How to use this R66 HOGE and HIGE calculator
- Choose HOGE or HIGE.
- Enter your gross weight. If you have just done your weight and balance on this site, the takeoff weight carries across when you follow the hover ceiling link from the results.
- Enter the outside air temperature at the landing site or pad.
- Tick the chart corrections that apply: engine anti-ice, cabin heat, generator load over 50 amps, or wind up to 17 knots. The chart is then read at the corrected temperature and weight, exactly as the POH notes instruct.
- Read the maximum hover altitude. It is a pressure altitude, so compare it with your altimeter set to 1013 hPa / 29.92 inHg, or with the site elevation corrected for QNH. The chart shows the POH OAT lines, your interpolated OAT line in blue, the dashed density altitude and ISA +35 limits, and the crosshair going up from your weight and across to the answer.
How the R66 hover ceiling chart works
The POH charts plot gross weight against pressure altitude with one line per 5°C of outside air temperature. To read one by hand you go up from your gross weight to your OAT line, then across to the altitude axis and read the maximum pressure altitude. Between two OAT lines you interpolate. This calculator does exactly that: each POH line is stored as a series of points, the two lines either side of your temperature are read at your weight, and the answer is interpolated linearly between them, the same method as in the Tool in the Cockpit app. The crosshair on the chart is the ruler.
Unlike the piston Robinsons, the R66 charts run their OAT lines all the way to the chart edge and grey out everything above 11,000 ft density altitude, and on the OGE chart beyond ISA +35°C. That grey data exists so that you can apply the anti-ice, cabin heat and generator corrections and still find a line. For an uncorrected reading the calculator caps the answer at the density altitude or ISA line, computed from the standard atmosphere, and tells you which one applied. The OAT lines are for the MGT 5 minute limit, anti-ice and cabin heat off, 50 amp generator load and zero wind.
Which R66 hover charts are included
- R66 Turbine: HIGE and HOGE, R66 POH Section 5, FAA approved 17 Mar 2021. OGE lines from -10°C to +45°C, IGE lines from 0°C to +40°C, density altitude limit 11,000 ft, OGE data beyond ISA +35°C only for use with the corrections.
- Not included: the cargo hook supplement OGE chart for 2,700 to 2,900 lb, and the older R66 chart revisions with 10°C lines.
R66 hover ceiling FAQ
What is the difference between HIGE and HOGE?
HIGE is hover in ground effect, measured at a 2 foot skid height in the R66 POH. The ground cushion reduces the power needed, so HIGE ceilings are higher than HOGE. HOGE is hover out of ground effect, which is what you need for a vertical departure or arrival over obstacles, a confined area, a pinnacle or a sling load. If your HOGE ceiling is below the landing site elevation, you can still land and lift off in ground effect, but you have no margin to hover away from the ground.
What is the R66 HOGE ceiling at max gross weight?
The R66 has a lot of power at low density altitude. On a standard day at 2,700 lb the OGE chart runs out at the 11,000 ft density altitude limit before the engine does, so the answer is about 11,000 ft pressure altitude. Heat is what limits it: at ISA +20 the HOGE ceiling at 2,700 lb is about 7,800 ft, and at 35°C it is around 5,000 ft. Use the calculator above for your exact weight and temperature.
What do the R66 chart corrections mean?
The POH charts assume engine anti-ice and cabin heat off and a 50 amp generator load, because bleed air and electrical load both cost turbine power. With anti-ice on you read the chart 10°C hotter, with full cabin heat 20°C hotter, and for generator load over 50 amps add 1°C per 20 amps. For wind up to 17 knots the POH says to subtract 50 lb (OGE) or 100 lb (IGE) from the allowable weight to allow for power transients. Tick what applies in the Chart corrections box and the calculator reads the chart at the corrected temperature and weight.
What do the 11,000 ft density altitude and ISA +35 lines mean?
Robinson only substantiates R66 hover performance up to 11,000 ft density altitude, and on the OGE chart only up to ISA +35°C. The chart still prints lines beyond those limits, greyed out, so that you can apply the anti-ice, cabin heat and generator corrections and still land on a line. For a plain OAT the calculator caps the answer at whichever limit comes first and tells you which one it was. The whole IGE chart sits above 11,000 ft density altitude, so in ground effect the R66 is always limited by that line rather than by power.
The answer is a pressure altitude. How do I compare it with my landing site?
Set 1013.25 hPa (29.92 inHg) on the altimeter subscale and read the altitude, then check it is below the maximum hover altitude. If you only know the site elevation and the QNH, add roughly 27 ft for every hPa the QNH is below 1013 (about 1,000 ft per inch of mercury below 29.92), or subtract if it is above.
Why does the R66 chart use MGT and 5°C steps?
The RR300 is limited by measured gas temperature (the 5 minute takeoff limit) rather than manifold pressure, and a turbine's power falls off steadily with temperature, so Robinson draws the R66 lines every 5°C from -10°C to +45°C on the OGE chart. Each 5°C costs roughly 900 ft of HOGE ceiling at max gross. The calculator interpolates between the lines the same way you would with a ruler.
What about hover performance above 2,700 lb with the cargo hook?
The cargo hook supplement has its own OGE chart for 2,700 to 2,900 lb, only up to 7,000 ft density altitude, achieved at the 100% torque limit. It is not included here; use the supplement chart for external loads above max gross. For weights up to 2,700 lb the supplement says to use the standard chart on page 5-8, which is what this calculator uses.
Is this R66 hover ceiling calculator free?
Yes. It runs entirely in your browser with no account. The chart lines come from the Tool in the Cockpit app and were checked against the R66 POH chart scans to within about 50 ft. If you want the same charts offline on your phone, with HIGE and HOGE updating live from GPS altitude and temperature in flight, download the free Tool in the Cockpit app.
