Final Glide Calculator

 

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You can use the calculator to determine how high you should climb in last thermal, and how fast to fly to finish depending on wind, climb rate in thermal and distance to finish site under assumption that there is no vertical air mass motion once you leave the thermal.

Calculations take into account drift with wind while thermalling. This results in a counterintuitive result that speed to fly to finish to minimise time is independent of wind (but limited by the fact that you have to be able to reach your goal - that is dependent on wind). 

For a complete solution one should also take into account variation of wind with altitude. This is disregarded in this calculator. Wind direction is also a factor, but here it is approximated by considering only the headwind component.

MacCready settings on the bottom of the results reflect how one would set a speed ring which does not know about wind, as compared to a computer that takes wind into account in order to come up with correct speed to fly.

Average speed is computed from the moment that one passes minimum altitude till one reaches the finish.

 
 1 nautical mile = 1.852 kilometers per hour
 1 knot = 0.5145 meters/second
 1 meter = 3.2808 feet
sink speed [knots] =  a*v*v + b*v + c    v in knots
values below are representative of a 40:1 performance glider

    

Distance [nautical Miles]
Wind [knots] (headwind is positive)  
Climb Rate [knots]
a
b
c

Results:

Minimum altitude [ft] at knots
Optimal altitude [ft] at knots
Average speed  knots
Speed ring setting  kts
Computer setting kts


 

 

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