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8.1 Helicopter Limitations


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Altitude Vs Gross Weight Limit Graph

Air density and weight is an important factor for a safe autorotation. If air density is low or you have a high density height (High Elevation) then you could expect poor performance while conducting an autorotation landing and hit the ground hard.

To ensure a safe autorotation landing for a gross weight refer to page 18 of the BELL 206L-1 Long Ranger II Handbook. Use the Altitude Vs Gross Weight Limit for Height-Velocity Diagram graphs to complete the following tables. For unit conversion refer to the ERSA.

To Find Gross Weight

First calculate the density height, then use the graph to find the maximum gross weight.

  • First calculate density height for the elevation to land on using: QNH 993, Elevation 2000ft and OAT +25 degrees. (Refer to the beginning of this work booklet to understand how to calculat density height).
  • Using the graph: Move from the density height line horizontally across to the line of the shaded area and drop vertically down to find the gross weight.
  • "A" = 4400ft DHT
  • 3700lb Gross Weight
To Find Chart Density Height

Use the graph to find the maximum safe autorotation density height for landing with a gross weight of 3600lb.

  • To find Density Height start with gross weight at the bottom of the graph.
  • Move vertically up to the line of the shaded area.
  • From this line move horizontally across to find the density height.
  • 3600lb Gross Weight
  • "B" = 5300ft DHT
To Find Elevation Density Height

To find a safe density height for a HLS elevation, Chart verse Elevation, compare the two of them to determine if an autorotation landing is possible.

  • First calculate the density height for the elevation using: QNH 1035, Elevation 5500ft and OAT +7 degrees.
  • Then calculate the density height off the chart with 3600lb gross weight.
  • If the Chart DHT is higher than the calculated DHT, a safe landing is possible.

Yes it is safe for landing.

  • Chart 5300ft DHT
  • Calculated 5080ft DHT