In helicopters, a hazardous flight condition caused by high rate vertical descent with power. Settling with power occurs when a helicopter descends through its own downwash. The natural tendency is to add power by increasing collective. This will only exacerbate the condition and lead to a potentially irrecoverable descent.

For settling with power to ocurr, all of the following conditions must exist:

• A vertical descent of at least 300 feet per minute
• Some available engine power is used, from 20% to 100%
• Horizontal airspeed less than 10 miles per hour

Settling with power only occurs when engine power is in use, it does not occur during autorotation. Settling with power can occur during these flight conditions:

• Hovering out of ground effect above hovering ceiling of the helicopter
• Hovering out of ground effect without good altitude control
• Steep approach at low horizontal airspeed

The initial effect of settling is an uneasy shuddering and poor cyclic control response. Corrective action is to immediately reduce power by lowering collective and increasing airspeed. Under extreme conditions, autorotation can be entered.

In general, the main rotor is most often susceptible to settling, but it is also possible for the tail rotor to settle. This can occur in strong cross winds and high lateral airspeed.

References

Basic Helicopter Handbook, US Department of Transportation, Federal Aviation Administration