This note presents the results of a preliminary investigation carried out in 1966 by Polhemus Associates, Inc., into the effects of atmospheric conditions and the operation of a supersonic transport aircraft. A further study is in progress using digital processing.

Section 2 shows the results of an analysis of performance data for the Concorde as published in the SUD/BAC Brochure on Performance and Operations. The basic performance data is developed and presented in a form which gives a direct indication of the sensitivity of the aircraft to temperature and/or weight variations.

Section 3 illustrates typical temperature and wind structures as they occurred in January 1963 over the route from Manila to Paris via Tokyo and Anchorage. The basic data on the atmospheric structures were developed originally by McGill University, Department of Meteorology. The data have been further developed to relate the atmospheric structures to the flight path of an S.S.T. during its climb and acceleration phase and general conclusions are drawn on die effects of specific occurrences on the performance of the aircraft.

An article on the French tidal energy schemes appeared four years ago in this Journal (16, 51). One of these was planned for the estuary of the Ranee, a small coastal river that falls into the Channel between Dinard and St. Malo, the other for the extensive sea-area stretching from MontSaint-Michel to the Chausey Islands, and from Cancale to Granville. These schemes had been drawn up in the years immediately following the second world war, at a time when the power-outlook in France seemed somewhat gloomy: demand was increasing continually with no quickly available new source in sight. It was, it is true, believed that ultimately nuclear energy might well be applied in industry but the time-lag was over-estimated and, in addition, it was feared that the cost would not be competitive. Tidal energy, therefore, was hailed as a welcome solution, and it seemed no wild dream to envisage its exploitation over so wide an area as the bay of Mont-Saint-Michel.

It was this that lay behind the Chausey Islands tidal energy scheme. Hitherto, hydraulic power had been drawn only from rivers; the sea might raise unexpected problems and it would have been rash to embark on so far-reaching an enterprise without first finding the answer to all the difficulties encountered on a smaller scale. In 1950 the Ranee estuary was accordingly chosen as a pilot-scheme, on a power-producing scale of about one-fiftieth. Initial studies were immediately pushed ahead, and building started at the beginning of 1961. Progress was rapid, but so much was involved that it took five years to complete the civil engineering work and another year to finish installing the equipment. Like all great enterprises that do credit to the nation's industry and contribute to the development of its economy, the plant was officially opened by the President of the French Republic on 26 November 1966.

Radio position-fixing systems employing the continuous-wave hyperbolic principle, such as the Decca Navigator and Loran C, are now used by ships and aircraft numbering tens of thousands and the theory of their operation has become part of the syllabus in many courses of instruction on navigational aids. Although accepting that these systems produce position-lines along which the difference in the distance from the user to a master and slave station is constant, and that such a line is obtained by time-difference measurement in the form of phase comparison between the two received signals, it may be asked whether this process is affected by the doppler frequency-shifts that will occur if the craft is moving with respect to the stations. Surely, the question goes, these must complicate or modify the behaviour of the system and give rise to an error unless the receiver is stationary ? It sometimes seems to come as a surprise to learn that, far from being adversely affected by it, the operation of these systems is a practical example of the phenomenon to which Prof. C. J. Doppler gave his name: they work not in spite of his ‘shift’, but because of it.

The Coast Guard is the leading agency in the United States for analysing collision statistics and generally preventing marine casualties. In this paper, which was presented at an Institute meeting held in London on 30 November 1966, Captain William C. Foster, Chief of the Merchant Vessel Inspection Division, Office of Merchant Marine Safety of the U.S. Coast Guard in Washington, describes the manner in which accidents of all kinds are investigated. The lecture was illustrated with examples of some of the extremely detailed forms which those involved in marine casualties are required to complete and of the statistical casualty returns; these are not reproduced here.

