Some discussion of the L-1011 analog system will be given before discussing the problems and advantages of digital implementation. It is the most advanced flight control system in operation today and one for which Category III certification was achieved simultaneously with the airframe certification. All L-1011s have been delivered with a full Category III system and all operators are performing automatic landings in service.

The work of the Greenwich Observatory throughout the three centuries of its existence has been characterized by the painstaking efforts of its eminent directors to attain an ever-increasing degree of precision in pinpointing the positions of the heavenly bodies, with a view to the improvement of the science of navigation. The pursuit of this purpose, in accordance with the express desire of its founder King Charles II, has been assisted by the steady improvement in the accuracy of the instruments with which it has been equipped, and these have naturally also been applied to investigating problems of a purely theoretical nature. Nevertheless, the tradition pioneered by the first Astronomical Observator (or Astronomer Royal) John Flamsteed (1646–1719) whom the King in 1675 charged with rectifying the coordinates and motions of the heavenly bodies, has remained predominantly practical and utilitarian.

According to Flamsteed's own account, the Royal Observatory was founded as a direct consequence of the representation in 1674 by a Frenchman, who described himself as Le Sieur de St. Pierre, to the English Court that he had discovered a method of determining longitude at sea ‘from easy celestial observations’, and claimed the appropriate award. The solution to the ‘longitude problem’ was then, as it had been for many years and was to be for a further 90 years, of paramount importance; several countries had offered large prizes for a practical solution, and l'Observatoire de Paris had been founded in 1667, a year after l'Academie Royale. (Observations were systematically made for the purpose of improving the determination of longitude by observation of the satellites of Jupiter; but this method, successful on land, was doomed to failure because of the impracticability of using long-focus telescopes at sea.)

One of the essential steps in the operations of war is to know where your enemy is, so that you may either make contact with him or avoid him: the same applies to any friendly force with which you may be operating. And in parallel with these steps you need also to establish your position relative to any natural hazards that you may have either to avoid or exploit. If you can establish the positions of yourself, your friends, the enemy, and the hazards relative to the Earth's surface, you can use the information to control your own movements as you wish; alternatively you can sometimes, by one means or another, directly establish the enemy's position relative to your own and proceed accordingly—a process equally useful in ‘homing’ or evasion.

Computer techniques have made an increasing contribution to airborne navigation equipment, particularly in the field of radio navigation where in the past computers had generally been too powerful and much too costly to be of practical use. This paper sets out to review some of the progress achieved during the last decade and then to illustrate the impact this has had on airborne radio navigation equipment. In recent years computers have made very significant strides from almost every viewpoint; they have increased in capability and speed of operation, decreased in cost and power consumption, and improved in ruggedness. One characteristic that is particularly relevant to the field of radio navigation is the cost of the minimum practical computer. There is always a limit to how simple a computer can be made before it ceases to be practical and this limit is interesting because it has dropped dramatically over the last decade to a level which makes a computer competitive for solving the simpler problems which were previously solved by other means.

Captain Emden of H.M. Coastguard's Dover Strait Operations Centre discusses the problems encountered in setting up the experimental Dover Strait Surveillance Scheme and inaugurating the Information Service. The paper, which was presented at a meeting of the Institute in London on 20 November 1974 with the President, G. E. Beck, in the Chair, describes the service today, the results so far achieved and what it hopes to do in the future. A note on the results of surveillance operation between April 1973 and December 1974 will be found at page 244 of this Journal.

Experience gained in the automation of air traffic control is of interest from more than one point of view, and not only because of the range and diversity of new and delicate problems to which this application of automation has given rise, and for which it is necessary to find simultaneous solutions. It has been necessary to design and develop new methods for the acquisition, processing and display of information and to link them with digital computers, for which a complex and voluminous ‘real-time’ software has had to be compiled and brought up to date without interrupting the procedure. But it is when it comes to visualizing the total pattern that the most difficult problems arise because the major decisions determining the success or failure of the operation have had to be taken without the possibility of acquiring any preliminary experience.

Man and the computer have to work together in real time as harmoniously as possible to obtain the best results from the modern data processing systems that it was proposed to employ; it was therefore essential to consider very deeply the complementary roles which each was intended to play.

