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Glide Ratio: Observed Segments and Polar Points

Calculate an observed descending ground-glide ratio or compare supplied still-air polar points, with explicit speed, sink and measurement bases.

Use this result well

Inputs that matter
Horizontal ground distance (m), Measured altitude loss (m), Segment duration (s), Sources and assumptions, and 1 more
Output to expect
Observed ground glide ratio, Compare supplied still-air polar points
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Observed ground glide ratio

Summarize one measured descending segment using horizontal ground distance, height lost and duration. Wind and vertical air motion are included in the observation, so this is not the wing’s still-air L/D.

Observed ground ratio = horizontal distance / height lost; mean ground speed = distance/time; observed descent = height lost/time.

Compare supplied still-air polar points

Calculate glide ratios at actual supplied speed/sink points and identify the best ratio and minimum sink among those points. No curve, unmeasured speed or optimum outside the table is invented.

Still-air ratio at each point = horizontal airspeed / positive sink rate.

Updated: September 2026

Example Scenarios

Use the example to inspect the method and breakdown, then enter your own documented observations or equipment data.

→ 9:1 observed ground glide

Use the example to inspect the method and breakdown, then enter your own documented observations or equipment data.

→ 10.909091:1 best supplied still-air ratio

FAQ

Summarize one measured descending segment using horizontal ground distance, height lost and duration. Wind and vertical air motion are included in the observation, so this is not the wing’s still-air L/D. Calculate glide ratios at actual supplied speed/sink points and identify the best ratio and minimum sink among those points. No curve, unmeasured speed or optimum outside the table is invented.

Retain the measurement time and location, equipment or source document, units and assumptions. Examples illustrate the calculation and must be replaced with your own actual data before saving a personal case.

Use Save planning case for an explicit local history entry. Copy MD includes inputs and notes; Download CSV exports the result breakdown. Keep portable copies and save a separate case after changing the assumptions.

About Glide Ratio: Observed Segments and Polar Points

Summarize one measured descending segment using horizontal ground distance, height lost and duration. Wind and vertical air motion are included in the observation, so this is not the wing’s still-air L/D. Calculate glide ratios at actual supplied speed/sink points and identify the best ratio and minimum sink among those points. No curve, unmeasured speed or optimum outside the table is invented.