An Assessment of the Economic Viability of Engine Wash Procedures on the Lifecycle Cost of an Aircraft Fleet

Aircraft operators find themselves in an environment in which the economic and ecological pressure on companies is constantly increasing. To address this, significant improvements of aircraft efficiency are necessary. One way to reduce both operating cost and the environmental impact is to regularly perform on-wing engine washes which reduce the exhaust gas temperature as well as improve aircraft fuel consumption. To estimate the lifecycle impact of engine cleaning procedures, a variety of factors must be taken into account, ranging from environmental to operational. The lifecycle costing method developed by DLR, known as LYFE (Lifecycle Cash Flow Environment), enables the consideration of various factors to investigate the impact of engine washes over the lifetime of an aircraft or fleet. LYFE uses discrete event simulation to model the product lifecycle from order to operation until disposal of an aircraft fleet. For this analysis the tool is extended to separate the lifecycles of the engines and those of the aircraft, which enables the modeling of switching engines among aircraft. To more realistically represent engine fouling and engine performance degradation, representative weather data at airports is also included in the simulation. Using this information, we have developed a prognostics model to monitor the health of the engine, predict the timing of engine shop visits and automatically and dynamically schedule engine wash events. For the latter, three different algorithms varying in the prognostic horizon were developed and compared to one another. The results show that engine washing can improve the time on wing of the engine by up to 2240 flight cycles. Due to lifetime limitations by life limited parts and assumptions within this study, no extension of the service life of the engine can be achieved within the scope of this investigation. On the other hand, the fuel cost could be reduced at an average of 1.2% while the total cost remained the same. With this holistic view of how engine washes within a fleet influence the time on wing of the engine and affect its lifecycle cost a much more realistic statement about this on-wing maintenance action is possible

A Modular Framework for the Life Cycle Based Evaluation of Aircraft Technologies, Maintenance Strategies, and Operational Decision Making Using Discrete Event Simulation

Current practices for investment and technology decision making in aeronautics largely rely on regression-based cost estimation methods. Although quick to implement and easy to use, they suffer from a variety of limitations, both in temporal space and scope of applicability. While recent research and development in this area addresses these to a certain extent, aerospace engineering still lacks a flexible and customizable valuation framework. To this end, a generic environment for economic and operational assessment of aircraft and related products named LYFE is presented. This tool employs a discrete event simulation which models the product life cycle from its order through decades of operation and maintenance until disposal. This paper introduces its key characteristics and default methods alongside its modular program architecture. The capabilities are demonstrated with a case study of on-wing engine cleaning procedures which are triggered by a customized decision making module. Thereby, the impact on engine health, fuel efficiency and overall economic viability is quantified. On the whole, the framework introduced in this paper can be used to analyze not only physical products but also operational procedures and maintenance strategies as well as specified decision making algorithms in terms of their impact on an aircraft’s or system’s life cycle

Comradeship of Cock? Gay porn and the entrepreneurial voyeur

Thirty years of academic and critical scholarship on the subject of gay porn have born witness to significant changes not only in the kinds of porn produced for, and watched by, gay men, but in the modes of production and distribution of that porn, and the legal, economic and social contexts in which it has been made, sold/shared, and watched. Those thirty years have also seen a huge shift in the cultural and political position of gay men, especially in the US and UK, and other apparently ‘advanced’ democracies. Those thirty years of scholarship on the topic of gay porn have produced one striking consensus, which is that gay cultures are especially ‘pornified’: porn has arguably offered gay men not only homoerotic visibility, but a heritage culture and a radical aesthetic. However, neoliberal cultures have transformed the operation and meaning of sexuality, installing new standards of performativity and display, and new responsibilities attached to a ‘democratisation’ that offers women and men apparently expanded terms for articulating both their gender and their sexuality. Does gay porn still have the same urgency in this context? At the level of politics and cultural dissent, what’s ‘gay’ about gay porn now? This essay questions the extent to which processes of legal and social liberalization, and the emergence of networked and digital cultures, have foreclosed or expanded the apparently liberationary opportunities of gay porn. The essay attempts to map some of the political implications of the ‘pornification’ of gay culture on to ongoing debates about materiality, labour and the entrepreneurial subject by analyzing gay porn blogs

The Changing Landscape for Stroke\ua0Prevention in AF: Findings From the GLORIA-AF Registry Phase 2

