• Abdullah Desai

Student thesis: Phd


A number of recent commercial aircraft and engine programmes add to the ever growing list of failing Large-Scale Complex Engineered Systems (LSCES). Across the engineering spectrum, LSCES are commonly over-budget, delayed, and under-performing. Some of the problems can be traced back to the early design stages, where design engineers select what they think is the ‘best’ design. This decision is made in the face of conflicting requirements, competition in the industry, and other elements of uncertainty and risk. A review of the current Engineering Design Environment revealed that existing design methodologies such as Requirements-Based Engineering Design (RBED) does not directly address decision-making nor can it differentiate between different conceptual designs. This leads to subjective decision-making and dead-weight loss over the Product Life-Cycle (PLC), which can create LSCES with little value opportunity, even before the conceptual design stages. As a result, there is a growing interest in Decision-Based Engineering Design (DBED), specifically the Value-Driven Design (VDD) methodology, for conceptual aircraft and engine design. DBED removes requirements and utilises an objective function for design optimisation and decision-making over the PLC. However, the most prominent VDD economic objective function, Surplus Value (SV), is limited by multiple assumptions that rarely hold true in the real world. The aim of this research is to improve the commonly employed conceptual aircraft and engine design methods currently used in the industry. The proposed VDD methodology addresses a number of assumptions inherent within the current SV method. This is achieved by creating a multi-stage, non-cooperative, competitive framework, which employs several models to characterise the behaviour of airlines and manufacturers within the commercial aviation industry. This provides a method to determine the value of a programme to enable design engineers to objectively select the best course of action. Design engineers can also track the effect of different designs, different competitor designs, competitors from adjacent markets, and the decisions of other market players. The capabilities of the proposed method are demonstrated using two case studies focusing on the notional Middle of the Market (MoM) and the Wide-body Market (WBM). The MoM case study demonstrated that without addressing the inherent assumptions of the SV method, the value of a new MoM programme can be calculated incorrectly by up to 400% or $780B. Furthermore, the WBM case study demonstrated how investing in a new programme could result in the engine manufacturer losing up to $320M or 16% value across its enterprise. The proposed method allows design engineers to analyse different strategies and evaluate the total impact on value across the enterprise. Ultimately, these characteristics enables design engineers to make informed, objective, transparent, repeatable, and traceable programme-level decisions.
Date of Award1 Aug 2019
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorIain Dupere (Supervisor) & Peter Hollingsworth (Supervisor)


  • Utility
  • Value Centric Design
  • Risk
  • Commercial Aviation
  • Framework
  • Value Driven Design
  • Decision-making

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