The math is very simple. If you divide forward speed (distance/time) by vertical speed (height/time) you end up with Distance per unit height.
Take airspeed in Knots (nm/hr), divide by 60 and you get Nm/min. Divide by the vertical speed (feet of descent/min) and you get Nautical miles of glide / foot of descent.
60 knots/60 = 1 Nm/min.
1.0 Nm/min/1200 feet per minute = .00083 Nm/ft or .83 Nm/1000 ft
Just do this for a spread of speeds, perhaps 4, and you can look for the speed that gives you the most Nm per 1000 feet. Use your flight instruments, they are quite accurate enough. Two auto descents with a clip board and a pencil, and you have the figures for your machine.
Last edited by ramen noodles; 25th May 2009 at 21:18.