Roadster280,
Sorry, just spotted that no one has answered your question. Think about a nav in a rally car and it's a good starting point. The Nav commentates the sequence, calls out check heights and cross checks them. Does timing and confirms alignments with respect to runway, display line, crowd line and other features. basically never stops talking
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Just in case you all think I've gone soft, the Nav then carries the pilot's bag, makes tea, drives him to the hotel and buys him beers and cleans his flying boots.