All the formulae you ever wanted ( & lots you never even knew existed ) can be found at:. .. . <a href="http://www.best.com/~williams/avform.htm" target="_blank">http://www.best.com/~williams/avform.htm</a> . .. .This is mainly for serious nav around the world.. .. .For local flights it's a bit different. I have some formulae that I use to calculate deviation, headings, GS & time that I could forward if you want.. .. .I havn't thought about any landing calcs etc though. .. .BtB. . . . <small>[ 06 March 2002, 14:47: Message edited by: Bertie the Badger ]</small>