R44 down in colorado

RotorTom

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Some friends of mine at Colorado Heli-Ops did an emergency auto into the side of a hill today! According to reports ... they were filming a downhill skateboard race, hovering with three people OGE ... and lost power.

Thank goodness they all walked away without a scratch.

Let the speculation begin.

Here's mine ... it was 80 degrees, they were hovering above Lookout Mountain (which is around 8000 ft.) and had three adults aboard. Mmmmm, wonder why they didn't have enough power?

It is very fortunate that the Pilot's skills were sharp enough to put it down in a very difficult area with no injuries.
 

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Resasi

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Never like to hear of a machine going down, but great to hear it all went well.
 

hillberg

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Not an auto, turned down wind at low speed-HOGE- limit exceded needed more power than he could get and down it goes. simple as that.
 

Vance

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NTSB preliminary report

NTSB preliminary report

The NTSB preliminary report says the tail rotor struck a tree.

It doesn’t look that way to me.

That was a very tricky situation with all the people.

I feel they were very fortunate that no one was injured.

Because you asked Tom, my observation is the helicopter appears to me to be in the shaded area of the height velocity diagram.

The way I read my Robinson 44 POH book it says if they were near gross weight that they were well above the stated out of ground effect hover ceiling.

It appears to me that they may have achieved a vortex ring state as they began to descend. The Helicopter appears to accelerate downward once the descent has started.

It appears to me that the pilot did not have an escape plan if things didn’t go well.

I would not want to second guess a professional helicopter pilot as to poor aviation decisions.

Thank you, Vance
 

RotorTom

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Bingo vance!

Bingo vance!

Vance ...

BINGO! RIGHT ON THE MONEY (IMHO).

Tom

The NTSB preliminary report says the tail rotor struck a tree.

It doesn’t look that way to me.

That was a very tricky situation with all the people.

I feel they were very fortunate that no one was injured.

Because you asked Tom, my observation is the helicopter appears to me to be in the shaded area of the height velocity diagram.

The way I read my Robinson 44 POH book it says if they were near gross weight that they were well above the stated out of ground effect hover ceiling.

It appears to me that they may have achieved a vortex ring state as they began to descend. The Helicopter appears to accelerate downward once the descent has started.

It appears to me that the pilot did not have an escape plan if things didn’t go well.

I would not want to second guess a professional helicopter pilot as to poor aviation decisions.

Thank you, Vance
 

JAL

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The first video shows the tail rotor impacting the branch of the tree then is rapidly decending. The second video looks like the descent commences before the tail rotor strike. If we had the 30 seconds of video before the crash on the first video you could then have the whole accident from both angles.

The second video looks like the accident sequence commenced before the tail strike but then I guess the NTSB is going on what the pilot and witnesses reported initially, with some video evidence to back up the findings. I think as far as preliminary conclusions goes I would guess the NTSB would feel comfortable that it is pilot error regardless of it is tail strike or settling under power and that can be determined later but more importantly there doesn't appear to be mechanical reason.
 

Resasi

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Some of the peanut gallery seemed to find that amusing.:mad:

Aircraft can be very unforgiving when taken out of limits and with no margin ie no altitude to recover. Guess that is why they call it dead mans curve.
 

StanFoster

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Its a shame this happened but thankfully no one was hurt. With these videos, we all can learn from these mishaps. In my opinion, it was settling with power and not a vortex ring state. There are differing views in books on the definitions of these two conditions, some books say they are the same, but in reality there is a difference according to some more in depth studies on these two conditions. I was trained to learn Vortex ring state developes when there is at least 300 fpm descent, but a heavily loaded chopper like this one and high density altitude, the descent rate necessary to enter a true vortex ring state would be higher because of higher inflow velocity through the rotor. A lightly loaded helicopter at low altitude actually can eenter vortex ring state with a lower vertical descent rate simply because it doesn't have near the pitch in the blades and a much less induced flow rate coming through the rotor.The rotor has to be descending at a higher rate to start eating its own downwash. I see the R44 descending very slow at first with a low rate of descent, and turning to the left. It looks like a classsic settling with power to me, with not enough descent rate to be in a vortex ring state, with at the end just starting to have enough descent rate to start entering a vortex ring state. Its possible the left yaw was his power was pulling down, less torque, and the left yaw would have happened. We should know more when the final report comes out.

