This article is based on a series of circulars compiled for and issued to shipowners and their ships. In the October number of this Journal, Captain Wylie dealt with the limitations of true-motion displays at slow speeds and of plotting when courses and speeds are varying. The present article groups relevant extracts from court cases and enquiries under the various points in the Collision Regulations. (Dates given refer to the court hearings.) Subsequently it discusses certain manoeuvres and radar practices and their effects on collision hazards.

The surveillance of the air space by ground-based radar is important in air navigation and its military applications may be particularly mentioned since they have led to many important investigations, while aspects of the problem of less military significance have been neglected. Shore-based radar has also been applied to the surveillance of shipping in congested areas, captains and pilots being advised by VHF telephone though the captain retains full responsibility. This brings out a fundamental difference between the sea and the air. Air navigation and the ground control are integrated and the responsibility is shared. At sea the responsibility remains with the captain, and the use of radar increases this responsibility although ships are not yet obliged by law to be equipped with radar. Several court rulings have penalized the incorrect use of radar because of the greater responsibility that its availability entails and the recommendations of the Conference on Safety of Life at Sea (1960) concerning the Collision Regulations must also be remembered.

Vertime is a system devised to solve the problem of navigation in the vertical plane. By use of existing navigational aids together with only small additions to cockpit instrumentation and controls, a flight path in the incline plane is defined which the pilot can follow from cruise altitude to end of descent point. In addition, provision is made for improving the accuracy of E.T.A.s at the end of descent. This system reduces pilot work-load in the cockpit, ensures an operationally efficient descent from cruise altitude and will be of material assistance to A.T.C.

The safety of a vessel is the prime interest in ice conditions and routes must be selected which afford the least risk. However, this is only one aspect of the safe conduct of a voyage. The other is the expert handling of a vessel in ice-encumbered waters, or even when beset in ice. Both these aspects, the selection of the safest route and the expert handling of the vessel when ice is encountered, are discussed in this paper.

The pioneers of air navigation used a simple magnetic compass as a heading reference. At first boat or surveying compasses were used but these were not really satisfactory for use in aircraft, as engine vibration caused them to rotate. The first successful magnetic compass for aircraft use was the Creigh–Osborne compass which took to the air on 27 October 1909, in the British Army Aeroplane flown by the celebrated Col. S. F. Cody. In the years following and throughout World War I magnetic compasses based on this early work, with either horizontal or vertical cards, were widely used.

This paper discusses navigation system accuracies achieved on North Atlantic routes by Air Canada, and the effect of doppler on the accuracy of navigation. Data are presented on track maintenance performance with doppler inoperative and operative, on performance over a prolonged recent period combining all results, whether doppler operative or inoperative, and on the frequency of gross errors.

Doppler was installed by Air Canada with the primary aim of reducing the gross track maintenance errors which seemed otherwise inevitable at jet speeds and altitudes. A comparison of the results given below indicates the deterioration which resulted when the DC-8 was introduced and no doppler was available, and show the improvement achieved after some experience with doppler.

The purpose of this paper is to discuss en-route separation criteria applicable to the supersonic transport. Separation standards are described; equations are given and analysed which show the factors influencing separation; finally, suggestions are made for a supersonic transport air traffic control system for the North Atlantic. The discussion is concerned with longitudinal and lateral en-route separation in a non-radar environment, as opposed to radar separation in the terminal areas. The terminal problems are so complex as to require separate consideration and have been investigated by other authors. An appendix on the derivation of equations expressing statistical parameters of errors and estimated aircraft separation has here been omitted.

Much is written about the use and misuse of radar, but little has been said of what the mariner really needs to help him in his use of radar as an aid to avoiding collision in fog. In considering this, one must have particularly in mind the bridge on which the radar observer is also the watch officer and navigator.

It is generally accepted that he needs to be sure which targets are potential hazards and this must include those with whom the collision risk will be increased by alterations of his own course and/or speed, made to avoid others or in the course of navigation. In the commonly encountered multi-ship situation, there will, therefore, be several ships, maybe six or eight, about which detailed and up-to-date information is highly desirable.

This detailed information is of two kinds, relative to own ship and true. The relative data gives the degree of risk of collision of each target, in terms of the C.P.A., or closest distance of approach on present courses and speeds, and the time interval before this position would be reached. As a means of assessing priorities, the time is just as important as the distance. The bearing of the C.P.A. is less important, except in so far as it indicates on which side the other ship would pass.

The true information required comprises the courses and speeds of the other ships for which the degree of risk is significant.

Gyro magnetic compasses are subject to a large number of errors, some of which may be eliminated, or at least greatly reduced, by careful design on the part of the instrument manufacturer and an intelligent operating drill on the part of the user. Table I shows errors under five basic headings, and allots to each error a symbol classifying it as:

(a) The responsibility of the instrument manufacturer (I)

(b) The responsibility of the aircraft manufacturer or its operator (A)

(c) Inadequate knowledge of the geomagnetic structure of the Earth's field (K)

Some sources of error in Table I are marked with an asterisk. It is these which the designers of the compass system described have endeavoured to eliminate.

This paper discusses the application of inertial navigation and guidance systems in civil air transport operations from the systems engineering viewpoint. The concept of an operational system for navigation and guidance is introduced to facilitate consideration of the relationships which will exist between the inertial system and the operating functions necessary for the conduct of a flight. Inertial system configurations satisfying the requirements implied by these relationships are presented. The general requirements for input data panels and system output displays for all flight phases are discussed. A discussion of system mechanization considerations and estimate of system performance requirements conclude the paper.

