Late 70's / early 80's ... I was on a 6A call out taking the water based hooligans and one of their ribs across the pond, doppler was being a pig and the LORAN then failed, just as we hit some crap weather so preventing astro ... Nav soon stated he was "unsure of his position" and suggested a diversion as things would only get worse .. not an unreasonable suggestion ... ALM relayed this to the passengers, and just as we started to negotiate with Gander ATC a piece of paper with a very accurate position and time was handed to the Nav.... hooligans had fired up some equipment which included GPS ... this continued every 10 minutes for the next few hours as we headed West !! On chatting to their leader he simply said he only had clothes for hot places and he was buggered if he was going to Kevlavik in the winter !! It was some years later that we got anything like decent Nav kit !!
I also vaguely recall ( and I think it was Dougie) doing a "Bulls Eye" competition with the nav using a GPS cobbled together from external bits that involved the aerial sticking out of the very pistol hole !!... at one stage the on board judge gave the instruction to switch off the doppler to simulate failure ... which was followed by a comment along the lines of ... "switch it off ?? ******* thing has not worked since start up!!"
