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The purpose of this study is to analyze influence of airfoil profile on lateral-directional flying quality of flying wing aircraft. The lateral-directional stability is always insufficient for aircraft with the layout due to the absence of vertical stabilizer. A flying wing aircraft with double-swept wing is used as research object in the paper.

The 3D model is established for the aircraft with flying wing layout, and parametric modeling is carried out for airfoil mean camber line of the aircraft to analyze lateral-directional stability of the aircraft with different camber line parameters. To increase computational efficiency, vortex lattice method is adopted to calculate aerodynamic coefficients and aerodynamic derivatives of the aircraft.

It is found from the research results that roll mode and spiral mode have a little effect on lateral-directional stability of the aircraft but Dutch roll mode is the critical factor affecting flying quality level of such aircraft. Even though changes of airfoil mean line parameters can greatly change assessment parameters of aircraft lateral-directional flying quality, that is kind of change cannot have a fundamental impact on level of flying quality of the aircraft. In case flat shape parameters are determined, the airfoil profile has a limited impact on Dutch roll mode.

Influences of airfoil profile on lateral-directional flying quality of aircraft with double-swept flying wing layout are revealed in the thesis and some important rules and characteristics are also summarized to lay a theoretical basis for design of airfoil and flight control system of aircraft with the layout.

Flying J was a family-owned company that operated travel plazas, oil refineries, a bank for trucking companies, and other related businesses. In early 2009, Crystal Call Maggelet, the majority shareholder and new CEO of Flying J, was tasked with saving the company founded by her father in 1968. In the intervening forty years Flying J had grown from four gas stations to a vertically integrated $18 billion company. Declining crude oil prices, decreased cash reserves, and multiple internal challenges forced most Flying J subsidiaries to file for bankruptcy protection. This came as a surprise to the company's lenders, suppliers, customers, and employees, who did not know the company was in trouble until it was unable to meet payroll just days before Christmas 2008.

Maggelet was determined not only to return her family's company to profitability but also to repay all of Flying J's debts, retain as many of the firm's 12,000 employees as possible, and avoid compromising employees' savings (e.g., 401K retirement accounts). All of the company's advisors told her it could not be done. They thought a more likely outcome would be paying creditors nine cents on every dollar owed. If that happened, Maggelet's family's holdings would be almost entirely wiped out according to the “priority of claims” rules in bankruptcy, and the family would end up with only 1.2 percent of a restructured Flying J.

However, to the surprise of its advisors and creditors, Flying J paid its debts in full, mostly by cutting operating costs before selling assets. The family was left with a smaller, but still very profitable company.

After students have analyzed the case they will be able to:

• Determine governance issues in family-owned businesses

• Identify the pursuit of growth as a typical cause of bankruptcy

• Understand why cash flow accounting is more important than GAAP accounting

• Grasp how huge variations can occur when calculating enterprise valuations of distressed businesses

• Understand the differences among law, governance, and ethics

Determine governance issues in family-owned businesses

Identify the pursuit of growth as a typical cause of bankruptcy

Understand why cash flow accounting is more important than GAAP accounting

Grasp how huge variations can occur when calculating enterprise valuations of distressed businesses

Understand the differences among law, governance, and ethics

To ensure the stability of the flying wing layout unmanned aerial vehicle (UAV) during flight, this paper uses the radial basis function neural network model to analyse the stability of the aforementioned aircraft.

This paper uses a linear sliding mode control algorithm to analyse the stability of the UAV's attitude in a level flight state. In addition, a wind-resistant control algorithm based on the estimation of wind disturbance with a radial basis function neural network is proposed. Through the modelling of the flying wing layout UAV, the stability characteristics of a sample UAV are analysed based on the simulation data. The stability characteristics of the sample UAV are analysed based on the simulation data.

The simulation results indicate that the UAV with a flying wing layout has a short fuselage, no tail with a horizontal stabilising surface and the aerodynamic focus of the fuselage and the centre of gravity is nearby, which is indicative of longitudinal static instability. In addition, the absence of a drogue tail and the reliance on ailerons and a swept-back angle for stability result in a lack of stability in the transverse direction, whereas the presence of stability in the transverse direction is observed.

