Following the destruction of a Royal Australian Air Force (RAAF) Orion Aircraft due to a fire which initiated in an aluminum component of the aircraft oxygen system , the authors have been requested to investigate a range of incidents in, and problems associated with, oxygen systems, of which several are described and discussed here.
While many of the incidents can be attributed to high levels of contamination or physical deficiencies or both. within the equipment, attention is given to the contribution made by the oxygen component designer, in mechanical design and materials selection.
Many of the tests for oxygen compatibility are carried out on single components. In practice, however, real oxygen systems become contaminated with frequent use or abuse or both. Therefore it is important for the designer to have information not only on material performance in oxygen, but also on the oxygen compatibility of the spectrum of potential contaminants and combinations of contaminants that come in contact with these construction materials.
Comments are made on valve designs which are considered particularly sensitive to system contaminants. It is suggested that design philosophy should address sensitivity to contamination and design codes should identify and if necessary bar “poor practice”, since the oxygen system user will not usually have ready access to the technical expertise needed to evaluate designs in the time frame required for critical decisions.
The severity of gaseous oxygen fires is intimately related to the period of oxygen flow. There is a need for an automatic shut-off device that would operate when abnormal flow conditions occur. One such device is described and its limitations discussed. It is concluded that a successful design would possibly be based on a mass flow characteristic.