High authority automatic flight control systems are now in wide use in both transport and combat aircraft. These have required the development of failure survival system architectures, and techniques in safety assessment to ensure that the risk of fatal accidents attributable to the automatic control aspect is acceptably remote.

Most of the current systems are analogue in nature, and employ sufficient redundancy to survive at least one failure during operation. Future systems will employ quadruplex or triplex-monitored architectures, capable of surviving at least two failures, and will be mainly digital in concept. The design and safety assessment techniques developed for analogue systems have been adequate for current systems, but the new digital technology and more extensive use of systems in safety critical applications will demand further development of the various aspects involved.

A major contribution to the design and safety assessment of safety critical systems was made during the past two decades in the programmes for the development of automatic landing for civil aircraft, culminating in the system in the Anglo-French Concorde.

Before beginning the main subject of my lecture, the Society may perhaps wish me to refer to some of the outstanding events of the year.

The honour of the first flight round the world has fallen to the countrymen of Wilbur and Orville Wright, and well have they deserved it. We can realise to the full the courage, endurance and skill that they brought to their task; and we can share to the full the disappointment of those of their own party, and of their friendly French and British competitors, who had the misfortune to fall by the way.

The flights round Australia, though less spectacular, and covering less distance, are perhaps equally worthy of recognition. With practically no organisation, complete reliance had to be placed on the aircraft and engines, as well as on the pilots; there, was no possibility of effecting any but quite minor replacements.

A VTOL aircraft which is in a state of hovering flight possesses no inherent stability of its own, consequently it may be found necessary to introduce some artificial form of control of the aircraft in both rolling and pitching motion. Such a control device may consist of an auto-stabiliser which enables the pilot to maintain the aircraft in a state of stationary hover, or to perform some manoeuvre by rolling or pitching the aircraft. This paper investigates the wing vibration problems associated with the roll attitude control of a transport aircraft in which the jet-lift engines are mounted in pods situated on the wings. Fig. 1 illustrates diagrammatically a typical transport aircraft configuration in which there are sixteen jet-lift engines mounted in two pods, one on either wing, each pod containing eight lift-engines.

The solution of a set of m ordinary linear differential equations of the nth order having variable coefficients can be provided by the use of a set of m2 indicial admittances and the solution is derived from that given by the use of impulsive admittances. The indicial admittances are easily derived from the impulsive admittances and vice versa.

An “indicial admittance” is a function representing the response of a system to an applied “input” in the form of a “unit step function” and the concept is due to Heaviside. When the indicial admittance is known, the response to an input which varies with time in an arbitrary manner can easily be found. Similarly, the response can easily be found when the “impulsive admittance” is known, where this is the response to a unit instantaneous impulsive input.

The inclusion of incidence wires in strength calculations, by the method of strain energy, makes very little difference in normal flight conditions, but shows, large changes in wing loads in nose diving and in centre section loads with a broken flying wire. There is a serious increase of load in the bottom plane in nose diving.

Airworthiness cannot be achieved by regulation. Regulation can establish a framework within which all who are concerned with the design, construction and operation of aircraft can work, and can set boundaries of responsible behaviour. Within that framework airworthiness can only be achieved by the actions of constructors, operators and authorities, and it is the management of those actions which is the subject of today’s discussions.

The safety of civil aircraft is regulated through a process of airworthiness certification and the application of operational regulations. The main elements of airworthiness are:

• (i) certification of the design,

• (ii) compliance with airworthiness requirements,

• (iii) maintenance and reaction to service problems -continued airworthiness.

The airworthiness requirements are developed through a process of discussion and consultation with all interested parties. Whilst the result is largely a consensus view, the ultimate authority rests with the airworthiness authority. In recent years there have been increased efforts to reduce national differences with the aim of producing a single international code. At present there are two, with European and US international pressures tending to work against ‘improving’ requirements unless there is a clearly recognised need.

