In 1951 the Ministry of Civil Aviation made an investigation into the acoustic screening offered by the use of a running-up pen. Tests at London Airport in which a Viking was run up behind an experimental wall constructed of corrugated cement asbestos sheeting fixed to a scaffolding of steel tubing showed that a reduction of some 25 phons could be obtained throughout most of the geometrical shadow of the wall and over a range of distances probably exceeding one mile. Unexpected acoustic characteristics of the experimental wall precluded the collection of the full design data on running-up pens that were sought, but did not detract from the efficacy that was demonstrated. Auxiliary tests suggested that little noise abatement can be achieved by the use of trees or buildings. A prototype running-up pen is now being built at London Airport to find what operational problems are associated with the use of running-up pens and, if possible, the design data still required.

Exactly what constitutes a design criterion is a matter on which there may well be differences of opinion. For practical purposes design criteria may be taken to be empirical numerical rules to aid the designer in forming his initial conception of a design. The formulation of such rules for aircraft fatigue is still a matter of some difficulty. Not only is the subject of aircraft structural fatigue still in its infancy, but its study has to be linked with systematic experiment in a somewhat unusual way.

In the criteria described in this paper, the structure has first to be subjected to a standardised laboratory test. This test is itself a gross simplification since it has to represent in a rough way a diversity of conditions occurring in flight.

It has been said that a rocket motor is the simplest “ prime mover.” This is correct in theory, since fundamentally a rocket consists of a chamber containing a gas under pressure, having a nozzle at one end through which the gas expands, forming a propulsive jet. Since the pressure ratio of the rocket is always greater than the critical pressure ratio, the nozzle is invariably of the convergent-divergent or de Laval type in which the velocity is subsonic up to the throat, sonic at the throat and supersonic in the divergent portion.

It is a popular fallacy that a rocket or jet engine obtains a forward thrust by allowing the rearward jet of gas to push against the atmosphere in which it is operating. This is not correct and it can be proved that a rocket will operate successfully, and more efficiently, in a vacuum.

This paper describes the construction of a simple electronic simulator for the solution of flutter problems in two degrees of freedom. It was intended as a prototype for a much larger machine to solve problems in six degrees of freedom.

Details of the construction and circuits are given, together with some typical solutions obtained on the machine. As a result of the successful operation of this prototype a larger machine in six degrees of freedom has now been built.

Never before in the history of aviation has the test pilot been so important as he is today. Now that military aircraft are travelling faster than the speed of sound and climbing to over 50,000 ft. in a matter of seconds, with powered controls, pressurised cabins, ejector seats, special oxygen equipment and such like being the order of the day, it is little wonder that the human being whose job it is to fly in these modern high-speed missiles requires more than ordinary Service flying experience if he is to take his place successfully in the team with today's technicians and designers. The day has long since passed when any good pilot could set himself up as a test pilot. The term “test pilot” covers a large field of work, testing aircraft and the complicated equipment fitted in the new revolutionary designs being produced.

Consider a thin-walled tube fixed at one end and subject to torque of known distribution. The problem is to find how the thickness of the wall should vary along the length so that the weight is a minimum for a given angle of twist at the free end.

At distance x from the fixed end, let T be the applied torque, A the enclosed area of the tube, P its perimeter and y the wall thickness.

This note describes brief tests made to check a proposed extension to the Royal Aeronautical Society Stressed Skin Data Sheets on stresses and deflections in flat panels subjected to normal pressure. Simple modifications to the test rig, which greatly improved the edge fixing, are also included.

Increasing interest has been shown recently in the measurement and interpretation of post-yield strains. Early investigators determined the nature and magnitude of such strains by observing the distortion of a grid of fine lines inscribed on the unstrained metal. A development of this method involved the use of a photographically deposited grid.

In the present instance the initial requirement (August 1948) was for the measurement against time of strains of the order of 4 per cent. occurring as “ fast transients.”

As the wire resistance strain gauge element was well established, it was natural to consider its extension to post-yield measurements, and it later became apparent that this had already been done by Swainger.