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Old 13th Aug 2018, 8:40 am   #14
M0FYA Andy
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Join Date: May 2007
Location: Preston, Lancashire, UK.
Posts: 2,510
Default Re: Is this a Rebecca unit ?

Cylindrical casings came into use in aircraft equipment post-war as a result of wartime experience. Equipment returning from a bombing mission at high altitude (for the time) would be soaked through with condensation in the unpressurised fuselage of a Lancaster or Halifax. You can read reports of it all being removed after a flight, dried out, and refitted for the next. Apart from the effort involved, it must have caused major reliability problems with connectors being repeatedly broken and remade.
So casings were introduced where the insides were installed dry and warm, and then the casing pressurised, often with nitrogen rather than air, through a valve akin to that on a bicycle tyre. A desiccator absorbed any residual water.
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