Performance, Speed-To-Fly & Instability Calculator

I was reminded recently that I had created a Performance, IAS & Atmospheric Instability calculator to satisfy my own curiosity and it was collecting dust in a long forgotten folder. So here it is, unleashed upon the public in Apple Numbers '09. It calculates:

• True Airspeed at Altitude
• Lapse Rate/Thermal Index
• Polar Curves based on 4 points corrected for weight and Density Altitude
• Altitude lost along course compensated for wind & weight
• Time to goal compensated for wind & weight
• Relative Altitude lost for comparing up to 4 gliders
• Altitude advantages compensated for early arrival time with an X climb rate along course
• Speed-To-Fly based on polar curve, wind, sink along course, and expected climb rate

• Scoring penalty percentage to handicap high performance gliders. Used this at Tater Hill '08 to level the field. DHV 1 gliders were scored evenly with 2-3 ships.
• Speed-To-Fly chart (Hoisington Chart) that can be printed and used in flight.

2/20/09- The Performance Calculator has been in constant development for the last few days and it now calculates Speed-To-Fly automatically! Still Apple Numbers 2.0 only but if someone wants to convert it to Excel, please do and send me the results! Email me if you find any bugs. I'm always curious about who is using it so if you do, send me an email!

2/21/09-Fixed a bug that relates to Speed-To-Fly calculations. New version is 2.5.1.

Flight Calculator 2.5.1

2/23/09-Updated to 2.5.2. Fixed a few bugs, added instructions, and the sinking air along the route is now included in the "altitude lost" along route. No idea why I didn't do that sooner.

Flight Calculator 2.5.2

3/5/09-2.5.4 is out. It fixes a few bugs, and adds a new sheet for generating a Speed-To-Fly chart that can be used in flight. It's an almost exact duplicate of the chart Zach Hoisington used for his Speed-To-Fly lecture at Woodrat a few years ago. This one you can customize to your gliders polar curve, wing loading, etc. Currently you have to enter some values manually, but I'll be working on an automatic solution for 2.5.5.

3/5/09-2.5.5 is out. It fixes a few more bugs, streamlines a few calculations, and makes the Speed-To-Fly values a little more accurate, now to the nearest .25 rather than the nearest .5. An automatic method for generating the Speed-To-Fly chart doesn't seem to be possible at the moment which is why 2.5.5 is so close on the heels of 2.5.4. It just isn't going to happen.

3/7/09-2.6 is done. A bunch of bug fixes to the Hoisington Chart in 2.5.5. Streamlined all the calculations to make future updates easier, and...*drumroll*...The calculations for the Hoisington Chart are now almost completely automatic AND you can choose which glider you want it to chart! The defaults should be fine but if you want to adjust it for slightly more accurate readings you can. The steps for generating the chart are now infinitely simpler. The ONLY known bug left is an artifact of how gliders are tested, and small errors in the Density Altitude calculations. The problem lies in the fact that most gliders are tested at 4,921 ft but are entered into the tables as if they were tested at sea level. So to get real sea level speeds for gliders the altitude has to be adjusted to -4,921 ft. Entering the gliders as if they were tested at sea level (slower speeds) results in an error of ~1.5 km/hr when the altitude is raised to 4921 ft. Treating 4,921 ft as your baseline altitude (entered as 0 in the chart) solves the problem, at least mentally.

For folks who don't have Apple Numbers 2.0 (part of iWork '09) and want to know what all this is all about, I've created a PDF of the default gliders. Calculator.PDF

3/9/09-2.6.1 is done. New life lesson, never declare all your bugs fixed. There's always one lurking in the shadows and this one was so obvious it's embarrassing to admit that I missed it the last 4 versions. So, the Expected Climb rate no longer affects the glide ratio in the Speed-To-Fly table above and beyond what the required speed bar would do to your glide ratio. Previously a 200 fpm expected climb would cut your glide ratio value in half....oopse. I've also cleaned up the layout a bit, removed some redundant stuff, etc. It should now also fit on a 13" widescreen monitor without scrolling.

3/17/09-2.6.2 makes a few big changes. I've added S2F Gain to the arrival altitude chart. It shows how much higher you would arrive if you flew at the proper Speed-To-Fly. The Time chart also shows times for S2F. The Polar curve graph now no longer allows the S2F indicator dot to exceed the 100% speed-bar value. That applies to the S2F table as well. The Polar Curves Table and Input tables have been changed to allow for different weights for each glider. That will allow two pilots to compare two different gliders, rather than one pilot looking at what their performance would be on each of the 4 gliders.