Turns, with and without the wind

[bones]

Ok guys here we go again, this time i pinched a couple of posts off Dave's thread about engine out, and want to ask Ron to explain this situation at the end..

Posted by Chopper Ried;
Theory is great stuff and most of the time it works very well, most of the time, when you fly low and I mean low as in zero feet agl to 100 AGL you are operating in an area that is subject to the turbulence caused by the wind blowing over terrain, trees hills etc then you throw in the effects of whirly wirly or dust devils, heat thermals and or hot weather, you bring in a lot of variable's that DO NOT conform to the theory we have learnt.

I do understand that a lot of you guys here might have trouble getting your heads around the fact that I have spent a lot of time in a gyro and a thousand hours or so in a FW, mustering and so have been subject to a few things that changed my mind on flying to the laws of theory, particularly when flying close to the ground.

I use the term 'downwind turns' cause thats what they are but to be technically correct, they should be termed "low level downwind turns and the effects that diferent conditions can have".

I'm going to get howled down for saying this but I have expereinced conditions [again, at low level] where it has been impossible to do a 'downwind turn', in fact I have on a couple of occassions, had to skim along at 10 to 20 feet AGL, not at full throttle but at a a power setting that should have had the gyro climbing at 300 ft per minute but the gyro would not climb and most certainly, had a turn been tried, would have seen me with a wrecked gyro. You dont find these conditions every day but they are there and if you are not vigilant, you will get caught, hopefully, you will hit better air and be your gyro suddenly starts to fly like it should.

Even FW get into trouble [down low] once in a while, its officially called 'pilot error' but when you read the pilots story, it generally says the aircraft did not seem to be operating at full power.

Anyway, I'm taking the heat off everybody else at the moment and I still have plenty of stuff to keep you shaking your heads for a while longer so stay tuned to reality gyro flying down low working stock.


Then posted by Gyron
Brian, flying that low to the ground, you are most certainly letting ground reference influence the way you fly. Again, if airspeed is kept constant, turning downwind or flying downwind is the same as flying in NO wind.

Maybe low to the ground with trees and buildings, all the wake turbulence may make it more dangerous to do some manuvering. But I still stand by my statement that if airspeed is kept in check you can fly as normal in any direction no matter how strong the wind is.

GUSTY WIND is a whole other animal though..... The wind is not a problem, but the gusts can be, but thats not the point.



Now make sure everyone understands that we(Brian and I ) are talking about low level stuff here, as he said real low....
Now this just happened to me yesterday, its blowing about 30kts fairly constant, ok now im just flying around doin my thing,now because the wind is so strong im being abit cheeky and pull it it into a hover just above the trees to start of cattle no problems, as the wind drops off abit im slowly moving to far forward, so and THIS IS THE IMPORTANT BIT, ok im hovering at about 30kts ASI, so i open the tap increase it to 40kt ASI before i start to turn, by the time im in the turn it is 50 kts ASI, now normally full tap and 50 kts this thing climbs like a rocket, but all day yesterday, with the motor screamin and between 45-50 kts ASI turning down wind it would drop like a rock, and i made sure a few times that the ASI was up to make sure of this so i could come back and ask, and low and behold the subject was already on.
So can any one please explain to me why this is happening, and if you think im full of it, get on a plane and come over here and i'll prove it to you..
I'm not picking anyone here its just that Ron has said that it dont matter up wind or down wind if you keep a constant ASI, and i'm saying it does matter, and like Brian said we do it often enough to know when the machine is just not performing like it should....

Also the flying down wind thing needing more throttle is back on again to, dont know why but it does, about 300 rpm more :confused:

I'll be in and out for a few days so i might not get back to answering for awhile,, but i will be back

[scott heger]

Gee Ron and Chuck, maybe I am not as full of s**t as you think I am. I found another believer here. Mark has experienced the same problems in low level downwind turning conditions as Tim Mc and I have. Airspeed/ASI 's don't tell the whole story here, if thats all you think it takes to fly low level, you are headed for trouble one day when you least expect it. Going to be hard to chock this up to a bunch of low time inexperienced and unknowlegable pilots not knowing anything. Thats kind of what you doubters have been inferring. You have to realize more is to this. I know I am baiting you guys, but only in the interest of keeping everyone safe and flying a little higher as the winds get stronger to leave a larger margain of safety. Ron, after reading these accounts, you still think it is a good idea to try to go flying around in circles at 5 feet off the ground in 20MPG winds like you said you were going to do? You might be missing a couple of details, I really don't want to see you get hurt.

I am also interested in reading your answers to my last thread in Dave's engine out post regarding the gyroglider.

Scott Heger,Laguna Niguel, Ca N86SH

[GyroRon]

I am telling you guys that you are not maintaining airspeed. You can glance down at the indicator from time to time and see what you want, but somewhere in your turn your loosing airspeed and hence the need for more power.

Want to prove it right or wrong... mount a cheap video camera on the gyro that points at the airspeed indicator and go flying in the wind and when your done go review the video tape and watch and see if your not loosing speed in the turns.

You do need to make sure your airspeed indicator is working properly and is calibrated for this experiment to work properly. Ultracruiser 41 on the forum here, his old Gyrobee's airspeed indicator pretty much read 60 mph no matter how fast or slow you went, so if would be useless in this experiment....

[scottessex]

OH NO! NOT THE DOWNWIND TURN DISCUSSION AGAIN!!!

[GyroRon]

:rapture:

I know Scott, and I got baited into it by being called out in the first post! Someone get me outta here!

[Heron]

If you guys could focus on specifics and understand what one is saying we can all profit from reviewing the topic.
My guess is that we may have some new guys here . . .
There are different kinds of citrus fruit and no one is bringing apples in to the debate.
thanks
Heron

[Ralph]

The problem is, the subject is treated like a debate where we can all hold a vote at the end to see what is "right". Unfortunately, reality is not subject to our whims. Turns flown at a constant bank and airspeed are the same, no matter what the relationship to the wind. Wind does impact the ground track and pilots, ground-referencing turns, have created a whole mythology on the subject. When you have debates contrasting reality with mythology, no one wins and no one is converted.

Ralph

[Aussie_Paul]

The problem is, the subject is treated like a debate where we can all hold a vote at the end to see what is "right". Unfortunately, reality is not subject to our whims. Turns flown at a constant bank and airspeed are the same, no matter what the relationship to the wind. Wind does impact the ground track and pilots, ground-referencing turns, have created a whole mythology on the subject. When you have debates contrasting reality with mythology, no one wins and no one is converted.

Ralph

Guys and gals, the problem with this debate is that the mustering guys do not operate like the sedentry flying majority, at a constant angle of bank or constant airspeed.:help:

Aussie Paul. :)

[Al_Hammer]

I see a problem in looking at the climb performance of the gyro at at, say, 45 mph, and trying to relate that to the downwind turn performance.

In a steady rate climb, lift does NOT need to increase above 1G, except initially, to get the climb started. The work of lifting the gyro against gravity is done by the prop in the form of increased thrust, which ovecomes the increased drag of the rotor at a higher angle of attack.

By contrast, in a quick turn to downwind , in a mustering situation, the bank angle may approach 60 degrees, I'm guessing. The lift would be now exactly 1/2 of normal. The gyro will sink like a stone unless the stick is held way back, requiring much additional power to hold airspeed.
It may be that sufficient extra power is not applied and the airspeed is maintained only by virtue of a descent.
Then the pilot wonders why a downwind turn results in a sink even though the airspeed is constant.

[scott heger]

Al, for reason of keeping this simple, the sink is occuring at a point after returning to level flight from the turn. It could be 10 seconds later, not just exiting the turn. I know this is easy to say that the pilot is not maintaining airspeeed, but I have watched the ASI, and it is not bouncing around lower as should be the case in a gust or other distubrance. Just 40-45 MPh indicated, and falling like a rock at WOT. I fully understand it does not follow what should be happening and is easy to disbelieve, but it does happen every now and then.

I am just warning those that have not experienced this that this can occur, and to fly at a higher altitutde that would give you enough time to take some action, like turning back into the wind .

Scott Heger, Laguna Niguel, Ca N86SH

[Al_Hammer]

Ok, Scott, I didn't fully understand the scenario.

[C. Beaty]

By contrast, in a quick turn to downwind , in a mustering situation, the bank angle may approach 60 degrees, I'm guessing. The lift would be now exactly 1/2 of normal. The gyro will sink like a stone unless the stick is held way back, requiring much additional power to hold airspeed.
It may be that sufficient extra power is not applied and the airspeed is maintained only by virtue of a descent.
Then the pilot wonders why a downwind turn results in a sink even though the airspeed is constant.
You’re right, Al, but that’s just another way of saying the people falling out of the sky are flying by ground reference.

I thought of you this morning when I tried to run a floppy that contained Marie Brock’s letter about Martin Hollmann. The floppy wouldn’t run on a computer that had either W2K or WXP operating systems.

I had to sort through my trash heap to find a motherboard that would run W95 and for which I still had drivers. What a miserable OS!

I imagine in your case, a P133 and W95 is just a prop like Jack Benny’s 1926 Maxwell.

[Al_Hammer]

What a miserable OS!
yes, Chuck, its miserable, but familiar, like an old shoe.
I'd love to tell you that it's a prop, like Jack Benny's fiddle, but, I'm not that talented a comedian.