To describe this research in detail or the solutions arrived at would not be of great interest to those other than specialists.

F. J. North reminds us that the well defined geographical entity now called the Bristol Channel should, on historical grounds, be called the Severn Sea. This was the name used by Giraldus Cambrensis (1146?–1223) in his Topographic Hibernica of 1188 and by Roger Barlow in his A Brief Summe of Geographic of 1540, among other early writers. But with Bristol's rise to fame as a great seaport the name Bristol Channel came to be used and, as early as 1693 we find the name ‘Canal de Bristol’ on a French sea chart by H. Jaillot.

An unknown writer of 1578, whose Discourse was published in John Stow's Survey of London of 1598, in explaining why a site on the Thames instead of one on the Severn was chosen for the metropolitan city, stated that:

‘… the Thames both for the straight course in length and reacheth furthest into the belly of the land, and for the breadth and stillness of the water is most navigable up and down the stream…. The river openeth indifferently upon France and Flaunders, our mightiest neighbours, on whose doings we ought to have a bent eye and special regard…

… For the Prince of this Realm to rest and dwell upon Severn were to be shut up in a cumbersome corner, which openeth but upon Ireland only, a place of much less importance…’

The marriage of the computer with the collision avoidance (C/A) radar permits a higher order of manœuvrability finesse than is possible with the plotting board. Given the computer as a new tool, the marine systems engineer is faced with the question of whether to attempt a radical improvement in the art of collision avoidance displays, or whether merely to introduce a marginal extrapolation of the existing art. That the first course of action may be necessary is evident from various studies of the modern marine traffic environment; thus a recent study by the United States Coast Guard for the Department of Transportation showed that ‘…the total probability of collision avoidance for this condition [surrounded by a significant number of ships] requires an analytical solution quite different from one which would relate to a sparsely populated area’. Indeed the increase in shipping density, collision rates, speed and size of the newer ships, economic pressures and ecological constraints demand a radically different approach to solving the collision avoidance problem. The marine electronics industry has responded by developing collision avoidance systems of various types. Many of these are relatively straightforward extrapolations of existing art but one at least, the Sperry CAS, goes beyond a simple extrapolation and is a radical departure from conventional practice.

Many papers have dealt with the advantages of using digital techniques and digital hardware in avionic systems. Attention has also been devoted to the special problems of software and the programming of digital computers, although not much of it has been devoted to specifically avionic applications. Very little has been published on the interaction between the hardware and software aspects of the design of avionic systems or on the trade-offs which are possible between the two. This paper deals with various aspects of these trade-offs.

Inertial navigation has been in airline use for some five years and a substantial amount of experience has been built up. The system seems to have fulfilled the expectations of operators. In this paper, which was read at a meeting of the Institute in London on 8 January 1974 with the President in the Chair, Mr. Edwards of British Airways discusses its accuracy and the cost of ownership.

In 1969 a paper was presented to this Institute by F. J. Sullings of the then B.O.A.C. which described some of the engineering aspects of INS and predicted in some detail the costs of operating such equipment for a fleet of twelve B747 aircraft. It is the purpose of this paper to refer back to those early predictions and to make comparison with what has actually been realized. Sullings also referred to the anticipated navigational accuracy of the equipment and this paper will demonstrate that the anticipated accuracies have consistently been exceeded since the first use of the equipment by B.O.A.C. in May 1970. Finally, since the equipment has now been in use for five years, it is considered appropriate to review some developments in which airlines are taking an active interest.

The submarine operates in three dimensions and whilst it has operating constraints in common with the surface ship it has others peculiar to the added dimension. This paper, which was presented at a meeting of the Institute in London on 18 December 1974 with Captain R. Maybourn in the Chair, discusses these constraints as they affect submarine safety and attempts to identify those which are caused by modern commercial activities. The views expressed are those of the author and should not be taken as a statement of Ministry of Defence policy.

This paper is mainly concerned with the movement of marine traffic in the Upper Bristol Channel, that is the present organization of pilotage services and docking facilities in the area, some of the present difficulties confronting Masters and pilots, and how these difficulties will grow with the increasing size of vessels. This must occur when the Port of Bristol's West Dock opens and would also occur if a new dock were to be constructed at Newport. The conclusion gives outlines of some ideas which have been put forward for providing a segregation and separation of vessels in the area and the possibility of a joint shore-based authority to assist in securing a reasonably safe and economic flow of traffic through the area.

