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.

The following amendments and additions to the existing (1960) Regulations for Preventing Collisions at Sea are offered for comment by Institute members and others interested in this problem.

The only comment which we wish to make about them at this time is that we do not claim that any of the ideas on which these suggested new rules are based are our original ideas—they have only been sorted out, into what we hope will prove to be a satisfactory arrangement, from many ideas which have come to light and have been aired during exercises and discussions that have taken place during radar simulator courses conducted at the Welsh College of Advanced Technology over the last five years and during discussions with many members of the staffs of other nautical colleges and with nautical surveyors of the Board of Trade. The ideas put forward by many notable persons in the various nautical publications have also been studied and have greatly influenced us.

It its early work, the Working Group decided to study amongst other subjects the problems of bringing the S.S.T. into a traffic control system; almost certainly there will be an effect on the flight profile of the S.S.T. and on the requirements for accuracy of the navigation. In the absence of special information on the characteristics and performance of the S.S.T., a study has been made of the trends in A.T.C. handling of terminal area traffic (T.M.A.). The term terminal area has been interpreted in its broader sense, that is to say the region in which present-day transport aircraft and a fortiori supersonic aircraft are not in the cruise phase but are either descending towards the destination airport or climbing from the departure airport. With this definition, the most important terminal areas (those in countries overflown by heavy traffic and in which there is a plenitude of radio navigation aids and control), have in practice the same limitations as the flight information regions in which they find themselves.

If we try to look ahead ten years to the period from 1965 to 1975, it is precisely in this period, in the countries overflown by heavy traffic, that the instruments and systems which have been recently devised and experimentally used to meet the problems of subsonic traffic control will, in fact, become operational. With these points in mind the following notes refer to the possible evolution of traffic control in the future.

Automation is generally embarked upon with the idea of improving the economics of some process, largely by reducing the manpower, but it may be used also as means of solving computations which would otherwise present an almost impossible task for ordinary human effort, or involve so many people that this also would entail problems of organization. It may be difficult to demonstrate that automation of aircraft navigation can cheapen the job by saving in manpower, but it can be seen that the same manpower can be provided with solutions to navigation problems which will improve the aircraft navigational capability, but which would otherwise have demanded more crew. Processing the data obtained from a navigation satellite might be so complicated as to be beyond the scope of what can be expected of human effort in an aircraft, and even if this is possible the time taken to compute the fix may make the information so out of date as to be of little practical value. It is quite certain that by introducing automation into aircraft navigation, the flight crew can be relieved of some tasks so that, particularly in respect of the captain, more time can be made available for the management of the aircraft. We are, in fact, dealing with the question of workload and, therefore, we must look at the size of the job and the time available to do it.

The publication of a new impression of Professor E. G. R. Taylor's first volume of Mathematical Practioners so soon after the appearance of her second volume makes it a particularly appropriate time to take stock and consider the next steps. Despite various criticisms, some of which will be discussed below, all reviewers agree that her volumes mark a great advance in this field and will be of ‘immense service to scholars’. Our debt to the author is all the greater when we realize that these books followed on a whole series of standard works in her own subject of geography, and that she was neither a mathematician nor a bibliographer. The best tribute to Professor Taylor is to continue the work recorded in these two volumes, but there are few who have the detailed knowledge and expertise to follow her in such a wide field. This article will, for example, offer little comment on instrument-makers who form such a large section of her practitioners and who left records of their work in museums and private hands all over the country; here we shall be much more concerned with the written work, with the bibliography of the subject.

Reviewers of her volumes have found it difficult to define the practitioners of whom she wrote and to decide in what sense they differ from mathematicians in the normally accepted sense of this country or overseas.

With the advent of increasing numbers of high-speed, high-altitude aircraft on the airways of the world, airlines, aircraft manufacturers, government agencies responsible for navigational standards and air traffic control, as well as military agencies are actively engaged in studies and action directed towards significant changes in longrange air navigation practices and procedures.

These changes have been dictated by the need to utilize to best advantage the ‘limited’ air space available on long-range air routes to each individual aircraft, because of the fantastic growth rate in numbers of aircraft operating the trunk routes of the world.

In order to limit the amount of airspace required around each individual aircraft separation standards are enforced by the various agencies responsible for control of air traffic along these major trunk air routes. These separation standards are based on longitudinal, lateral and vertical limits between adjacent aircraft. In order to ensure that operating companies and flight crews are aware of these requirements, appropriate legislation is introduced by either international or national agencies and promulgated in readily assimilable form in regulations, orders, or flight or operation manuals.

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.

There is no doubt that everyone is agreed that a combination of visual and sound signals are a necessity, but, in view of the large disparity in the speeds of light and sound, the method of achieving this has not really been agreed upon, although a few countries supported the system of synchronizing the light and sound signals, thus bringing about the addition of Rule 28(c) to the Collision Regulations. I am, however, of the opinion that this synchronized system is not suitable, mainly because of the disparity between the relative speeds of light and sound. This could lead to confusion and misinterpretation by the receiving vessel; the degree of confusion depending on how far distant the receiving vessel is from the vessel giving the signals, when there is a sudden alteration of course immediately following the previous alteration.

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.

Newton'sPrincipia contains a neglected passage, which is nevertheless the true source of inertial navigation, occurring in De Motu Corporum Liber Primus, toward the end of ‘Sect. X. De Motu Corporum in Superficiebus datis, deg; Funipendulorum Motu reciproco’ as ‘Corol. 2’ to Prop. LIII. Prob. XXXV. Concessis figurarum curvilinearum Quadraturis, invenire vires quibus corpora in datis curvis lineis Oscillationes semper Isochronas peragent’. The corollary reads in the first edition:

‘Corol. 2. Igitur in Horologiis, si vires a Machina in Pendulum ad motum conservandum impressae ita cum vi gravitatis componi possint, ut vis tota deorsum semper sit ut linea quae oritur applicando rectangulum sub arcu TR & radio AR, ad sinum TN, Oscillationes omnes erunt Isochronae’.

This text shows only one or two very minor changes in the second and third editions, but the two extra drawings added in the third edition are helpful. Cajori, in a readily available publication quite adequate for reference here, gives these drawings, and his version of Motte's translation reads:

‘Cor. II. And therefore in clocks, if forces are impressed by some machine upon the pendulum which continues the motion, and so compounded with the force of gravity that the whole force tending downwards will be always as a line which is obtained by dividing the product of the arc TR and the radius AR, by the sine TN, then all the oscillations will become isochronous.’

Having studied marine statistics for a number of years, especially those concerning casualties at sea and in particular collisions between ships, the opening paragraph of the Traffic Separation Working Group's report (this Journal, 19, 4) is, to say the least, lacking confirmatory evidence on two counts.

I refer to the general statements which allege that:

(i) ‘The main risk at sea today arises not as it used to from stranding and shipwreck, but from collision’.

(ii) ‘In the open sea, where nearly 30 per cent of all collisions occur…’

As both include the words ‘at sea’ or ‘open sea’ it is not unreasonable to suppose that they imply freedom to manœuvre under own power unhampered by depth of water or similar navigational restriction.

This being so, and not an irrational definition of the area of concern to the Working Party, what are the facts and how exactly do casualties at sea compare with those in other areas of marine interest throughout the world.

To find the right answer to the global problem is not easy and there are no short cuts, such as for example making a sample analysis in a limited area where traffic density is high, in order to arrive at fairly large numbers which are then used to deduce the statistical probability applicable to all areas.

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 ?