The Eighteenth British Commonwealth Lecture, “Australia's Internal Air Transport” by Mr. John L. Watkins, O.B.E., B.E., D.I.C., F.R.Ae.S., Director of Engineering, Trans-Australia Airlines, was given in the Lecture Theatre of the Society on 11th October 1962. The President of the Society, Mr. B. S. Shenstone, M.A.Sc, F.R.Ae.S., F.I.A.S., F.C.A.S.I., presided.

Before the lecture Sir Roy Dobson, President of the Society of British Aircraft Constructors, presented certificates of S.B.A.C. University Scholarships to the following who had completed, or were about to complete, their courses: J. M. Chaney (Blackburn Aircraft, College of Aeronautics and Massachusetts Institute of Technology), B. C. Latter (Blackburn Aircraft and College of Aeronautics), R. A. Newnham (Handley Page—College of Aeronautics), R. A. Williamson (A. V. Roe & Co.—College of Aeronautics), D. F. Pilkington (A. V. Roe & Co.— Imperial College), R. J. G. Archer (de Havilland Engine Co.—Imperial College) and C. E. H. Joy (Bristol Siddeley—Imperial College).

Introducing the Lecturer, Mr. Shenstone said that unlike many of the lecturers in this series, Mr. Watkins had been raised in the country of which he was to speak. He had taken his degree of Bachelor of Engineering at the University of Adelaide in 1930 and then took a post-graduate course at Imperial College, London. In 1932 he joined Vickers-Armstrongs and worked on early geodetic work under Dr. Barnes Wallis. Returning to Australia in 1934, Mr. Watkins joined the Air Board, which later became the Australian Department of Civil Aviation. During the war Mr. Watkins had worked on special projects for the RAAF in the Australian Department of Aircraft Production, with the Army Inventions Directorate, and on many other projects. When Trans-Australia Airlines was formed in 1946 he was appointed Technical Superintendent and since 1953 had been Director of Engineering. One of the jobs he was most noted for outside Australia was his responsibility for choosing aircraft for TAA and also for British Commonwealth Pacific Airlines when that Airline existed as a separate entity. In 1950 Mr. Watkins had been loaned to the Government of India as Technical Adviser to the Indian Air Transport Inquiry Committee.

Mr. Watkins had been awarded the O.B.E. for his services to Australian Civil Aviation in 1958 and had been a Fellow of the Society since 1956. He was a past Chairman of the Melbourne Branch of the Australian Division.

A class of delta wings is considered, whose under-surface has an inverted-V, or inverted-W, cross section of such a form that, at the “design” Mach number and incidence, the shock waves formed are plane. The geometry of the shock-wave system and surface is described briefly, and comments made about the utility of the concept in relation to hypersonic flow studies.

My intention is to give a generalised résumé of the Flight Testing of the H.P.115 from the pilot's viewpoint. It is my belief that, in many respects, the flight testing of an aircraft, so far as the pilot is concerned, starts from its inception in that common sense pilot participation right from the word go can do much to help to ensure the ultimate success of the project. This is one of several reasons why, instead of just discussing what goes on up at the front end of the H.P.115 during flight. I shall trace briefly the growth of the aircraft. It is an interesting and, in many respects, an involved story: I will try to work along its main thread with occasional excursions into some of the more pertinent by-ways.

Some aerodynamic properties of auto-rotating or forcibly rotated cylinders and aerofoils were investigated even prior to the beginning of aviation and, somewhat surprisingly, it was Maxwell who wrote the earliest (1853) known paper on the subject. That entirely non-mathematical paper tried to explain the curious behaviour of an oblong card which, left to fall freely in the air, started immediately to rotate about its longitudinal axis while deviating from the vertical in the horizontal direction perpendicular to the axis of rotation. Steady “terminal” conditions are soon reached in which speed, rate of rotation, and path angle, are all constant. This simple experiment revealed at once two important properties of an “aerofoil of large aspect ratio“: (1) ability to autorotate, and (2) ability, when rotating in an air stream, to create an asymmetrical pressure distribution resulting in a force normal to both axis of rotation and mainstream velocity. About the same time, the famous “Magnus effect” on rotating circular cylinders was discovered, but it was not before the Kutta-Joukowski theory of aerodynamic lift appeared some 50 years later that a more general understanding of the “lift through circulation” principle became possible. Magnus effect found important applications in ballistics, and one serious (although not economically successful) attempt was made to apply it in maritime navigation (Flettner's rotorship). As to the use of aerofoils rotating about a horizontal transverse axis for generating lift in aircraft, very little indeed has been done apart from some early publications. The concept of a wing with rotating flap as a lift-augmenting or control device arose from suggestions by Riabouchinsky and Chappedelaine, and there were some early French and German patents based on this concept. However, the matter was soon abandoned. It was taken up again during the last war in Germany, where some interesting experimental and theoretical research was done on a small scale. The subject has apparently never attracted any attention in Britain until 1957 when a short review of the existing information was given by Crabtree. This was followed by the lecturer's own effort which concentrated on the relevant mathematical theory.

In their paper, “A Theory of the Cylindrical Ejector Supersonic Propelling Nozzle”, Pearson, Holliday and Smith analysed the conditions under which two unmixed streams of air pass together through a nozzle. Two criteria were used to determine the flow conditions at the exit, when the nozzle is choked: —

(a) That the stagnation pressure in the secondary (subsonic) jet should be a minimum for a given flow quantity.

(b) That the velocity of propagation of small plane waves at the exit should be zero.

Either criterion, applied independently, led to the same result but, as the authors observed, neither has the status of an axiom in fluid mechanics, and a direct proof without invoking either would be preferable.

In reference 1 a general analysis was presented for the calculation of thermal stresses and deflections due to temperature gradients in long rectangular plates having lengthwise edges supported elastically. The edge support was idealised as equivalent rotational and extensional stiffnesses depending on the elastic characteristics of the surrounding structure. The special case of infinite extensional stiffness and freely hinged edges (see Fig. 1) was discussed in greater detail and a number of graphs were included for the calculation of edge reactions in terms of the thermal force and thermal moment parameters. Since these graphs used an excessive number of non-dimensional parameters their practical application is unwieldy; four non-dimensional parameters were used instead of three parameters which would be sufficient to describe the required functional relationship. This note shows an alternative presentation of the results which can be used more conveniently in any design calculations.

To an increasing extent, aero gas turbine manufacturers are supporting high speed rotors on spring bearings, in order to escape the consequences of lightly damped and inconveniently placed critical speeds. While experience has been generally good, engineering doubts periodically arise.

(a) By introducing the flexible bearings, the critical speed is reduced, say, from 9,000 r.p.m. to 3,000 r.p.m. At 3,000 r.p.m. a peak amplitude response is experienced, although the bearing load is comparatively low. (Some spring bearing designs incorporate damping as an accidental feature, many do not, and very few have damping designed into them.) The peak amplitude at 3,000 r.p.m. can rub the seals or overstress the spring, and to prevent this the bearing amplitude is restricted by a circular stop known here as the “snubber.”