oge hover

rightstick

scott wolf
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The other day I was thinking if anyone who fly's a helicycle has hovered out of ground effect. Where I fly the R22 they are real particular about not hovering OGE. I was just wondering if done at a safe altitude would the helicycle do well in the midwest where MSL is 1000 ft.
 

StanFoster

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Rightstick- The Helicycle HOGE just fine! I have an indicator that tells me exactly how many degrees of pitch I am pulling. It takes about 1 more degree to HOGE than to HIGE. There is plenty left even at 100 degrees here in Illinois at 750 feet asl. Stan
 

WaspAir

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Where I fly the R22 they are real particular about not hovering OGE.

If you respect the H-V avoid region, there is no problem with HOGE operations in the R-22.
 

Oskar

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I once did a hover at 700ft to see what it would be like.

For the first few seconds everything was fine, but then things turned eerie. At that height with no airspeed there is no feedback telling you in which direction the heli is moving. After about 10 seconds the heli started a slow yaw, which even full rudder would not stop. The yaw got faster and after one revolution I had enough, dropped the collective (which immediately stopped the yaw) and flew away.

It was an unsettling experience which I won't be repeating anytime soon.
 

Oskar

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Yep, was the Mosquito.

And no, it wasn't much fun. When a flying machine doesn't do what you tell it to do it's not much fun.
 
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An OGE (out of ground effect hover) hover takes the most power of any maneuver to maintain altitude. The biggest concern is getting into settling with power. There are three requirements for getting into settling with power- 1. airspeed less than 10 knots 2. 20% power or more going to the rotor. 3. greater than 300 ft per minute descent rate. If any of these are lacking, you won't get into settling with power. So how does settling with power occur, what are the events that lead up to it, well lets talk about that!!
Any wing producing lift has a vortex produced on the tip, usually the vortex is small and has a negligable effect on lift , as the angle of attack on that wing increases the size of the vortex increases. So let's say you are in your helicopter in level flight at 1000 ft. and 35 knots and it takes 20 inches of manifold pressure to maintain level flight. So you decide to slow down to a hover. As you slow down the efficiency of the rotor disc decreases, requiring you to pull more collective to maintain altitude, this increases the angle of attack and the vortices on the end of the blades gets bigger, but as long as a descent is not allowed to develop the vortex still has a relatively small effect on lift production. As long as you have power available to maintain blade rpm as you pull additional collective, AND YOU DON'T GET INTO A DESCENT, then life is good. But let's look at what happens when you allow a descent to develop at the same time.
As the aircraft descends this increases the angle of attack. (Why? Well instead of the airflow coming pretty much straight at the leading edge of the blade because of the rotation of the blade, the descent changes the relative wind as it descends and angle of attack increases, the higher the rate of descent the greater change in relative wind and the greater the increase in angle of attack) As the angle of attack increases the size of the vortex on the tip of the blade increases, the vortex on the tip of the blade gets bigger and decreases the lift. As you are now producing less lift, the descent rate increases, this further increases your angle of attack, the vortex gets bigger further reducing lift. If this is allowed to continue the more the descent increases the greater the increase in the size of the vortex, the less lift produced the greater the descent and so on. This effect becomes critical at a descent rate of 300 ft/min or so, and the sink rate increases exponentially. Descent rates of several thousand feet per minute can develop.
Remember the tip of the rotor blade is exponentially more important than the root of the blade. (as speed doubles lift increases by 4-fold) the roational speed of the blade increases as we move from the root to the tip, so those "lift killing vortices" are decreasing lift on the section that is the most critical, specifically the tips.
So what are some situations leading to the development of settling with power? Commonly, as pilots will slow to an OGE hover if they don't increase collective enough to prevent a descent from developing they can get into it. Just like coming to a hover in ground effect as you slow to below ETL the amount of power increases signigicantly, if you are lazy on getting the collective up, you can inadvertantly get into a descent which leads to settling with power. IF YOU ARE SLOWING TO AN OGE HOVER PAY ATTENTION TO THE VSI, AND DON'T GET INTO A DESCENT, IF ANYTHING YOU WANT TO MAINTAIN A SLIGHT CLIMB, SAY 100FT/MIN. AS YOU SLOW TO A HOVER, DON'T GET LAZY ON THE COLLECTIVE.
Another situation occurs when the winds are relatively light but you get a wind shift from the time you take off to the time you land, and you don't recognize it. This happens most often in light winds of say 5-7 knots. When the winds are blowing 25 knots it's easy to recognize what direction the winds are from!!! So here's the scenario, the winds have swapped 180 degrees and you come in to land and don't realize the swap has occurred. On approach you find that you are tending to overshoot the landing so you lower the collective to increase your descent, but that alone isn't quite enough so you raise the nose to slow down. Your speed across the ground is still about 20 knots, but you haven't been watching the airspeed indicator, so you failed to notice that your airspeed is now about 5 knots (by the way they don't read well below 20 knots) and your lowering the collective earlier has increased your descent rate to 500 ft/min.- CONGRATULATIONS, YOUR GOING TO MAKE THE EVENING NEWS. You just got into settling with power at low altitude, which is nearly unrecoverable. By the time you recognize it you ran out of altitude and luck at the same time.
 

