Reginald J. Mitchell of Supermarines—a North Staffordshireman, like myself, and, in the words of Joe Smith, “ a practical engineer possessed of an abundance of plain, straightforward common sense; a man of drive and genius”—will go down to history as among the most inspired of those who had the good fortune to live and work in Aviation's pioneering days. During the short span of his active designing and engineering life—for the 16 years between 1920 and 1936—he produced 24 different aircraft types, so brilliantly and affectionately discussed by the great Joe Smith in his foundation Mitchell Memorial Lecture in January 1954. Mitchell's aircraft included, in the civil transport field, the “ Sea Eagle ” of 1923, which opened air services to the Channel Islands, the unique “Air Yacht” of 1929 and the very advanced 75,000 lb., 174 ft. span, six-engined, 40-passenger commercial flying boat of 1930 (Fig. 1), the contract for which was unfortunately cancelled as an economy measure in January 1932 after work was well advanced.

The whole process of designing an aero engine, from the original concept to the production of the first of the type, called a prototype, normally takes about two years.

The prototype design may originate from proposals put forward by the engine maker from specifications for military aircraft engines, issued in the United Kingdom by the Ministry of Supply, or from the Aircraft Industry.

It is not usual for engines to be designed specifically for civil aviation requirements. More often they are adaptations of military engines de-rated to increase their reliability, and to extend the overhaul period. With the growth of civil transport and the development of guided missiles, it is possible that this state of affairs may be reversed and engines for civil aircraft may become more important than those for Service use. At the present time, it is difficult to foresee a potential civil or private aircraft engine market that would justify the cost of designing and developing a small jet engine on that score alone.

Two types of intermittent wind tunnel drives, the pressure storage drive(with atmospheric exhaust) and the vacuum storage drive (with atmospheric inlet), are examined and found to match well the tunnel pressure ratio-mass flow characteristics over a wide Mach number range (0 to 4). The design of components of intermittent wind tunnel installations, their operation and instrumentation are then considered in some detail. In order to increase the output of intermittent wind tunnels to a level comparable to that of continuously running tunnels, it is proposed to drive the models during each tunnel run through a range of incidence. This technique is at present under development in the National Aeronautical Establishment's High Speed Aerodynamics Laboratory and results so far obtained are discussed. Two tunnels are considered as examples of large intermittent installations: a 4 ft. square pressure-driven tunnel and a 6 ft. square vacuum-driven tunnel. The former is found to be a more compact and economical installation. Relative merits of continuous and intermittent installations are discussed.

When I accepted the invitation to give a lecture on “The Uses of the ACE Computor” my first thought was to ask for the title to be corrected. The “ACE” as such has yet to be built and the machine that has been in use in the Mathematics Division of the National Physical Laboratory is a pilot model. However, to an audience whose chief interest is in aeronautics, the ambiguity of a title including the phrase “Pilot ACE” probably outweighs the advantage of its accuracy.

As its name implies, the Pilot Ace was built,at the N.P.L., with the intention of testing out the practicability of various ideas in the design of a full scale automatic computing engine, or ACE as it was called. The over-riding consideration was economy of equipment but, despite the rudimentary nature of the facilities provided on the machine, it was found to be a fast and powerful computor and has been fully and successfully employed for the past three years on a 13 hour basis.

The Quasi-Cylinder and slender body theories for the supersonic flow past bodies of revolution have been much used in recent years because, for reasonably simple body profiles, these theories permit a simple and rapid calculation of the first-order pressure distributions and aerodynamic forces. It is assumed in both theories that the body profile slope is small; in the quasi-cylinder theory it is also assumed that the body radius is nearly constant, whereas in the slender body theory it is assumed that the thickness ratio of the body (maximum diameter/length) is small.

In the present note these two theories are combined completely. From a strictly mathematical point of view nothing is gained by this combination, and, furthermore,application of the combined theory to a particular case is in general a little more laborious than application of either of the original theories.

The Purpose of this note is to present a table of the receptances of simple epicyclic gears and to show how they may be used. This table of results has two main uses. In the first place the receptances simplify the calculation of the natural frequencies of torsional systems containing these gears by the methods explained previously. Secondly, responses of systems (which incorporate these gears) to given harmonic excitations may be estimated, either in the absence of damping, or when there is damping present of known amount in the component sub-systems. This second use of receptances is illustrated by a simple example in this note; it is based upon the fact that the receptances of a compound system may be built up from those of its sub-systems irrespective of whether there is damping present or not.