When you heard the title of my paper you were probably disappointed. Indeed, other lecturers have already discussed very similar subjects on this same occasion. To recall the most recent:

• I. G. Bloch in 1963: “The Aeronautical Industry in the Europe of Tomorrow”

• Mr. Handel Davies in 1968: “Some Thoughts about the Future of European Aeronautics”.

• M. Louis Giusta in 1969: “European Co-operation in the Aviation Industry and its Future Development”.

On reading again these three papers, I was struck by the pertinence of most of the points which were made. In that case, one may ask, why refer to them again? The reason is that many predictions have failed to materialise and many warnings do not seem to have been sufficiently heeded.

The purpose of this paper is to record the structural design experience obtained during the construction of the Puffin aircraft. The paper starts with some fundamental considerations, follows by outlining the specific solutions adopted on the Mk I and Mk II versions of the Puffin, and concludes with some suggestions on future structural development possibilities.

The setbacks and frustratons encountered in the desgn and construction of man-powered aircraft are well-known. Many machines have been completed only after the expenditure of several man-years’ effort. Often, groups have reaped little reward in proportion to their labours. The majority of man-powered aircraft have suffered severe damage early in their flight career either from storage accidents, from mismanagement in ground handling, or following loss of control while in flight. The record underlines the vulnerability of these lightweight, flimsy aircraft and emphasises the difficulty in conducting safe operations while simultaneously achieving productive flying.

Aviation is an advanced technology, constantly pursuing higher performance, and backed by painstaking research into new materials and techniques. The target of “performance” has changed with the period, but the extent to which energy can be provided for propulsion has always been rated of major importance. Since propulsive energy is stored on board in a fuel medium, the more obvious criteria for the fuel are the energy density (based on mass and/or volume) and the proportion of this energy usable within the propulsion system. At the same time, the fuel must respond safely to reasonable handling procedures. The more subtle requirements to emerge over recent years include those of a minimum potential for pollutant formation and, in the case of very high speed flight, a maximum capacity for heat absorption.

The purpose of this note is:

1. (a) to provide a method for evaluating the fuel mass penalty incurred in flight after fitment of a system to an aircraft. The method relies only on a limited number of parameters and should prove particularly useful in the early design stages of a new project.

2. (b) to show the relative importance of the parameters involved, in particular the relationship between the fuel penalty due to system basic mass and that due to system drag (other than mass drag) which, depending on the flight conditions, could be significant or even greater.