RotorTom

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I once did a hover at 700ft to see what it would be like.

For the first few seconds everything was fine, but then things turned eerie. At that height with no airspeed there is no feedback telling you in which direction the heli is moving. After about 10 seconds the heli started a slow yaw, which even full rudder would not stop. The yaw got faster and after one revolution I had enough, dropped the collective (which immediately stopped the yaw) and flew away.

It was an unsettling experience which I won't be repeating anytime soon.

You're post really puzzles me. There is plenty of feedback to tell which direction the heli is going. For one there are visual clues, also instruments.

And when you describe the yawing, It is pretty clear that your heli required near max power, which took away from your tail rotor, which caused the yaw.
 

bryancobb

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Reason

Reason

If you respect the H-V avoid region, there is no problem with HOGE operations in the R-22.

Wasp,

Flight schools who use the R-22 have almost eliminated OGE Hovering maneuvers because of a few accidents in the 90's.

One in particular, was when a photographer hired a commercial pilot and they rented one of Prestige Helicopter's R-22's and flew to the Atlanta Zoo to do some aerial photography for some literature.

All the flying was OGE hovering and as they were maneuvering around to get the best shot, they hovered into a tailwind condition and lost control.

They crashed right into the zoo while people were there! If I remember right, no one on the ground was hurt. The pilot was killed and the photographer had two broken legs and some spinal injury.
 

trunkmunki

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I once did a hover at 700ft to see what it would be like.

For the first few seconds everything was fine, but then things turned eerie. At that height with no airspeed there is no feedback telling you in which direction the heli is moving. After about 10 seconds the heli started a slow yaw, which even full rudder would not stop. The yaw got faster and after one revolution I had enough, dropped the collective (which immediately stopped the yaw) and flew away.

It was an unsettling experience which I won't be repeating anytime soon.

That sounded more like a LTE (loss of tailrotor effectiveness) situation than "settling with power" or vortex ring state.
 

WaspAir

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Wasp,

Flight schools who use the R-22 have almost eliminated OGE Hovering maneuvers because of a few accidents in the 90's.

One in particular, was when a photographer hired a commercial pilot and they rented one of Prestige Helicopter's R-22's and flew to the Atlanta Zoo to do some aerial photography for some literature.

All the flying was OGE hovering and as they were maneuvering around to get the best shot, they hovered into a tailwind condition and lost control.

They crashed right into the zoo while people were there! If I remember right, no one on the ground was hurt. The pilot was killed and the photographer had two broken legs and some spinal injury.

I hate to sound something like a stab-less RAF enthusiast (never thought I'd be in this position!), but the aircraft is quite capable of safely hovering out of ground effect, and it smacks of a training issue to me. Given that photo flights are a common use for Robbies, a bit of training for that environment might well be called for in anticipation of what former students might end up doing after licensing.

Perhaps insurance companies are determining the curriculum for those schools.

Does the Robinson factory have an official view on the topic?
 

StanFoster

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My instructor had me HOGE several times in the R22....then had me demonstate getting into and out of vortex ring state. I saw no problem HOGE with the R22, of course at an altitude above the HV curve. My fading memory recalls this altitude to be at a minimum of 400 feet agl, when at 0 mph.

Oskar- I dont understand not being able to stop the yaw...with pedals, and not with " rudder" as was mentioned.....
Stan
 

bryancobb

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Perhaps insurance companies are determining the curriculum for those schools.

Does the Robinson factory have an official view on the topic?

Oh I'm quite sure Frank does not object to hovering OGE in his ships. The insurance folks are the controlling entity.
 

Oskar

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Great feedback with lots of good theories. It was definitely LTE, just don’t know what caused it yet.

Here's some more info about the actual event.
The heli was not moving forward, the airspeed indicator said zero.
It could have been moving up, down, left, right or backwards, or a combination of the above.
Don't have a VSI, but am pretty sure that it wasn't moving downwards. I’d guess climbing at maybe 50 to 100ft/min.

The problem is that at 700ft you have completely lost the visual ground reference that is used when hovering low (up to 100ft or so). Plus it only requires a few knots of breeze up there to really complicate the issue. With the ASI at zero and the piece of wool (yaw indicator) of not much use it all of a sudden becomes quite lonely up there.

I suspect that the heli was moving upwards, backwards and sideways fast enough that the tail rotor could no longer keep up. Certainly would like a better explanation than that if anybody has one.

There are some horror stories of gyros with negative airspeed at altitude, might be something similar was happening here.
 

trunkmunki

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If you had a tailwind or backwards movement, you could easily have had a weathercock instability and once it started to swing it would develop into an unrecoverable (by just yaw correction) tail rotor vortex ring state. This would cause the rotation to continue past the "headwind" condition.

But hey, it's all speculation, but isn't that what these forums are about?
 

laflyboy

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I actually climbed up to 6500 ft in my helicycle and had no trouble hovering it at that altitude. I had zero ground speed on the gps and airspeed indicator showed 18 mph and 0 on the vsi.
 
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