Settling with Power (vortex ring state) Front Range Helicopters

Definition of Settling with Power or Vortex Ring State FAA Definition: A transient condition of downward flight (descending through air that just previously was accelerated downward through the rotor) during which the main rotor is being forced to operate at angles of attack above maximum. Blade stall begins near the hub and progresses outward as the rate of descent increases.

Definition of Settling with Power or Vortex Ring State Ok…….lets try again….something easier to understand…… Settling with power is descending in a near vertical attitude where the descent rate causes an upward flow through the rotor system that begins to exceed the induced flow coming down through the rotor system. If continued, a stalled condition will result that begins at the rotor head and works it way outward along the blade as more collective is added in an attempt to arrest the descent. The addition of collective pitch and power only increases the decent rate and stall.

Definition of Settling with Power or Vortex Ring State In very simple terms the helicopter is descending near vertically at a rate that overpowers the rotor systems ability to generate lift regardless of the amount of collective and power applied. In short we are settling into our own down wash……. Now lets look at how that happens……

The Aerodynamics of Settling with power (Vortex Ring State) As the helicopter descends the rate of descent up flow begins to interfere with the rotors ability to produce sufficient induced flow to maintain altitude. Pilot tries to compensate by increasing collective pitch and power.

The Aerodynamics of Settling with power (Vortex Ring State) As rate of descent increases the up flow begins to over ride the induced flow and as our pilot continues to increase collective pitch blade tip vortices enlarge and a set of vortices become established along the length of the blade.

The Aerodynamics of Settling with power (Vortex Ring State) At this point the helicopter is settling into it’s own down wash. Pitch angle is very high and the blades are entering a stalled condition, starting at the rotor mast. Allowed to continue the stall will develop over the length of the entire blade, cyclic control will be lost and without corrective action on the pilots part the helicopter will impact the ground.

The Aerodynamics of Settling with Power (Vortex Ring State) Another diagram of the airflow transition during settling with power Vertical descent begins to impede induced flow from the main rotor Descent rate increases and some reversal of flow begins. This is the beginning of vortex ring state Fully developed vortex ring state (settling with power)

Conditions Leading to Settling with Power A powered descent at low or approaching “0” airspeed (out of ETL)* Steep Approach (greater than 35 degrees)* Descent Rate exceeding 300 FPM* Downwind Approach* High Density Altitude conditions* Hard Flair at the Bottom of the Approach with an abrupt addition of collective. Any out of ground effect hover operations. Particularly when the aircraft is heavy and high DA conditions exist. Low rotor rpm in combination with any of the above.

Symptoms of Settling with Power Aircraft vibration, usually associated with main rotor resulting in cyclic stick shake Random yawing, rolling or pitching moments. Excessive left pedal application to correct yaw rate. Increasing descent rate and altitude lose with application of power. Reduction of cyclic effectiveness (aircraft feels sloppy)

How to Avoid Settling with Power The Best way for a pilot to avoid getting into settling with power is early recognition of the conditions that lead to settling with power… BASICALLY…..AVOID FLIGHT OPERATIONS AND CONFIGURATIONS ASSOCIATED WITH ITEMS ON THE LIST!!!!! This is particularly important when you combine items from the list and you are flying a heavy helicopter in high DA conditions.

Make Your Own List What Flight Maneuvers and Configurations can you think of that may get you into the potential for settling with power? ________________________________________

Recovery from Settling with Power Let’s go back to the basic concepts of settling with power: The helicopter is descending near vertically with near “0” air speed There is a large pitch angle on the blades (high power/a lot of collective) Additional collective and slower forward airspeed makes the problem worse.

Recovery from Settling with Power To recover we have to get the rotor system flying again. Pilot should increase forward airspeed with the cyclic (get above ETL). Reduce collective pitch slightly to decrease the angle of attack on the blades, eliminate the stalled condition.

Recovery from Settling with Power During the recovery : Expect a loss in altitude, potentially 300 to 500 ft and more if vortex ring state is fully developed…… This is why getting into settling with power on an approach or low level maneuvering is dangerous! If you are close to the ground and reduction of collective is not practical apply forward cyclic and be prepared to complete a run on landing. Maintain your RPM and cushion the touch down with the collective

Question: Where else could the Helicopter experience Vortex Ring State? __________________________ What conditions would cause this situation? _________________________