Lufthansa Technik (LHT) is a provider of maintenance, repair and overhaul (MRO) services for aircraft. While LHT has traditionally performed the MRO services in-house, the subcontracted operations business is gaining momentum.
With about 90,000 outsourced MRO purchase orders (POs) per year, the process becomes increasingly complex. In the past, the company set the objective of achieving an average turnaround time (TAT) of five shop calendar days (SCD) for internal repair operations.
One of the main goals of LHT is to achieve an average TAT of fifteen SCD for the subcontracted MRO operations, between the monitoring points ‘Creation PO Requisition’ (i.e.: TS 29) and ‘Receive Unit Transaction’ (i.e.: TS 69). The current TAT is significantly higher, with substantial process variability.
The repair subcontracting value-chain consists of several processes, which fall under different areas of responsibility. Due to the stochastic nature of the series of processes and because
many variables influence the overall performance of the system, a simulation study needs to be conducted. The present thesis aims to develop an analytical input model for a simulation study in technical procurement.
Practical relevancy of the research problem
The building of the analytical input model and subsequent simulation model is a substantial
milestone towards the process optimization in the subcontracted MRO operations business.
The modeling of processes as an M/M/1 queuing system is the first step needed in order to
i) Simulate the processes and leverage optimization methods from the field of Production Logistics;
ii) Identify whether the application of queuing theory elements for process
description and analysis within technical procurement would aid in improving the processes.
Theoretical relevancy of the research problem
The thesis aims at applying already existing elements from queuing theory and statistics to a relatively new field – technical procurement, as to bring a contribution to the queuing science, an interface between queuing theory and practice.[...]
Table of Contents
1 Introduction
1.1 Problem of the Thesis
1.2 Aims of the Thesis
1.3 Course of Research
2 Critical Perspective on Queuing Theory Approach
3 Theoretical Foundations
3.1 Queuing Theory
3.2 Probability Theory and Statistics
3.3 Production Logistics
3.4 Discrete Event System Simulation
4 Methodology
4.1 System Analysis
4.2 Raw Data Collection
4.3 Data Preparation and Modeling Procedure.
4.4 Inputs for the Analysis
4.5 Output of the Analysis
4.6 Assumptions and Simplifications
5 Implementation
5.1 Exemplary Procedure Funnel 1
5.2 Table of Results
6 Final Consideration
6.1 Results and Critical Reflections
6.2 Implications for Further Research
6.3 Implications for Practice
Objectives & Topics
This thesis aims to develop an analytical input model for a material-flow simulation study in technical procurement by applying queuing theory and statistical methods to identify appropriate probability distributions for arrival rates and service times within the subcontracted maintenance, repair, and overhaul (MRO) operations business.
- Process mapping and system analysis of the outsourced MRO value chain.
- Evaluation of queuing theory applicability in a fragmented technical procurement environment.
- Statistical modeling of arrivals (Poisson distribution) and service durations (Exponential distribution).
- Implementation of input models based on historical enterprise resource planning (ERP) data.
- Verification of null hypotheses using goodness-of-fit tests.
Excerpt from the Book
3.1 Queuing Theory
The research is contained within the general area of queuing theory, a theoretical discipline used to mathematically model real world processes that involve waiting and service times. Queuing theory has its origins in the early 1900s for the design of telephone systems. For analyzing production systems queuing theory plays an important role, since it provides a good conceptual model of waiting line conditions, providing one with an understanding of the influencing factors like arrival distribution, service distribution or number of servers.
By a queuing process will be meant a mathematically specified operation in which units arrive, wait and then leave. Units are arriving at the queue, and departing from the server, which, is conceptualized as a delay block.
Summary of Chapters
1 Introduction: Discusses the growing complexity of outsourced MRO services at Lufthansa Technik and sets the research goal of developing an analytical input model for simulation.
2 Critical Perspective on Queuing Theory Approach: Critically evaluates the limitations of standard queuing models and justifies their selection over other tools like Logistics Operating Curves for this specific application.
3 Theoretical Foundations: Provides the necessary mathematical and logistical background, including queuing theory, probability, statistics, and discrete event system simulation.
4 Methodology: Details the approach to system analysis, raw data collection from ERP systems, and the procedure for identifying and fitting probability distributions.
5 Implementation: Presents the practical application of the methodology, demonstrating the computation of arrival rates and system times, and summarizes the statistical results.
6 Final Consideration: Reflects on the findings, discusses the validity of the chosen models, and provides implications for future research and practical simulation implementation.
Keywords
Queuing Theory, MRO, Technical Procurement, Simulation, Input Modeling, Poisson Distribution, Exponential Distribution, Material-Flow, Logistics, Process Mapping, Statistical Analysis, Goodness-of-Fit, Work in Process, Turnaround Time, System Performance
Frequently Asked Questions
What is the core focus of this research?
The research focuses on creating an analytical input model for material-flow simulations in the context of outsourced aircraft maintenance, repair, and overhaul (MRO) services.
What are the primary themes covered in the thesis?
The thesis explores the application of queuing theory, production logistics, stochastic modeling, and the specific challenges of modeling technical procurement processes.
What is the main research question or objective?
The main objective is to determine which probability distributions best represent arrival rates and service times in order to build a functional input model for a simulation study.
Which scientific methods are employed?
The study utilizes system analysis, statistical distribution fitting (such as Poisson and Exponential distributions), and goodness-of-fit tests like the Kolmogorov-Smirnov test.
What does the main part of the thesis examine?
The main part covers the theoretical foundation of queuing systems, the methodology for data collection from ERP systems, and the step-by-step implementation of modeling three distinct procurement processes.
Which keywords best characterize this work?
Key terms include Queuing Theory, Material-Flow Simulation, Technical Procurement, Stochastic Input Modeling, and MRO Value Chain.
How does this thesis address the stochastic nature of MRO processes?
It addresses stochastic variability by using historical data to identify and validate probability distributions that represent the arrival patterns and processing times of repair orders.
What are the practical implications of the results for Lufthansa Technik?
The models developed serve as a foundation for future simulation studies, which can help in optimizing load leveling, increasing the number of servers, and improving overall system turnaround times.
- Arbeit zitieren
- Ileana Constantinescu (Autor:in), 2011, Process Mapping and Stochastic Input Modeling, München, GRIN Verlag, https://www.hausarbeiten.de/document/181775
