The subject of aircraft production is obviously a very wide one—books have already been written on it—books which have been consulted when preparing this lecture. It is proposed to sketch in broad outline the various methods generally known for the manufacture of aircraft, dwelling perhaps more particularly on some with which I am more familiar and which have recently been used very successfully in French factories. Familiar processes which have been in use from the earliest stages of aviation development up to recent years will not be discussed, but an attempt will be made to bring out the salient particular features of the new processes and the new production methods which seem to offer interest not only from the historical, but also from the technical, aspect at the same time indicating the extent to which aircraft engineers have had to exercise their ingenuity in order to build and mass produce aircraft which are being constantly developed and improved by the Design Offices in different countries.

When Viscount 720 aircraft were delivered to Trans-Australia Airlines it became clear that increased attention would have to be given to performance analysis and the preparation of flight planning data.

Previous operational experience had been restricted to piston-engined aircraft which, for flight planning purposes, could be regarded as cruising at a certain air speed and burning fuel at a certain rate. Temperature effects were negligible because it was the accepted practice to restore power on hot days by slightly increasing boost settings. Altitude effects, although not truly negligible, were certainly small and could be covered by using flight planning figures from the conservative side of the range. With the Viscount, however, the specific range at cruising altitude was found to be almost twice its sea level value and a 10°C. rise in temperature was capable of reducing true air speed by 20 knots.

Ram-jets in Great Britain have, until now, been associated with Guided Missiles and, for this reason, tight security regulations have been in force. In fact, it is only recently that it has been possible to talk about ram-jets at all. Even now, quite a number of features in these engines are classified and, for this reason, some portions of this paper may appear perhaps a little thin and inconclusive, but I have done my best to discuss the subject as fully as possible.

It is now generally known that the work of the Bristol Company has led to the adoption of the Thor ram-jet engine for production by the Ministry of Supply but security restrictions remain and in this lecture I have drawn upon general experience and thoughts in this field and avoided giving information directly related to a particular engine. In these circumstances, of course, the choice of any operating condition for the purpose of giving form to the lecture has had to be a purely arbitrary one.

An Artificial Satellite set to start on a circular orbit round the Earth, will have to be given a known velocity, at right angles to the radius vector, which depends upon its distance from the Earth's centre.

It will, from the start, begin to spiral downwards towards the Earth, owing to the resistance of the atmosphere, but if it begins its path at a sufficiently high altitude, the decrease of height after one revolution will be small.

Should the initial “ tangential ” velocity be greater than the value calculated for a circular orbit, the satellite will, according to the text books, describe an ellipse instead of a circle; and, if at a sufficient distance for the air resistance to be at first ignored, will return after one revolution to the distance at which it started, this point being the perigee of the ellipse. It will never return to a point outside the starting point.

Several Attempts have been made lately to reduce the drag due to lift of wings by means of camber and twist. Slender wings in particular have been considered and a typical theory is that by Tsien on the supersonic conical wing of minimum drag, where the lift forces on the wing are calculated from conventional aerofoil theory so that the overall lift of a flat wing turns out to be proportional to the angle of incidence. For convenience, this is called a “ linear theory.” It is usual to consider two cases: (1) Wings where the drag is calculated by the same theory so that the full thrust component and the suction at the leading edge are included. (2) Wings where the drag is not calculated by the same theory as the lift but where the thrust at the leading edge is omitted.

In the recent paper by Warren a summary was made of current data on two-dimensional bow shock wave detachment distances. It was shown that the experimental results of Griffith and Alperin, as well as the detachment distances computed by Vincenti and Wagoner, could be collapsed into a single curve by using Spreiter's Transonic Similarity Parameter. This has been confirmed by the present authors who have found that the experimental results for wedges obtained by Bryson also correlate favourably with the curve given by Warren (Fig. 3 of Ref. 4).

The results of the foregoing workers have been for steady flow conditions. However, it has been noted by Lilley et alia that a steady shock wave pattern can be established in free flight only after steady motion has been maintained for a considerable (infinite) time. In general, the locus of detached bow shock waves depends on the time history of the motion whenever a body is accelerated from subsonic speed.