[Udi]

There are so many things I don’t completely understand in life (still trying to figure out my wife…) and at work. It is true that reality, or the laws of physics, don't care about our opinions, but it would be pretty arrogant of us to claim that we have a complete understanding of the aerodynamic problem presented above. "The gyro doesn't care about upwind or downwind because it is moving inside a moving mass of air - bla bla bla" -- is the simplified version of this problem. The real problem is much more complex, and I don't think anyone here has an answer for it. Does anyone here have special glasses that allow him to SEE the true air flow close to the surface? For example, are the trees generating rotors? What is the size of the rotors? What is the vertical component of the rotors? How would these rotors interact with the rotor blades, as they hit them from the front, from the back, and from the side?

I don't know whether wind rotors have anything to do with the problem Mark has posted above, but I wouldn't be so cocky as to suggest that Mark had one too many pints before he went flying. Mark has described the problem very carefully and he made sure his airspeed was in check all the time. Do you have a reason to doubt Mark’s observations? If we don't have an explanation to the problem as presented maybe we should just say, we don't know...

Mark – I have some questions. When you made your downwind turn – in addition to maintaining airspeed, did you maintain altitude? What was your bank angle? Would a shallow bank be as bad as a steep bank?

Udi

[brett s]

It's pretty easy to figure out to me, there are really only two reasonable explanations:

1. Flying by using ground reference & not maintaining airspeed.
2. The air mass you're flying through is moving vertically as well as horizontally.

Or a combination of both of course - as Udi pointed out, we can't see air currents. But you can sure figure out after a while where you're likely to see issues from anything disrupting the wind (or there's be a very short life expectancy for mustering or ag pilots). That includes buildings, trees, or even terrain features...

[C. Beaty]

Brett, the wind is always tilted near the ground due to surface drag. That’s why Dutch millwrights always tilted their windmill axes ~10 degrees nose up. A balanced horizontal axis weathercock will show the tilt angle.

But flying with respect to the air mass isn’t any different upwind or downwind. It does take more power to fly in the tilted region between OGE and say 50 ft. due to the downward component.

[Heron]

Udi
Every time this discussion comes up, one is changing some parameter and the other one still on the prior subject.
Two different situations will never equalize opinions.
The discussion should be how the wind affects turns . . .
Funny thing is, the glider tied up against the wind will get airborne and not the other way.
Remove the rope and all changes (pilot in or not)
One component of lift always change in turns, no matter what altitude you are.
Yes . . .everyone is right!
I still loose 100 ft in every round around the pattern, cant keep that nose were it belongs . . .
I need more low level flying to get the feeling and make my approaches better.
So far flying is easy.
thanks
Heron

[Udi]

Chuck - the wind, on average, cannot be tilted as you say, due to conservation of mass. For every cubic meter of air going down there must be another cubic meter of air going up somewhere. Wind, on average, must flow parallel to the ground. Thermals and wind sheer are classic examples of localized wind with a vertical component, but in both cases there will be areas with opposite vertical wind direction. I am not sure why the Dutch built their mills facing 10 deg up, maybe because the mill was facing obstacles that were causing the wind to flow down into the mill.

Whatever phenomenon we are looking for must be symmetrical on average in order to conserve the mass but localized enough - i.e. smaller than one rotor diameter, to affect the lift in relation to the direction of movement.

Udi

[Fl90]

Hi, when I make low level down wind turns I have to make a concious effort to exagerate the turn. If I don't, I find myself banking into the turn to shorten it. Upon exiting the turn, my airspeed will be the same, but my disk angle will be on the back side of my power curve (i.e. same speed, 300 rpm more). The gyro feels like mush and will sink. To correct the sink I have to move stick forward, gently. This always looses a small amount of altitude, and when you're 10 or 15 AGL it is hard to convince yourself to do it. But, I have found as long as your ASI is correct you begin to gain airspeed and altitude quickly. Also, it seems to loose less altitude the closer I am to the ground.

This is just my observation. This is not a recomendation or an explanation for or of anything.

If anybody feels this is obsurd, fire away. I have thick skin. I do things that work for me, however, I can't say they are right or wrong. Phil.

[Harry_S.]

Aarrgh...I stayed away from this topic as long as I could.:puke:

Way back...when I first started in the gyro movement, I didn't know much more about *gyro* physics, than I know know.

I had many hours of glider time...with no instruments and when I transitioned to powered flight...I still had no instruments. The only *instrument* I had was the useless, pith ball wind gauge. I flew for many hours in this manner. I didn't need any gauges; by that I mean, flight inst. eg, IAS, altimeter, compass etc. Don't get me wrong now, inst. are good if you learned to fly by the numbers. I have a good supply of inst. in my RAF and I really only look at the eng. inst. most of the time.

I still essentially fly by feel and seat of the pants, if you will, and I have no problems...I'm talking of gyro flight now...not FW.

I have experienced *sink* in turning downwind and it was at full throttle and...let's forget that weak suggestion... as to looking at the ground. If you're holding a stationary point over the ground, into a 25 mph wind, at full throttle and you turn left or right, how are you not goin' to *sink*...explain that to me. To recover you must maintain full throttle, and apply forward stick to gain additional airspeed.

Ron and others...may I offer a suggestion...if you trust your flying prowess...cover over the ASI, Rotor Tach, Eng.Tach, ALT. and go fly. I'll wager you will like flying a bit more...after a bit?!;)

I'm open for questions.


Cheers :)

[C. Beaty]

Yes, Udi. I know that energy must be conserved.

On a macro scale, the net movement is indeed zero.

On a local scale, however, the descending air flows outward before again rising.

I’l try to find the reference to descending air and Dutch windmills.

[bones]

I am telling you guys that you are not maintaining airspeed. You can glance down at the indicator from time to time and see what you want, but somewhere in your turn your loosing airspeed and hence the need for more power.
Ron and im telling you that i was watching it to make sure it didnt drop below 45 kts ASI, and it works fine, has checked it a few times for other reasons..

Guys and gals, the problem with this debate is that the mustering guys do not operate like the sedentry flying majority, at a constant angle of bank or constant airspeed
Paul, to prove this piont i WASNT doing a sharp drop off AS turn, this time i was doing a graduall 45-50 kts ASI turn at 5' above the tree tops, to prove a point. Please dont start saying that im trying to mislead people here..

Al, for reason of keeping this simple, the sink is occuring at a point after returning to level flight from the turn. It could be 10 seconds later, not just exiting the turn. I know this is easy to say that the pilot is not maintaining airspeeed, but I have watched the ASI, and it is not bouncing around lower as should be the case in a gust or other distubrance. Just 40-45 MPh indicated, and falling like a rock at WOT. I fully understand it does not follow what should be happening and is easy to disbelieve, but it does happen every now and then.

Exactely right Scott, i can do the turn then it starts to drop, with the same ASI

[PW_Plack]

Phil says,

Hi, when I make low level down wind turns I have to make a concious effort to exagerate the turn. If I don't, I find myself banking into the turn to shorten it.

Phil, exactly. This is what we believe is happening to the guys who observe the downwind sink. You're tightening the turn to maintain a desired ground track, because if you don't, the increased ground speed will cause you to overshoot the landmarks on the ground which define your desired pattern. That increased bank angle requires more energy be added, or you'll convert potential energy stored as speed or altitude into energy used to create rotor thrust.

What we're trying to figure out here is the claims that there's more to it than this explanation in certain situations near the ground.

[bones]

I have experienced *sink* in turning downwind and it was at full throttle and...let's forget that weak suggestion... as to looking at the ground. If you're holding a stationary point over the ground, into a 25 mph wind, at full throttle and you turn left or right, how are you not goin' to *sink*...explain that to me. To recover you must maintain full throttle, and apply forward stick to gain additional airspeed.

Ron and others...may I offer a suggestion...if you trust your flying prowess...cover over the ASI, Rotor Tach, Eng.Tach, ALT. and go fly. I'll wager you will like flying a bit more...after a bit?!;)

I'm open for questions.


Cheers :)
Harry, with all due respects, you didnt read my post properly, here is the bit you missed;
THIS IS THE IMPORTANT BIT, ok im hovering at about 30kts ASI, so i open the tap increase it to 40kt ASI before i start to turn, by the time im in the turn it is 50 kts ASI,
You see Harry, my gyro will fly at 30 kts, at about 4800rpm,i can go to just under 20kts on full niose and still be holding straight and level, but with the wind on the nose it was only about 4500 rpm, so when i opened the tap, i had about 1000rpm extra, to increase AS, which i did BEFORE starting the turn, ok so i wasnt sitting there on full noise, then just start a turn of course you will loose hieght if you do that, that is not what i was doing....

