The advances made in the development of gas turbine engines during the past two decades have been remarkable. The engines have been improved tremendously in terms of power, weight, efficiency and cost. They are now being applied successfully as the prime movers for helicopters, VTOL aircraft, ground power units and for many other diverse purposes, besides the more conventional military and civil aircraft.

There have been parallel advances in the development of gas turbine engine fuel systems (which for convenience may be subdivided into the “control” and the “pumping arrangement”). These systems were originally wholly hydro-mechanical in nature. Sixteen or so years ago, the first supplementary electronic devices were introduced into fuel control systems. Since then, progressively more complex hybrid electronic/hydro-mechanical systems have been employed, with a corresponding easement of the demands on the hydro-mechanical portion. In 1957 Sturrock described to this Society what is now the classic Proteus engine control system used in Britannia aircraft. The satisfactory experience gained with the Proteus system led to the adoption of a comprehensive electronic fuel control system, coupled to a relatively simple fuel pumping system, for the supersonic Olympus engine. This system has been described by Hunt and by Colburn, Tweedy and Dent in papers presented at the joint RAeS/IEE conference “The Importance of Electricity in Aircraft” in 1962. Further papers by Rush presented at the same conference and by Airey in 1963, were devoted to the more general aspects of control.

Boost-gliders offer the possibility of rapid long distance travel (e.g. England-Australia in 75 minutes) and boosters using similar technology offer the possibility of “everyday” travel between the earth and space stations. This paper uses simple parametric methods to assess conditions for boost-gliders to be commercially competitive and to discuss their evolution in relation to other boosters and advanced aircraft. It is concluded that booster-gliders using a similar state of the art to presently-projected aerospace transporters (i.e. winged, two-stage, hydrogen-fuelled vehicles) would be reasonably economical given cheap hydrogen fuel and a market large enough to support about 50 aircraft each making 5 antipodal flights per day. In addition, numerous problems would be involved in developing this type of vehicle to an acceptable level of design and operational familiarity but, at first sight, none of these appears to be insurmountable.

To Describe the development in France of small gas turbines of necessity confines one to the products of the Turbomeca Company. It is therefore not through lack of modesty that I speak of those engines which have been designed and built under my direction.

After the Second World War our aims were quite ambitious. We envisaged the creation of jet engines up to 6000 kg (13200 lb) thrust, as well as the aircraft to suit. We soon realised that such ideas were far beyond the industrial and financial possibilities of the time.

For a number of years it has been the practice at Rolls-Royce to determine the basic aerodynamic characteristics of the turbines of our engines by tests of model turbines. The first model of the single-stage Derwent I turbine was tested In 1945 and a design point efficiency of 75 per cent was measured. Since then over 600 different turbine configurations have been tested and many of the more recent turbines have achieved efficiencies appreciably better than 90 per cent. Typical of modern turbines is the Spey two-shaft turbine in which the four stages reach a design point efficiency of a little over 92 per cent. This paper presents a description of the test techniques which are used in this work and also a simple method of correlation which relates the efficiency of some 70 turbine stages to the velocity triangles and enables the efficiency of those turbines, which fall within the scope of the correlation, to be predicted with an accuracy better than ± 2 per cent. The measured value of turbine efficiency can be markedly influenced by the measurement technique, so the way in which the turbines are manufactured and tested is described in some detail.

In speaking to the Air Law Group of this Society, I speak as no lawyer and offer no legal profundities. I speak as an airline man, with some experience in bilaterals. I propose to talk upon some practical aspects of bilaterals as they appear to an airline man and to touch little upon “-isms” and “-ologies”. The philosophical profundities matter only if they help an airline to trade where it wishes and to plan ahead with some hope of continuity and flexibility of routeing.

I would like first to pay a tribute to the “only true begetter” of British policy in the bilateral field—Sir George Cribbett. It can have fallen to few Civil Servants to have had such influence on the commercial side of a great industry; it must be unique for such a man never even to have reached the principal post in his own Ministry. The very qualities which made his name so revered in the world at large were probably those which blocked his path at home. Our worldwide networks of today are his memorial. In the civil aviation field his epitaph might well be that on Wren's tomb in St. Paul's Cathedral—“Si monumentum requiris, circumspice”: if you seek his memorial, look around.

It is necessary at the outset to discuss the limitations that are imposed by (1) the security classification normally attached to approved requirements and (2) the inter-relationship of technology and the establishment of formal requirements.

“Military requirements” may be defined broadly as formally stated military needs that are considered technically obtainable at reasonable cost in a specified time period. The required and obtainable performance will normally be classified as security information, as will the details of the intended concept of military operation and application. Hence, it is possible to deal with the subject only in a rather generalised manner.

The revival of flying in the British Army dates from the Air OP flights of the Second World War, manned jointly with the RAF and highly successful in their limited role. In 1957 the Army took over full responsibility for its own aviation and in the previous year had already agreed with the Air Ministry and the Ministry of Supply to purchase the Saunders-Roe Skeeter. This two-seater aircraft had been under development since 1948. It was designed for worldwide use and with its 215 hp Gypsy Major engine it was supposed to have a service ceiling of 10 000 ft and an ability to climb at 180 ft/min outside ground effect at 4000 ft and ICAO + 30°. By 1958 the Skeeter had been accepted into service, but on its tropical trials in Aden in 1959 and 1960 it could produce only marginal power and the cylinder head and oil temperatures were above limits. It was therefore relegated to use in temperate climates and the Army was faced with the situation of still having no helicopters deployed in the Far East and Middle East. We had to make do there with the Auster, a fine, if rather senior reconnaissance aircraft, able to carry out only a few of the many roles required of an Army aircraft. A new aircraft, the Saunders-Roe P531, which became the Westland Scout, was ordered in 1959.

An account of the solution of a quadratic equation associated with a gas dynamic problem is given. Numerical examination of the equation Indicated that a conditional statement was required In a computer programme to determine the sign to be used in front of a square root. The necessity for this conditional statement was examined by studying a general quadratic equation. The study has also led to the formulation of a rule on the selection of a “desired root” of a quadratic equation.

Dr. Stratford (p. 133, February 1965 Journal) is to be supported in his endeavour to apply boundary layer theory to the prediction of optimum loading requirements in flow through blades in cascade. Inevitably some simplification of the general flow system in a blade passage is necessary if undue complexity is to be avoided. In the simplified flow model, however, care must be taken to avoid over-simplification, and the limitations imposed by legitimate approximations must be appreciated.