This paper presents some preliminary conclusions about navigation requirements for supersonic aircraft, in particular those which relate to management of the aircraft along its vertical flight path.

The conclusions are based on an evaluation of some 200 computer-simulated flights of the mach 2 Concorde. The simulation contained models of real-world atmospheres for polar, temperate and tropical latitudes taken from actual upper-air observations and integrated over selected great circle routes used in the study.

The computer programme was designed to permit three kinds of flight schedule: operation according to the manufacturer's recommended mach-altitude profile, operation with respect to a set of arbitrary A.T.C. profiles, and operation along an optimum-energy profile. The results permit us to suggest objectively, performance capabilities, airspace requirements, and limiting conditions which are essential factors in specifying the vertical requirements.

In this paper M. Villiers, Ingénieur en Chef de la navigation aerienne, and M. de Barbeyrac, of the Société d'Etudes des Systèmes d'Automation, discuss the application of a satellite monitoring system to A.T.C. procedures.

The paper first discusses control of lateral separation under the headings of present navigation accuracy over the North Atlantic and by a satellite monitoring system. It goes on to discuss control of longitudinal separation with and without monitoring, and finally discusses intervention procedures and aids.

The writers conclude that it is possible with a mathematical model to establish a general relationship between the performance of aircraft navigation systems and a monitoring system on the one hand, and the lateral and longitudinal separation of aircraft and the mode of A.T.C. action on the other. From this relationship the number of A.T.C. interventions can be computed and it appears that the reduction of separations resulting from a satellite monitoring system will fit such a system to the forecast air traffic beyond 1975. In addition, the requirement for voice communication, specific to A.T.C., would be extremely limited. The paper was presented to the S.S.T. Working Group, sponsored jointly by the French, German and British Institutes of Navigation.

In this paper, which was presented to the Institute at an Ordinary Meeting in London on Wednesday, 14 February, the Managing Director and Chief Operator of Hoverlloyd describes his company's experiences in operating hovercraft across the Channel and its hopes with regard to the 250-passenger SR.N4. The characteristics of hovercraft and their implications for navigation are described.

Cross-Channel operations in SR.N6 hovercraft. In 1965 the Swedish Lloyd and Swedish American shipping groups placed an order for two SR.N4 hovercraft for introduction to the cross-channel route in 1968 and 1969. As a prelude to this service, an order was placed for two SR.N6 machines with which the parent companies intended to operate a pilot service between Ramsgate and Calais during the summer months of 1966 and 1967. These craft were delivered in the spring of 1966 and have now completed two years' activity, not only in the cross-channel field but in all spheres of commercial hovercraft activity.

For a considerable time fishing vessels, merchant ships, long-range forecasters and oceanographers have needed up-to-date sea ice information. This paper describes how the heterogeneous mass of ice information combined with the very thorough climatic analysis now available has been used to produce for the first time an up-to-date picture of the entire distribution of ice in the Polar Basin and areas adjacent to the Atlantic Ocean.

For over a century a function of the Marine Division of the Meteorological Office has been the recording of Arctic and Antarctic sea ice, particularly since the Titanic disaster. However, the comprehensive hemispherical ice maps produced internationally have been several years in arrears. Ice information supplied to ships was therefore usually based on average conditions which suffice for planning well ahead or on long-range weather forecasts where it is necessary to follow ice development closely. It was decided in 1959 to organize a synoptic ice map with up-to-date ice and sea temperature information. Ice being more conservative than the weather, a map produced every ten days has proved to be sufficient.

On 30 March 1966, Captain A. Wepster, of the Holland-America Line, presented a paper to the Institution on collisions in Western European rivers. Through its publication in the Journal it had considerable impact on opinion abroad and in particular in the Netherlands where it became popularly known in nautical circles as the Wepster Report.

The Netherlands Pilots’ Association invited its nautical committee for the areas most concerned to investigate the findings of Wepster's paper and it is their report which is presented here.

The Wepster Report is a general discussion of the dangers and problems of navigation on the five main navigable rivers of Western Europe. It attempts a critical investigation into the causes of the decline of safety on these rivers and a good deal of attention is paid to the working methods of pilots and of the various institutions charged with organizing river traffic. Captain Wepster concludes his lecture with the remark: ‘… it is now to be hoped that others will throw some light upon it from another angle.’

The following article is a summary of a paper presented by the author to a meeting of the Liverpool branch of the Institute on 26 January 1968.

Many people believe that there is a compelling need to discuss much more seriously than we do the whole way ahead into a new era in the conduct of ships; to scale the heights that lie above the chaos of detail and the log-jams of orthodoxy, and to discover where the truth is most likely to lie in this respect, for obsolete thinking is far more harmful to progress than obsolete equipment and this thinking, therefore, can often become a dominant factor.

The paper describes a method by which ‘history’ in the form of tracks of all vessels appearing on the PPI is projected on a flat plotting surface, and the use that can be made of such information to ascertain either the true or relative tracks of all such vessels and also the effects of own ship alterations of course or speed or both on the relative tracks of other vessels.