[JohnEvans]

Believe it or not Lillienthal gave us the answer to this problem in the century before last!
As some have pointed out the musterer's environment is somewhat different from what is experienced at higher levels. Even here inertia effects do play a part, particularly downwind gusts. I am assured that a jumbo joining a jetstream requires full power, with autopilot taking care of pitch, even then AS sinks close to minimum control speed. But that's not the real story.
I'm no aerodynamicist or physicist, but I think there is a simple explanation for what Bones, Brian and Lillienthal OBSERVED. Accusing them of failure to observe accurately is insulting and smacks of pseudointellectualism.Just a few days ago while talking to Rusty Ferguson and listening to his evidence at an Inquest he referred to the dangers of the downwind turn several times.
The best way to resolve this matter would be to repeat Lillienthal's experiment.
He set up a 10 metre tall mast (that's right in the musterer's turf). On this mast at say 1 m intervals he attached wind direction vanes with horizontal pivots, they were linked together and attached to a pointer scratching a trace on a clockwork powered smoked drum.
While the indicated direction varied a bit - up to a rise of 9 degrees the average was apparently 3 degrees. Thus the difference between an up and downwind take-off is an average of 6 degrees angle of attack.
I would suggest that critics repeat this historic experiment before accusing other observers of inaccurcy. Citing "ground referencing etc " is unhelpfull if not dishonest.
How to explain it?
I will try using the principle of conservtion of energy.
We all accept the concept that air being accellarated through a venturi results in reduced pressure, that's how a carburettor and part of the explanation of how a wing works. As I understand it part of the energy in that air mass is taken by the accellaration resulting in reduced pressure.
Now think about the converse, a mass of air moving along the earth's surface is subject to friction from various objects, so the lower bits are slowed, the energy in the air in the form of kinetic energy now becomes expressed as a rise in pressure, so the air expands, pushing following air up.
When this phenomenon was discussed a while ago on the old ASRA Forum one critic pointed out that this would leave a vacuum, however it becomes clear that conservation of energy prevents this.
Chuck, perhaps the windmill designers in Holland predated Lillienthal's experiments and so inclined the axis of their sails the wrong way. They were a bunch of Dutchmen after all! Seriously though it may have more to do with throwing the loads back into the tower for structural reasons. What do you think?

John Evans

[Papa Smurf]

Scott, Mark, A couple of questions if I may, what's the disc loading of your machines? Is the sink more pronounce with a left or right turn? Or, no difference?


My gut tells me the rotor inflow is being affected....I'm not sure exactly how.

What's rotor RPM doing?

I know that's more than a couple of questions and I appreciate your indulgence.

[Harry_S.]

Harry, with all due respects, you didnt read my post properly, here is the bit you missed;





Mark:

I wasn't referencing nor giving that impression. I was merely stating what I did in my early years. I was totally ignorant of the physics involved in flying a gyro. I am still somewhat ignorant of the physics involved and don't try to impress anyone that I do know. I flew the gyro because of the pure joy I derived from it, which I could not achieve in a FW.

I will say this...I definitely know how to fly a gyro and have done so for almost 40 yrs.

I don't intend to go into great detail of my past flying other than to say that I flew and maneuvered in much similar fashion as you musterers do today. I seldom flew above 50 ft. and enjoyed being around trees and such...and as I said before...sans instrumentation.


Cheers :)

I don't have the desire nor the *balls* to fly in that manner anymore.

[bones]

Mark:

I wasn't referencing nor giving that impression. I was merely stating what I did in my early years. I was totally ignorant of the physics involved in flying a gyro. I am still somewhat ignorant of the physics involved and don't try to impress anyone that I do know. I flew the gyro because of the pure joy I derived from it, which I could not achieve in a FW.

I will say this...I definitely know how to fly a gyro and have done so for almost 40 yrs.

I don't intend to go into great detail of my past flying other than to say that I flew and maneuvered in much similar fashion as you musterers do today. I seldom flew above 50 ft. and enjoyed being around trees and such...and as I said before...sans instrumentation.


Cheers :)

I don't have the desire nor the *balls* to fly in that manner anymore.

Harry i'm sorry but i meant to put it in the last post, if you were refering to my post,, so no probs :usa2: ,, thanks for replying,,,:rapture:

[bones]

Scott, Mark, A couple of questions if I may, what's the disc loading of your machines?
Umm i think its 1.11,, well i running 27' rotors and the gyro weighs about 515Lbs
Is the sink more pronounce with a left or right turn? Or, no difference?
I seem to find myself doing mainly right hand turns, they just feel more comfortable to me


What's rotor RPM doing?

Not sure as i dont have a rotor tach on it :yo:

[Papa Smurf]

Mark, Thank You!

I have no answer....yet.... the quicker more learned ones will probably figure it out before I......cyphering a little though..

[C. Beaty]

John E., the difference for cowherds chasing cows as a vocation and someone flying constant radius circles for recreation is the environment.

I can fly constant radius, constant speed circles at a height of less than 50 ft. all day long, or at least until I run out of space, without gaining or losing height. But that’s in an open area where ground track is irrelevant. I wouldn’t think of doing the same thing boxed in by trees or other obstructions.

Cows don’t know much about air mass so I presume musterers must maintain contact with their animals, which restricts their maneuvering space. Their downwind turns have to be as tight as their upwind turns so they can’t fly at constant bank angle. They are forced by circumstances to fly by ground reference.

I don’t think anyone has discovered a new scientific principle.

As for windmills, I took a quick look and couldn’t find a satisfying reference for the tilt of the wheel axis.

The book, “A History of Mechanical Inventions” by Abbott Payson Usher says:

“…The desirability of setting the sail beam at an angle to the horizon is discussed at some length by Jerome Cardan in his attempt to analyze the mechanics of a windmill. We may thus infer that the increase efficiency yielded by this arrangement began to be commonly known at least by the beginning of the sixteenth century…..” But that’s nothing I would care to take to the bank.

[scott heger]

Papa, mine are 25X8 SportRotors , all up weight with me and half tank of fuel is 530lbs. Again I am trying to not factor the turns in, but the worst one I ever had was about 5-10 seconds after a shallow bank right turn(not before). I never make steep angle downwind turns in stronger wind conditions. The sink happens when there is plenty of groundwind, straight and level, downwind after the turn maybe one out of 100 or 200 times. Airspeed is normal and conditions don't have to be gusty for it to happen. It has only happened at El Mirage, but it is also the only place near me(Los Angeles) where flight at 1 foot is legal, if so inclined. Normally I fly in congested city airspace with much higher minimum flight levels. I have been pushed up and down much further in mountain passes, but this is to be expected. Here is a picture of the area to give you an idea. It just does not get any flater or smoother.

Scott Heger,Laguna Niguel, Ca N86SH

[mceagle]

A Dutch Windmill ?

[dragonflyerthom]

OK Guys

Now I am not a physicist. Altho My middle Step son is studying in his last year at University to be an engineer and has quite a few hours in physics and math.
I posed this question to him and he asked these questions. When hovering near the tree could the air have been denser (increased pressure)? When making the turn even tho the Airspeed was increased could the air have been less dense to cause this loss in altitude. Could lift have been lost during the maneuver of turning? Can the DA be variable on these set planes when low to the ground with these air mass vorticies?

I thought it was a fresh approach and could be an answer also.


Thom

[Udi]

I have a theory that I think might help explain these low level, downwinder, trouble makers' observations. I don't have it completely worked out but maybe some of you can pick up some ideas and take it to a higher level of coherence.

It has to do with the wind gradient and how the rotor disc is working within a wind gradient. When flying into strong head wind close to the ground, the forward part of the rotor disc, which is located on average oh, maybe 2-3 ft higher than the rear part of the disc, is facing a stronger relative wind than the rear part of the disc (the advancing blade is flying into increasingly strong headwind, if you will, and the retreating blade is flying into a slower headwind). As a result, the forward part of the disc is making more lift than the rear part of a disc. To overcome this imbalance the pilot has to use more fwd stick than usual for the same airspeed.

Now, when flying with a strong back wind, the opposite happens. The forward part of the disc is facing a slower relative wind than the rear part of the disc. So the rear side of the disc is making more lift than the fwd part of the disc and the pilot has to use more back stick than usual for that given airspeed.

In the transition from a strong headwind to a strong back wing the pilot has to transition from holding more fwd stick than usual entering into the turn, to holding more back stick than usual coming out of the turn.

I know this is not a perfect explanation, but it's the best I’ve got so far.

Udi

[C. Beaty]

Tim, that’s a very interesting drawing of what appears to be a relatively modern windmill.

There were a few Dutch style mills in the US dating from colonial times but most have long ago been scrapped.

The multibladed sheet metal windmills were once everywhere for pumping water before the country was wired for electricity. You still see one from time to time pumping away and kept, I suppose, for nostalgic reasons.

[mceagle]

This might well be the plan of the only one left in Australia too. It is in Western Australia outside Perth and was disassembled and transported to its current location by a Dutch immigrant couple where they have set up a resturant business. I believe it is fully operational but is only a tourist attraction. I have a photo of the finished article somewhere.
I do not believe that the head angle would be necessary for structural purposes - perhaps the wind angled down after blowing over the Dykes?

[JohnEvans]

All very interesting Tim and Chuck, as Tim knows we have lots of windmills pumping water in Australia, I don't recall seeing the axis being inclined either way, nor do they seem to incline the axis on wind turbines. What does it matter anyway, the Dutchmen might have simply got it wrong
For some time I have been suggesting that those who doubt Lillienthal's observations, and the explanation I have offered for the musterer's observations should take the simple step of repeating Lillienthal's experiment,I would like to do it, but other projects have priority, and frankly I am prepared to believe Lillienthal!
It seems that the rising wind is known to dinghy sailors, in mild breezes they sit on the windward side of the boat in an endeavour to get the rising wind to hook under the sail and so lift the boat as well as propel it.
Come on you sceptics, this is a great opportunity to prove Lillienthal wrong, just find a flat area, erect a 10m tall pole, attach suitable vanes linked together and record where they point. If you show he was right we have a good explanation for the musterers observations, if you show he was wrong - ---well I for one will be amazed! I don't think you will!