The analysis of the stability characteristics of the sample aircraft provides the foundation for the subsequent establishment of the control model for the flying wing layout UAV.

DURING the past 40‐odd years or so, a number of experimental aeroplane types have been invented, visualized, designed, constructed and even flown which, in a quite unorthodox manner, had neither behind the wing nor in front of it any sort of stabilizing and/or controlling surfaces.

Forecasting techniques improve supply chain resilience by ensuring that the correct parts are available when required. In addition, accurate forecasts conserve precious resources and money by avoiding new start contracts to produce unforeseen part requests, reducing labor intensive cannibalization actions and ensuring consistent transportation modality streams where changes incur cost. This study explores the effectiveness of the United States Air Force’s current flying hour-based demand forecast by comparing it with a sortie-based demand forecast to predict future spare part needs.

This study employs a correlation analysis to show that demand for reparable parts on certain aircraft has a stronger correlation to the number of sorties flown than the number of flying hours. The effect of using the number of sorties flown instead of flying hours is analyzed by employing sorties in the United States Air Force (USAF)’s current reparable parts forecasting model. A comparative analysis on D200 forecasting error is conducted across F-16 and B-52 fleets.

This study finds that the USAF could improve its reparable parts forecast, and subsequently part availability, by employing a sortie-based demand rate for particular aircraft such as the F-16. Additionally, our findings indicate that forecasts for reparable parts on aircraft with low sortie count flying profiles, such as the B-52 fleet, perform better modeling demand as a function of flying hours. Thus, evidence is provided that the Air Force should employ multiple forecasting techniques across its possessed, organically supported aircraft fleets. The improvement of the forecast and subsequent decrease in forecast error will be presented in the Results and Discussion section.

This study is limited by the data-collection environment, which is only reported on an annual basis and is limited to 14 years of historical data. Furthermore, some observations were not included because significant data entry errors resulted in unusable observations.

There are few studies addressing the time measure of USAF reparable component failures. To the best of the authors’ knowledge, there are no studies that analyze spare component demand as a function of sortie numbers and compare the results of forecasts made on a sortie-based demand signal to the current flying hour-based approach to spare parts forecasting. The sortie-based forecast is a novel methodology and is shown to outperform the current flying hour-based method for some aircraft fleets.

At the end of the case study discussion, students will able to state the importance of outsourcing with comparing pros and cons in business decision-making; review the value bestowed to the community in using sustainable raw material while at the same time conserving the ancient style of artwork particular to the area; discuss the utility of the products manufactured by “Flying Colours,” especially for the lockdown period which was because of the pandemic; and demonstrate and interpret the use of shark and mosquito bite matrix.

Arun Kumar Patni, 47, and his wife Neelima Patni, 43, are co-founders of Flying Colours, a start-up company based in Jaipur, in the state of Rajasthan, India. Their enterprise was engaged in the manufacturing and marketing of bird products and accessories, including bird feeders, bird houses, earthen water bowls, etc. In July 2020, post-lockdown, they were desperate to hire carpenters to restart their factory. However, COVID-19 posed a serious challenge, making it very difficult to replace their skilled carpenters, who had returned to their native places and had not come back. This disrupted production and order fulfilment. Keeping this situation in perspective in anticipation of the continuing pandemic crisis, Neelima was in favour of outsourcing basic production and designing the birdfeed decoration and artwork in-house. Meanwhile, Arun instead favoured continuing full in-house production as before, by hiring replacement carpenters. Yet for an in-house full-scale production, procuring raw material was a difficult task because of the lockdown. The situation had earlier taken a turn for the worse when Arun had advertised an exchange marketing policy to let customers return their old bird feeders for a 20% discount on a new one. This campaign was a huge success and resulted in a sales spike but unfortunately it caused a huge stock of returned products in their warehouse. Arun initially planned to repair and resell them as refurbished products. It now seemed impossible, because local carpenters demanded higher labour charges than the regular carpenters did. Flying Colours had provided skills workshops and hired external trainers to train unskilled carpenters prior to lockdown, so now all the training investment was in vain. Cash liquidity, sales, marketing, etc. were almost at a standstill.

