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.

There are endless regulations concerning the speed and size of vehicles on our roads, but none that apply to vessels using our maritime routes, even though there is a regular increase, in step with technical advances, in both the size and speed of ships. For reasons of economy roads are narrow, and the necessity to avoid obstacles means that they have to be winding. No such considerations apply at sea; changes of direction are slight and widely spaced out, nor are there any ditches or hedges to limit the width of the routes that are used. Nevertheless, studies of maritime traffic have shown that overcrowding is becoming more and more pronounced on the busiest routes, and the present tendency to develop oneway routes is an implicit recognition of the fact that the remedies for such overcrowding on the roads and at sea have something in common. One-way traffic, for example, is derived from the Collision Regulations (Rule 25). It is worth examining what help the Regulations can give in solving problems raised by the size and speed of ships.

The Eva G. R. Taylor Lectures were founded in 1959 to mark the occasion of Professor Taylor's 80th birthday. Following an appeal signed by the Presidents of various learned bodies, including the Institute, it was agreed to endow an annual lecture to be presented by a distinguished scholar in any of the branches of learning to which Professor Taylor made such notable contributions. Rear Admiral Ritchie's lecture was presented at the Annual General Meeting of the Institute held in London on 26 October 1966, with the President, Rear Admiral Sir Edmund Irving, K.B.E., C.B., in the Chair.

The problem of underkeel clearance is not new; since time immemorial navigators have been concerned to know the minimum depth of water in which they can sail with a ship of given draught. Until quite recently, underkeel clearance requirements were determined almost entirely empirically, and in many cases the rule of thumb values used can be shown to be greater than the requirement of navigational safety would dictate.

In the years since the war the pattern of the oil industry has changed and very large ships are now commonly used to carry crude oil cargoes to a large number of ports around the world. It is obvious that use of these ships, with their deep draughts, has meant that a number of expensive dredging projects have been put in hand to provide adequate access to the ports served. Continuing escalation in size means this will probably continue.

These notes on collision avoidance by an experienced airline pilot are presented in the form of practical advice to young pilots. The paper deals first of all with blind avoidance and then with visual avoidance.

Collisions are rare and about one quarter of colliding aircraft have landed safely. Collisions are not always fatal to everyone, but they are serious accidents. Pilots need knowledge, skill, good habits and/or a little luck to avoid them. Collisions have occurred for years although in many cases the investigators have proved that the approach of the aircraft and the layout of the windows around the pilots were such that some of the pilots could have seen the other aircraft. Yet they still collided, so that obviously visual avoidance is not easy. In other cases especially in the circuit the aircraft approached and collided without much possibility of seeing each other; so remember there may be someone under your nose or above your tail who can't see you either. We all know how the high closing speed of fast aircraft is too high for human visual acuity to sort out the situation and prevent collision visually. But a number of collisions have occurred at low closing speeds and a number have occurred between light aircraft (e.g. two Convair 240's over U.S.A. in August 1953, and two light aircraft over Reading a few years ago).

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.

In the following paper, which was presented to a meeting of the Institute held in London on 30 March 1966 Captain Wepster describes the results of an investigation undertaken by the Holland-America Line into collisions on the main navigable rivers and inland waterways of north-west Europe, including the United Kingdom. On the basis of a previously published paper by Beattie, it was estimated that the main rivers worth investigating were the Schelde, the Thames, the Elbe, the New Waterway and the Weser. A speed analysis and plot of casualties of these rivers is presented.

A continuing study of ship's bridge design and ship control conducted by the Defence Research Board of Canada has recognized that the conventional method of issuing and executing verbal orders contains inherent delay and is a possible source of error in ship control. As a partial solution to this problem, it was proposed that ‘the officer originating decisions to change the course and speed should implement these decisions himself through the direct control of helm and engines on the bridge’ (p. 21). It was further proposed that the direct controls be located on a console positioned at the front of the bridge on the centre-line of the ship.

The conventional location and arrangement of the bridge restricts visibility, however, in areas close to the ship, and this limited visibility from the bridge often causes manœuvring difficulties. In some instances, distances as great as 800 ft. ahead of the bow and 50 ft. abeam are ‘blind areas’. In most cases, areas aft on the centre-line cannot be seen at all. In an attempt to alleviate these problems, bridges have been extended to the sides of ships, or bridge wings provided so that much of the ship's side can be seen by the conning officer. With direct control from the centre-line and the use of a television system, bridge wings could possibly be eliminated, while still providing better close-in vision.