[kc0iv]

All very interesting Tim and Chuck, as Tim knows we have lots of windmills pumping water in Australia, I don't recall seeing the axis being inclined either way, nor do they seem to incline the axis on wind turbines. What does it matter anyway, the Dutchmen might have simply got it wrong


I think the windmill axle is inclined because for the fact the blades have to clear the tower. As a example on my 55 foot tower you would have to have the axle shaft lenght of about 15 foot just to clear the tower legs.

As John said modern wind turbines do not have an axle that is angled.

Leon
kc0iv

[Al_Hammer]

.. As a result, the forward part of the disc is making more lift than the rear part of a disc. To overcome this imbalance the pilot has to use more fwd stick than usual for the same airspeed. -Udi

If you had greater lift at the front of the disc, then you would need to hold left stick to compensate, not forward stick. All aeronautical inputs are delayed by approx 90 degrees, whether they are a result of stick movements, or wind gradients. For example forward stick produces an angle of attack change at the 90/270 degree positions. :wave:

[Ron Iaconis]

The only time I could ever see a problem with ground reference,,,,is like Chuck says,,,,,when chasing cows at low level. And trees around.
When flying in a medium( AIR ) and your are moving in that medium ( AIR ) you should not use the stationary ground below you as a reference. Always use the airspeed instrument as your reference. And you will never encounter any such thing as a ( downwind turn ) By only using your airspeed instrument,,,,,you will adjust ( or move) your joystick accordingly to Keep you air speed at the desired mark( like at a constant 50 mph) or the throttle,,,,,The throttle is a very BAD way to do this,and it has much delay,,,,but if for some reason you are in a situation and the joystick doesn't alleviate you keeping the air speed constant,,,,,then adding throttle and joystick adjustment may help,,,,but throttle is not the way to do it. Any lowlevel flying ( when I did it) was usually at full throttle and hot doggingn it and showing off,,,,and then it was for just a very short time and when the wind wasn't blowing . Otherwise,,,,,,with wind,,,,,stay high,,,,and use you airspeed indicator,,,,,,

[Papa Smurf]

Scott, Thanks for the info. Still plotting and looking. Udi's comments make sense until you think of it as Al pointed out. I'm thinking it's to do with rotor thrust velocity coupled with the vector change necessary for level flight. I don't know.

These disc loadings seem alittle on the low side for wind and rough air.

[Mayfield]

If you had greater lift at the front of the disc, then you would need to hold left stick to compensate, not forward stick. All aeronautical inputs are delayed by approx 90 degrees, whether they are a result of stick movements, or wind gradients. For example forward stick produces an angle of attack change at the 90/270 degree positions. :wave:

Hi Al,

I believe the "output" of a cyclic change occurs 90 degrees later in the direction of rotation.

In the above "forward stick" analogy maximum downflap velocity (advancing side) occurs at the 90/270, but maximum downflap occurs over the nose.

I believe that if we "froze" the rotor at 90/270 we would see the advancing blade nose down, and the spindle tilted slightly forward.

The "lift/thrust" would be perpendicular to the tip path plane.

Am I missing something?

Thanks Al,

Jim

[Al_Hammer]

Jim, what you say makes sense in terms of a normal control input. The stick is used to put in an aerodynamic input 90 degrees in advance of the desired result.
Forward stick does, of course, result in the advancing blade nosing down and vice versa on the retreating blade.
I believe that any aerodynamic input will do the same thing. If the wind gradient Udi described causes an increased AoA as the blade moves over the nose and reaches into higher faster air, then the blade will have maximum displacement 90 degrees later at 90/270, which is a right roll response, in US rotor systems anyway.
To counter this, the excess AoA at the nose would be reduced by putting in left stick, as I see it.

[Mayfield]

Thanks Al. I need to think it through but I see your point,

R/S

Jim

[Al_Hammer]

Jim, even if my point is correct, I don't think anyone needs to lose sleep over the possibility of needing to cross-control because of a super intense gradient effect that springs up as they turn downwind, anymore than they need to worry about methane bubbles from the sea floor causing their plane to lose lift or their boat to sink in the Bermuda Triangle.

[mceagle]

Al and Jim, you both have a grip on opposite ends of the same stick.

[C. Beaty]

As Al suggested, imbalance of lift front to rear produces a sideward tilt of the rotor.

In normal flight, as a result of coning, the front blade always operates at a slightly higher angle of attack than does the rear blade, causing a rightward tilt with the usual direction of rotation.

It doesn’t amount to much in gyros with coning angles in the range of 3º but was quite pronounced with early Sikorskys that operated with as much as a 10º coning angle. The sideward tilt is in the opposite direction because the rotor is tilted forward.

It is also a concern with coaxial rotors where clearance shrinks on one side of the rotor disc.

The Nolan Brothers (Eagles Perch or something like that) were quite concerned about clearance as their rotors were closely spaced. They had head-on videotapes of their machine in forward flight and the clearance reduction was striking.

[scott heger]

Jim M, kindly help me out here;


Scott said in the my first engine out post:

"Tina, experienced pilots or not, if the wind starts to rise, so should the altitude you fly at. Ron, you asked how I fly into a headwind in stronger wind conditions at a lower level. Because I have the power reserve to get out of a sink.YaYa, it is all about airspeed. But there is more. Even the FAA Rotorcraft Manual mentions this point. For every 10MPH of headwind, it is like loosing X amount of pounds of aircraft weight, i.e. more power to get you out of trouble. The opposite is true in a downwind, the aircraft acts like it is heaver than it is with less than normal power available"
++++++++++++++++++++++++++++++++++++++++++++++++++
Chuck B then said


"Everybody knows an aircraft is heavier going downwind than when it goes upwind. I think it has something to do Einstein’s theory of relativity.

Or maybe it’s that downwind air is lighter than upwind air.

Or maybe Scott’s trying to be funny."

*************************************************

The FAA Rotorcraft Flying Handbook says in the gyro section regarding jump takeoffs in Chapter 20-6:

If the density altitude is above 2,000 feet, a jump takeoff in
this aircraft should not be attempted unless wind and/or
a weight reduction would compensate for the decrease
in performance. Using the equation, if the density altitude
is 3,000 feet (1,000 feet above a satisfactory jump
density altitude), a reduction of 100 pounds in gross
weight or a 10 m.p.h. of wind would still allow a satisfactory
jump takeoff. Additionally, a reduction of 50
pounds in weight combined with a 5 m.p.h. wind would
also allow a satisfactory jump. If it is determined that a
jump takeoff should not be conducted because the
weight cannot be reduced or an appropriate wind is not
blowing, then consideration should be given to a
rolling takeoff. A takeoff roll of 10 m.p.h. is equivalent
to a wind speed of 10 m.p.h. or a reduction of 100
pounds in gross weight.
*****************************************

What is flawed with my original statement? To me both helicopters and gyros seem to require less power to climb and lift additional weight (like a sling load in a helicopter) while faced into the wind. This makes them act as if they are lighter and better performing especially near the backside of the performance curve.

Scott Heger,Laguna Niguel, Ca N86SH

[bones]

So am i to guess from this that every one woh thinks that if you hold a constant AS, and vary the bank of your turn there is no difference in perforance of your gyros????

Well i'll bet that even if you take up your gyro in windy conditions, and try this you willl be surprised,, and dont just rely on your altimater in your gyro take something else more sensitive,,,, and i proved it again today with my gps, showing what i thought, you turn down wind with a constant AS, and you loose hieght...
Any way it seems the conversation of windmills is more fun so i'll leave you all to it..

[scott heger]

Mark , I am still trying to figure how Chuck is going to bail himself out of that "tilted wind" comment. Thanks for taking the time showing others what should happen according to book knowledge, does not always hold truth in the real flying world. Remember, this was started to prevent a fellow gyro pilot of falling into this trap. When I get out to the desert soon, I am going to keep my gps with me and pay particular attention to every detail of the flight.

Scott Heger,Laguna Niguel, Ca N86SH

[C. Beaty]

So am i to guess from this that every one woh thinks that if you hold a constant AS, and vary the bank of your turn there is no difference in perforance of your gyros????
Mark, you’re misinterpreting what has been said about constant radius turns.

Constant radius means constant radius with respect to the moving air mass, not to a point on the surface.

If you’re changing bank angle, you’re flying a constant radius turn with respect to the surface.

When you fly a constant radius turn with respect to the moving air mass, the bank angle will also be constant. You won’t orbit about a fixed point on the surface but could orbit about a balloon that was drifting with the air mass.

When you orbit a point on the surface in the presence of wind, beware of downwind turns.

When you orbit a balloon drifting with the wind, there is no upwind or downwind.

[bones]

Mark, you’re misinterpreting what has been said about constant radius turns.

Constant radius means constant radius with respect to the moving air mass, not to a point on the surface.

If you’re changing bank angle, you’re flying a constant radius turn with respect to the surface.

When you fly a constant radius turn with respect to the moving air mass, the bank angle will also be constant. You won’t orbit about a fixed point on the surface but could orbit about a balloon that was drifting with the air mass.