Marine casualties and accidents, whether or not loss of life is involved, are investigated by the U.S. Coast Guard for the purpose of determining the cause of the casualty and the persons, if any, who are responsible and to obtain information for the prevention of similar casualties. The Coast Guard regulations require the owner, agent, Master, or person in charge of the vessel involved in a marine casualty to notify the nearest marine inspection officer whenever a casualty results which causes physical damage to property in excess of $1500, material damage affecting the seaworthiness or efficiency of the vessel, any stranding or grounding, any loss of life, or injury incapacitating a person for a period in excess of 72 hours. When a casualty occurs in international or foreign waters, this notice is frequently given upon the American vessel's arrival in the continental limits of the United States on forms CG-2692 (Report of Vessel Casualty or Accident) and CG-924E (Report of Personal Injury or Loss of Life).

The proposals of Calvert and Hollingdale (Journal, 13, 127; 14, 234, 379; 18, 141) are of considerable interest. Soviet research work similarly leads to the conclusion that the principle of anti-clockwise rotation of the line of sight is the best if not the only way to solve the problem of manœuvring in fog whilst using radar. A rule of manœuvre embodying this principle was described in Morskoi Flot No. 5, 1958 and later proposed by the Soviet Delegation at the Safety of Life at Sea Conference in London in 1960. The instructions to Soviet ships on the use of radar for collisionavoidance were published and deposited with I.M.C.O. as an official document.

Some years later Die Seewarte (Hamburg, October 1961) and Navigation (Paris, July 1962) published an account of an electronic manœuvre indicator constructed in the U.S.S.R. and described in Morskoi Flot No. 2, 1959. The trials of this instrument were described in Morskoi Flot No. 12, 1964. These publications should be of interest to members of this Institute.

In recent years there has been growing concern over the adequacy and distinctiveness of navigation lights in use at sea. This has expressed itself in a series of modifications to the lights shown by various specialized vessels, and by and large the more unusual users of the sea are now clearly and distinctively lighted by night. However, despite the noise being made about it, little has so far been done to improve ordinary ship's navigation lights. There can be little doubt that something urgent does need to be done about them; the survey carried out by Shell International Marine1 indicated this statistically, and any practising navigator need only think of the difficulties encountered at sea from other ships showing wrong or inadequate lights to realize it.

The range of navigation lights in general is the first and most obvious matter for improvement. The present statutory ranges were laid down when oil lamps were still the normal means of providing light, and when in addition ships were much smaller and slower than the average today. In view of the current size and speed of ships, and the obvious fact that in the future they are going to get even bigger and faster, it seems senseless to have their navigation light ranges prescribed on a datum established by oil lamps. The mind boggles at the prospect of two crossing supertankers, each with side-lights visible for no more than the statutory 2 miles, maintaining course and speed until each saw the other's side-lights (a common practice at sea).

If the position of a vessel be determined from two or more position lines of known accuracy, it is possible to construct an error zone about the plotted fix, such that there is some given probability (for example 95 per cent) that the true position lies inside this zone. It is convenient for many purposes, such as ease of plotting, and preparation of accuracy diagrams, that this zone should be a circle, since in this case the figure of merit attaching to a fix is defined uniquely in terms of just one parameter, the radius of the circle. The object of this paper is the theoretical study, followed by practical example, of the circular zone round a vessel's plotted position inside which it may be asserted, with 95 per cent confidence, that the true position really lies.

This sets down in extremely simple terms the principles by which navigation aids may be coupled to autopilots and autohelmsmen. These principles apply to human pilots and human helmsmen for a craft cannot be navigated by positional aids alone.

Control by an aid that provides position only is shown to be unstable and, therefore, heading is introduced. This quickened system will be stable unless the control is unduly fierce. Such a system may not allow a craft to follow a required track exactly and, accordingly, ‘over-burdening’ may be required or, alternatively, course substituted for heading.

The type of navigation aid introduces special problems. Approach to a point source aid such as a radio beam leads to an increasingly acute sensing of deviation which tends to reduce stability. The craft will, therefore, need to be settled on to the beam at a reasonable distance from the transmitter and this need will introduce special problems in ‘capturing’ the beam.

Coupling to navigational aids is a basic technique in air navigation which will affect the choice of future air navigation systems. Coupling has not, however, been introduced into marine navigation. In space navigation coupling is confined to precise terminal navigation which at present is limited to launch and docking.