This case particularly focuses on undergraduate-level students pursuing business or commerce programs, especially those studying core course: Entrepreneurial Strategic Management.

Teaching notes are available for educators only.

CSS 3: Entrepreneurship.

THE usual methods for obtaining data on the hydrodynamic characteristics of flying boats during flight tests involve motion pictures of an instrument panel and records of oscillograph traces. The analysis of the photographic records is so time consuming that the results are not always available when needed, and in many cases more data are accumulated than is physically possible to analyse. In order to conserve manpower and to obtain directly usable data, new methods have been developed for making quantitative hydrodynamic flight tests. The test techniques were devised to relate, whenever possible, numerical values to sensations experienced by the pilot of a flying boat during take‐off and landing.

Hill equations have definite limitation in the design of multiple spacecraft formation flying in eccentric orbits. To solve the problem, the design method of spacecraft formation flying in a circular reference orbit based on Hill equation can be generalized and applied to spacecraft formation flying in eccentric orbits.

In this paper, T‐H equation is expressed as the explicit function form of reference orbit true anomaly, and the state transition matrix of relative motion of spacecraft formation flying in eccentric orbits is derived. According to the requirement that relative dynamics equation of spacecraft formation flying in eccentric orbits has periodicity solution, the paper theoretically gives the initial condition needed by the long‐term close‐distance spacecraft formation flying including the relationship between relative position and relative velocity. Without perturbation the spacecraft formation, which satisfies the initial periodicity restriction, can keep long‐term close‐distance flying without the need of active control.

Based on the theoretical analysis, some numerical simulations are carried out. The results demonstrate that each spacecraft in eccentric orbits can run in a periodic motion surrounding the center spacecraft under some conditions. And spacecraft formation reconfiguration is implementing according to missions.

Combined with the periodicity restriction primary condition a new method about spacecraft formation reconfiguration is put forward. The method given by this paper can be applied to eccentric orbits of arbitrary eccentricity, and provides theoretical reference for orbit design of spacecraft formation flying in eccentric orbits.

EACH September the eyes of the aeronautical World turn towards the S.B.A.C. Air Display and Exhibition with interest unequalled by any other event. It is fitting that the Display is now held each year at the airfield of the Royal Aircraft Establishment, one of the world's most prominent aeronautical research centres. This interest becomes increasingly keen too, as the preview day comes closer, because new prototypes of unorthodox designs often appear a short time before the Show to illustrate the results of years of careful planning, development and research of the particular company. These designs often mould the path of progress for smaller countries without the economic resources to forge the way ahead alone. Most British citizens are very proud of their country's place in aviation today, both in the military and civil fields. This is understood by most foreigners because it is clear that Britain has won a place in aeronautical development second to none.

The proposed model aims to consider the flying hours as a criterion to initiate maintenance operation. Based on this condition, aircraft must be checked before flying hours threshold is met. After receiving maintenance service, the model ignores previous flying hours and the aircraft can keep on flying until the threshold value is reached again. Moreover, the model considers aircraft age and efficiency to assign them to flights.

The aircraft maintenance routing problem (AMRP), as one of the most important problems in the aviation industry, determines the optimal route for each aircraft along with meeting maintenance requirements. This paper presents a bi-objective mixed-integer programming model for AMRP in which several criteria such as aircraft efficiency and ferrying flights are considered.

As the solution approaches, epsilon-constraint method and a non-dominated sorting genetic algorithm (NSGA-II), including a new initializing algorithm, are used. To verify the efficiency of NSGA-II, 31 test problems in different scales are solved using NSGA-II and GAMS. The results show that the optimality gap in NSGA-II is less than 0.06%. Finally, the model was solved based on real data of American Eagle Airlines extracted from Kaggle datasets.

The authors confirm that it is an original paper, has not been published elsewhere and is not currently under consideration of any other journal.