The main objective of the paper is to evaluate the potential of reducing theenvironmental impact of civil subsonic aviation by using hydrogen fuel. Thepaper is divided into three parts of which this is Part III. In Part I thebackground, prospects and challenges of introducing an alternative fuel inaviation were outlined. The aero engine design when using hydrogen was coveredin Part II. In this paper, Part III, the subjects of optimum cruising altitudeand airport implications of introducing liquid hydrogen-fuelled aircraft areraised.

For minimum global warming, the results of a preliminary analysis associated withlarge uncertainties suggest that cryoplanes should cruise at an altitude ofabout 2-3km below where conventional aircraft cruise today. Ignoring the costimplications, from an airport infrastructure point of view, it seems feasible tochange to hydrogen use. With respect to the availability of energy, it would bereasonable to change from kerosene to liquid hydrogen as fuel for all civilaviation refuelling in Sweden.

In the present investigation, a potential flow model based on panel method has been developed for calculation of two dimensional separated flows past square and rectangular cylinders. Free vortex lines are assumed to emanate from the points of separation that converge downstream of the body. The converged wake shape is iteratively obtained by integrating the velocity vectors at the collocation points. For solving separated flow past square and rectangular cylinders, four different versions of the solver have been developed for a wide range of incidence, namely, for zero, low, moderate and high angles of incidence. For validation of computed results, experimental investigations have been carried out in a low speed wind tunnel to obtain the surface pressure distribution on square cylinder and rectangular cylinder over a range of angles of incidence. Comparison is reasonably good.

This paper looks at how the aerospace industry can achieve the Acare goal of greener manufacturing, maintenance and disposal. It looks further than merely reducing waste and eliminating hazardous materials and processes and suggests that the organisational structure of the industry will play an important role in facilitating a move towards such a goal. Greater co-operation or integration within the industry at all stages of the product life cycle chain is a fundamental requirement as individual companies run a risk of increasing the total environmental burdens if they concentrate solely on reducing their own impacts without considering the effect a change they make may have on other companies. The use of comprehensive environmental supply chain management systems and end of life plans can smooth the implementation of extended product responsibility and accelerate the benefits of greener manufacturing, maintenance and disposal.

The recent decline in the USA aerospace industry has resulted in fewer programs, fewer engineers, and a potential loss of capability for future technology development. As engineers retire or leave the industry, their corporate memory or retained knowledge must be preserved for future use. A process to capture their expert knowledge is described, and a framework which provides a means to retrieve and use this valuable technical information is shown. Four examples of integrated design and analysis systems for four diverse technologies and applications are discussed.