Aircraft Glide Ratio, Glide Range & Emergency Descent Calculator
Calculate maximum engine-out gliding distance (NM & km), descent time, and wind corrections.
Last reviewed by the myCalculator Editorial Team
Input Parameters
e.g. 9.0:1 for Cessna 172, 10.0:1 for Piper Cherokee, 17.0:1 for Motorglider, 40:1 for Sailplane
e.g. 68 KIAS for C172, 73 KIAS for PA28
Calculation Results
Visual Growth Breakdown
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Formula & How Aircraft Glide Ratio, Glide Range & Emergency Descent Calculator Works
The glide ratio is the horizontal distance covered for each unit of height lost, so L/D of 9 gives 9 ft forward for each 1 ft of descent. From 5,000 ft AGL with L/D of 9, the still-air glide distance is 5,000 × 9 ÷ 6,076 = about 7.4 nautical miles. At a best glide speed of 68 knots the rate of descent is 68 × 101.27 ÷ 9 = about 765 ft/min, giving about 6.5 minutes of gliding time. A headwind shortens the distance covered over the ground and a tailwind lengthens it. Planning for an engine failure means knowing the glide speed and the distance you could cover. Actual performance varies with weight, flap setting and propeller drag, so use your aircraft's flight manual.
- Enter Height Above Ground Level AGL (feet) (ft AGL): Input your target parameter value.
- Enter Lift-to-Drag Glide Ratio (L/D): Input your target parameter value.
- Enter Best Glide Airspeed Vg (KIAS) (KIAS): Input your target parameter value.
- Enter Headwind (+) or Tailwind (-) Component (knots) (kts): Input your target parameter value.
- Apply Formula: Calculate using
Glide Distance (NM) = (Altitude AGL × L/D) ÷ 6076.12 | Rate of Descent (FPM) = (Vg × 101.27) ÷ L/D | Time = Alt ÷ ROD. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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Frequently Asked Questions (FAQs)
How far can a Cessna 172 glide from 5,000 feet?
With a 9:1 glide ratio at 68 KIAS, a Cessna 172 glides approximately 7.4 Nautical Miles (13.7 km) in zero wind, taking about 6 minutes and 30 seconds to reach ground level at a descent rate of ~760 FPM.
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Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
CASR Part 91 general operating and flight rules, Part 121 fuel reserves, and flight crew licensing standards.
Aviation weather services, standard atmosphere (ISA) profiles, METAR/TAF aerodrome weather reports.
Aeronautical Information Publication (AIP), En Route Supplement Australia (ERSA), and airspace procedures.
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Operational Scenario
Operational Scenario: Rough Running on Descent, +19 °C and Humid
Descending into Wollongong (YWOL) on a humid afternoon at +19 °C with the throttle near idle, the engine runs rough and RPM falls by about 150 with no control input. The conditions sit inside the serious-icing band of the CASA carburettor icing probability chart.
Practical Decisions
- •Apply full carburettor heat early and leave it on. Expect a brief further RPM drop and rougher running as the ice melts, then recovery. Partial heat can make icing worse.
- •Plan for icing before it appears: select carburettor heat before prolonged descents and extended low-power operation, and check it periodically in cruise when conditions are conducive.
- •Brief the engine-failure-after-take-off plan before every departure: lower the nose, hold glide speed, and land broadly ahead — no turn back below your pre-briefed height.
- •For a partial power loss, fly the aircraft first, then run the checks — carburettor heat, fuel selector and quantity, mixture, primer, magnetos, throttle — and commit to a landing area if power does not return.
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