The VLF Omega would drop out in heavy rain. The Department of Changing Names were most concerned and insisted on dual Omega for any Pacific flights. A couple of the aeroplanes were subsequently fitted out with two units. Off we went into the blue and when in heavy rain they both failed.
I was told by a man in a white coat it was something to do with the 'H' type field antenna. All you can do is smile in agreement and pretend you understand.