Helicopter Urban Myths
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Farmer 1
No, no, I didn't assume you were doing anything other than adding to the mix - fair play!! I just remembered I had that piece of information stashed away and thought it opportune to throw it in!!
A bit off-thread but the memory that stands out from the powerline work is my first experience of blade tape coming off a 206 blade after flying in heavy rain. Not having experienced it before, I thought the aircraft was about to come apart and the 50kts at 50ft became a very slick run-on landing and wind-down to idle in what seemed like an instant. This was very much to the amusement of the Electricity Company observer who, after 30 years doing the work, had seen it before, knew what it was and was able to tell me before I shut down to inspect it!!!
I still don't view those days as "nightmares" but I agree they do look rather better when viewed from a distance! :-)
No, no, I didn't assume you were doing anything other than adding to the mix - fair play!! I just remembered I had that piece of information stashed away and thought it opportune to throw it in!!
A bit off-thread but the memory that stands out from the powerline work is my first experience of blade tape coming off a 206 blade after flying in heavy rain. Not having experienced it before, I thought the aircraft was about to come apart and the 50kts at 50ft became a very slick run-on landing and wind-down to idle in what seemed like an instant. This was very much to the amusement of the Electricity Company observer who, after 30 years doing the work, had seen it before, knew what it was and was able to tell me before I shut down to inspect it!!!
I still don't view those days as "nightmares" but I agree they do look rather better when viewed from a distance! :-)
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VRS, longlines and downwind
**disclamer: this relates primarily to longline work and VRS** 
Just to add to the discussion; working seismic and shakeblocks on 150' longlines teaches a lot about VRS. It seemed I'd get into it once a day on some jobs (particularly on the Astar). Because of the nature of the work it was a risk that we were aware of and managed. Here's a link I found that gives you a basic idea - it's a 500D dropping off some bags at staging.
http://youtube.com/watch?v=FDJkllGnN5k
Schools teach students to push forward on the cyclic (as do some books) to recover from VRS (along with lower the collective, etc), however, chances are you got into it because of the conditions already mentioned or a combination of those conditions and being even just slightly downwind (seems to me to be the biggest contributor). To me, pushing forward is the wrong response because you are looking for clean air to get the disc into. If you're getting into VRS then you can be sure that your clean air is not in front of you. When you only have 150' or, in a lot of cases, much much less (150' longline - 80' trees = 70' to recover), lowering collective and pushing forward will not provide recovery before hitting the trees. A little peddle and some lateral cyclic (without touching the collective) has always solved the problem for me. The idea is to get the disc into clean air.
Just to add to the discussion; working seismic and shakeblocks on 150' longlines teaches a lot about VRS. It seemed I'd get into it once a day on some jobs (particularly on the Astar). Because of the nature of the work it was a risk that we were aware of and managed. Here's a link I found that gives you a basic idea - it's a 500D dropping off some bags at staging.
http://youtube.com/watch?v=FDJkllGnN5k
Schools teach students to push forward on the cyclic (as do some books) to recover from VRS (along with lower the collective, etc), however, chances are you got into it because of the conditions already mentioned or a combination of those conditions and being even just slightly downwind (seems to me to be the biggest contributor). To me, pushing forward is the wrong response because you are looking for clean air to get the disc into. If you're getting into VRS then you can be sure that your clean air is not in front of you. When you only have 150' or, in a lot of cases, much much less (150' longline - 80' trees = 70' to recover), lowering collective and pushing forward will not provide recovery before hitting the trees. A little peddle and some lateral cyclic (without touching the collective) has always solved the problem for me. The idea is to get the disc into clean air.
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fly boyz,
You must have all the vrs allocated for the entire industry if you get into it every day.
Must be scary descending at 1500 feet a minute with 150 feeet of long line under you, what rubbish.
Of course you fly into clean air if you are nose into wind, you are probably over pitching, try carrying a lighter load or handle your aircraft better.
I personally have never read so much ill informed crap in my long flying life, I hope no one takes any notice of your ideas or your techniques.
If the video is supposed to demonstrate flying that could induce this fabled problem it does exactly the opposite.
Dont you read Nicks writings, they are correct and I am sorry to inform you that there is absolutely no argument you could put that can change this fact.
Get over this VRS fetish and get on with flying. I would hate to be a young flyer being fed this tripe, i would have to go through the rest of my career living in fear for no good reason. I know a hundred long line pilots who have worked in the most hostile environments and to a man they have never experienced VRS. Try to keep it over your side of the pond, we don't need it here.
Another ill informed pilot was mustering the other day and said "I am getting a bit of LTE over here, are you gettig any over there?"
