variable. Moreover, the use of individual subjective assessment of prior sleep as a component of an overall fatigue risk management system is reinforced.

Nonlinear aeroelastic response of slender wings based on Wagner function

This paper presents a method for nonlinear aeroelastic analysis of Human Powered Aircraft (HPA) wings. In this type of aircraft there is a long, highly flexible wing. Wing flexibility, coupled with long wing span can lead to large deflections during normal flight operation; therefore, a wing in vertical and torsional motion using the second-order form of nonlinear general flexible Euler–Bernoulli beam equations is used for structural modeling. Unsteady linear aerodynamic theory based on Wagner function is used for determination of aerodynamic loading on the wing. Combining these two types of formulations yields the nonlinear integro-differentials aeroelastic equations. Using the Galerkin's method and modes summation technique, the governing equations will be solved by introducing an iterative numerical method to predict the aeroelastic response of the problem. The obtained results for a test case are compared with those of linear study which shows good agreement for speeds less than the flutter speed, but the nonlinear model shows limit cycle oscillations for the wing beyond the flutter boundary.

IT Autopilot: A flexible IT service management and delivery platform for small and medium business

IT Autopilot is a flexible architecture to support the delivery of information technology (IT) systems management services. Complex services that involve several tools require integration between the tools and automated processes that can invoke multiple tools. Designed primarily for the small and mid-sized enterprise, the architecture of IT Autopilot allows it to be deployed as a set of local and remote services delivered by the enterprise or by service providers as a flexible and extensible service offering. The IT Autopilot integrated IT service management platform is able to combine different tools and services to create specific, customized IT service solutions. Using the analogy of an autopilot on an airplane, the pilot first performs a set of manual operations to get the airplane off the ground and flying. Next, the autopilot is engaged to carry on normal flight operations. In our vision, there is an initial manual configuration step before IT Autopilot is enabled to take over and maintain the customer's normal IT operational state. In this paper we explain our vision and describe the prototype system we have implemented.

Predictors of Threat and Error Management: Identification of Core Nontechnical Skills and Implications for Training Systems Design

In normal flight operations, crews are faced with a variety of external threats and commit a range of errors that have the potential to impact negatively on the safety of airline operations. The effective management of these threats and errors therefore forms an essential element of enhancing performance and minimizing risk. Recent research has reinforced the need to examine a range of nontechnical or crew resource management skills that form threat and error countermeasures. This article provides an analysis of the predictors of threat and error management in normal flight operations within the context of a Southeast Asian airline. Through the structured observation of crews' performance during normal flight operations, data were collected in relation to a set of contextual factors and nontechnical skills. Crews' threat and error management actions were then analyzed in relation to these factors, and predictive models of threat and error management at various phases of flight were developed. The results of this study demonstrate the ways in which this type of data analysis can highlight the strengths and weaknesses of operational performance and suggest that this type of performance evaluation can offer individual organizations invaluable information for enhanced training system design through the further development of scenario-based training.