It often happens that in a plane truss all joints are not transversely stiffened. If one joint of the compressed girder of a beam is free, the girder is liable to fail by buckling perpendicular to the plane of the truss, between the adjacent joints. The chart given here enables a rapid determination of the critical loading to be made. The compression and moment of inertia are assumed constant along the length of each bay, but may be different in the two bays.

Relatively simple theoretical procedures enable the pressure loss of the simpler forms of baffle used for flame stabilisation in combustion chambers to be computed, while tests made under non-burning conditions are available for ad hoc testing of the geometrically more complicated forms. Both these methods, with the appropriate corrections for the momentum changes due to burning, have in the past proved suitable for the prediction of the drag of aero-engine combustion chambers under operating conditions. Recently, however, it has been found that under certain conditions, associated especially with very high rates of heat release, the drag of combustion systems can become very much greater than would be predicted either from simple theoretical considerations or from conventional “cold” tests, and vary in an unexpected manner with the normal flow parameters.

The MacRobertson Air Race, with its carefully thought out rules and conditions, has turned out to be one of the greatest incentives to the progress of aircraft design in the history of aviation. The fixing of the average distance between control points along the route of the race, together with the necessity for compliance with a British normal Certificate of Airworthiness, and the need for high speed all combined to make a problem for the aircraft designer the solution of which cannot but benefit very materially the advancement of aeroplane design.

Many long range records have been taken in the past, but never with an aircraft possessing a Certificate of Airworthiness. Many speed records have been taken, but few with an aeroplane which complies with Certificate of Airworthiness requirements. Here we had a contest which demanded of the aircraft the utmost range and speed consistent with the possession of a Certificate of Airworthiness.

The lecturer opened with a brief and general description of R. 100, which has an overall length of 709 ft. and a diameter of 133 ft., with a cubic capacity of 5,250,000 cu. ft. There are three power cars, each with two engines. These cars are situated at a considerable distance fore and aft from the passenger accommodation, and there was therefore a minimum of noise and vibration in the latter. The ship contained some 11 miles of special spiral seam tubing. Her displacement was 156 tons. In the Graf Zeppelin the cross sectional area of the girders equalled some 12 sq. ins., whereas in the British ship the cross sectional area amounted to 3 sq. ft.

Never, at any time since the Wright Brothers made their first flight have the means of propulsion exercised a more dominant influence over the shape of aircraft or the shape of things to come, nor can it have been so difficult to forecast the form resulting from that influence. It has been a platitude for some time past to say that aircraft and engine design are mutually interdependent: now it is more than a platitude, it is a fact, and one to which we have not yet grown accustomed.

That power installations can no longer be procured “off the peg” is to-day an article of faith which is generally professed: what is rarer is an appreciation of the implications of this state of affairs. Pursued to its logical conclusion, the implication is that a new aircraft and its means of propulsion should originate in the same brain, and be designed, developed and manufactured under the guidance of that brain.

In being honoured by the request to deliver a lecture on “ The Problems of Blind Landing,” I am set to some extent a task different from that normally presented to the Society's lecturers. In general the results of successful research are presented to you, whereas I am merely asked to outline the problems — with the implication that constructive suggestions for their solution may result. Personally, I feel that this is a most appropriate type of lecture, particularly in regard to a problem which embraces specialist fields in radio and radar, in aerodynamics and aircraft instruments, to an extent that few can claim to be expert in all.

The problem of blind landing can best be discussed after reviewing existing methods of blind approach and proposals now current for solving the landing problem.

The Men who could best lay claim to the title of “Aeronautical Engineer” were the early pioneers like Wilbur and Orville Wright. They were their own research workers, their own designers, their own draughtsmen, their own constructors, their own test pilots and, later on, their own salesmen. The Wright brothers carved and steamed the bamboo ribs and struts of their aeroplane themselves, brazed and spliced the wires and cables, while their sister Kathleen stitched the flimsy fabric. But the day of the craftsman-designer is gone.

This paper is concerned with the present-day professional aeronautical engineer in industry and in particular, with the aircraft designer. A distinction must be drawn between the aeronautical engineer and the aircraft technician; both may be intimately concerned with the design of an aeroplane, but the technician—the stressman, the aerodynamicist, the draughtsman—is at the most an embryo aeronautical engineer.

With the rapid advances made during the war in the power output of piston engines, together with the introduction of straight jet and gas turbine units, the time is very opportune to consider the future scope of the propeller as an efficient means of aircraft propulsion on the types envisaged for the future.

The aircraft designer has taken full advantage of these advances in power unit development by introducing aircraft with ever improving aerodynamic characteristics, thus enabling these increases in power to be utilized efficiently.

The propeller designer has been fully cognisant of these combined developments, and in meeting them has had to make rapid strides in research and development throughout the war period.

In examining the future scope of propellers it is as well to review first the rate at which aircraft and engine development has proceeded over the last six years, as this development would never have been achieved in this space of time had it not been for the intervention of war.

For US in the early evening of life, who have witnessed the development of aviation since the Wright brothers flew in 1903, for us, it is hard—and a little sad—to realise that some of our great pioneers are already becoming almost mythical characters. They were our personal friends with whom we worked most happily; yet, to the young men of today, who are now carrying, or are about to don, high responsibilities in the aeronautical world, they are indeed just names. And so it is fitting that the Royal Aeronautical Society should have inaugurated these Memorial Lectures, of which this is the third. I am deeply sensible of the honour and responsibility which have fallen to me by the choice of the Bristol Branch to pay this first tribute to Captain Barnwell. May I say at once how indebted I am for so much of the detail of this appreciation to Mr. C. W. Tinson, who served with Barnwell for most of his career at Bristol; to Mr. C. H. Barnes, who has written the history of the Bristol Aeroplane Co.; and several other “ old hands.” It is significant that in all my conversations with them, they referred always with obvious affection and deep respect to “the old man.”

This paper reviews work on the flexural centre of elastic cantilever beams and contains a number of hitherto unpublished results, including a formula giving the position of the flexural centre in terms of the Prandtl torsional stress function.

The appearance of the note by Jacobs has prompted the preparation of a review of this subject which is all the more desirable as several of the investigations made shortly before the 1939-45 War were never published and others, although published, seem to be in danger of being overlooked. The present paper contains a number of hitherto unpublished results. The question of nomenclature is worthy of mention since general agreement is lacking. Some of the names used are flexural centre, centre of flexure, elastic centrum and centre of shear but a complete search of the literature would probably lead to the discovery of yet other names. The terms “centre of shear” and “elastic centrum” seem vague and fail to indicate that the point referred to has any special relation to flexure. We shall here use the name “flexural centre” exclusively.