It has recently been suggested that 24-hour satellites might be used as navigational aids. To what category of position determination aids should these be assigned ? Is a satellite of this kind as it were a landmark, because, at least in theory, it remains fixed over the same point on the Earth's surface, in which case it should be classified under land-based navigation aids ? Is it a celestial body, although only one tenth as far from the Earth as the Moon ? If so, it is an astronomical navigation aid. Or is it a radio aid ? After all, its use for position determination depends on radio waves. In this paper I shall favour this last view. For automation is most feasible when an object of observation can be manipulated. This is easiest with radio aids, but it is, of course, impossible with natural stars.

At present artificial satellites have the advantage over all other radio aids of world-wide coverage.

Both civil and military aircraft are increasing in size and complexity and the range of height and speed over which they operate is extending. At the same time, cost of training aircrew is exerting pressure on managements to reduce crew numbers, usually by eliminating the need for specialists. These more expensive aircraft with smaller crews justify more elaborate computing and control systems to exploit their military capability or commercial earning power. Therefore, the need for the more extensive use of airborne computers is already well established.

Due to high cost and poor reliability, analogue computing systems have only marginally satisfied the demands for increased automation in aircraft. However, recent advances in digital computer technology offer advantages in size, accuracy, flexibility and particularly in reliability over analogue methods and show promise that digital computer systems can be designed to meet the future requirements for airborne computing.

Modern hydrofoil ships have evolved in response to the need for a fast reliable means of sea transportation which is capable of operating in all sea conditions. It is the purpose of this paper to describe how the application of modern stabilization and navigation technology to hydrofoil ships has contributed to the achievement of these goals.

First, consider the subject of stability. In particular, consider the source of roll stability in three types of ships: a displacement ship; a surface piercing hydrofoil and a submerged-foil hydrofoil. A roll disturbance of each of the ships is depicted in Fig. 1. In both the displacement ship and in the surface piercing hydrofoil, the righting moment is produced entirely by the change in attitude of the ship relative to the water surface. In the case of the displacement ship, the righting moment is due to the shift of the centre of buoyancy. For the surface piercing hydrofoil, the moment occurs due to the shift of the hydrodynamic pressure centre of the foils. However, for the submerged-foil hydrofoil, no righting moment is produced by the change of the relative position of the water surface. The righting moment for this ship must be produced by underwater control surfaces in response to the change of ship attitude relative to inertial space, as sensed by a vertical gyro. It is this transfer of stability reference from the water surface to an inertial reference that leads to the superior seakeeping capabilities of the submerged foil hydrofoil.

Long-range transport aircraft of the next decade will almost certainly contain a navigation system capable of providing accurate and reliable fixing and flight director information over any part of the world. Over the North Atlantic Ocean die navigation system must be reliable enough to ensure safety at an agreed separation between aircraft flying in a controlled environment. At the conclusion of the en-route part of a flight these long-range aircraft pass through an interface of some 200 or 300 n.m. radius around the terminal airfield before they come within the close terminal control, with its specialized aids to approach, landing, take-off guidance and holding. The interface is currently served by a variety of radio and radar aids, all ground based at the present time. Aircraft are monitored by primary radar on the ground while they fly along airways some 10 n.m. wide with the aid of VOR/DME, Decca/Harco or A.D.F. The aids used depend upon the traffic density experienced in the area, the geographical environment and many other factors. At this time when consideration must be given to the development of an accepted navigation system for the interface, it is important that close attention should be given to the employment wherever possible of a rational navigation system compatible with all en-route systems and terminal area aids. The system used in the interface should use as much of die en-route and terminal equipment as possible, perhaps eventually removing the airways interface, as we know it, altogedier. Several techniques should be considered, diey include die use of ground radar for die precise up-dating of doppler and inertia navigation aids, die use of differential Omega for up-dating widi conventional Omega and ground radar for gross-error monitoring, and die use of ILS localizer beams used in conjunction with a downwind localizer aerial for the provision of a service presendy supplied by VOR and ADF.

