The Convention for the Suppression of Unlawful Seizure of Aircraft—to give the treaty its official title—was drafted by a subcommittee of the Legal Committee of the International Civil Aviation Organisation (ICAO) in September/October 1969, considered by the Legal Committee itself in February/March 1970, signed at a diplomatic conference meeting at The Hague on 16th December 1970, and came into force on 14th October 1971 amongst those States that had ratified it. While the coming into being of the Hague Convention has been fairly expeditious, so far only 15 States (Bulgaria, Costa Rica, Ecuador, Gabon, Hungary, Israel, Japan, Jordan, Mali, Niger, Norway, Sweden, Switzerland, USA, USSR) have accepted it. It is to be hoped that the United Kingdom, which took a leading part in developing this Convention, will do so before long, especially as the necessary legis-lation has already been passed—the Hijacking-Act which received the Royal Assent on 5th August 1971.

The purpose of this paper is to outline the “operational angle” of the hijacking problem and of the measures which might be taken to combat it.

Before considering what can be done on the aircraft itself to prevent or deter the hijacker from achieving his or her objective, I think it important to first review the likely circumstances of a hijack incident. By this I hope to ensure that my conclusions are seen against an essentially practical background.

The object of this paper is to assess the efficacy of various measures, legal and physical, for the prevention of hijacking. I limit myself to examining the inherent limit-ations of different measures; and I propose to elaborate certain proposals, already made, for closing the ring. First, it is desirable to see what conclusions can be drawn from past events.

Reports from the airlines on hijacking incidents, during a period of three years from July 1968 to August 1971, have been recorded by IATA. Summaries of these reports have been made available to us, by courtesy of the Director General, through Sir William Hildred. I base my analysis in Tables A to D (see Appendix) on these records, for they are the only source of information available on the course of events and the consequences of each incident.

In a recent paper (Ref. 1) Dr. Hilton proposed the use of manoeuvres for creating zones of “no boom” which could be employed to protect cities situated along the flight path of a supersonic aircraft. The basic idea was to make use of the fact that curved flight causes a local focus of shock waves and that, in regions closer to the centre of curvature than this focus, shocks do not form.

In investigating this intriguing suggestion, the author found it advantageous to abandon the Huygens-type construction used by Hilton and employ in its place a technique which permits plotting the shock front directly. In applying this approach to manoeuvres of the type proposed for shock avoidance, regions of single, double and even triple shocks were found, but no shockless region. The method used and the results obtained are outlined briefly in the following sections.

It is commonly recognised among operators of modern commercial aircraft that maintenance is a significant and costly part of their operation. In fact, it is estimated that 28% of all aircraft operating costs can be attributed to maintenance-related activities. A major portion of this activity can be classified as unscheduled, that is, maintenance other than regular servicing and periodic overhauls. Much of the cost of unscheduled maintenance derives from the actual man-hours and materials involved in isolating and replacing faulty components. However, additional consideration must be given to the fact that an aircraft which is detained beyond its scheduled departure time is neither producing revenue for the operating airline during that period, nor promoting goodwill among passengers inconvenienced by delays or cancellations.

In my paper “Mediaeval Kites and Windsocks”, I attempted to throw some new light on the curious dragon-shaped objects shown flying on the ends of lines, or fixed to the tops of poles, in a number of mediaeval and Renaissance books of military technology. Until recently these have usually been interpreted as primitive aerostats whose lift is supplemented by wind-forces similar to those which raise a kite.

A further illustration of the flying dragon is reproduced here (Fig 1). As it does not belong to any of the general categories or groups into which the other illustrations fall, it is worth considering in detail. Its three-part tail and general outline indicate that it bears some relationship to the dragons depicted in Figs. 6 and 7 of my paper.

The helicopter rotor probably represents one of the most difficult of all power-transmission problems in the fact that high power is required at relatively low rotational speeds. High power at low speed defines high torque, and high torque in a mechanical transmission requires large, heavy gears. In addition, since every action has an equal and opposite reaction, the shaft torques must be reacted, and this requires a tail rotor system for the shaft helicopter.

A jet-propulsion system offers certain distinct advantages in comparison with a shaft-drive system for powering a helicopter rotor. It delivers a driving torque to the rotor in the form of a tangential force at the tip of the rotor rather than by twisting a shaft at the centre of the rotor.

The prediction of the forced vibration response of rotating cantilever blading is of considerable importance in the design of turbine and compressor blading where the rotational speeds are relatively high. Non-linearities in the blades arise from the effects of Coriolis accelerations due to the rotation of the blades mounted on the periphery of the disc.

Lo and Renbarger derived the differential equations of motion of a cantilever beam mounted on a rotating disc at a given stagger angle and show, for a linear case, that the frequencies of a bar vibrating transversely to a plane inclined at an angle to the plane of rotation can be found by a simple transformation of the frequencies of vibration perpendicular to the plane of rotation. Boyce, Di Prima and Handelman applied the Rayleigh-Ritz and Southwell methods to the case of a turbine blade vibrating perpendicular to the plane of rotation and determined the upper and lower bounds of the natural frequencies.

An investigation of design procedures in high technology engineering organisations is being undertaken by the Divi-sion of Industrial Systems Engineering at University College of Swansea. To ensure comparable levels of en-gineering sophistication the study has been confined mainly to the aircraft component industry.

Initial work in this study has revealed some interesting facts about the prediction of design and development costs. Detailed information about design and development expenditures, estimated and actual, has been collected from one company and less precise data indicating similar trends has been gathered from three other companies.

Nothing in the Concorde could be more conventional in this day and age than its navigational equipment installation. Triple inertial systems, dual VOR/DME, dual ILS and even dual ADF are fitted to the basic aircraft. About the only thing we do not have is a navigator.

This is really where the story starts, about 12 years or more ago, with a three man crew which did not include a navigator. His absence was only loosely related to being supersonic. Admittedly, the flight deck of any faster aircraft is very likely to get cramped, particularly in its width, and space for crew members costs money but it is economic pressures which apply to all aircraft which have gradually displaced the specialist crew member. The skill of the equipment designer has made this possible by providing simple controls capable of being operated by the pilot without distracting him from his main task. The specialist radio operator has gone and we are how entering an era in which the navigator will also disappear.