In a recent survey of collisions and from experience on board ships it has been found that, in heavily congested waters and low visibility, even vessels with sophisticated radar equipment and associated plotting facilities and sufficient personnel may find themselves ‘saturated’. Vessels with simpler radar and plotting facilities and less staff consequently become saturated in less heavy traffic conditions.

In the sixteen years since the last paper on this subject was published in the Journal (1951, 4, 288), some notable changes have taken place in the design and capabilities of submarines. Nautilus, the world's first nuclear submarine, was laid down in 1952 and completed in 1955. Since then a further 120 nuclear submarines have been commissioned. Now, a large proportion of the world's submarines are ‘true’ submersibles, self-sustaining over periods of months in everything except food; capable of proceeding submerged faster than the average surface ship; and rarely requiring to surface or even to come to periscope depth.

There is an urgent need, both at international and national level, for more operational research into marine traffic and the associated collision casualties. At the present time marine traffic research is in its infancy and official analysis of collision is on a national basis with few attempts to correlate the two together and on an international basis. Without this basic information and research on the traffic and accident pattern, it will not be possible to plan effectively to reduce the high cost of collision casualties to ships' operators and to make the necessary improvements in safety over the next decade. This decade will see increasing carriage of dangerous cargoes in bulk, a continual large increase in the number of pleasure boats and the current trend of increasing numbers of merchant ships, fishing and other work-boats will probably continue. Due to this large increase and the trend to mammoth ships, the effective amount of sea space is being rapidly reduced and traffic control is inevitable in some areas.

Mr. J.G. Carr and Sq.-Leader D. Scott, R.A.F., have devoted sections two, three and four of a total of 21, and a few other remarks here and there in their excellent paper, ‘The testing of airborne inertial navigation systems’ (Journal, 20, 405), to the above title as an exposition ‘first necessary’ to their main purpose, limiting themselves to ‘the types of system of which we have practical experience’. They do not otherwise identify these types explicitly, but do include them among the ‘many ways of mechanizing this concept', viz., ‘The feature which is common to all inertial navigators is the measurement of acceleration of the vehicle by measuring [and in effect they add also “or metering”] the force required to constrain a proof-mass carried in the vehicle to move with it,’ and from this deducing velocity and position of the vehicle. This statement seems well put to me and quite sound, but in the fourth paragraph of Section 4, which includes ‘Fig. 1. A Schuler tuned inertial navigator’, they imply that at least their types, if not all inertial navigators, are based also on ‘Schuler tuning [so named] after the discoverer of the principle', and here I do not follow them. (I note in passing that the by-line of Schuler's 1923 paper, Physik. Zeitschr. XXIV, 344–50, spells his name without the umlaut used consistently by them.)

F. C. Bell in his contribution raises most interesting philosophical questions. In commenting on them, I will refer to a recent translation (Navigation U.S.A., 14, 26) of Schuler's paper and use the same notation.

The impossibility of distinguishing by any physical measurement between a gravitational force and the inertial reaction force of an accelerating frame of reference is fundamental. In Fig. 1 our observer in an enclosed laboratory is observing the compression of a linear spring supporting a ‘proof mass’ m (he knows the natural uncompressed length of the spring).

Mr. Sadler rightly emphasizes one aspect of time: that is to say time is one coordinate of a space-time set of coordinates that locate an event. The other aspect is that of time interval and it is this that the S.I. second defines. Thus if S.I. units are used the time interval between two events is measured in S.I. seconds; the orbital period of the Earth on its axis (referred to a specified frame of reference) is a certain number of S.I. seconds and, in this context, unless this happens to be 86,400 it is surely incorrect to call this interval a day.

Charles Cotter says my note is controversial. I do not think this is so. The controversy lay in the decision to adopt S.I. units. My purpose was to indicate the implications of this decision. The S.I. unit of plane angle is the radian and hence the argument for the retention of a unit of distance related to the minute of arc is not relevant. The problem involved in adapting rhumb-line sailing to S.I. units is not difficult and has already been dealt with with great clarity. The advantages of a single universal coherent system cannot be over-emphasized and it is to be hoped that difficulties will not be prolonged by isolated areas of resistance.

The Forum comments about small craft lights by Bernard Hayman clearly shows up a shortcoming in the original argument put forward. In relegating the single white light to small craft, and then forgetting it, I have failed to develop this particular argument to its conclusion.

Although I cannot agree with Mr. Hayman's reasoning, the shortcoming must be rectified. To this end, may I propose that: ‘Vessels of less than 65 ft., propelled by any means (sailing vessels by definition are excluded from this), to show a single white light, visible all round the horizon for a distance of at least 5 miles. This light to be not less than 9 ft. above the gunwale. These vessels also to show sidelights prescribed in Rule 7(a(ii)), or if less than 40 ft. in length, may show in lieu the lantern prescribed in Rule 7(d).’