Before making an appreciation of present knowledge about a single metal, it is not inappropriate to say something of all metals, for the ever-increasing tempo of material civilisation has largely depended on man's increasing knowledge of these constituents of his World. His first discovery in this field was copper. To it and to its alloys he gave an exclusive allegiance for some 100 generations, then about 3,000 years ago iron became, and still continues to be, the predominant metal of his needs.

In the eighteenth century, when alchemy finally gave way to the logic of scientific thought, the metals employed by man for purposes other than currency and decoration were practically confined to iron, copper, tin, zinc, mercury and lead. Today, when over seventy metallic elements are known, only a small number of these are used by the engineer.

Measurements have been made in the exit flows of the fan, diffuser, settling chamber and contraction of a low speed blower windtunnel driven by a centrifugal fan. A velocity deficit and streamwise vortex were observed at the diffuser exit when the fan was operating at less than about 0·9 of maximum efficiency but not when operating above. Unacceptably large unsteadiness (-0·7% rms) occurred at low speeds when the fan speed was increased from rest, but not when the fan speed was decreased from full speed. This unsteadiness was at the rotor frequency, and appears to have been caused by laminar boundary layer separation on one or more adjacent aerofoil blades, coupled with slight asymmetry in the rotor. Unsteadiness at the rotor frequency and of comparable magnitude has also been seen in another, larger fan, but was not eliminated in the same way. Attaining high quality flow is likely to require careful attention to the characteristics of individual fans.

An analytical solution is given for the one-dimensional distribution of temperature in a web of an idealised multi-cell wing structure when the adiabatic wall temperature variation is assumed to be either an instantaneous or a linear function of time. The maximum temperature difference between skin and web centre is computed for a range of structural geometries and thermal parameters. Thermal stresses are calculated assuming a parabolic temperature distribution in the web.

Part II deals with the development, from a simple flight simulator used in tachistoscopic studies of attitude displays, to more advanced equipment used to study an instrument system for high-speed low-level flight. This involved the concept of information flow in parallel and visually-mediated control loops, for visual and instrument flight, requiring developments in the simulation of visual flight, by a tele-visual method, and in the assessment of tracking performance, by a method of mean modulus errors; these developments allowing observation of performance of concurrent visual tasks. Flight trials confirmed simulator studies of learning effects, information capacity and instrument to visual transition. The complete scheme of simulation included ground control and autopilot facilities.

The problem of the helicopter is one which has intrigued inventors for centuries, and which has perhaps attracted more attention and effort than any other phase of design of heavier-than-air craft.

Even as far back as the fifteenth century we find Leonardo da Vinci devoting several years of his life to studying- bird and mechanical flight, and he has left many sketches showing- flying machines. Of particular interest to us is a design showing- an aircraft consisting of a sustaining screw driven about a vertical axis.

The first helicopter actually to fly was a small model, little more than a toy, which was shown before the French Academie des Sciences in 1784 by Launay and Bienvenue, and since that time literally thousands of schemes have been proposed by inventors all over the world. The patent files of all countries are full of helicopter specifications, the greater part of them being based on faulty physical principles, and obviously impracticable.

This paper presents a study of a novel type of magnetic nozzle that allows for three-dimensional (3-D) steering of a plasma plume. Numerical simulations were performed using Tech-X’s USim® software to quantify the nozzle’s capabilities. A 2-D planar magnetic nozzle was applied to plumes of a nominal pulsed inductive plasma (PIP) source with discharge parameters similar to those of Missouri S&T’s Missouri Plasmoid Experiment (MPX). Argon and xenon plumes were considered. Simulations were verified and validated through a mesh convergence study as well as comparison with available experimental data. Periodicity was achieved over the simulation run time and phase angle samples were taken to examine plume evolution over pulse cycles. The resulting pressure, velocity, and density fields were analysed for nozzle angles from 0° to 14°. It was found that actual plume divergence was small compared to the nozzle angle. Even with an offset angle of 14° for the magnetic nozzle, the plume vector angle was only about 2° for argon and less than 1° for xenon. The parameters that had the most effect on the vectoring angle were found to be the coil current and inlet velocity.