1. INTRODUCTION. The distribution of jet streams over the North Atlantic, Europe and the Mediterranean for the two years 1957–8 was described in an earlier paper (Crossley, 1961); the present paper extends the study to the area which is here referred to somewhat loosely as the Middle East —it extends between latitudes 40° N. and 10;° N., and from longitude 30° E. to 90° E. in the north but to only 65° E. in the south (Fig. 1). The aircraft trunk routes intersecting this area include those from the Eastern Mediterranean across Arabia and the Persian Gulf to West Pakistan and north-west India.

The jet streams which affect the Atlantic-European area in the upper troposphere are mostly of the ‘polar’ type with a core in the neighbourhood of 300 mb. so that they can be conveniently located as a rule on the contour charts for 300 mb.; in the Mediterranean region and in the corresponding latitudes of the North Atlantic the westerly subtropical jet stream is also concerned and charts for both 300 and 200 mb.

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 lessons to be learnt from a collision are not necessarily proportional to the damage it has caused. The great catastrophes arouse passions which often hinder the use of reason; on the other hand, when there has been no loss of life and when material damage has been slight, the accident may be seen as a warning which it is possible to contemplate in a detached manner, to see how it might have been avoided and how similar or worse accidents might be averted in future. Such was the collision between the Placid, a 50,000 ton tanker in ballast, and the Tenacious, a cargo vessel of 4000 tons, laden, some years ago on a foggy day in the summer, between Le Havre and Barfleur. (Both names are fictitious to safeguard the anonymity of the companies involved.) The collision claimed no victims and the compensation amounted to 180,000 francs for the Placid and 90,000 francs for Tenacious.

A ship will drift regardless of whether she is stopped or underway due to the action of the wind and sea. A knowledge of this movement is necessary in order to correct the course, to deduce the estimated position, for manœuvring at slow speeds and for search and rescue work. The causes of drift are the force of the wind on the upperworks, drift current whose strength depends on the wind, rolling which is caused by the action of sea and swell and, finally, ocean currents and tidal stream currents. To study the effect of wind on drift an experiment was carried out in which this effect was isolated from the other causes mentioned above.

A salmon drifter was used in which a gill-net was observed by radar from the time of the net being shot until it was hauled in. The net was then allowed to drift with the ship with the ocean current, the tidal stream current, the drift current and the wind and sea. The ship itself, however, was also subject to drift from the wind whereas the corner reflector on the net (which was several miles long) was not subject to this effect, the net acting as a sea anchor. It was thus possible to isolate the effect of wind drift.

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 limitations to the accuracy of an inertial navigator are first of all the inherent accuracy of the inertial components—gyros and accelerometers; secondly the accuracy with which these are controlled, i.e. by power supplies, and electronic circuitry; thirdly the accuracy of the associated navigation computer. All these three can be checked during manufacture and by laboratory testing of components and systems. However, there remains the effect of the aircraft environment on accuracy. It is possible to simulate some of the environment, for example vibration and temperature, in the laboratory, but it is not possible to simulate realistic accelerations, velocities and displacements, and so flight trials form an essential part of the evaluation of an inertial system. Flight trials may be preceded by trials in a land vehicle on grounds of economy, but such trials are of limited value because of the limited velocities and displacements available. In this paper we shall attempt to summarize our experience at R.A.E. and A. & A.E.E. of laboratory, van and flight testing of inertial navigators which has been acquired in joint trials over the past five or six years. During the next twelve months we shall be associated in trials of three further inertial navigators, the Elliott E5, the Sperry SGN 10 and the Ferranti FMP-B, and we shall also describe in this paper some of the techniques which will be used for the first time in these trials. This is not intended to be an exhaustive treatment of system testing, but will be mainly confined to the systems and tests of which we have practical experience.

Contour charts are of great value ‘providing’, as Hughes says, ‘the navigator with a quick and sure means of comparing the echo sound record he has just made with the variations in contour and so enabling him actually to plot his line of position by soundings’. But it is evident that the most useful method of using contour lines would be if the position lines based on them are plotted in the same way as every position line, i.e. by plotting the intersection of two or more of these lines. The object of this paper is to propose such a method.

