Settling with power and Vortex Ring State?

RyanB

RyanB

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Can someone help me better understand settling with power? I understand the basics pretty well. But what about some of these helicopters that hover 100ft AGL trying to pick someone up (SAR). I know if you get too slow without being in ground effect VRS can set in. So how do you deal with being in a hover that is above ground effect, and not settle into your wash?
 
Just a wild ass guess from someone who thinks helicopters fly by witchcraft. I'd say you need a vertical descent more so than a hover to get SWP, greater than 500fpm (just a WAG). Seems like a tailwind with slow forward speed would be the danger zone in a descent.
 
Vortex ring state (VRS) occurs when the aircraft descends through the rotor downwash. So if you don't descend vertically you can avoid VRS.

Typically you will start to encounter VRS with a descent rate of approximately 1/2 of the downwash speed. Helicopters can come to an out of ground effect hover without encountering VRS by simply not allowing the helicopter to descend once the aircraft starts losing airspeed. I typically instruct my students to climb into an out of ground-effect-hover to avoid VRS. The usual envelope to avoid for helicopters is partial to full power on, speed below 30kts, with a descent rate greater than 300feet per min.

Slowing aggressively with a tailwind can also put you into VRS, because the downwash will be directed forward of the aircraft.

Settling with power is often used as a synonym for VRS but in foreign countries it is used to refer to not having enough power to maintain altitude.
 
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Pretty much what info said above but to add, SWP is highly dependent on type aircraft.

For instance, you get into it by descending vertically at around 50-60 % of the speed of your down wash. In a Black Hawk you're looking at around 2,500 fpm. That's some serious descent rate. SWP, unless extremely maxed out at high DA (Mt Hood accident) you're generally not going to get into it with a 60. Smaller helicopters that aren't producing as much down wash and don't have as much power in reserve are more susceptible.

In the EMS community it's a flight regime that we're in on a regular basis. Hot, heavy, descending vertically into confined areas. You have to really watch your VSI and not get fixated on the LZ...especially at night with little contrast / ground references. Preflight planning making sure you have hover OGE power for the LZ is also critical in staying out of SWP.

SWP and VRS are used interchangeably in the FAA and Army rotorcraft training books. There are those who vehemently disagree and they are two different things. A topic for diehard helo dudes and not worth discussing here. Simply put, you're descending with power applied and you can't arrest the descent. That definition applies to both terms.
 
Thanks guys, flew a dual ride in a 206 out in NM a few weeks ago. As a fixed wing guy I've been enjoying helicopters lately. Just trying to brush up on some of my knowledge. Hoping to get dual rated soon
 
I like to divide SWP into vortex ring state and overpitching.

VRS is actually more likely to be encountered when the helicopter is light, since the downwash speed to maintain altitude or a certain descent rate is actually less when the aircraft is light. Overpitching occurs when the engine cannot provide enough thrust to keep the helicopter from descending, and is likely to occur when the aircraft is heavy, and during hot and high operations.

I agree with velocity, it's all academic, when you can't arrest a descent with power!
 
High DA, High Gross weight and a descent profile from a profile in-ground effect OGE hover and unless you drop the collective and pitch forward and fly out of it...expect a hard landing...never experienced it with it being light but have issues planting one with the above...
 
One of our competitors lost a tail boom to SWP a couple months ago as well. It happens.
 
Ryan, it is the best flying you can do, hope you get your rating. Glenn
 
Came across this video on Youtube, could this be a possible SWP accident?
 
Most of the helicopter community thinks that that this was a short-shaft failure in the drivetrain, where the engine continued to run and power the tailrotor, but couldn't power the main rotor.

Good luck on getting the rating, it's the most fun you can have flying. If you are in the Seattle area send me a PM and we'll go flying.
 
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