When you orbit a point on the surface in the presence of wind, beware of downwind turns.

When you orbit a balloon drifting with the wind, there is no upwind or downwind.

Chuck and others how many times do i have to say that i wasnt in this particular instance focusing on a fixed piont on the ground, beleive it or not you do have to make adjustments with the stick in high winds to keep the same AS in a circle. :rant:
Things in the real world sometimes dont make sense, but they do happen, and the drop of hieght isnt like 100' it may only be 10-20' but if your only 20' above the ground that maens your in trouble :confused:

[C. Beaty]

Mark, when you have some time to kill, try it this:

Find an open area where there’s no danger of drifting into trees or other obstructions and set up a constant bank angle turn with stick and throttle fixed or at least no more than minor stick corrections to keep the machine upright and the bank angle constant.

There will be no change of height or airspeed but your ground track won’t be at all circular if the wind is blowing. You will be drifting with the wind.

[birdy]

Hmmmmm.
How come Bones dont get hit with a comment bout STABILITY?
I had a topic like this go'n and had the same problems Bones is haven.
Scott n Udi are the only ones close to the mark, the rest of you are insulting his intelligence with crap about 'keepn a constant AS and bank'. F%$#nell, this bloke knows that if you fly with constant AS and bank in wind, the GROUND PARTH will be in ovals. If he didnt understand this logical mundain crap, he wouldnt be alive now.
Give him some credit for at least a little inteligence, coz if he was as thick as your assuming, he wouldnt be able to fly like he CAN.


I also find it interestn to note, noone has asked him wot sort/size prop he's flyn. Coz its VERY relivent.[ he even gave you a hint;)]

Bonsey, we got the same problem on this forum. We're the gineapigs of sorts.
We encounter all sorts o stuff most of these bloke will never experiance, and coz of that fact, their answers are irrelivent.
Bit like askn a doctor why it wont rain.
Theory can only give accurate answers to questions where ALL conditions AND variables are concidered.
Leave out the effect of just one of a myriad of variabls, and the answer is wrong.
And you cant factor the effects of ALL the vairiabls if you dont know them.
Thats logical.

I'll shuddup now.:)

[JohnEvans]

Well said Dave, I know you won't believe the stuff I put on about the wind rising as it moves along, but you've got to admit it would explain what you guys are experiencing.
I find it amazing that a serious observation by one of the early pioneers of flight, which accords with Bernouelli should be brushed aside by people with inquiring minds, without even attempting to either duplicate or refute his findings.
Chuck, you referred to this as "a new scientific principle", come off it mate! its just the other side of what Bernouelli found.

Windmills
"Old Watermills and Windmills" by R Thurston Hopkins, published by Phillip Allan & Co Ltd of London gives the reason for the windshaft being inclined 8 to 15 degrees to the horizontal on page 45.
"The slant of the windshaft brings the uppermost sail in turn within the diameter plan of the cupola, and thus throws a part of the weight well back, so preventing the tendency of the rotating sweeps to pull forward".

Sounds to me like the sails were generating lift which had to be counterbalanced, not to mention the mass of sails etc cantilevered out on the windshaft.

[GyroRon]

Notice I am trying to stay out of this discussion....?...... It hurts my head reading some of the nonsense posted here!


All I ask of the believers.... that would be the Bones, the Scotts, the Johns.... Please give a explaination for this statement Scott made. To me both helicopters and gyros seem to require less power to climb and lift additional weight (like a sling load in a helicopter) while faced into the wind. This makes them act as if they are lighter and better performing especially near the backside of the performance curve.

also Scott, flying at the desert to prove or disprove some of this stuff is great, I look forward to hearing the results. LEAVE THE GPS HOME SCOTT!!!! It is obvious you still haven't accepted that all the trouble with flying in the wind is related to flying by ground reference. Well.... a GPS is a ground reference instrument. There is nothing it can tell you that will help with the true understanding of this experiment.

[C. Beaty]

"So am i to guess from this that every one woh thinks that if you hold a constant AS, and vary the bank of your turn there is no difference in perforance of your gyros????"

I don’t know how many times this has to be said Birdy, but constant radius turns require constant bank angle if you’re not flying by ground reference.

[dragonflyerthom]

If this concept were true we wouldn't need to crab into a landing or worry about the wind getting under our rotors when we land. Based under this concept we could just set up a little up wind and land on the runway without a crab. When we made these constant angle turns we wouldn't have to worry about the wind getting under our rotors in the up wind portion or haveing to steepen the turn on the down wind portion of the turn. Even if you are not using the ground as a reference it is still necessary to lessen and steepen in windy conditions to keep the gyro at the same angle of bank.:rip:

So I would say I agree with Birdy.

Thom

[C. Beaty]

Here’s a pretty good explanation by the University of Illinois of why the wind near the surface is tilted:

http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/fric.rxml

PS: Ops! The stuff above is for horizontal deviation from geostrophic.

[GyroRon]

Thom, email me or PM me your phone number. I will call you right back on my dime to explain this stuff to you. My fingers hurt..... I am home, no working today in the rain.

[Heron]

You are still talking different situations and trying to fit it in the same hat.
more litf = more fluctuation = less wheight relative to been airborne
moving air mass is a component of lift.
one says: the air mass will affect flight and the other say: it does not matter if you are not going anywhere groundwise.
Enough horse power will make a machine take off against the wind but never down wind in any situation, ground or not.
Heron

[Chuck Roberg]

If this concept were true we wouldn't need to crab into a landing

I hope you mean a "slip" and not a crabbed landing in a gyro.

[C. Beaty]

I hate to have to admit it but Ralph Taggart is a lot smarter than I am.

He states the facts and gets the hell out.

“The problem is, the subject is treated like a debate where we can all hold a vote at the end to see what is "right". Unfortunately, reality is not subject to our whims. Turns flown at a constant bank and airspeed are the same, no matter what the relationship to the wind. Wind does impact the ground track and pilots, ground-referencing turns, have created a whole mythology on the subject. When you have debates contrasting reality with mythology, no one wins and no one is converted.”

[Udi]

...the wind rising as it moves along... I find it amazing that a serious observation by one of the early pioneers of flight, which accords with Bernouelli should be brushed aside by people with inquiring minds, without even attempting to either duplicate or refute his findings...
John - if the wind were to rise there would be vacuum on earth. The wind must move in layers parallel to the ground in order to preserve the conservation of mass. I don't see what Bernoulli has to do with that. Any changes in localized pressure are negligible and therefore you should not expect to see air expanding or contracting.

Any type of vertical flow must have an equal and opposite vertical flow somewhere else. I used to ride with a hang glider on rising air (wind) coming up at the edge of a mountain. Mountain waves are a similar phenomenon. But this discussion is about flight in the plains where you wouldn't expect any rising air due to large topographic features. On average the air must flow in parallel layers. Local phenomenon might include rotors and other type of turbulence due to friction with the ground, trees, thermals etc.

Udi

[scott heger]

Ron, the only reason I want the GPS along is to measure altitude more closely than the altimeter. It has nothing to do with looking at the ground. I still say I or you won't be able to hold within 5 feet of altitiude in a 20MPH wind while making 180 turns. Maybe the daily fliers from down under can. Are you starting to see a pattern of comments from experienced pilots here why flying low when windy just by airspeed indication is not such a great idea and can get you into trouble?


Scott heger, Laguna Niguel, Ca N86SH

[dragonflyerthom]

:laser:

Personaly I think it has something to do with the teetering rotor head. All of the examples might work with a fixed wing but the physics of the teetering rotor allows other forces to come into play.

Chuck gave us a really good example of the layes of air mass. This didn't take into consideration the rotation of the earth or the different vorticies of the air mass it self(High and Low pressure areas) The Air itself is held in place by gravity. The earth turns at approximately 1000 miles per hour. The speed of rotation deminishes the closer to North we get. So if I am standing at the north pole and facing south I will be traveling at zero mph but I will turn completely around in a 24 hour period.
The friction of the earth causes the air mass to move more at the surface , then as elevation increases the speed of air mass increases to a point(Jet stream) then it decreases as the gravity deminishes:rolleyes:

Now someone with more experience with the teetering rotor head will have to explain how the wind effects the rotor as the turns are initialized. But this is not a strech by any means.

But I have a feeling it is because of the different lifts in the rotor head itself.
The wind is on top in a down wind turn and get under the rotor in a cross in to the wind turn

Well I am spent and will wait to see what you think of this


Thom:lalala:

[chuter]

The wind is on top in a down wind turn and get under the rotor in a cross in to the wind turn

...............huh!!?? If the wind was "on top" the rotor would stop spinning......:boink:

[GyroRon]

Ron, the only reason I want the GPS along is to measure altitude more closely than the altimeter. It has nothing to do with looking at the ground. I still say I or you won't be able to hold within 5 feet of altitiude in a 20MPH wind while making 180 turns. Maybe the daily fliers from down under can. Are you starting to see a pattern of comments from experienced pilots here why flying low when windy just by airspeed indication is not such a great idea and can get you into trouble?


Scott heger, Laguna Niguel, Ca N86SH


Scott, I think some of these experienced pilots could possibly fly the box their rotorblades came in, but that doesn't mean they know what the hell their talking about. Wrong is wrong no matter if you chase cows, fly gyros for a living or own a bell jetranger helic :boom: opter !

