In the period since the inception of civil jet transport, during which a dramatic increase in travel and commerce by air has taken place, the research and development directed towards the containment and reduction of aircraft noise has spread across a steadily broadening front. The noise of the simple jet engines which propelled the first civil transport aircraft was almost entirely due to the high exhaust jet velocities that were used to obtain thrust from comparatively small mass flows. This is illustrated in Fig. 1(a), where it is seen that noise from other sources, such as the compressor and turbine, is comparatively insignificant. Thus aero engine noise research in the late fifties and early sixties was concentrated mainly on the prediction of jet noise and the development of noise-reducing propelling nozzles. It was not until bypass engines began to appear, with higher propulsive efficiencies resulting from lower exhaust jet velocities and higher mass flows, that the noise of their larger compressors drew attention to the turbomachinery as an additional source requiring investigation.

When one is asked to present a paper in a series honouring a particular person from the past, it is always fascinating to review what is available in the way of background of his life and work. As have other Lawrence Hargrave lecturers before me, I have followed this course.

Hargrave's aeronautical work and the papers describing it show clearly the patience and logical thinking which motivated him in all he did. He was a prodigious recorder of data and kept all of this until the untimely death of his son during the first world war. Although of course the concept of airworthiness was unheard of when he was carrying out his experiments at Stanmore, airworthiness control today, some three quarters of a century later, depends almost entirely on the same processes—the proper and logical use of vast amounts of recorded data gathered from all parts of the world.

It is now over twenty years since the first experimental inertial navigation system was built and tested in America, by MIT. Over that period inertial navigation has come of age as a technology, and many thousands of inerital systems are in service in civil and military aircraft.

Ferranti Limited have been active in this field over 15 years, developing and producing both the basic inertial instruments and complete systems for a range of aircraft and space applications. The first system was produced for the TSR-2, which was cancelled at the prototype stage. But a first generation production system has now been in RAF service for some time. A second generation system, now at an advanced stage of test and development, will equip the European Multi Role Combat Aircraft (MRCA). A version of the same system has been adopted in Japan.

The Jaguar programme resulted from a successful international collaboration in all the relevant disciplines between companies having very different backgrounds in the aviation field, namely British Aircraft Corporation and Breguet Aviation (since merged with Dassault) for the airframe and Rolls-Royce and Turbomeca for the engines. It also involved collaboration in depth between government officials having different civil service structures and national practices in the two countries. Before entering into a description of the various phases of the programme and some of the problems which were met and solved it is worth briefly reflecting on the background leading to the formal start of the project in May 1965.