A conceptual design methodology for evaluation of alternate propulsion system modifications on small aircraft

A conceptual design methodology for evaluation of alternate propulsion system modifications on small aircraft

Conceptual design is often considered to be the most important step in the design of a new product or the modification of an existing product. The important steps in this conceptual design phase is the synthesis of potential solutions into concepts, the evaluation of these concepts within a repeatable and robust design methodology framework and analysis to identify and characterise the preferred solution concept. This research has arisen from problems associated with developing aircraft-based design modification concepts and predicting the impact of these changes as they propagate or flow down through the various aircraft subsystems, impacting engineering design, and leading to certification and operations challenges. This research problem is particularly evident in highly integrated systems such as high-performance military aircraft, helicopters, and complex civil aircraft. To illustrate this methodology the author has selected two case studies which apply two different alternate propulsion system technologies to small aircraft. These case studies were selected to provide a diverse design modification space encompassing differing aircraft roles and mission types, differing technologies and subsystems integration scope, and different data sources collection and analysis methods.

In order to combine the elements of design synthesis, evaluation of concept alternatives and analysis of outputs, this thesis has formulated a matrix-based conceptual design methodology. This methodology extends current knowledge by implementing the concepts of design synthesis, evaluation and analysis as an iterative process, and building and linking together existing techniques. This new methodology combined various techniques and methods such as Quality Function Deployment (QFD), quantified morphological matrices (QMM), Pugh’s decision matrices, change options Multiple-Domain Matrices (MDM), and has adapted the Change Propagation Method (CPM).

The second extension to current knowledge in this area was the development of Engineering and Certification Domain Mapping Matrix (DMM) techniques based on Design Structure Matrices (DSM). This extension into engineering and certification domain was undertaken to ensure that important modification-related risks and costs were incorporated into the early stages of design. The extension adopted existing DSM and DMM-based techniques and tools to evaluate the impact of changes to subsystems and hence impact of risks and costs resulting from aircraft modifications using change propagation method analysis techniques.

The validation of this conceptual design methodology was achieved by verifying and assessing the adequacy of its application through an analysis process which examined (1) coverage of the design space attributes; (2) validation of the methodology against accepted scientific and industry conceptual design frameworks; and (3) confirmation of the existing techniques, structures and tools applied within the methodology.