Pay close attention to this I don’t know how many times this has to be said Birdy, but constant radius turns require constant bank angle if you’re not flying by ground reference. Make sure that registers in your mind when flying your gyro to prove this experiment . No matter the wind, you will bank the gyro over to a constant angle and add whatever power is needed to maintain that airspeed while in the bank and if you do not move the stick or throttle you should be able to do circle after circle. But like Chuck has said, it won't appear to be a circle, more like the letter "e"

[Tina]

Pay close attention to this Make sure that registers in your mind when flying your gyro to prove this experiment . No matter the wind, you will bank the gyro over to a constant angle and add whatever power is needed to maintain that airspeed while in the bank and if you do not move the stick or throttle you should be able to do circle after circle. But like Chuck has said, it won't appear to be a circle, more like the letter "e"

Ron, I think all pilots here understand that fact. I may be a newbie but its like you and Scott are talking about two different things here and your stuck on one aspect of flying and Scott talking about another.

[C. Beaty]

This may very well be an exercise in futility but let’s see if I can phrase this in a way that anyone can understand.

Imagine 2 people are floating down a river on inner tubes side by side.

Let your toes and fingers as well as your backside dangle in the water. You can detect no motion of the water since you’re moving with the current. If you couldn’t see stationary objects along the riverbank, you’d have no idea you were moving.

You can paddle in circles around your companion as long as you like even though your paddling speed may be 1 mph while the river is moving at 5 mph.

If there was a post or piling attached to the river bottom, it would be impossible to circle it in your inner tube.

The first example is equivalent to flying through the air mass without regard to ground reference; i.e., circling a drifting balloon. You do not fall out of the sky when turning “downwind” since there is no downwind.

The second example is equivalent to flying by ground reference. You indeed fall out of the sky when turning downwind.

I expect a number of people can and likely will come up with an infinite number of anomalies; swirl over the trees, dust devils, wind shear and whatever that are irrelevant in the context of upwind vs. downwind turns but can cause difficulties no matter which way you’re going or turning.

As Ron has said, lots of people fly just fine without understanding why.

A monkey can learn to ride a bicycle without having the foggiest notion of what keeps it from falling over.

[Steve McGowan]

Yall really making me pull my hair out, trying to re-invent the wheel with every subject in the world.. Wait till the answer hits Ya just before ground inpact:wacko:

I sure ain't that smart.... and the monkey is called a "BUTTER FACE"

the body is a killer,, BUTTER FACE kills it all..

Kinda like somea these questions,,,

I GIVE UP:noidea:

[chuter]

For some reason that monkey picture is very disturbing........

[bones]

Ron, the only reason I want the GPS along is to measure altitude more closely than the altimeter. It has nothing to do with looking at the ground. I still say I or you won't be able to hold within 5 feet of altitiude in a 20MPH wind while making 180 turns. Maybe the daily fliers from down under can. Are you starting to see a pattern of comments from experienced pilots here why flying low when windy just by airspeed indication is not such a great idea and can get you into trouble?
Scott heger, Laguna Niguel, Ca N86SH
Thank you Scott that was the only reason i meantioned the gps, cause mine is set to read by 1' inclements, alot more actuate than the altimiter.. Not ground referencing, i didnt care where the hell i went, i was only looking for hieght lose or gain..

Personaly I think it has something to do with the teetering rotor head. All of the examples might work with a fixed wing but the physics of the teetering rotor allows other forces to come into play.
Damn maybe your on to something Thom

The first example is equivalent to flying through the air mass without regard to ground reference; i.e., circling a drifting balloon. You do not fall out of the sky when turning “downwind” since there is no downwind.
Chuck,, trust me i understand the therie of it all, of course it makes sense that it should work in this way,,,, but in the real world on this one, I and a few others have found that it dont quiet work that way, that is why im asking the question, WHY? but it appears that noone can accept that i can fly in a constant AS bank and loose hieght,
This from one of Thom's posts;
Even if you are not using the ground as a reference it is still necessary to lessen and steepen in windy conditions to keep the gyro at the same angle of bank
This is all im saying, it just doesnt work the way all the therie says it should

[Udi]

Chuck - I believe a more proper analogy would be sitting in a raft that is floating in a class 5 river, paddling up the river, then paddling down the river. Still a bad analogy because it does not take into account dissymmetry problems associated with gyro aerodynamics. Your analogy invalidates Mark's observation, and I am not sure this is the right thing to do.

Udi

[birdy]

Didnt i tell ya Bones, ya wastn ya time ere.;)
These people just cant accept that there may just be sumone in the world that mite have experianced sumthn wen flyn in compleatly different situations to them, that they may just encounter sumthn that is hard to explain, and goes against all theory.

Ya gota remember Bones, these people, wen they are responding to your queiries, are thinkn along the lines of wot they KNOW.
And coz they dont know all of the variables, they think your full o sh1t, like me:)

It shows in their responces.
One mention of a gps and they instantly assume your readn the ground speed with it.

I don’t know how many times this has to be said Birdy,
No sh1t sherlok!
But did i say that Chuck?

“The problem is, the subject is treated like a debate where we can all hold a vote at the end to see what is "right".
Your rite Chuck, he is smarter n most.
Unfortunatly democrosy will only apease the mass, that dont make it rite tho.
And coz the 'mass' here dont have a clue wot bones is on about, the vote will be fair, but rong.

but that doesn't mean they know what the hell their talking about.
But no dout you do tho Ronny, even tho you have no idea wot they're refern to.

Ron, I think all pilots here understand that fact. I may be a newbie but its like you and Scott are talking about two different things here and your stuck on one aspect of flying and Scott talking about another.

Tina's hit the nail on the head:)
Unfortunatly for us Tina, they always assume we cow chasers are as thick as bricks, and cant accept we mite just know sumthn.;)

See, Tina hates my guts, but atleast her mind is open:)


Askn a self acclaimed 'spert' is fraught with danger, coz his judgment is clouded by his own self importance, and cant be proved to not know everythn.

[scott heger]

Hey Birdy, at least you got one real believer (me) here in the States. I am very comfortable flying in 30+MPH winds, as long as it is not completely gusty. Can fly that also, but it is not much fun. I wonder how many other of the disbelievers spend very much time flying when it is "howlin"(or something like that you say). The only other recreational pilot I know out here that will fly in that much wind is Mike "Madman" S, and he is staying real quiet on this subject so far.


Scott Heger, Laguna Niguel, ca N86SH

[C. Beaty]

Mark, when I first started flying gyros more years ago than I like to admit, the “old timers” warned me about downwind turns but try as I might, couldn’t find one.

Then I began to wonder if I might be wrong and most everyone else might be right. So I invented my own theory based on kinetic energy.

It was completely bogus but seemed to make sense at the time: going downwind, the kinetic energy of the machine with respect to the ground is higher than when going upwind which very nicely explains the height loss/gain in turns when the wind is blowing.

Ralph Taggart unmecifully shot me full of holes by pointing out that kinetic energy with respect to the ground is irrelevant unless you smack into it.

Kinetic energy is always relative; when you drop a brick off the roof, its kinetic energy is quite high when it hits the pavement. But when you drop two bricks at the same time, the kinetic energy they have with respect to one another is zero.

In a flying machine, the only kinetic energy that counts is that with respect to the air mass.

I’ve probably spent as much time hunting for downwind turns as some people have spent trying to avoid them.

Florida was practically paved over with concrete for WWII training fields both for US and British cadets.

These fields sat idle until our population explosion of the last dozen or two years. Now they’re housing subdivisions, shopping malls, lunatic asylums and industrial parks.

The gyros used to have the run of these old airfields; they weren’t well maintained but concrete doesn’t need much maintenance. The runways were typically three 5,000 footers arranged in a triangle. The infields were always overgrown with weeds.

Whenever a discussion of downwind turns would come up, I’d jump in my old 90 hp Mac, literally stick one blade in the weeds and fly 360s until I ran out of infield. Never smacked the ground.

I’ve never mustered for a living but most of my flying has been at treetop level and below.

Uninhabited areas of Florida are teeming with feral hogs –formerly domesticated hogs that have escaped captivity- and which inhabit the swamps or what we call ‘bayheads,” low circular areas overgrown with cypress trees and underbrush.

The hogs can be caught out in the open meadows or pastures in-between when feeding but make a beeline for their dens in the bayheads when approached. They’re nearly impossible to turn but it’s fun to try.

I’m not a professional pilot and certainly don’t come close to your experience in low level flight but have never encountered a “downwind” turn.

[Aussie_Paul]

Come to think of it Chuck, neither have I. :confused:

Aussie Paul. :)

[C. Beaty]

Chuck - I believe a more proper analogy would be sitting in a raft that is floating in a class 5 river, paddling up the river, then paddling down the river. Still a bad analogy because it does not take into account dissymmetry problems associated with gyro aerodynamics. Your analogy invalidates Mark's observation, and I am not sure this is the right thing to do.

Udi
Udi, the last time this discussion came up in a big way a couple of years ago, Stan Foster confessed to circling a hot air balloon and admitted he could circle it while holding constant radius turns
without sensing upwind or downwind or an altitude loss.

Circling a hot air balloon is essentially no different than circling an inner tube in a river.

