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Settling with Power
#1
Been practicing hover autos and quick stops and want to make sure I don't get into settling with power. Would someone mind informing me of the specific specs. of the dangers involved in that? I learned it in training but have forgotten it already. Never let 2 of the 3 situations happen at the same time? Rapid vertical decent, low air speed and partial power applied? :o .........Love..Love..Love doin quick stops. Yeah baby! I'm getting to the point where I'm dropping the collective so much that the engine drops to idle. I think that means I'm starting to enter an auto. This is just way too much fun!!!
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#2
The rotorcraft flying handbook, advertized on this site, is the best source I have found.  I read something in that book every day.  
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#3
Gary, you will be hard pressed to get into settling with power (establishing the vortex ring state) while practicing quick stops. The parameters you want to avoid are descents of 300 fpm or greater (some say 200), little or no forward airspeed (and that is relative wind) and 20-100% power applied. As long as you are doing your quick stops into the wind you should have no problem especially if you are getting into autorotation as that is the exact opposite of the airflow that needs to be present to start the vortex ring state. If you do quick stops downwind then you are asking for trouble and should expect to get into the vortex ring state. This is another reason you always want to make all approaches in to the wind as much as possible. High rates of decent on approach should be offset by forward speed above ETL. Keep in mind that a high rate of decent with a 15-20 mph headwind satisfies this requirement. It's all about having some wind going through the disk at a speed that will keep the disk out of the possibility of recirculating it's own downwash or best put keeping it in clean air. It sounds like you are working a little autorotation training in there as well and you are actually getting exposure to the most critical part of the auto (the windmill brake state). This will pay off big when you actually start doing autos with power recovery. Keep practicing, you are doing great and working on good skills. Keep the rotor RPM in the green!!!!!
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#4
Gary, as Mark says, you will not get into trouble doing quick-stops into wind. However, you could be in trouble doing it downwind. That is when recirculation (vortex ring) may occur.

However the answer is simple. As you start to flare, you turn into wind, terminating in a hover. If you are hearing,
(dont go looking into the cockpit now!), the engine dropping to idle, you are already in autorotation.

Just one observation; be aware that if the engine should quit while you are practicing quick stops, you'll be on the ground in the blink of an eye. So just be sure that you can land with zero or forward motion; absolutely NO backward or sideways motion!

Rob1
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#5
Thanks guys. This just keeps gettin better and better. Smile
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#6
Gary, as Mark says...

He is good at regurgitating those phrases from the Programmed Text at Ft. Rucker. Fact is, drilling these phrases in your mind on every occasion is a good way to make sure that one day, when on a steep approach into a LZ, when you pull a little collective and your descent rate INCREASES, you recognize what is happening before it's too late.
(Vertical or Near Vertical Descent Between 200 and 300FPM, Using 20% to 100% of Available Power, With Insufficient Power to Arrest Sink Rate)

In simple terms, Settling with Power is most likely to happen to you when your rotor is blowing a LOT of air straight or almost straight downward, and you are descending down into that rapidly sinking air. On shallower approaches at 30 deg. descent angle and less, SWP is NOT a factor. During portions of autorotations or quick stops where the collective is very low or full down, air is flowing UPWARD through the rotor and entering SWP is impossible. At the termination of an auto or quick stop when you level the ship and pull in collective, you are NOT descending at all so you are nowhere near the 200-300 FPM descent rate required to enter SWP.

Anything that makes the rotor have to blow harder, increases the likelyhood of SWP. (I.E. Heavy Helicopter or Pilot, Steeper Descent Angle)
Anything that make the air less dense, increases the likelyhood of SWP. (I.E. High Altitude, High Density Altitude, High Humidity)
Anything that moves that sinking column of air so it stays below you longer, increases the likelyhood of SWP. (I.E. Tailwind, Other Aircraft, Turbulence)

ALL recovery techniques require altitude. Safest answer is don't ever go there. Always do approaches into the wind and as close to 30 deg as possible. Be aware of where you are blowing. If you are blowing downward and in front of you, be careful!

BC
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#7
All of the main points have been covered. I'd like to add that Quick Stops are a coordination maneuver, not a speed maneuver. So when doing them, do not try to do them too quickly. I have seen many get into trouble trying to do QS's too fast.

As noted, they are usually the last segment of an auto. Do them until they look the same each time and you can do them as second nature. I like to use visualization techniques to get the process in mind before practicing.

You are doing great Gary. Take it slow and you'll get even more enjoyment and confidence from your machine.

Darwin N. Barrie
Chandler, AZ
XET on order
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#8
bryancobb,

"Vertical or Near Vertical Descent Between 200 and 300FPM, Using 20% to 100% of Available Power, With Insufficient Power to Arrest Sink Rate"

Where does insufficient power to arrest sink rate come from? Once in SWP or VRS the more power you apply the worse the situation becomes. Saying "insufficient power to arrest sink rate" seems to imply that if you had some more horse power you could get out of it by pulling more collective. I agree that early recognition is key but the proper response is to reduce collective if altitude permits and use cyclic to get out of the disturbed air before the disk looses aerodynamic effciency for directional control. I had a friend who was the co-pilot in a Blackhawk that crashed because of SWP. The Blackhawk has the best power to weight ratio of any helicopter I know of and in this case they were empty and light and even then he said that as the pilot on the controls pulled more collective the faster the helicopter seemed to sink. He also gave full forward cyclic and the disk didn't respond at all and they ended up making a crash landing.
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#9
UH-60Pilot - 9/16/2010 10:19 AM

bryancobb,

"Vertical or Near Vertical Descent Between 200 and 300FPM, Using 20% to 100% of Available Power, With Insufficient Power to Arrest Sink Rate"

Where does insufficient power to arrest sink rate come from? Once in SWP or VRS the more power you apply the worse the situation becomes. Saying "insufficient power to arrest sink rate" seems to imply that if you had some more horse power you could get out of it by pulling more collective. I agree that early recognition is key but the proper response is to reduce collective if altitude permits and use cyclic to get out of the disturbed air before the disk looses aerodynamic effciency for directional control. I had a friend who was the co-pilot in a Blackhawk that crashed because of SWP. The Blackhawk has the best power to weight ratio of any helicopter I know of and in this case they were empty and light and even then he said that as the pilot on the controls pulled more collective the faster the helicopter seemed to sink. He also gave full forward cyclic and the disk didn't respond at all and they ended up making a crash landing.

You're right! I guess I just pulled that out of my arse! I know I remember it though, from some CFI lesson plans or FAA Rotorcraft Handbook or somewhere?????
I guess wherever I got it from, they felt if an 85 degree descent using 25% power is ""conducive"" to SWP, then when you notice the onset of symptoms, the other 75% can be used to "muscle out" of the situation?????
You make a very important point that after you are in VRS, the way the air is moving about the blades can very likely make the cyclic less effective or non-effective...to the point that nosing forward to fly out of it may be impossible.
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#10
I have about 900 hours in a 300C and most of it has been gathering spanish goats out of rim rock country. It gets pretty western at tree top level [trees in West Texas don"t get over 20 ft]. As bad I as I hate to admit it I have made this mistake numerous times and luckly been able to recover. Where I get into a jam is running down wind and make a tight turn and quick stop into the wind. It seems that turbulance left behind in the tail wind gets blown right back into the rotor system when I make that quick 180. Regardless of how much power I have or how lite I am I can't pull out of the sink without doing a cyclic push over. I better have left myself at the very least 3or4ft. Not confortable situation.
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