The purpose of this paper is to look at the nature of the advances being made in inertial navigation and in navigation displays. In avionics as a whole the advance from one generation of equipment to another can take different forms; sometimes, notably in flight control and instrumentation, the potential of new technologies is exploited almost immediately to provide more advanced operational facilities and systems become more complex. Alternatively, as in the application of solid state electronics to produce equipment for general aviation, the technology is exploited to reduce weight, volume and costs. Inertial navigation exhibits both trends but to a comparatively small degree; the basic system requirement is simple to define and has changed very little, one of the reasons being the particularly demanding nature of the technology and the very long development time scales involved.

This paper was presented at a joint meeting of the Institute with the Institution of Electronic and Radio Engineers in London on 15 January 1975. The theme of the meeting at which six papers were discussed (a selection of which will be published in the Journal) was Advances in Airborne Equipment for Navigation and Freight Control.

Modern data processors because of their increasing power and flexibility are increasingly used for a variety of functions in modern aircraft, both civil and military. It might seem that a flight control system could be designed of the form shown in Fig. 1, with a powerful central processor taking in signals from all the relevant sensors, gyros, pressure sensors, radar, &c., and operating the control surfaces so as to drive the aircraft along any desired course. But such a system would be quite inadequate in two vitally important aspects: there is no facility for inputs from the aircrew and no account has been taken of failure cases. These and other factors drive the control system designer inexorably towards a total system structure very similar to the type currently used in operational aircraft. There are of course a wide variety of such systems, but most of them are characterized by a number of common features.

Sir George Deacon, F.R.S., a past president, has recently written a most persuasive case for founding a Chair in Navigation. He mentions Sir Isaac Newton's insistence that Christ's Hospital should teach ‘not only what is necessary to make a mariner skilful in his ordinary road, but also what would assist him to invent new things and practices and to judge what comes before him’. It was in this spirit that a basic analysis of navigation was begun some years ago although it was not expected that Sir Isaac Newton's great conception would be realized. Indeed, the object was only to try to suggest to educators the potential of navigation as a scientific discipline.

Elements of the work dealing with probability and with information theory have already appeared in the Journal and certain ideas have been crystallised into patents taken out by Smiths Industries Limited. Other results are presented here in a condensed form starting with a definition which leads on to a pattern of equipments by using a particular development of dimensions and which highlights the special difficulty of collision avoidance. Linkages between gimballing error, precession and coriolis effect are suggested, and the significance of frames of reference is emphasized, suggesting a unified approach to the trigonometry needed by the navigator. If these crude tools can be tempered by the fire of criticism or replaced by finer cutting edges, the effort will not have been wasted.

Position fixing with the Omega hyperbolic navigation system requires the use of charts or tables unless the receiver itself is able to display the geographical coordinates directly. Plotting position lines on Omega charts is a simple operation but owing to their small scale (1 : 2, 187, 400 for the Mediterranean area) it is impossible to obtain a satisfactory accuracy of fix, while the use of Omega tables becomes particularly laborious when frequent fixes are required.

Behavioural science research on seafarers has snowballed throughout the maritime industries of the western world in the last five years or so. The reasons for this may be quite complex, but there is one significant identifiable factor that has given impetus to this research; those countries which are most active in this specialized field extensively employ their own nationals as ships' officers, and increasingly they have had to choose whether or not they wished to continue to do so. Seafaring as a career has few attractions in competition with the wider career opportunities provided by economic growth. That growth has also provided higher standards of education for young people, and consequently a greater awareness of the career choices available to them. The difficulties in recruiting and retaining the able seafarer have become more pressing within each country.

This paper deals with the facilities for landlall that can be provided by lighted aids to navigation. The relationship between the navigational errors of ships approaching from the open sea and the performance to be selected for a landfall light is worked out. The probabilities of a successful landfall in various circumstances are then analysed. Finally the limitations of light as the sole aid to navigation in the process of making a landfall are discussed. Rear Admiral van Hooff was for long head of the Netherlands Pilotage and Lighthouse Service; Ir. Sirks is technical director of the Netherlands Lighthouse Service.