Historically, the navigation of a civil transport aircraft has been the responsibility of a specialist crew member. In the performance of his assigned task, the navigator has applied a complex set of mathematical and intuitive procedures by which he made navigational information useful. Now, because of increased accuracy requirements and of economic considerations, it is becoming apparent that the job of navigator must become an automated task.

An improved navigation system which meets present and future operational constraints does not lie in the development and implementation of more navigational sensors. While this approach may provide an equitable solution in the future, its present contribution would serve only to further burden crew members who are already functioning at or near their limit. Instead, the problem must be approached with the view of optimizing the tasks of a crew member who will ‘manage’ the navigation systems as a collateral duty.

Some degree of automation is a necessary part of commercial shipping because it can reduce labour requirements, permit some redeployment of crew and help improve ship efficiency. It has sometimes, however, been applied indiscriminately.

The ship must be considered in its entirety and navigational requirements, for example, are only a sub-system. The value of an investment in automation cannot be measured solely in terms of labour saved, since some of the cost may be recouped in improved performance, saved time, enhanced safety and widened knowledge. It is particularly difficult to place a true value upon the latter two. Training, expensive specialist maintenance and the cost of spending money have to be added to first costs.

Whilst the contribution of each sub-system and its component units can be evaluated to see whether investment is justified, a measure of automatic control in the modern ship is not only desirable but inevitable. As manufacturing techniques and scientific knowledge advance, the shipowner can also expect to be able to equip his ships with cheaper, better and more compact equipment, and this will be a further encouragement to reconsider his operational methods from time to time.

Despite the fact that there is a large number of plotting aids available there must be many vessels in which radar plotting for anti-collision purposes remains a drawing exercise (transferred plotting), or is not attempted because it is believed to be a process too lengthy for the exigencies of practical work.

Quoting J. R. Webster of the Board of Trade—‘Most of the collisions which have occurred have been in conditions when there were no other ships in the close-quarter situation, and in my opinion the relative display is better for judging the degree of collision risk in this case, with a simple plot to ascertain the effective avoiding action’.

Believing this to be so, the following suggestion is made for simplifying plotting procedure.

The information used in the plot should not require conversion in the time-distance-speed sense and this should apply to the information derived from the plot. The plot should enable the navigator to answer these questions:

i. Will a collision take place if present courses and speeds are maintained ?

ii. What will be the distance off at nearest approach of the target even if there is no collision ?

iii. What alteration of course and/or speed is required in order that this distance off can be increased to some safe value ?

iv. What time is available for action ?

Captain A. Wepster's able and professional analysis of this subject, contained in the January issue of the Journal, confirms what many seamen have long known. That these rivers—the Schelde, the New Waterweg, the Weser and, finally, the teeming Elbe, from Brunsbuttel seaward—are the world's most difficult and demanding stretches of navigation for seamen and pilots. The Captain's excellent treatment focuses attention on this and in his final paragraph he offers several considerations which, if followed, could reduce the number of collisions.

I refer to page 29; ‘Improving River and Port Authority Organizations and, if necessary, traffic control. On page 17, with reference to changing pilots in Flushing Roads in the Schelde; who has not, when proceeding outbound, ‘overshot’ the mark when approaching the pilot ground off the Commercial Harbour ? There follows the business of making a complete circle midst moving traffic as an apologetic pilot comes a puffing to the bridge, showering abuse on the man he relieved because 'he failed to slow down in time’.

I would add a specific recommendation to those offered by Captain Wepster: For vessels outbound from the Schelde, to disembark their pilots and take on Oostgat or Wandelaar pilots at a point approximately three miles upriver, say at Sloehaven. A pilot station could be maintained at that point in the manner of the present pilot office at the Flushing Mole.

The amendments and additions to the existing (1960) Regulations for Preventing Collisions at Sea which were offered in the Journal, 20, 103, by Captain Burger and Captain Corbet have been studied with interest. While clearly we have the same objectives at heart it will be seen from the comments that follow that the proposals are virtually unacceptable.