Background GLORIA-AF (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients with Atrial Fibrillation) is a prospective, global registry program describing antithrombotic treatment patterns in patients with newly diagnosed nonvalvular atrial fibrillation at risk of stroke. Phase 2 began when dabigatran, the first non\u2013vitamin K antagonist oral anticoagulant (NOAC), became available. Objectives This study sought to describe phase 2 baseline data and compare these with the pre-NOAC era collected during phase 1. Methods During phase 2, 15,641 consenting patients were enrolled (November 2011 to December 2014); 15,092 were eligible. This pre-specified cross-sectional analysis describes eligible patients\u2019 baseline characteristics. Atrial fibrillation disease characteristics, medical outcomes, and concomitant diseases and medications were collected. Data were analyzed using descriptive statistics. Results Of the total patients, 45.5% were female; median age was 71 (interquartile range: 64, 78) years. Patients were from Europe (47.1%), North America (22.5%), Asia (20.3%), Latin America (6.0%), and the Middle East/Africa (4.0%). Most had high stroke risk (CHA2DS2-VASc [Congestive heart failure, Hypertension, Age  6575 years, Diabetes mellitus, previous Stroke, Vascular disease, Age 65 to 74 years, Sex category] score  652; 86.1%); 13.9% had moderate risk (CHA2DS2-VASc = 1). Overall, 79.9% received oral anticoagulants, of whom 47.6% received NOAC and 32.3% vitamin K antagonists (VKA); 12.1% received antiplatelet agents; 7.8% received no antithrombotic treatment. For comparison, the proportion of phase 1 patients (of N = 1,063 all eligible) prescribed VKA was 32.8%, acetylsalicylic acid 41.7%, and no therapy 20.2%. In Europe in phase 2, treatment with NOAC was more common than VKA (52.3% and 37.8%, respectively); 6.0% of patients received antiplatelet treatment; and 3.8% received no antithrombotic treatment. In North America, 52.1%, 26.2%, and 14.0% of patients received NOAC, VKA, and antiplatelet drugs, respectively; 7.5% received no antithrombotic treatment. NOAC use was less common in Asia (27.7%), where 27.5% of patients received VKA, 25.0% antiplatelet drugs, and 19.8% no antithrombotic treatment. Conclusions The baseline data from GLORIA-AF phase 2 demonstrate that in newly diagnosed nonvalvular atrial fibrillation patients, NOAC have been highly adopted into practice, becoming more frequently prescribed than VKA in Europe and North America. Worldwide, however, a large proportion of patients remain undertreated, particularly in Asia and North America. (Global Registry on Long-Term Oral Antithrombotic Treatment in Patients With Atrial Fibrillation [GLORIA-AF]; NCT01468701

An Analysis of the Influence of Network Effects on Lifecycle Based Aircraft Technology Assessment

Assessing the anticipated economic performance of a product is an important part in the development and decision making process. This is especially true for businesses operating in low-profit and high-cost environments such as airlines. Frameworks and tools that aid in this process typically focus on direct operating cost (DOC) or lifecycle cost (LCC) of a single aircraft. However, airlines rarely operate only one aircraft and to transfer the singular results to the complete fleet is not necessarily as simple as a multiplication. Therefore, the assessment framework LYFE (Lifecycle Cashflow Environment) developed by DLR had to be revised and modified in order to evaluate technologies on fleet level. This paper presents the new fleet assessment capability and demonstrates it on an assessment of Hybrid Laminar Flow Control (HLFC). For this study, HLFC was applied as a retrofit on the horizontal and vertical tailplane of Lufthansas A330 fleet during their D-check. The analyses comprise a fleet wide and time dependent fuel burn evaluation, average maintenance cost and overall economic feasibility. Combined with the LYFE inherent discrete event simulation, this modification enables the inclusion of network effects into detailed technology assessment

A Modular Framework for Life Cycle Assessment of Aircraft Maintenance

Facing the increasing environmental awareness and the growing pressure on aviation, life cycle assessment is becoming an essential prerequisite to quantify the ecological impact of aircraft. However, such evaluations are typically confined the manufacturing, flying, and occasionally disposing processes, while maintenance activities are often neglected or simplified. This paper presents a process-based approach that is able to ecologically assess different maintenance operations using a normalized inventory. The developed approach divides aircraft maintenance into different segments and then evaluates them individually. By using a modular and discrete-event driven framework, which can model the entire life cycle of an aircraft, the economic and, above all, ecological consequences of maintenance activities are then considered and analyzed. The process based life cycle assessment approach is applied using the example of a jet engine wash and, with the help of a parameter study, conclusions are then drawn regarding the ecological impact of this maintenance task. The results show that taking environmental aspects into account can positively affect the decision-making process of otherwise economically driven airlines. In the case of the engine wash, for example, this means that even a small economic investment can lead to significant ecological benefits

Estimating Maintenance Costs of New Aircraft Concepts under Uncertainties: A Feasibility Study

The push for greener air mobility has led to innovative aircraft designs. To ensure their viability, it is essential to minimize environmental impact and ensure profitability. This requires analyzing life cycle costs, including maintenance. Despite technological advances such as hydrogen storage systems, research into maintenance costs remains limited. This study aims to estimate the maintenance costs of hydrogen storage systems as part of the life cycle costs of a hydrogen-powered aircraft. By comparing conventional and hydrogen-powered aircraft concepts, technical differences of the fuel storage systems are examined, and expert insights on initial cost, lifetime, and maintenance effort are gathered. Initial scarcity of data prevents using typical probabilistic methods, so the Dempster-Shafer Theory of Evidence is used to harness expert opinions. A global sensitivity analysis quantifies the impact of input uncertainty on maintenance costs, identifying key cost drivers and parameter effects. Systematic input variation identifies critical factors for further investigation and design improvements. This study demonstrates the early estimation of maintenance costs through an innovative framework. The results improve the understanding of maintenance costs and associated conditions and serve as a basis for decision-making on the integration of hydrogen storage systems and new aviation technologies. Further information will be published soon