The effect of higher turbine inlet temperature on the performance of an aircraft gas turbine engine can be quite dramatic. It can be used to increase the exhaust velocity of a dry turbojet to provide a higher specific thrust; to increase the by-pass ratio of a turbofan engine to improve its propulsive efficiency; to optimise the thermodynamic cycle at a higher pressure ratio to improve its specific fuel consumption; to reduce the amount of afterburner fuel flow in an augmented turbojet to improve its specific fuel consumption, or to increase the work output of a turbo-shaft engine. If the thrust or power of the engine is held constant, a size, cost and/or weight reduction can result. If the size of the engine is held constant growth capability can be provided.

The structural use of fibre composites in helicopters, both for primary and secondary structures, has been recognised for some time. In 1964, Westlands developed a glass fibre composite tail boom and tailplane for the Wasp helicopter (Fig. 1) and the results were encouraging. The non-corrodable structure of the glass composite is considered a great advantage, especially for Naval helicopters. Strength testing of the tail boom was successfully completed with a weight of the component close to the existing metal tail boom, but resonance testing showed that a small additional weight was necessary to meet the stiffness requirements. The tailplane in glass fibre composite showed an appreciable saving in weight and after satisfactorily completing static and fatigue testing, one is now flying on a Service aircraft.

While in the design of aircraft hydraulic equipment and landing gear, the final choice of materials used is obviously influenced by a large number of factors including space, wear corrosion resistance, fatigue and, the achievement of minimum weight at an economic cost is usually a primary consideration, the acceptable premium for each kg of weight saved varying from under £5 to over £200 depending on the aircraft type.

The range of materials available to the equipment designer is wide and it is therefore desirable to formulate some guide lines to assist the designer in making the most appropriate material selection for the type of equipment being considered.

To the majority of an aircraft manufacturer's technical staff the words “Flight Test” conjure up a vision of a ramshackle collection of seedy looking huts on the far side of the company's airfield, which itself may be 20 to 30 miles away from the main organisation. Within these huts dwell a small band of dedicated enthusiasts who apparently are willing to subjugate most of their waking hours and personal lives to performing their function in spite of the machinations of their two greatest enemies—aircraft unserviceability and the weather. While starting work at 08.30 hrs. (if not earlier) their working day always seems to reach its climax about one hour before sunset, irrespective of the time of year, and goes on for long after the last test aircraft has landed. However, they are a fortunate few, in that they have the privilege and responsibility of working with the company's end product in its functional form, an experience that today is denied to, or at least is remote from, the large majority of design and manufacturing staff.

Scientific and technological development over the past 20 years has been tremendous. It presents the military planner with a dazzling array of possible developments to meet a wide range of operational requirements. Unfortunately, in every country resources are limited and a choice between the various alternatives has to be made. An objective and, if possible, quantitative method of examining alternative proposals is required. This is what cost-effectiveness analysis attempts to do. It can be and is applied at any level. For example, the government may require a study examining the implications of the different allocations of national resources to defence, foreign aid, civil industrial research, social security benefits, etc.; the Ministry of Defence may require a study examining the balance between the forces on land, at sea or in the air (force structure) and the contribution each make in a number of scenarios; a single service may require a study of the resources that should be allocated to defensive or offensive action; within a single role a study may be required of the alternative weapons that could be deployed to meet a particular requirement. In this paper, only questions arising in the study of defence systems will be considered.

Most guided weapon projects are inherently very difficult to bring to a successful conclusion, and the management methods necessary to achieve the required performance and time-scale, and at the same time to maintain control of costs, have had to be developed and are still developing; the procedures in use are being continually improved and refined. The essential problem in the overall control of a programme is in matching the technical achievement at any time against the corresponding expenditure, hence the involvement of an R & D establishment. There is room for many views on how this objective might best be achieved; those expressed in this paper are the author's and do not necessarily reflect official Government policy.

In university research on the flow through turbo-machines it is often necessary to produce blades which can be manufactured in a small workshop at relatively low cost. As part of a project to investigate the development of the annulus wall boundary layers in a compressor, a set of rotor blades were designed and manufactured for the large rotating cascade wind tunnel at Cambridge University. The apparatus is shown in outline in Fig. 1 and a detailed description of this wind tunnel has been given by Oxford. The air passes through the research rotor and then through the auxiliary fan and throttle. The combination of a variable speed research rotor with variable speed and pitch on the auxiliary fan and variable throttle leads to a highly versatile apparatus with a wide range of operation. An important feature of this apparatus is the sixteen channel pressure transfer device which allows pressures measured on the rotating blade to be transmitted out to a stationary multi-tub manometer.