Rule 16 (b)

It is felt that the proposed re-wording is inappropriate as the words ‘hearing, apparently forward of her beam’ and ‘the position of which is not fully ascertained by sighting’ do not make sense in one sentence. Moreover, the proposed addition of the word ‘particular’ before ‘caution’ is not likely to deter the delinquent any further than the original wording.

It is agreed that the present wording of Rule 16 (b) may leave something to be desired in the interpretation which can be put on ‘ascertainment of position’; this has in fact been evident by some of the different interpretations which have been given by the Courts.

In the Nippon Yusen Kaisha v. China Navigation Co. case of the pre-war era (1935), Lord MacMillan said, ‘In order that the position of a vessel may be ascertained by another vessel within the meaning of the Regulation she must be known by that other vessel to be in such a position that both vessels can safely proceed without risk of collision’.

Recently the author was asked to suggest how an old (Scottish?) sun-dial, inscribed on a slate slab about 50 cm across and 3 cm thick, could be put into working order and set up correctly to tell the time. Upon examination the dial was found to be of considerable historic interest. Although it was quite a well-known type of dial—an equatorial—the furniture and inscriptions suggested a definite connection with the sea. Moreover, no other identical instrument is known to exist; possibly the publication of this note may help to bring other specimens to light. For this reason it is felt that a description of the various features of this multi-purpose dial will be of some interest.

Both surfaces of the dial are shown in the accompanying photographs. For clarity, a fine talcum powder was sprinkled on the dial to fill all the incised markings which would otherwise be invisible. Unfortunately the gnomon is missing. This gnomon would have passed vertically through the dial extending on either side for not less than 10 cm. Probably two circular discs with pointers were mounted centrally on the upper surface, with one of these discs bearing an arm with the ‘dioptera’, but unfortunately these items are also missing. The discs would have been capable of rotating around the gnomon. It would appear that some modifications became necessary after its construction as the four holes around the inner circle have spoilt the lettering.

In the October issue of the Journal (19, 529), Commander Clissold puts forward a type of radar display which might be useful for collision avoidance, as it intends to show the aspect of the ship representing the danger. To achieve this a long afterglow screen would be used and the display would be oriented head-up, i.e. ship's head at the top of the picture to correspond as closely as possible with a possible visible situation. An electronic cursor, bearing line, would indicate a danger of collision if on constant bearing. This type of display is said to show tracks true relative to own ship's course.

Apart from the fact that 30 seconds afterglow, decaying exponentially as an excited phosphor screen would, might be too short for showing up tracks efficiently, there are some other difficulties as well with such a display. Obviously aspects of target ship would not be shown but implied only by the afterglow track. Furthermore, a display of this kind would be a true-motion type display not necessarily north stabilized but nevertheless showing all motion of other ships in true, if own ship's speed is compensated for in displacing the origin of the radial scan. The difficulty will arise if own ship changes heading and unless this heading change is also compensated for, like in a north-up stabilized true-motion display, smearing of all echoes will occur. A heading change of own ship, therefore, will produce additional apparent tracks of other ships and the apparent displacement of fixed targets.

In an article in this Journal some years ago, the late Professor E. G. R. Taylor and Dr. D. H. Sadler drew attention to and discussed Hariot's calculation of meridonal parts. The question was raised but not answered as to ‘how Hariot discovered the extremely complex and far from obvious method’ that he used. This note draws attention to a possible, and indeed a very likely, way in which the method may have been discovered.

The conformal property of the stereographic projection of the surface of a globe from a pole on to its equatorial plane has been known since antiquity. It is used in the design of the astronomer's astrolabe. Hariot's manuscripts contain in more than one place a diagram for a proof of the property. One of these is reproduced in a recent article on Hariot. Halley, in an article on meridional parts, says of the conformal property, ‘But this not being vulgarly known, must not be assumed without a Demonstration’. From this result he obtains the formula for meridional parts, unaware that the same proof may have been used almost exactly a hundred years previously. In fact, he says, ‘I hope I may be entituled to a share in the emprovements of this useful part of Geometry’ on the basis of ‘having attained … a very facile and natural demonstration of the said Analogy’.