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The purpose of the present study was the development of a methodology for translating predicted rates of decompression sickness (DCS), following tower escape from a sunken submarine, into predicted probability of survival, a more useful statistic for making operational decisions.

Predictions were made, using existing models, for the probabilities of a range of DCS symptoms following submarine tower escape. Subject matter expert estimates of the effect of these symptoms on a submariner’s ability to survive in benign weather conditions on the sea surface until rescued were combined with the likelihoods of the different symptoms occurring using standard probability theory. Plots were generated showing the dependence of predicted probability of survival following escape on the escape depth and the pressure within the stricken submarine.

Current advice on whether to attempt tower escape is based on avoiding rates of DCS above approximately 5%–10%. Consideration of predicted survival rates, based on subject matter expert opinion, suggests that the current advice might be considered as conservative in the distressed submarine scenario, as DCS rates of 10% are not anticipated to markedly affect survival rates.

According to the authors’ knowledge, this study represents the first attempt to quantify the effect of different DCS symptoms on the probability of survival in submarine tower escape.

This paper addresses special reliability-centered maintenance (RCM) strategies for one-shot devices by providing fuzzy inferences system with the assumption that, to data, there is no data available on their maintenance. As far as one-shot devices are concerned, the relevant data is inadequate.

In this paper, a fuzzy expert system is proposed to effectively select RCM strategies for one-shot devices. In this research: (1) a human expert team is provided, (2) spatial RCM strategies for one-shot devices and parameters bearing upon those strategies are determined, (3) the verbal variables of the expert team are transformed into fuzzy sets, (4) the relationship between parameters and strategies are designed whereupon a model is developed by MATLAB software, (5) Finally, the model is applied to a real-life one-shot system.

The finding of this study indicates that the proposed fuzzy expert system can determine the parameters affecting the choice of the appropriate one-shot RCM strategies, and a fuzzy inference system can help for effective decision making.

The developed model can be used as a fast and reliable method for determining an appropriate one-shot RCM strategy, whose results can be relied upon with a suitable approximation in respect of the behavior test. To the best authors’ knowledge, this problem is not addressed yet.

UNDER the stimulus of military interest helicopter development went ahead (notably in America and Germany) during the war years and helicopter production resulted which, while very modest, was on a scale never previously approached.

The gas tungsten arc welding (GTAW) process is a widely used process that produces quality weldments. But the high heat generation from the GTAW arc can cause extreme temperatures as high as 20,000°C. The residual stresses and deformations are high accordingly. One of the methods for decreasing residual stresses and deformations is to change the welding pattern. In the literature, there are not so many examples of modeling dealing with welding patterns. This paper aims to investigate the influence of welding patterns on the deformations.

In this work, back-stepping patterns and partitioning of the weld line were investigated and the distortions and residual stresses were calculated. By doing this, temperature-dependent thermophysical and thermo-mechanical material properties were used. The temperature distribution and deformation from experiments with the same welding conditions were used for validation purposes.

Seven different welding patterns were analyzed. There is only one pattern with a single partition. There are three patterns investigated for both two and three partitioned weldings. The minimum deformation and the optimum residual stress combination is obtained for the last pattern, which is a three partitioned and diverging pattern.

The most important aspect of this paper is that it deals with welding patterns, which is not much studied beforehand. The other important thing is that the structural part and the thermal part of the simulation were coupled mutually and validated according to experiments.

THIS year's Paris Salon was conspicuously successful, and notably justified the adherence to the international biennial show formula. The permanent building was extended with two large wings of match‐boarding, and there were nearly 200 stands, many representing groups. An increased British participation reflected the opinion that this show is becoming the most important of its kind anywhere.

IN the September, 1956, issue of AIRCRAFT ENGINEERING, Mr McClements and Sq./Ldr. Armitagc surveyed ‘Helicopter Developments during the Post‐War Years’. The purpose of the present article is to discuss the subsequent developments which have taken place during the last six years. This period has been one of continued expansion in helicopter development and of much more widespread utilization of helicopters in both military and commercial operation. Since their initial development, over 150 different types of helicopter have been successfully flown. This figure includes many experimental machines or prototypes built by small groups. The major helicopter constructors have put about 40 types into quantity production and over 10,000 helicopters have been built in the Western countries. These have been predominantly for the military services, the large majority being built in U.S.A., but something approaching 2,000 have been used in commercial operations.

This article outlines the procedures being used at Westland Helicopters Limited to establish the fatigue lives of the dynamic and structural components of the Lynx and to demonstrate how an adequate safety level is achieved under the loading sustained by the aircraft. For the newcomer to the fatigue problem a brief introduction to the phenomenon of fatigue will be provided and it will be shown how it is applicable to a helicopter. A philosophical outline of the fatigue procedures in current use at Westlands follows and then a description of the Lynx is given. The article will then describe the fatigue testing, flight testing and substantiation procedures used with the Lynx and it will be shown how the eventual fatigue lives are estimated. Finally some thoughts are put forward about the future of fatigue substantiation.

EVER since the inception of the hcavier‐than‐air flying machine, the need to refuel in flight has been apparent. The cartoon reproduced in fig. 1 was first published in Punch in 1909, at a time when the payload of the aeroplane was very small, due to the large tare weight of the airframe and engine. Present day aircraft have a much higher payload capability, in relation to tare weight, but it is still necessary to carry the energy for propulsion within the aircraft, with the result that long range can only be achieved at the expense of payload. The propulsion energy in orthodox aircraft has always been carried in the form of hydrocarbon fucls,bccause of their ready availability, high calorific value per pound weight and high calorific value per cubic foot. Work has been in progress for some years to develop solid fuel conversion, in the interests of saving weight and space, but such fuels are likely to be extremely expensive and potentially dangerous to handle. However, the problem remains that a consumable fuel source must be carried in the aircraft, with consequent reduction of payload or range. The use of nuclear engines for aircraft has been contemplated, but it seems probable that the weight of shielding and coolant, associated with this type of engine, will limit its use to very large aircraft.