Note- I just edited this as I found one explanation of settling with power versus vortex ring state.

http://blog.aopa.org/helicopter/?p=84


You can read here and see some are trained they are the same...but if you read some of the intense posts, you can see there definitely is a difference between vortex ring state and settling with power.

http://helicopterforum.verticalreference.com/topic/10982-vortex-ring-state-vs-settling-with-power/


You can also Google vortex ring state/ settling with power and find many places that say they are the same....while the experts like Ray Prouty and others clearly explain there is a difference.



In my simple understanding....settling with power can be hovering at near max weight with just enough airspeed to hold a hover...then the airspeed reduces a little and now you have a less efficient rotor that demands more power than is available. You start to settle and there isnt much of a way out of it if you are near the ground. This can also occur if you are hovering at gross into a slight wind and turn downwind....now you start to settle with power because you dont have as much clean air coming into the rotor. Another situation for settling with power is say I am flying on a high density altit ude day with high gross weight....and just barely able to hold a hover. Lets say now I am descending to land into a confined area like my hole next to my stairshop. I am coming in at a steep descent although maintaing just a 200 foot per minute descent rate. That rate of descent will not get me into a vortex ring state....but....it most definitely could be the straw that breaks my hovering camels back as before entering that descent rate....I could barely hover....now I have to arrest that descent rate while coming down into my confined area. I may very well find myself with ZERO options as I could now not have enough power to stop the descent, I will crash because of settling with power, and not entering a vortex ring state. Definitely a difference here.

There are always vortex ring circulation going on in a hover at the tips, but they are small. When you start descending at greater than 300 feet per minute...then those vortices start increasing as you are descending into your own downwash more. The downwash velocity is much more than 300 feet per minute and the heavier the helicopter is...and the higher the density altitude, the higher the rate of this downwash. It takes a higher vertical descent rate to enter a vortex ring state at gross weight/ high density altitude than does a lightly loaded helicopter at low density altitude. This case was a high density altitude and heavily loaded.......and it just had a slow rate of descent that did get higher at the time of impact.


Stan
 
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bryancobb

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Mr. Stan,

By the way... your Helicycle is beautiful.

According to the FAA Rotorcraft Flying Handbook, The FAA Written Exam Questions, and what I was taught in Army Flight School...

The Vortex Ring State, BY DEFINITION, is the same thing as Settling With Power.

Not trying to dispute, Just trying to avoid getting early helicopter students confused.

This R-44 was not experiencing Settling With Power which REQUIRES a DESCENT RATE OF AT LEAST 300 FPM. It simply exceeded OGE power requirements for some unknown reason.


 

StanFoster

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Bryan- Likewise I am not trying to debate here. I mentioned that you can indeed find sources that say that settling with power and vortex ring state are the same...and yes..it says that in the FAA book.


But...all the places I have read say that vortex ring state requires at least 300 fpm descent....this is an aerodynamic condition.

Settling with power most definitely can occur at much less than 300 feet per minute descent rate...and by definition can occur and not be a vortex ring state which must have at least a 300 fpm descent rate.

This vortex ring state/ settling with power as being the same is not correct. Though very similar....there are distinct differences as I have mentioned and provided links to.


Again, I am not trying to drag this out into an long debate. The answer is there if one digs deep enough. I wont say anymore because I cant.


Stan
 

JAL

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I just assumed that settling with power was the helicopter equavalent of being behind the power curve. Cant all aircraft can get behind the power curve, where essentially the drag from lift exceeds the maximum available engine thrust and the aircraft cant accelerate (or in the helicopter limits rotor speed and the therefore the amount lift available), to recover you need use utulise gravity and trade height for airspeed.
 

RotorTom

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As one settles with power, they quickly enter a vortex ring state -- as the rate of descent increases. The very beginning of the "settling" is technically not yet a vortex ring state but quickly develops into one.

You can not have settling without a vortex ring state unless you are so close to the ground that the descent never reaches 300-fmp.
 

brett s

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Here in the US the terms used are a bit different than what most of the world teaches.

In the FAA world the terms "VRS" & "settling with power" are used pretty much interchangeably, elsewhere they are distinctly different things as Stan said.

Just one of things things...
 

choppergabor

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Well I don't know anything about helicopters so bear that in mind please. He was doing his left pedal power turn and you can clearly see as he parallels the mountain side his tail gets a healthy gust (almost like fighting an airpocket he goes back and forth with the tail) that required him quite a bit of correction and he dropped a bit of rpm right there so to top it he makes another power turn and loses lift. Just listen to the blades barking very very loudly during the turn. So obviously the air was separating from the blades by than! He probably tried to drop a bit of collective to regain rpm but too close to the ground he made the best out of the situation. Hats off to the guy to pull it off though......he really made the best of it.
 
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