In considering reliability, it is logical to look at sources of uncertainty, variability and inaccuracy. British Civil Airworthiness Requirements - Section D defines the factor of safety in terms of several sources of unreliability, as follows:

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.

This paper is concerned especially with the reliability of inspection in the nondestructive testing of military aircraft structures. The first part considers design philosophies, examines how the requirements for inspection arise and highlights the difference between the approaches being adopted in the USA and in the UK.

The second part examines what data are already available on the reliability of inspection and discusses the UK programmes that are aimed at gathering more data.

Uncertainties exist at practically all stages of the design and construction process because of incomplete knowledge. Extreme environmental forces on offshore structures are uncertain because of the stochastic nature of the underlying physical phenomena. The actual strength and fatigue characteristics of structures can be predicted only approximately at the design stage and these predictions can be refined only partially by compliance tests during and after fabrication, and then only at high cost.

This paper presents a review of the current status and potential future use of reliability methods in the design, fabrication and operation of offshore oil production platforms.

An overview of the traditional design process is presented and key areas where reliability methods have contributed to the development of codes of practice are described. Future applications in the design stage include the optimisation of framing configurations and the treatment of uncertainties in basic design parameters.

This paper describes a series of steady and time-dependent pressure measurements on a half-model of a rectangular wing of aspect ratio 4. The wing was mounted on a half-body attached to a sidewall of the RAE 8 x 8 ft wind tunnel and the tests were made at Mach numbers of 0·20, 0·42, 0·70, 0·80 and 0·85 with fixed transition and a Reynolds number of about 2·5 x 106 at the highest Mach number. The wing was oscillated about its mid-chord axis at four frequencies giving frequency parameters up to 1·15 at M = 0·20 and 0·25 at M = 0·85. The static angle of incidence was varied from –10° to + 10°.

Selected mean and oscillatory measurements are offered as a challenge to computational fluid dynamicists for this simple three-dimensional configuration. Comparisons are made with calculations by means of subsonic linearised theory and recent transonic small perturbation methods. The measurements are of particular interest at transonic speeds, where both attached and incipient separated flows are considered.

An analysis is presented of the output of a pressure probe, comprised essentially of four yawmeters, which was designed to yield vorticity information.

It is shown that if the probe is utilised in flows which have vorticity dominated by variation of either the direction or the magnitude of the velocity then the probe output may be easily related to vorticity. It is argued that such flows should be readily recognised, and they include many situations of interest involving vortex flows, boundary layers and wakes.

Earlier work had already demonstrated that the probe is useful in exploring regions of predominantly streamwise vorticity. The present work shows a result with the probe used in a boundary layer flow where the vorticity is nearly normal to the local flow.

Use of the probe in unsteady flow is briefly examined.

A method is described for calculating wall interference in solid-wall wind tunnels from measurements of static pressures at the walls. Since it does not require a simulation of the model flow, the technique is particularly suited to determining wall interference for complex flows such as those over VSTOL aircraft, helicopters and bluff shapes (e.g. cars and trucks). An experimental evaluation shows that the method gives wall-induced velocities which are in good agreement with those of existing methods in cases where these techniques are valid, and illustrates its effectiveness for inclined jets which are not readily modelled.