The actual conduct of an airline flight requires the performance of a number of distinct operational functions. The totality of these functions constitutes the complete operational system for the flight. The functions which are of interest in the present study are those directly related to establishing and maintaining the desired flight path. These constitute the operational system for command and guidance which can be viewed as a sub-system of the complete operational system. For simplicity, however, the command and guidance operational system will be referred to hereafter as the operational system.

The paper describes an experimental analogue computer used with a civil marine radar set for determining the closest point of approach of selected ship's echoes and the time to closest approach. The equipment was installed on shore and measurements made of shipping passing to and from Portsmouth and Southampton harbours. The projected track of a ship echo was displayed on a 5-in. diameter cathode ray tube and the closest point of approach read as the distance of this track from the centre of the tube. The results show a high probability that under these conditions errors in C.P.A. will not exceed ±0·5 n.m. for targets between 10 and 6 n.m. range, and ±0·3 n.m. for targets nearer than 6 n.m.

In recent years the Regulations for Preventing Collisions at Sea have been the subject of considerable interest to mathematicians. It has been demonstrated that the Rules as they stand are not entirely satisfactory, and this confirms a certain uneasiness which most navigators have in this respect. One of the imperfections in the Rules is that they are not universal: they do not apply in fog, when vessels are not in sight of one another, they do not apply to certain classes of vessel, they are affected by limitations of weather and sea-room, and so on. It does not seem unreasonable that a set of Rules could be devised, based on the mathematical work lately carried out, which would be more rational than the present Rules.

It has been said that the mathematician accepts the gaussian distribution because he believes it to be supported in practice, and the practical man accepts it because he believes it has a sound mathematical foundation. Presumably it is for such reasons that the gaussian distribution is known as the ‘normal’ distribution and ‘probability paper’ has scales specially distorted so that a gaussian distribution will appear as a straight line.

The principle of applying controlled direct current to the flux valve to simulate rotation of the aircraft in a compass swing is discussed. The validity of the technique is demonstrated for the measurement of single cycle error and the MC-1 and MC-2 are shown as implementations of this technique. Work is now in process to eliminate calibration procedures, and to extend the technique to the pilot's standby compass and to aircraft with significant soft-iron error.

The precise navigation of modern aircraft requires an accurate source of heading information. In the primary mode of operation this signal is often obtained from an inertial reference, but the advent of inertial navigation has not eliminated the role of accurate magnetically slaved systems. A flux valve is often used to provide magnetic information to platform systems for use in initial alignment or in standby modes of operation and a magnetically slaved compass system, teamed with a doppler navigator, is still an excellent reference for long flights. For both applications full performance can only be obtained if the signal from the flux valve is carefully compensated in a compass swing.

Under the title Man or Machine? (Journal, 18, 10) a discussion took place in London on 25 April 1964, at a technical session of the Institute, on the extent to which automation could usefully be introduced into navigational procedures. Automation was taken to mean the use of machines which derive or accept navigational information and operate on it to provide a function for the control of craft. The discussion printed below took place at another technical session, held in London on 10 March 1965, when the purely economic aspects of the same problem were considered.

In this paper Mr. Katayama of the Idemitsu Tanker Company describes some of the advantages and problems of operating mammoth tankers. The size of average tanker tonnage over the past seven years has increased from 33,000 to 55,000. The paper first of all discusses the economic advantages of large tankers and then describes the limiting factors to size, both from a shipbuilding and operating point of view. The handling and manœuvring characteristics of the Nissho-maru, the world's largest tanker which is operated by the author's company, are then described, and finally some navigational details of the passages made by this ship are given.

Latitude by meridian altitude is one of the commonest position lines used in the Merchant Navy today, and the traditional method of obtaining it is to observe the Sun until it reaches maximum altitude, at which point it is said to dip. With the advent of power-driven vessels, however, this method became liable to an error of 5 minutes of arc, and as faster surface craft are developed it is reasonable to assume that the error could be even greater. This is because the rate of change of altitude of a body is related to the observer's speed over the Earth so that the body will dip either before or after meridian passage depending on whether the observer is moving towards or away from the geographical position of the Sun.

This paper describes development trends of one particular navigational technique (automatic star tracking) and its associated instrumentation methods one of which, the application of pulse code modulation theory to sensor design, is discussed in detail. Plans for the future development of this most promising concept are also included and the effects of military research and development efforts on civilian aircraft requirements are indicated. An appendix provides a glossary of special terms used.

Automatic star-tracking systems have been used in military aircraft navigation for position fixing and heading correction for a number of years and the development of the equipment has been actively pursued by the U.S.A.F. since as early as 1946. Basically, star trackers are automatic devices that probe a portion of the celestial sphere for the purpose of detecting, acquiring and tracking stars or other celestial bodies. In using astronomical inputs for cruise vehicle navigation, advantage is taken of the well-known principle that sights on two or more stars when referred to the true vertical and time can be used to provide a position fix. It is the intent of this paper to review techniques used to instrument star trackers, discuss their application to long-range aircraft navigation, indicate development trends and introduce a new concept of employing pulse code modulation theory to the design of a simple, low cost automatic astro-tracker.