[GyroRon]

Udi, the last time this discussion came up in a big way a couple of years ago, Stan Foster confessed to circling a hot air balloon and admitted he could circle it while holding constant radius turns
without sensing upwind or downwind or an altitude loss.

Circling a hot air balloon is essentially no different than circling an inner tube in a river.

And Stan has private messaged me several times about how he can't believe what he is reading here. He has better things to do with his time than get involved with these threads I guess or he would come here and speak his peace....

[C. Beaty]

The FAA rotorcraft manual is a good source of information if not misinterpreted. It was contracted out to Jeppesen.

The tech writer who put it together was Dan Mowrey, a cut above the run of the mill.

Most of the gyro specific information was supplied by Bill Clem.

I was in a number of conference calls with Dan and Bill and supplied some of the technical information but most of the credit goes to Bill Clem.

Typically, these kinds of contracts are for a certain number of pages at a fixed price so part of the fill consists of canned FAA boilerplate. The section about jump takeoffs was lifted directly from the A&S 18-A flight manual.

The FAA had previously attempted to rewrite the rotorcraft manual in-house some time prior to Jeppesen receiving the contract but the effort petered out. I don’t know whether or not the individual assigned to the job retired, was transferred or what.

[dragonflyerthom]

Ron

I would be interested in knowing what the prevaleing wind was at the time the ballow was up. I would bet it was under 15 mile per hour.

Not enough wind speed to do the things these guys are saying it when the altitude loss occures.


Thom

[StanFoster]

Chuck: Thanks for bringing that hot air balloon analogy up. I was going to post it...but like I told Ron...whatever anyone says here....no matter what side of the downwind turn you are on....no ones mind will be changed.



You know what would be cool....is to circle a balloon for a few miles with my GPS on. My gps records my actual ground track. It would clearly show a bunch of elongated loops as I did a constant bank turn around the balloon. I could post a picture of the ground track.

I clearly remember that day. It was a steady 15 mph wind...because the balloon pilot said that was the most he wanted to fly in. It was very easy to hold a constant circle around him. There wasnt any lessening or steepening of my bank whatsoever. When I see that balloon again...its local....I am going to radio the pilot again for permission to again circle him and psot a picture of my ground track. I doubt I could post anything to prove my point...but what the use anyway. The same ones will deny it ...just as the same ones will believe it. Not one opinion will be changed....except mine because I will again re-experience it.

Stan

[StanFoster]

One more thing....it was without a doubt the easiest turn around a point I ever had to do. The "point" was moving with the wind....and I had to do NOTHING whatsover to the cyclic like you do when circling a fixed point on the ground when the wind is blowing.


There is absolutely no difference whatsover circling a balloon that is traveling with whatever wind speed you want ....than there is circling a cow standing still in a pasture on a windless day.

Stan

[C. Beaty]

You’re 100% correct Stan; it’s a mental condition that is unresponsive to facts.

[Udi]

I am disappointed in you, guys. You haven’t been paying attention to the details of this discussion -- you are assuming that this is yet another stupid downwind turn discussion. I guess I can't blame you; you got so used to the same knuckleheads arguing the same stupid points over and over.

Udi, the last time this discussion came up in a big way a couple of years ago, Stan Foster confessed to circling a hot air balloon and admitted he could circle it while holding constant radius turns
without sensing upwind or downwind or an altitude loss.

Circling a hot air balloon is essentially no different than circling an inner tube in a river.
Did you think for a second, Chuck, that I don't know that? I became thoroughly familiar with these very basic principles of piloting, to be precise, oh, 25 years and 2 months ago.

This discussion has been brought up by a pilot who understands these very basic principles. You don't want to believe his report - don't. But you are wasting your time explaining the standard downwind turn analogies because we are already past that point - at least in this discussion.

To repeat Marks reports shortly:

1. While flying in a ~30 knot headwind and flying low level, doing a gradual turn from upwind to downwind while maintaining a fixed airspeed of 45-50 knots, lost altitude at the end of the turn. This apparently happened repeatedly.

2. Flying downwind in these conditions requires 300 rpm more than flying upwind (same a/s I presume).

I know you can't explain it, me neither. This is either a problem with the perception of the pilot and not an accurate report or – there is some other aerodynamic phenomenon specific to gyro that none of us can explain.

Mark - have you considered that this may have something to do with your cattle?:violin: or with the location where you choose to make your turn?

Udi

[bones]

Didnt i tell ya Bones, ya wastn ya time ere.
Begining to understand now Birdy :flame:

Orrr for crying out loud,,,, Stan and Ron and others,,,, im not saying that it isnt the case for high flight, i was talking about and always was talking about low level stuff.
Sorry but i give up, Ron you have sad that you dont fly in these conditions so why are you so expert at this, for once and all, the conditions were blowing about 25-30 kts, and i was at about 40' up about 10' above the tops of the trees, believe what you will....

I guess we just got to go and learn how to fly proppa, hey Birdy any tips on how to fly :o :rip:

[Mike Schallmann]

Scott --I'll fly in the wind this year -- "I aint skeered" --I just WONT do hover TO's and Landings

[C. Beaty]

Udi, you can’t get much lower to the ground than sticking a rotorblade in the weeds.

I think what we have in Bones’ case is an anomaly resulting from terrain features, temperature inversion or whatever.

I don’t believe a previously unknown scientific principle has been discovered.

[scott heger]

Chuck, you kind of skirted your position on the issue about the FAA Handbook quote I used. Do you think it (and the A&S 18A one) is factually wrong or right? You have to agree it does tend to support the point I made. I had not read it for a few years so I forgot the exact weight calculations used before rereading it.

I can't believe you went around being a flying weedwacker with your rotors in the grass....yee-ha, what are we going to do with you crazy gyro pilots. Ron needs to learn this so he can get his jobs done faster. You could also start a service for "rotorblade sharpening" when they get too dull and won't cut the weeds anymore. Stiill have a feeling you were not doing this in 20-30MPH groundwinds, but maybe ......



Mike S, "Skeered" would never be a term I would use to describe your flyin' in just about any conditions out there.


Scott Heger,Laguna Niguel, Ca N86SH

[Chuck_Ellsworth]

This discussion is never going to be agreed upon because of perseption of what is happening.

When anyone flying a constant airspeed power setting and angle of attack encounters a loss of altitude it is "always " due to turbulence or wind sheer in the airmass.

I have been flying low level for decades including fifteen years as a heavy water bombing captain and what kept me alive is knowing where to expect instability in the air mass....and fighting forest fires gave us lots of that.

Bottom line is if you are to close to the ground and encounter a loss of lift due to instability of the airmass caused by either mechanical turbulence, extreem temperature thermals or wind sheer it will bite you equally up wind or down wind.

If you do not understand these basic laws of flight do not fornicate around at low level in windy conditions.

It's really that simple.

[C. Beaty]

Scott, jump performance is better when performed with airspeed. It is completely irrelevant whether it’s a rolling jump at 10 mph or a stationary jump at zero ground roll with a 10 mph wind.

What’s the point? Once in the air, performance and handling is in every respect identical.

I’m told that running takeoffs in overloaded Hueys was somewhat the norm in Vietnam.

[mceagle]

This discussion is never going to be agreed upon because of perseption of what is happening.

When anyone flying a constant airspeed power setting and angle of attack encounters a loss of altitude it is "always " due to turbulence or wind sheer in the airmass.
I have been flying low level for decades including fifteen years as a heavy water bombing captain and what kept me alive is knowing where to expect instability in the air mass....and fighting forest fires gave us lots of that.
Bottom line is if you are to close to the ground and encounter a loss of lift due to instability of the airmass caused by either mechanical turbulence, extreem temperature thermals or wind sheer it will bite you equally up wind or down wind.
If you do not understand these basic laws of flight do not fornicate around at low level in windy conditions.
It's really that simple.Chuck E. This post might be the closest to hitting the nail on the head that we have here.
Your statement "if you are to close to the ground and encounter a loss of lift due to instability of the airmass caused by either mechanical turbulence, extreem temperature thermals or wind sheer it will bite you equally up wind or down wind." could be partially the key to the whole phenomena(?). It could well drop you equally upwind or downwind but the downwind drop is far more dangerous and risky requiring any good pilot to use more height to ensure a good safety margin downwind in such conditions. You would have to admit though that mechanical turbulence and extreme temperature thermals are normally ground position related and as such you fly through more of them in a given space of time, and at a greater speed when flying downwind.

Chuck B, thank you for being so patient. Where is the line drawn between ground driven vehicles and air driven vehicles, when we talk about acceleration of mass?. Where does a hovercraft fit in and what does its mass answer to?

Stan, he was a brave man in the Balloon. I have not seen one tackle a 15mph wind yet. Perhaps they are wimps here as they prefer nothing more that a fast walking pace (3 to 5 mph) Any more than that and they can't land.

[Chopper Reid]

This discussion is never going to be agreed upon because of perseption of what is happening.

When anyone flying a constant airspeed power setting and angle of attack encounters a loss of altitude it is "always " due to turbulence or wind sheer in the airmass.

I have been flying low level for decades including fifteen years as a heavy water bombing captain and what kept me alive is knowing where to expect instability in the air mass....and fighting forest fires gave us lots of that.

Bottom line is if you are to close to the ground and encounter a loss of lift due to instability of the airmass caused by either mechanical turbulence, extreem temperature thermals or wind sheer it will bite you equally up wind or down wind.






