In its initial version, the L-1011 TriStar (the Dash One) is designed for short/medium-haul routes—typically carrying 250/270 mixed-class passengers distances of from 300 to more than 3000 nm. A general arrangement is shown in Fig. 1. As indicated in Fig. 2, the L-1011-1 payload/range curve is placed between those of the DC-8-61 and the Boeing 747. It should be noted that both these aircraft are designed for long ranges and are suited only for operation from major airports. On the other hand, the TriStar has airport performance, in terms of field length, comparable to that of the much smaller short-range types, typified by the Boeing 727. This, in broad terms, illustrates the primary design objective of the Dash One. The dashed line on Fig. 2 shows the payload/range curve of the L-1011-2 which will, of course, have an airport performance at the heavier gross weights more in keeping with long-haul requirements.

The general subject of this session is the effect of shortages of raw materials on the development of aircraft. It is most important at the outset to distinguish between two related but essentially different situations.

• (a) A genuine shortage in which the material in question just cannot be obtained in anything approaching adequate quantities.

• (b) A situation in which, for some reason or other (possibly associated with some moderate limitation in supply), the price of the material increases rapidly.

In either case there is a pressure to reduce the amount of the material that is used, but in the first case one must do so almost regardless of cost or operational effects, while in the second case purely economic and competitive considerations apply. This is most clearly illustrated in the case of fuel—I shall show later in this paper that we could hope to achieve very large savings in fuel usage— perhaps as high as 40%—in a new generation of aircraft, but some of this saving can only come at the cost of reduced speed, reduced operational flexibility or increased complexity. The major decision that must be made is how far along this line should we go—nevertheless, if we are to have the freedom to make that decision we must continue to pursue with all energy the R & D necessary to achieve the maximum improvements.

Man-powered aircraft have been built in which a man generating between 0·5 and 0·6 horse-power has remained airborne in straight flight for upwards of 3 minutes. Noone has yet succeeded in demonstrating sustained turning flight nor can sufficient endurance be expected in order to achieve the difficult Kremer prize course.

It seems probable that refining the current design of aircraft is unlikely to bring the required horse-power down by a factor approaching two and therefore a radically new approach is required if the Kremer course is to be successfully completed.

The transport of thermal energy from one location to another, for example from a heat source to a remote heat sink, has been a major topic of study over the past decade.

Most of the work has been directed at improving the efficiency of heat transport, while retaining the simplicity and reliability of what is, in general, considered as a secondary part of any system.

One device which has fulfilled most of the requirements of such a heat transport system is the heat pipe. The heat pipe was first proposed by Gaugler of the General Motors Corporation (US) in 1942, and was the subject of a patent published in 1944. Because the heat transfer problems of that time could be solved by more conventional methods, Gaugler's ideas remained unexploited for approximately 20 years. It was not until the early 1960s that Grover, without knowledge of Gaugler's proposals, in effect re-invented the heat pipe while working at Los Alamos Scientific Laboratory. Grover and his colleagues were working on spacecraft power generation systems at the time.

In many branches of engineering there is an increasing demand for light materials which will operate in conditions of elevated temperature and /or under severe temperature gradients. Magnesium alloys have found extensive use in the field of aviation, due to their lightness and retention of structural strength at elevated temperatures. When this type of structure is subjected to service conditions, it is likely that the general temperature level will change, in addition to the establishment of temperature gradients. A detailed analysis of the structural displacement, loading and stress under such conditions would undoubtedly be aided by a knowledge of the mathematical “law” describing the coefficient of linear thermal expansion as a function of temperature. A single integration of this equation over the limits of temperature will give the displacement per unit length. Integration of the product of this equation and Young's modulus of elasticity, ie integration of the thermal modulus, provides an accurate determination of the thermal stresses promoted by internal restraint, resulting from temperature gradients in the structure.

The effect of imperfections on the behaviour of a thin-walled strut designed for simultaneous local and overall buckling, the theoretical optimum design, has been illustrated by van der Neut. Local deviations from flatness remove the discontinuity between the pre- and post-buckled states, and loss of stiffness prior to local buckling may initiate premature failure in an overall mode. Imperfection sensitivity of this kind is most severe when the two modes are coincident. Thompson and Lewis have examined the optimum design of a strut with imperfections and show, in a simple example, that maximum efficiency is achieved by ensuring that overall buckling occurs before local buckling and that the actual failing load may be significantly reduced. For larger imperfections the optimum may be virtually eliminated.

It is well established that the change of entropy across a normal shock is of third order when expressed in terms of the static pressure rise. The purpose of this note is to draw attention to weaknesses in one method of establishing this result, and to put forward an alternative analysis.