When British Aerospace, Brough, were first tasked with carrying out a study of mechanical systems and component reliability it was anticipated that the installed environment would be a significant parameter in the investigation. Consequently it was decided to carry out a separate study of the environment of equipment on a number of aircraft to assess how this had influenced the design and subsequent reliability of the components and to see if the initial assumptions had been valid. This study was to make use of measured data from routine development flying as well as tropical and cold weather trials. In addition the reliability of appropriate equipment was reviewed to determine the incidence of problems arising from environmental factors.

The installed environment can be broken down badly into two separate factors. Firstly, those which are external to the components in question, e.g. altitude, ambient temperature, humidity, vibration levels, solar radiation and contaminants such as salt, sand and dust. Secondly, there are those factors which are internal to the component in question or are influenced by the installation of the component in a larger system. These factors include internal pressures, temperatures and contaminants, the effect of the system flows and interaction with other components.