It is possible to plot a contour-based position line by means of the sight line to one point of a contour line and its range, because if we draw (Fig. 1) from every point of contour line A, parallels of the same length to the sight line, all points at the other end of contour line define such a position line, which may be called a range-bearing (RB) position line. Better accuracy can be obtained by sextant, using a second sight line to the same or another contour line (Fig. 2), measuring the angle α between them—then we have a position line which may be called a two-range position line. When it is possible to measure the minimum range to a contour, the angular datum can be omitted, using the position line which may be called a mini-range position line.

In December 1958 and in February 1961 meetings of the Institute were held at the suggestion of the Hydrographer of the Navy, so that the Admiralty chart could be discussed with sea-going chart users. This forum produced a number of valuable suggestions for the improvement of the charts including those affecting an improvement in chart coverage; and a request for routing charts, since published for the North and South Atlantic and the North Pacific Ocean, with those covering the remaining ocean areas in preparation.

A basic parameter of a ship's motion is its velocity, a knowledge of which is important to both seaman and ship designer. Often it is sufficient to know the ship's mean speed at given engine revolutions. Sometimes the knowledge of its instantaneous velocity may also be required.

Instantaneous velocity measurement is possible by means of a doppler radar. The radar is located on the ship and at a selected point of reference on shore, or on a buoy, a reflector is placed which strongly reflects the electromagnetic waves; the ship is then steered directly towards or away from the reflector. The radar emits a beam of electromagnetic waves directed toward the reflector. Due to the ship's motion in relation to the reflector, the received signal returned by the reflector is shifted in frequency from the transmitted frequency by a doppler frequency. This frequency is proportional to the instantaneous velocity. The mean velocity may be measured by counting the number of signal periods of doppler frequency. This number is the measure of the distance covered by the ship. Simultaneous measurement of the time enables the mean velocity over the given distance to be determined.

This method makes possible the measurement of the instantaneous velocity and acceleration of the ship. Simultaneous observation of instantaneous velocity when measuring the mean velocity allows a measuring length along which the velocity of the ship reaches a steady value to be chosen and the maximum velocity to be measured.

The Central Inertial Guidance Test Facility (C.I.G.T.F.) at Holloman Air Force base, New Mexico, has the responsibility for testing all aircraft inertial navigational systems, aided and unaided, for Department of Defence applications. From 1963 to the present, ten systems have been evaluated. The experience derived from past test programmes has always been valuable to the C.I.G.T.F. engineers in the design of increasingly sophisticated programmes.

This paper retraces some of the experience of the C.I.G.T.F. in its inertial navigation system testing. Test philosophy, objectives and approach are discussed briefly. Flightpath design, radar coverage, range instrumentation, aircraft instrumentation, data reduction and analysis of system performance are then considered. In addition, some mention is made of the test programmes presently being designed, and the technical problems of INS evaluation that the C.I.G.T.F. is now attempting to resolve. Because of the breadth of subject material, ideas are presented mostly at the concept level. Technical details are contained in the references.

The C.I.G.T.F. test method is to fly the test specimen within the coverage of the FPS-16 radars or other instrumentation of the White Sands missile range. An airborne tape recorder records where the system ‘thinks’ it is, along with a range reference time signal (irig-b). Likewise, the FPS-16 radar site records where the radar ‘knows’ the aircraft is, referenced to the same time base. Post-flight data reduction compares the outputs of system and reference at each sample/time, and forms an error plot of the differences in position in each channel. This is the basic error data used to describe system performance.

During the summer 1966 the Executive Secretary sailed his bout Jester single-handed to the Azores and back. The passage from Gosport to Horta (Faial) took 17 days, and 13 days back from Graciosa light to Newhaven, having passed 20 miles south of the Lizard 11 days out. Jester, it will be recalled, was owned by H. G. Hasler, her designer, who completed four transatlantic passages in her. The boat is 19 ft. 9 in. on the waterline, with a consequent maximum theoretical speed of about 6·2 kt. Her average speed on the return voyage was just under 4¾ kt. The following notes refer mainly to the navigation.

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.