When the Society asked me to give a short introductory paper on overall costs at a meeting where the emphasis will be mainly concerned with financial aspects of aircraft and airports, I felt it might be of some interest to you in the short time I have available to discuss overall costs in terms of urban transport systems. My reasons for thinking this are that for air trips between European cities and particularly within the UK, the convenience or otherwise that a passenger experiences in getting from his home, for example, to the airport and again from the airport at the end of his journey to his point of business, depends largely on the urban transport situation and as you will all know it is a very significant factor in the competition between land based modes and air based modes.

I would begin by asking whether cost benefit analysis has any place in this symposium. It is not directly concerned with finance although one could say that it is a technique for deciding whether a thing is worth the money or, if there is more than one thing, which thing is best value for money. But we need not bring money in at all. The real object is to decide whether a thing, or which thing, is in the best interests of the community.

As such it is a proper prelude to an investment and deserves a place in the symposium.

It is a prerequisite that by investigating the financing of aircraft procurement in relation to transport systems, we first accept the predominance of the defence budgets on all aircraft projects. However, because the penalty of democracy is public accountability, defence procurement is supposedly in one ledger and civil projects in another. Whereas budgets, accounting and technical errors in the defence category cause only domestic problems with the electorate, similar mistakes in the civil field can have far more disastrous effects on overseas clients and world trade. How short this paper would be in the USSR. Just a case of debiting the manufacturer with research, development, raw materials, labour and overhead—if that exists—and then, when each aircraft is ready for delivery, credit the manufacturer with total cost—surely profit is unthinkable—and debit the USSR Air Force and Aeroflot.

To say that air transport is a complicated business is trite but nevertheless true. Only part of the job of providing service to the public is done by the airline itself. To operate efficiently in the complex environment of the world's airways, some clearly defined, some not, an airline requires a co-ordinated system of highly developed technical equipment, skilled personnel and competent management, largely financed by Government authorities who believe it is in their best interests to do so. In the beginning, the airlines were creatures of Government, either actually owned by them or supported and subsidised by them in one way or another. Then and now, the airlines are subject to close Governmental control both as regards their technical standards and performance and their commercial environment. The airline industry has now grown up and is big business. Many airlines are still owned by Governments wholly or in part but all are now expected to operate on a commercial basis.

The title of this paper has been chosen for several reasons. To take financing first: problems of financing in transportation occur at several distinct levels, namely

—systems suppliers, for example, aircraft manufacturers;

—terminals and infrastructure, for example, ports and airports;

—operating companies, for example, airlines.

We shall essentially be focusing attention on financing of systems.

Secondly, innovation will receive attention within the systems, because while financing of conventional systems may not be easy, that of innovatory systems is often almost impossible. An innovatory transportation system may be defined as a package of equipment or components, at least some of which are radically new and which are designed to meet the requirements of a given transportation market.

A recent study by digital computer of the theoretical characteristics of a family of low drag aerofoil sections was prompted some time ago by the need to redesign a particular NACA 6-series aerofoil of high camber (which was not producing the desired pressure distribution). Understandably, therefore, this new family of aerofoils—christened the GU series—was patterned on the NACA sections, and designed to provide the characteristic region of uniform velocity over the forward portion of one surface at the extreme of the low drag range, followed by a compression region of roughly constant adverse pressure gradient.

Velocity defect law has been accepted as a universal velocity distribution for a turbulent boundary layer along a flat plate. The two necessary conditions for such a similarity to exist are not fulfilled with flat plate boundary layer having smooth or uniformly rough surfaces. Rotta has proved that a linear increase of surface roughness in the stream direction is necessary to ensure such a similarity. This note is an experimental investigation into turbulent boundary layer along a flat plate with linear increase of roughness height. It is obvious that, under such conditions, complete similarity characteristics are fulfilled.

Recently Professor Black showed a photograph of a baby seal swimming in a shallow pool at a speed greater than the speed of the surface waves. In terms of the hydraulic analogy the seal may be said to be a “supersonic” swimmer.

In lighter vein, it may be wondered whether supersonic flow extends to the insect world! The attached Schlieren photograph shows, for example, a blowfly in a flow at a Mach number of 1·4. The blowfly, suitably stiffened by a film of clear plastic to prevent it from shattering, was sting mounted in a shock tube containing freon as the working fluid.

A lecture called “Some aspects of buffeting” was given to the Society in 1961 by my colleague Mr. R. Fail. In that lecture the emphasis was primarily on the prediction of buffet onset in flight from model tests in wind tunnels, and on the prevention of buffeting. In the subsequent 11 years there has been much more interest in the prediction of the severity of buffeting above the buffet boundary, for both transport and fighter type aircraft, if buffeting cannot be prevented or alleviated. I have tried to reflect this interest and I hope that the title of this paper will also suggest a cautious examination of the physical processes at work above the buffet boundary, when the boundary layer has separated. We still really know very little about these processes but I hope that the paper may stimulate further research and questioning.