The 893rd Lecture to be given before the Royal Aeronautical Society was held under the auspices of the Belfast Branch on 10th December 1953. Rear Admiral M. S. Slattery, C.B., President of the Belfast Branch, presided, and welcomed the visitors. He expressed the regrets of the Branch that the President of the Society, Sir William Farren, C.B., M.B.E., M.A., F.R.S., F.R.Ae.S., was unable to be present, but welcomed the Secretary, Dr. A. M. Ballantyne.

The Branch President, introducing the lecturers, said: —Mr. Ringham is the Manager and Chief Engineer of the Flight Similator Division of Redifon Ltd. He has been connected with the design and development of communication and electronic equipment for over 25 years. He joined Rediffusion (now Redifon Ltd.) in 1939, and worked extensively on the development of navigational training aids during the war years.

His co-lecturer is Dr. Cutler, Chief Designer of the Flight Simulator Division of Redifon Ltd. He worked on naval navigational aids with the Admiralty Signal Establishment during the war, returning to the development laboratories in Haslemere at the close of the war in Europe. He re-entered Nottingham University later and obtained his B.Sc, Special Physics, and then did research work and was granted his Ph.D. in 1952.

Following the Lecture Rear Admiral Slattery said that it was the practice in the Belfast Branch to present a small memento to lecturers who did them the honour of coming to Belfast and he had much pleasure in presenting the lecturers with a small memento each of Irish linen.

The Lecturers presented their paper and then showed a film depicting sections of a simulated flight from Rome to London.

The supply of meteorological information for Comet operations began long before the first prototype was in the air, since information on aerodrome temperature and pressure and ambient air temperature up to 40,000 ft. was required to assess engine performance. Thus it was found that extremes of temperature at 40,000 ft. range from about – 80 °C. over the United Kingdom to – 35°C. over Northwest India and performance curves were constructed to cover this range.

Statistics on low temperatures were required in connection with the performance of the de-icing system on descent; statistics on high temperatures were required for engine performance throughout flight.

Looking back to the early days of aircraft hydraulic systems, a steady upward trend in the operating pressures used can be observed.

One of the reasons for this increase is weight saving, which has become of particular importance in recent years on account of the increased complexity and power demand of the modern hydraulic systems.

The trend in the direction of higher pressures has been necessarily gradual because of the lack of knowledge and experience in this field, and prudence has precluded the adoption of large steps.

Another step has been achieved in Great Britain by successfully raising the working pressure to 4,000 lb./in.2 on several modern aircraft.

One of the many problems facing the aeronautical engineer is to make a vehicle, the reliability of which is tolerable, from an assembly of bits and pieces which, individually, are more or less unreliable. The practical answer has been to duplicate, triplicate, and generally to multiply the items about which doubt is felt.

This approach to reliability (and hence to safety) finds its way into codes of airworthiness, either as straightforward demands for duplication, or as requirements that no single failure should cause trouble.

On the whole these intuitive assessments of the probability of failure, and the design consequences in terms of duplication, seem to have been sound. It is, however, as well to examine the problems numerically, if we can. Possibly no very clear and decisive answers will emerge, but a little light may be shed on the paths we seek to follow.

The available methods of braking a modern aeroplane with its high landing speed are not entirely satisfactory. This difficulty in braking is particularly noticeable with pure jet aircraft. Owing to the absence of propellers, reversible pitch propellers are no longer a solution to this problem and the under-carriage can be simplified so that it occupies a smaller fraction of the all-up weight of the aeroplane.

When a turbulent fluid flows past a solid surface whose temperature differs from that of the fluid, the shear stress at the surface and the heat flow from it can be related by means of the Reynolds analogy. This analogy has been improved by Prandtl, Taylor, von Kármán and others, and its validity has been tested for flow through tubes and past flat plates by several investigators. In this note the analogy is checked against shear stress data and heat transfer data for a cylinder rotating in “still” air, when the flow is turbulent.

The largest air transport at present operating on air routes is the Douglas Globemaster which is able to lift up to 130 passengers and a considerable load of mail and freight. Experience of flying Globemasters many times on the military route between Seoul City Airport (Korea) and Tashekawa Air Force Base (near Tokyo) suggests the following observations. They may be of value to those aircraft manufacturers in Great Britain now building 130/150 seater jet air liners and to British Overseas Airways Corporation and other air lines who will be concerned with operating them, possibly by 1960.