Calculator Inputs
Example Data Table
| Scenario | Observed Distance | Altitude Loss | Measured Ratio | Available / Reserve | Wind | Adjusted Reach |
|---|---|---|---|---|---|---|
| Baseline test | 9.00 km | 750 m | 12.00:1 | 1800 m / 300 m | Calm | 17.99 km |
| Headwind planning | 9.00 km | 750 m | 12.00:1 | 1800 m / 300 m | 15 km/h headwind | 15.15 km |
| Tailwind planning | 9.00 km | 750 m | 12.00:1 | 1800 m / 300 m | 15 km/h tailwind | 20.83 km |
Formula Used
1) Measured glide ratio
Glide Ratio = Observed Horizontal Distance ÷ Observed Altitude Loss
2) Glide angle
Glide Angle = arctan(1 ÷ Glide Ratio)
3) Usable altitude
Usable Altitude = Available Altitude − Reserve Altitude
4) Time aloft
Time Aloft = Usable Altitude ÷ Sink Rate
5) Still-air reach
Still-Air Reach = Airspeed × Time Aloft
6) Wind-adjusted ground speed
Ground Speed = Airspeed ± Wind Speed
7) Wind-adjusted reach
Wind-Adjusted Reach = Ground Speed × Time Aloft
8) Altitude needed for a target distance
Altitude Needed = (Target Distance ÷ Measured Glide Ratio) + Reserve Altitude
How to Use This Calculator
- Enter measured horizontal distance from a known glide segment.
- Enter altitude lost during that same segment.
- Provide current available altitude and your chosen reserve altitude.
- Input airspeed and sink rate for the expected glide condition.
- Choose headwind or tailwind and enter wind speed.
- Enter the target distance you want to evaluate.
- Submit the form to view ratios, angle, reach, margins, and chart.
- Use CSV or PDF export to document calculations.
Frequently Asked Questions
1) What does a glide ratio of 12:1 mean?
It means the craft travels twelve units forward for every one unit of altitude lost, assuming similar conditions and stable performance.
2) Why does the calculator use both measured ratio and sink-rate estimates?
Measured ratio reflects observed performance. Airspeed and sink rate estimate planning range over usable altitude. Comparing both helps detect unrealistic assumptions.
3) How does headwind change the result?
Headwind lowers ground speed, so horizontal reach decreases even if sink rate remains unchanged. That reduces wind-adjusted range and effective planning ratio.
4) Why is reserve altitude included?
Reserve altitude protects a safety margin. It ensures the planning range is not based on consuming the entire available height.
5) Can I use feet, miles, knots, and metric units together?
Yes. The calculator converts units internally. Just choose the correct unit beside each input before submitting the form.
6) What is the difference between still-air reach and wind-adjusted reach?
Still-air reach assumes no wind. Wind-adjusted reach includes headwind or tailwind effects, so it better represents real route distance.
7) Should this replace certified performance data?
No. It is best for estimation, engineering checks, and planning studies. Always verify against approved performance documents and operating limitations.
8) Why might measured and computed ratios differ?
Differences can come from trim, turbulence, configuration, weight, pilot technique, instrumentation, or wind conditions during the observed glide segment.