NavList:

John and Frank.  I agree the universal plotting chartlet described by you is not Mercator straight off the pad, but when you divide the nm easting by the cosine of the latitude to get chlong, aren’t you effectively doing something very similar to what Mercator incorporated automatically into his chart.  That’s why it’s stood the test of time.  Not that there’s anything wrong with flat earth flying.  The V Force flew around the World for 30+ years using an analogue navigational computer that added w/v N/S to TAS N/S (obtained from sine cosine resolvers) and w/v E/W to TAS E/W to give GS N/S and EW before compounding them together to give track and groundspeed and passing the eastings though a secant gear prior to winding onto the longitude counters. 

However, despite this, they were able to make the Sun stop still.  If you flew west at around 480 kts at 57N (I’m working from memory; please don’t check my figures too closely) you could make the Sun stop still in the sky apart from the effects of tiny changes in declination. DaveP