Glide Ratio Extractor (From POH Chart or Flight Test)
Derive your real glide ratio from the POH chart's numbers — or from your own timed descent — and see how it degrades with speed-discipline errors.
Flight-test version: trim hands-off at best glide, idle (or practice safe simulated), time 1,000–2,000 ft of descent in smooth air. TAS×101.3/sink is the ratio your airplane — with its antennas, rigging and age — actually owns.
Formula
⚠️ For flight planning and education only — verify with your POH/AFM and official sources. Not for primary navigation or in-flight emergency decision-making without POH data.
Derive your real glide ratio from the POH chart's numbers — or from your own timed descent — and see how it degrades with speed-discipline errors.
About Glide Ratio Extractor (From POH Chart or Flight Test)
Your POH's glide chart was flown by a new airframe decades ago; your airplane has since grown antennas, gap seals (or their absence), and rigging history. This tool extracts the glide ratio two ways — from any point on the POH chart, or from your own ten-minute flight test (TAS held over sink rate timed) — and shows the degradation that ±10 knots of speed slop inflicts, which is the practical answer to why instructors obsess over best-glide discipline.
How to use Glide Ratio Extractor (From POH Chart or Flight Test)
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula chart: ratio = dist×6076/alt; flight test: ratio = TAS(ft/min)/sink = kt×101.3/sink substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Glide Ratio Extractor (From POH Chart or Flight Test)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula chart: ratio = dist×6076/alt; flight test: ratio = TAS(ft/min)/sink = kt×101.3/sink with sources cited on the page
- ✓Flight-test version: trim hands-off at best glide, idle (or practice safe simulated), time 1,000–2,000 ft of descent in smooth air. TAS×101.3/sink is the ratio your airplane — with its antennas, rigging and age — actually owns.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
How do I run the flight test safely and well?+
Smooth morning air, altitude to spare: trim precisely to best glide, power idle (carb heat as your engine requires), let it stabilize 500 ft, then time a 1,000–2,000 ft block with a stopwatch while holding speed within 2 knots. Average two runs in opposite headings to cancel wind's vertical component bias. TAS × 101.3 ÷ measured fpm is your number — typically half a point to a point below book.
Where does the 101.3 factor come from?+
Unit conversion: one knot is 101.269 feet per minute of horizontal travel, so TAS in knots times 101.3 gives horizontal ft/min, and dividing by sink (vertical ft/min) yields the dimensionless ratio. The same arithmetic inverted gives expected sink at best glide — a 9:1 ship at 68 kt should sink about 765 fpm, a useful in-flight cross-check.
How sharply does the ratio fall off-speed?+
The L/D curve is a rounded peak: ±5 knots costs a few percent, ±10 costs ~7% (the tool's estimate), ±15–20 — common under stress — can cost 15–20%. Too slow is worse than too fast (the back side steepens toward stall, and stall margin in turns matters more). The discipline 'pitch for the number, trim, confirm' exists because the penalty curve is real.
Does my derived ratio change the other glide tools' inputs?+
It IS their input: feed your measured ratio into our glide distance, wind-glide and range-ring calculators rather than the book value, and the entire engine-out planning chain inherits the honesty. Re-test after avionics/antenna changes or rigging work; gliders re-polar after every modification for the same reason.
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