Fire Safety Science Digital Archive

Aircraft fires on the ground can be divided into two categories, those associated with crashes and other fires. The aircraft crash fire is usually serious, since there is often a large spillage of fuel and the primary object in fighting the fire is to save life rather than to save the aircraft. In fact, no case could be made for the large expenditure of equipment and manpower needed to fight these large fires on the score of the relatively small saving in property, and it is with these intense fires that there is most need for special clothing. Most other fires associated with aircraft are often comparatively small and can often be dealt with before they have reached serious proportions. It is important to keep this distinction clear as the size of fire and the time-scale of the fire-fighting will have a bearing on the clothing most suitable for fire-fighting duties. It is interesting first to get some idea of the characteristics of aircraft crash fires. This is difficult at present, because crashes are mercifully few, and also because there is no uniform system of reporting such fires. It is hoped to remedy this in the next few years, with the co-operation of both the Services and the Ministry of Transport and Civil Aviation. In the meantime the only evidence available is that which can be obtained by measuring photographs of aircraft crashes in various parts of the world. An analysis of forty aircraft crashes has shown that one-third had a ground plan area of 200 ft or less, two-thirds an area of less than 1,000 ft2 and the largest fire of the sample a ground plan area of 5,000 ft2. The elevation areas of the fires were generally less, one-third having an elevation of less than 180 ft2, two-thirds less than 600 ft2, and the largest fire reported in the sample had an elevation of 1,600 ft2. These figures are probably not very accurate but they give some idea of the orders involved, and it is hoped that as time goes on they will be improved. There is even loss evidence on which to base the time necessary for fighting such fires. This will be governed by the time of human survival, and the only reliable evidence is that from a series of tests carried out for the National Advisory Committee for Aeronautics in the United States and reported by Pesman (1). These results would suggest that for the severe crash fires studied, the maximum time for human survival would be about 5 minutes, and that in some cases it might be as low as 50 seconds. The requirement, therefore, is for clothing that will resist intense heat radiation for a short time, probably of the order of 10 minutes at the outside. Experiments have recently been started at the Joint Fire Research Organization in order to decide which material assemblies show most promise for use in the design of clothing for fire-fighting. It is, of course, not possible to predict the performance of such clothing under field conditions, as in addition to the effect of the design of the clothing, both physiological and psychological factors will have to be taken into account. It is possible however to place the material assemblies in order of effectiveness.