Glide Ratio Testing Procedure
and Data Reduction
have no professional or expert qualifications of any kind.
1. Find an abandoned or very low use airport or suitable emergency field.
2. Load the plane to gross weight with full fuel. (It helps if part of that load is a passenger who can run the stopwatch and record data for you.)
3. Climb to about 4,000' agl near the emergency landing field such that you can make the field in spite of a power loss at any time in the procedures.
4. Slowly, slowly, slowly pull power back to idle to avoid shock cooling. Take several minutes to do this. Maintain altitude as long as you can as you slow to the target glide speed for that run. The first thousand feet of descent is for the shock cooling prevention and to get stabilized on the target glide speed for the run.
Before you get to the test start altitude, you want to have been at idle for a bit and be stable on the target airspeed.
5. When the altimeter hits your start altitude (an even number about 3,000' above the emergency field), start the stopwatch.
6. At 2,000' agl, record the outside air temperature on your data sheet (for density altitude and true airspeed computation).
7. When the altimeter hits your stop altitude (an even number about 1,000' above the emergency field), stop the stopwatch and slowly, slowly apply power to avoid shock heating. There's no rush to get to full power.
Record the number of seconds on your data sheet.
8. Climb back up for the next run, 5 mph faster (or slower according to your chosen method).
9. Repeat steps 3-8 till finished. In a perfect world, you'd repeat the tests two or three times at each 5 mph increment to improve data quality. In practice, you should see a smooth progression after a single set of tests.
Enter the data in the spreadsheet. Download Glide_ratio in Microsoft Excel format. I'd appreciate it if you'd e-mail me a copy of your resulting spreadsheet and I'll collect the data.