Soon after the middle of the eighteenth century, improvements in the design and construction of astronomical and nautical instruments, coupled with the increased accuracy of tables of the Moon's motion, at last made the accurate determination of longitude at sea by lunar distance a practical possibility. The Astronomer Royal, Nevil Maskelyne, was quick to appreciate the importance of publishing the calculated solar and lunar ephemerides, together with other relevant tables and explanations, in the form of a Nautical Almanac, which was first printed under his supervision in 1766 and immediately distributed to mariners in different parts of the world. The present article is concerned with the circumstances relating to the origin and development of this publication during the first fifty years of its existence.

This article may be regarded as a continuation of the previous article in this Journal (18, 203) and it has the same basis and purpose. It deals first with an unusual case of collision, while overtaking in the presence of a second threat, and secondly with an Appeal case.

The lessons of the Nassau–Brott collision relate to the duties of the overtaking and overtaken vessels, poor look-out, and too short a range-scale.

The Crystal Jewel–British Aviator case relates to excesssive speed, failure to stop, failure to avoid close quarters and the cumulative turn.

The Nassau–Brott case was an extremely interesting one in which one ship, Brott, was being overtaken in open waters by another, Nassau, and, at the same time, having a third ship, Haminella, coming down from ahead. The latter presented the more immediate threat.

The 16th Technical Conference of the International Air Transport Association was held in Miami, U.S.A., from 22-30 April, 1965. The theme of the meeting was Air Navigation. Some 450 delegates attended, representing the world's airlines, aircraft manufacturers, national state agencies of one kind and another, and manufacturers of navigational equipment. The Institute was represented by the Executive Secretary.

This paper discusses a method for determining the collision risk implicit in horizontal and vertical separation standards which has been developed in the U.K. in accordance with Recommendation 7/1 of the RAC/OPS Divisional meeting. The acceptable collision risk for the North Atlantic is assessed; this must be related to airworthiness criteria and an accident rate of one in ten million is adopted. It is concluded that no immediate change in separation standards can safely be made but that the standard of navigation should be improved to allow a 90 n.m. standard; that with more data a 1000- or 500-ft. vertical separation may prove to be safe; and that longitudinal separation standards require further study. The improvement in traffic capacity which would result from changes in separation standards is also considered.

This and the following nine papers were presented at the 16th I.A.T.A. Technical Conference, of which a report appears opposite. An analysis of long-range air traffic systems made by the Mathematics Department of the Royal Aircraft Establishment for the Ministry of Aviation was presented in several preliminary papers at the Conference. These studies will be described in a series of papers specially prepared for the Journal.

The paper proposes highly stable moored ocean platforms and a transatlantic submarine telephone cable to provide a reliable v.h.f. communication service and other A.T.C. facilities to civil aircraft on the main air routes across the North Atlantic. The main features of the platform and cable system are discussed and some idea of the time scale and costs is given.

The planning of facilities needed to enable future operations over the North Atlantic to accommodate reduced separation standards and to satisfy the specialized requirements associated with operating S.S.T. aircraft has emphasized the present unsatisfactory standard of communication services in the area.

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.

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.

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 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.

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.

This note provides some qualitative impressions of the need for precise navigation in the S.S.T. operation having due regard to performance and noise. It highlights the increased signific ance of the vertical plane, but quantitative conclusions as to horizontal ability cannot be made in the absence of knowledge of traffic amounts. It suggests that any tactical ‘chasing’ of noise reduction through performance variations not planned before flight is impracticable.

In common with other aircraft types, the S.S.T. has three distinct phases of flight apart from take-off and landing: climb to cruise altitude, cruise and descent. The S.S.T. climb is characterized by an acceleration phase dividing the subsonic portion of flight from the supersonic. Similarly, the descent profile includes a deceleration phase which restores flight to the subsonic region. Contained in these three phases of flight unique to the S.S.T.—acceleration, supersonic flight and deceleration—are some of the special factors affecting aircraft navigation.

Present criteria for aeronautical charts need further investigation in preparation for S.S.T. operations in respect to the facilities to be charted, the format for supplemental information, symbols and scale. For projection displays the negative presentation has decided advantages, while the use of colour has both advantages and disadvantages. Pre-loaded film cassettes for quick insertion into the dynamic display system can be maintained in libraries at S.S.T. terminals, which will also facilitate the frequent updating of the material.

In recent years the interest in dynamic map display systems has increased with the advent of S.S.T. planning and higher speed tactical aircraft. There are several approaches including a static chart with a mechanically driven ‘bug’, a moving paper chart with a static ‘bug’ in the form of a stylus, and several projected displays utilizing 35 mm. and 70 mm. film. This paper is chiefly concerned with projected displays.

A Joint Navigation Satellite Committee has been formed to determine the potential for a common satellite system to meet the needs of various agencies. As a potential aid to air traffic, satellites would appear to be most effectively used in cooperation with ground stations at which measurement and computation would be made. Possible user benefits include more effective communications, more reliable and possibly less expensive airborne navigation equipment, reduced diversions and delays, obstacle avoidance capability, more effective emergency warnings, and reduction of communication traffic. For the provider States benefits may include more reliable communications, reduction in number of control centres, improved data collection and distribution capability, reduction in number of facilities, and improved search and rescue capability. A systematic approach to long-range goals is indicated.

A paper by Captain J. F. Kemp under this title was published in the April number of this Journal together with some comments on these proposals. Further contributions to the discussion and a reply from Captain Kemp are printed below.

In the April issue of this Journal Captain Kemp has put forward a carefully considered proposal for making the Rule of the Road more effective. His proposal is well considered because he is aware of the audacity which its careful presentation conceals; he is also careful to suggest a change in the Rules only as a basis for discussion. His suggestion is precise, for it is simply to extend Rule 18 to all encounters, or in other words to require both vessels, when crossing or overtaking, to rotate the line of sight in the normal direction as required in Rule 18.