Autorotation Glide Distance Calculator
Estimate how far you can glide in a forced-landing autorotation from a given altitude. The calculator uses the published glide ratio and descent rate for common helicopter types and adjusts for wind component. Output is still-air glide distance and a wind-corrected reachable-circle radius. Useful for pre-flight forced-landing area selection.
Calculator inputs and results
Aircraft profile
Flight condition
Wind component: negative = headwind (reduces distance over ground), positive = tailwind.
Source: FAA-H-8083-21B Helicopter Flying Handbook Ch 11 + manufacturer POH autorotation performance. Glide ratio is at the published best-autorotation airspeed with rotor RPM in the green arc. Reduce expected radius by 10-30% for wind shear, terrain, and the time required to recognize engine failure, enter autorotation, and identify a forced-landing area. Practice autorotations regularly with a CFI-H per 14 CFR 61.109(c)(3).
How this calculator works
Glide ratio is the horizontal distance traveled per unit altitude lost during stabilized autorotation at the recommended airspeed and rotor RPM (green arc). For most common helicopters this is between 4.0:1 and 5.0:1.
Still-air glide distance (ft) = altitude AGL (ft) x glide ratio. Convert to nautical miles by dividing by 6,076. This gives the theoretical maximum reach in zero wind from the current altitude at the published best-autorotation airspeed.
Wind adjustment: descent time = altitude / descent rate. Ground speed = autorotation TAS + wind component (positive = tailwind, negative = headwind). Wind-corrected distance = descent time x ground speed. Headwind shrinks the reachable circle, tailwind extends it.
Pilot reaction time and energy-trade altitude (typically 50-150 ft) are NOT modeled - subtract that from the published glide distance for a realistic operational planning number.
Default assumptions & sources
Every default value the calculator starts with, the realistic range you'd see in the field, and the source we used to set it.
| Input | Default | Typical range | Source |
|---|---|---|---|
| R22 glide ratio | 4.0:1 @ 65 KIAS | POH | Robinson R22 POH Section 3 |
| R44 glide ratio | 4.7:1 @ 70 KIAS | POH | Robinson R44 POH Section 3 |
| Bell 206 glide ratio | 4.5:1 @ 69 KIAS | POH | Bell 206 POH Performance Section |
| AS350 glide ratio | 4.2:1 @ 65 KIAS | POH | Airbus AS350 Flight Manual |
| Descent rate range | 1450-1700 fpm | POH | POH autorotation performance |
What's not modeled
The calculator covers the major cost and time line items. These additional factors apply in some cases but aren't included in the estimate:
- Pilot reaction time - approximately 1.5-3 seconds before initiating autorotation entry, costs 35-75 ft of altitude
- Energy trade altitude - the altitude expended to accelerate to autorotation airspeed if you were below it at engine failure
- Rotor RPM management during entry - failing to maintain rotor in green arc reduces glide ratio significantly
- Terrain elevation - the calculator assumes flat ground; mountainous terrain reduces effective glide
- Gross weight and density altitude - both affect actual descent rate and glide ratio
Frequently asked questions
What is the glide ratio of a Robinson R44?
Approximately 4.7:1 at the published best-autorotation airspeed of 70 KIAS, per the Robinson R44 POH Section 3. This means from 1,000 ft AGL the R44 can glide approximately 4,700 ft (0.77 nm) in still air. Wind adjusts this significantly - a 10 kt headwind shortens it; a 10 kt tailwind extends it.
#How accurate is the calculator output?
It is a planning estimate, not an operational guarantee. The output assumes a perfect autorotation entry at the published airspeed with rotor RPM in the green arc and ignores pilot reaction time, energy trade for airspeed acquisition, and terrain. Reduce the calculated distance by 15-30% for realistic operational planning.
#What is the best autorotation airspeed?
It is published in each helicopter POH (often called 'best glide' or 'minimum rate of descent' speed). Common values: R22 65 KIAS, R44 70 KIAS, Bell 206 69 KIAS, AS350 65 KIAS. Best glide and minimum rate of descent are not always the same airspeed - check your POH for which one is published as the recommended autorotation entry.
#How does training requirement 14 CFR 61.109(c)(3) relate to this?
14 CFR 61.109(c)(3) requires a minimum of 3 hours of dual instruction in autorotation procedures for the Private Pilot Certificate (rotorcraft-helicopter). This calculator's output is only useful if you are proficient at executing the autorotation - practice with a CFI-H regularly is the actual safety enhancer, not pre-flight glide-distance math.
#What about turbine vs piston for glide performance?
Pure aerodynamic glide ratio is set by rotor system design, not engine type. However, turbine helicopters typically have higher disk loading and slightly worse autorotation performance than light piston trainers. Bell 206 (turbine) and R44 (piston) have similar published glide ratios despite different powerplants.
#Related guides & tools
This calculator provides estimates only. Actual aircraft performance and regulatory compliance vary by specific aircraft serial number, density altitude, gross weight, equipment installations, and operator's FAA-approved General Operations Manual / OpSpec. Always verify with primary sources: the FAA (faa.gov), 14 CFR (eCFR at ecfr.gov), your aircraft Rotorcraft Flight Manual (RFM) or Pilot Operating Handbook (POH), the relevant FAA Advisory Circular, and NTSB safety studies for the operational profile.