There are currently numerous government and industry entities engaging in aviation technology development programs [1,2,3]. Due to the number of technologies being investigated there exists an understandable desire to rank technologies in order to identify the most beneficial ones. Historically, this has been done through the use of “waterfall” or technology stack-up charts .One purpose of such waterfall charts is to show the amount of benefit each technology provides to the integrated system. This approach is valid, and extremely useful, for verifying the modeling of such technologies; however, there are shortcomings in using a waterfall chart to assess the relative contribution of individual technologies to the overall system level benefit. This is due to several considerations that are not taken into account when developing conventional technology ranking charts. For example, the relative impact of each technology can be highly dependent on the order in which technologies are applied, the system the technology is applied to, the relative design changes that occur either before or after the technology is applied, and other technologies that are present on the system. In order to explore these characteristics this paper uses propulsion technologies since there are strong interactions between the various components of an engine. Engine technologies also commonly rely upon enabling technologies which provide less benefit, but without them the larger “bigger hitting” technologies are not feasible.
This research explores and quantifies the issues associated with several conventional methods of creating technology ranking charts. Propulsion technologies targeting both thermal and propulsive efficiency are applied to a baseline aircraft and engine configuration. Several conventional technology ranking and stack-up techniques are applied in order to evaluate how the relative impacts of individual technologies vary greatly depending on the assessment method. In all cases the same technology packages are applied such that the final benefit is the same, regardless of ranking method. It is suggested that a range of currently used ranking techniques all used to determine a more robust estimate of the impact.