I am so glad for you that you think the books and years of experience are wrong, write one of your own.
You must have all the vrs allocated for the entire industry if you get into it every day.
Must be scary descending at 1500 feet a minute with 150 feeet of long line under you, what rubbish.
Of course you fly into clean air if you are nose into wind, you are probably over pitching, try carrying a lighter load or handle your aircraft better.
I personally have never read so much ill informed crap in my long flying life, I hope no one takes any notice of your ideas or your techniques.
If the video is supposed to demonstrate flying that could induce this fabled problem it does exactly the opposite.
Dont you read Nicks writings, they are correct and I am sorry to inform you that there is absolutely no argument you could put that can change this fact.
Get over this VRS fetish and get on with flying. I would hate to be a young flyer being fed this tripe, i would have to go through the rest of my career living in fear for no good reason. I know a hundred long line pilots who have worked in the most hostile environments and to a man they have never experienced VRS. Try to keep it over your side of the pond, we don't need it here.
Another ill informed pilot was mustering the other day and said "I am getting a bit of LTE over here, are you gettig any over there?"
I am so glad for you that you think the books and years of experience are wrong, write one of your own.
Last edited by deeper; 22nd Nov 2007 at 01:46.
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fly_boyz
I share the same feeling fly_boyz.
On high hovers with some amount of wind, I am almost sure to get one when making a 360 (as I stated before on a R44-II, did not experience that on the R44-I). So I tend to agree with some kind of TR/MR or other interference (slow translation unawareness) that catalyses VRS.
I cannot comment on your recovery, because I always had hight and got out of it according to the books (using more than 150 ft...).
My statistics are so bad that I would not do a high 360 without a positive vario of at least 200 ft/min
d3
On high hovers with some amount of wind, I am almost sure to get one when making a 360 (as I stated before on a R44-II, did not experience that on the R44-I). So I tend to agree with some kind of TR/MR or other interference (slow translation unawareness) that catalyses VRS.
I cannot comment on your recovery, because I always had hight and got out of it according to the books (using more than 150 ft...).
My statistics are so bad that I would not do a high 360 without a positive vario of at least 200 ft/min
d3
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I have to call BS on this one:
5) Winds affect the power we require when we are in forward flight.
A helicopter does not know which way the wind is coming from. You would not either if you could not see the ground nor had any instruments to reference position over the ground.
5) Winds affect the power we require when we are in forward flight.
A helicopter does not know which way the wind is coming from. You would not either if you could not see the ground nor had any instruments to reference position over the ground.
Last edited by before landing check list; 15th Mar 2012 at 12:03.
Crazy Scandihooligan
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No. 7 - Only applies if you are one of those pilots that uses the kebab house / Curry house more than you should...hang on... oooppps... Sorry guys 
No. 16 has to be a Coriolis thing.... shouldnt it?.... dunno much about this spraying about a circle thing.... thought it was a part of training...ooops
MD
No. 16 has to be a Coriolis thing.... shouldnt it?.... dunno much about this spraying about a circle thing.... thought it was a part of training...ooops
MD
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5) Winds affect the power we require when we are in forward flight.
Of course this is correct. The only thing that affects the power required in forward flight is Gross Weight and Density Altitude.
However, Hovering IGE is a different matter
Of course this is correct. The only thing that affects the power required in forward flight is Gross Weight and Density Altitude.
However, Hovering IGE is a different matter
Ladies/Gents* (*delete where applicable),
Just to remind you what the opening post actually says:
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When you are flying (Not at a stationary hover ref the ground) there is no relative wind. The helicopter is moving through a moving airmass. Imagine a free balloon in a 100 kt wind. If you could see the ground you would know you were moving however you could strike a match since there is no wind relative to the balloon.
If you took away all ground referencing devices and you could not see the ground and did circles all day long the helicopter would not care however if you were able to draw your ground track afterworlds you would see connected elongated circles over the ground if you had a wind. If at the same time you could have your track drawn in the air you would see one circle. (Assuming you kept a constant speed, rate, bank turn)
Jerry
If you took away all ground referencing devices and you could not see the ground and did circles all day long the helicopter would not care however if you were able to draw your ground track afterworlds you would see connected elongated circles over the ground if you had a wind. If at the same time you could have your track drawn in the air you would see one circle. (Assuming you kept a constant speed, rate, bank turn)
Jerry
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BLCL, I disagree. There is always relative wind. In your balloon example above the RW value is zero.
In flight, you create a RW result by combining the aircraft flight vector and the wind vector. The the resultant relative wind is the airflow observed relative to the observer or object (aircraft, airfoil or arm out the car window).
Or I could be wrong. Happy Thanksgiving to all. Fly safe.
In flight, you create a RW result by combining the aircraft flight vector and the wind vector. The the resultant relative wind is the airflow observed relative to the observer or object (aircraft, airfoil or arm out the car window).
Or I could be wrong. Happy Thanksgiving to all. Fly safe.
Does not "relative" connote a comparison to some reference....thus would not there be an infinite range of values possible?
The key would be to identify the reference being used to form the comparison.
The key would be to identify the reference being used to form the comparison.
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I would like to add one thing to the discussion about VRS.
There is the chance of getting into VRS whenever the downwash velocity is equal to the rate of descent.
Don't forget that in a descent at less than hover power, the downwash velocity will likewise be less, so that there are a large number of ways to get into VRS.
There is the chance of getting into VRS whenever the downwash velocity is equal to the rate of descent.
Don't forget that in a descent at less than hover power, the downwash velocity will likewise be less, so that there are a large number of ways to get into VRS.
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Marc, you are correct and I was not clear with my explanation. Yes there is relative wind, that is relative to the helicopter or the car etc. However the wind that is relative to the ground given the circumstances that I mentioned earlier is not a factor because it does not exist to the helicopter.
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"11) The helicopter is perched on a ball of high pressure air when close to the ground, and "falls off" this ground cushion when it moves forward."
If it walks like a duck and talks like a duck, call it a duck.
I would like to see hard evidence whether there is or is not high pressure air beneath, but whether there is or not, this is how it feels to hover, especially for a new pilot.
I'm happy keeping it an urban legend, but how about one with some value?
If it walks like a duck and talks like a duck, call it a duck.
I would like to see hard evidence whether there is or is not high pressure air beneath, but whether there is or not, this is how it feels to hover, especially for a new pilot.
I'm happy keeping it an urban legend, but how about one with some value?
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Shawn Large number of ways, indeed
Add for instance to this helicopter loading. A very lightly loaded heli will also produce a smaller induced velocity, its almost as simple as that : at 750 kg you have approx 16% less induction than at 1100 kg (R44), the weight difference being 30%. Induction goes approx with the square root of weight: at hover this is 6.3 m/s resp 7.5 m/s which is a difference of 16% .
SAS, of course. My question is how do you determine you have near zero speed, based on what ? IAS doesn't help, because near zero, GPS doesn't help because of wind, no visual clues, unless there is hot air balloon in the vicinity...
d3
SAS, of course. My question is how do you determine you have near zero speed, based on what ? IAS doesn't help, because near zero, GPS doesn't help because of wind, no visual clues, unless there is hot air balloon in the vicinity...
d3
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The pressure ball
Matthew
The power curve works positive in all directions, so in that sense the top of the curve can indeed be visualised as a half spere.
But fysically there is no pressure ball...
I would at least call it a good analogy. And as said many times before these simplifications have pros and cons...
d3
The power curve works positive in all directions, so in that sense the top of the curve can indeed be visualised as a half spere.
But fysically there is no pressure ball...
I would at least call it a good analogy. And as said many times before these simplifications have pros and cons...
d3
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Matthew is right, if it works for your basic understanding, then the myth has uses. Just don't let someone sell you a "pressure enhancer" for your Robbie to increase payload.
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delta3,
I'm not totally convinced. The rotor downwash is blown downwards, and then deflects horizontally. Something has to act on the air to change its velocity. The ground doesn't do it...that would lead to upwards air. In the end, you need air pushing air away from center. I'd say a pressure gradient would be the culprit.
Just because I think there is a gradient, I'm not saying there is a 'ball of air' as discussed above. Hard numbers would be required to determine the magnitude and extent of this gradient.
Matthew.
I'm not totally convinced. The rotor downwash is blown downwards, and then deflects horizontally. Something has to act on the air to change its velocity. The ground doesn't do it...that would lead to upwards air. In the end, you need air pushing air away from center. I'd say a pressure gradient would be the culprit.
Just because I think there is a gradient, I'm not saying there is a 'ball of air' as discussed above. Hard numbers would be required to determine the magnitude and extent of this gradient.
Matthew.
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"Pressure Enhancer"
Careful, Nick. DaveJ will consider that idea as public domain and you won't be able to patent it.
Maybe if we hovered an R22 over an empty hot tub we'd get more pressure....
Careful, Nick. DaveJ will consider that idea as public domain and you won't be able to patent it.
Maybe if we hovered an R22 over an empty hot tub we'd get more pressure....