If you do not understand these basic laws of flight do not fornicate around at low level in windy conditions.

It's really that simple.
aid.


Very well said and from my memory, this is at least the second time you have said the same but mayby not too many read what you said or disagreed with something you said
Its probably that you notice airmass instability more when flying downwind as airspeed might well be a bit slower or that rising terrain /trees are looking at you very closely or that we might be expecting to be climbing at a better rate than what the gyro is delivering. I was kind of hopeing you would chime in here somewhere .



Chuck Beaty , I note well your point about doing circles /turns all day long and not finding any problems while doing so, I have never said that you will find problems turning every day, In fact, I have done many hours and even slow unbalanced, flying to a ground reference, using rudder turns etc and not had any problem turning any direction BUT there is the odd time something happens that shouldnt, sometimes its when the wind is up, sometimes when its hot and there is not a breathe of wind. I really cant say that I could tell you that right now or in 10 minutes time, that you could find a problem. I can tell you that I reckon a problem is more likely to arise when the breeze is blowing at more than 5 knots or so but I havent documented anything to prove that this is so !!

[Canadian Rhino]

I dont know but the picture in my mind here is like the way that smoke can roll next to the ground or like a tumble weed rolls.
If you could imagine flying just ahead of an imaginary 50 foot high tumble weed, yes you would be being pushed down and seem like you had no power.
Course up here in Canada with no tumble weeds we use pine trees for that!:lol:
Vortexes created by odd things on the earths surface could and do create these types of things. Rocks,trees ridges, whatever!
A grassy field would in my mind have mini ones but low and mushy.:noidea:
Up here we dont have any balloons to fly around so we practice on thunder clouds!:angel:

[birdy]

Come to think of it Chuck, neither have I.
That dont supprise me the slightest PB, but at least your smart enough to NOT comment on sumthn you'v never experianced.;)

Whenever a discussion of downwind turns would come up, I’d jump in my old 90 hp Mac, literally stick one blade in the weeds and fly 360s until I ran out of infield. Never smacked the ground.
Thats good t hear Chuck.
Wish these critter were in paddocks like your HUGE, OPEN and FLAT playground.

There is absolutely no difference whatsover circling a balloon that is traveling with whatever wind speed you want ....than there is circling a cow standing still in a pasture on a windless day.
Anyone who dont understand sumthn as symple as that Stan, shouldnt be alowed t fly.........anythn.

I am disappointed in you, guys.
I'm so glad that there are sum people with their minds open.:)
Your the only one so far in this thread who's mentioned one of the causes of wot Bones is talkn bout Udi.
Did you think for a second, Chuck, that I don't know that?
Kinda insults one's inteligence ay.
I dont have much inteligence, but this forum is good and capable at insulting it.

I guess we just got to go and learn how to fly proppa, hey Birdy any tips on how to fly
Dont fly 'proppa', it appears to cloud one's mind, and close it............perminatly.

I think what we have in Bones’ case is an anomaly resulting from terrain features, temperature inversion or whatever.
FINALY!!!!!
The brains are on track:)


I'm very perplexed tho, that noone has asked one of the vital questions..........still:(

[StanFoster]

Birdy/Bones....

I was going to add to my post that this balloon flying was of course at an altitude away from any ground disturbances. I KNOW you guys agree with what I said. I understand that a lot is going on with the wind below tree top level. You guys have my utmost respect with your piloting skills being able to handle that stuff like you do.

Please dont take my scenario like I am trying to imply you guys dont know that stuff.


The balloon pilot was very concerned because he was not wanting to be drug on the ground when he landed. He kept aloft another hour and the wind subsided and he just had his basket tip over. This guy flies often in winds others dont.


Stan

[JohnEvans]

Anybody erected a pole with wind vanes on it yet? You're all BSing until you do.
Anybody who thinks a 6 degree difference in their angle of incidence to the relative wind makes no difference appears to be a bit thick.

Ron don't you think that just might account for what Scott observed?

Chuck, I'll ask again,what's this new scientific principle you're accusing me of putting forward, can't you see it's Bernouelli?

Someone suggested that there would be a vacuum if the wind was always rising, please read my earlier post.

[Heron]

It seems to me that the "wind" is not constant and it is made of blobs of air, waves actually with crests and imperfections.
When moving against it you will find more crests than when going with it, so you can sink more in between those "vacuums" when downwind.
. . .and then are structural turbulences and ground deflectors.
Lets convencionalize flight should we? It is moving while airborne from point A to point B on the ground . . . most people dont have the time to just fly disconnectd from the need to do it.
And please keep the parameters fixed?
Heron

[scottessex]

And all this time I thought it was from the trees sneezing!:wave:

[C. Beaty]

Chuck B, thank you for being so patient. Where is the line drawn between ground driven vehicles and air driven vehicles, when we talk about acceleration of mass?. Where does a hovercraft fit in and what does its mass answer to?
Tim, it is often difficult to separate absolute quantities from relative quantities but we get into trouble when we don’t.

Mass, weight/gravity, is an absolute quantity that would be the same whether on Earth or on the moon.

Force, mass and acceleration are all absolute quantities.

Speed is a relative quantity which must be defined as, for example, airspeed or ground speed.

Humans are Earthbound critters for whom flying is not a natural state and we have to force ourselves to believe that ground speed doesn’t matter with respect to flight behavior.

[C. Beaty]

So am i to guess from this that every one woh thinks that if you hold a constant AS, and vary the bank of your turn there is no difference in perforance of your gyros????
Udi, Birdy; This is Dr. Bones comment that led me to believe something was fishy.

Of course there is a difference of performance with a different bank angle but if the bank angle isn’t constant, a constant radius turn relative to the air mass is not being flown.

[Al_Hammer]

the sink is occuring at a point after returning to level flight from the turn. It could be 10 seconds later, not just exiting the turn.-Scott

Which makes me wonder if we shouldn't be discussing the lag time of the typical altimeter and VSI. There is a reason that glider pilots and helicopter pilots often pay a lot more for instant reading VSI and variometers.
IFR Steep Turns
Practice with both full and partial panel
--Roll into steep turn
--Use VSI for pitch because of its sensitivity
--Altimeter lag will make holding pitch/altitude more difficult.
--Lock arm and elbow
--Increase power as needed
--Rollout requires immediate forward pressure and rudder application
--Advanced practice would be doing 360s or 720s linked in both left and right turns

=========

An instantaneous VSI (IVSI) has two aircraft pitch-sensitive accelerometers that eliminate the lag time of the VSI.

===========
2. ALTIMETER: The altimeter senses the normal decrease in air pressure that accompanies an increase in altitude. The airtight instrument case is vented to the static port. With an increase in altitude, the air pressure within the case decreases and a sealed aneroid barometer (bellows) within the case expands. The barometer movement is transferred to the indicator (see Pneumatic Altimeter figure, on the right), calibrated in feet and displayed with two or three pointers. Different types of indicators display indicated altitude in a variety of ways.

Generally, this instrument responds immediately to altitude changes. During climbs and descents, however, the altimeter may lag behind the air crafts actual altitude. For this reason, some lead is necessary when leveling off to compensate for this characteristic. A simple rule of thumb is to lead the desired level-off altitude by 10% of the vertical velocity.

===========
The vertical speed indicator will either indicate false or excessive movement under abrupt control input and may have up to a 12 second lag. The altimeter also may lag. The accuracy of the instruments is proportional to the smoothness of any change.
==========

[Udi]

Well, boys and girls, I am very happy to announce that I have figured it out. I have a perfectly good explanation for the two phenomenon reported by Birdy Mark and Scott (one being a sink after a downwind turn and the other being more power required flying downwind than upwind). What do you know - physics works.

As I suspected, this problem is pretty unique to gyroplanes. Some FW and helicopters might suffer from it, to a lesser degree. There is one type of aircraft that I think will suffer from it even more than gyros, but these guys don't fly in strong winds anyway. This is your hint.

I will give others the opportunity to come up with the explanation - because now I know it exists, and it's not difficult or far-fetched. Go for it.:first:

Udi
p.s. Chuck - this indeed is not a new scientific discovery.
p.s.2 - No, I haven't been drinking.

[scott heger]

Al, true our "cheapo" Altimeters and VSI's can have a few seconds of lag. That is why Mark used a GPS to verify altitude. However the ASI's are pretty much spot on to what is happpening within a second. The airspeed indicator is what we are all depending on in these reports of sinking with plenty of airspeed. Frankly, I use the seat of the pants feeling (my butt-meter)for first indication of sink and climb, verifed by the instruments. The altimeter and VSI are just going to tell you how soon and how far till you hit the ground.

I still think there is some kind of thrust or lift componet factor combined with higher winds we are missing here explaining this besides the airspeed issue. The feeling of sinking when all standard factors says that it should not happen, can be a little unnerving and tends to keep you on your toes.

Scott Heger,Laguna Niguel, Ca N86SH

[Heron]

Udi
Anything to do with interaction rotor x wind?
Enough rrpm to keep airborne will require more power to overcome wind?
thanks
Heron

[Al_Hammer]

Of course. How silly of us to overlook the obvious, Udi.
There are more left handed isomers of air going downwind, right? Or is it those pesky clouds of dark matter? I just hate it when that happens.
Oh yes, lets not forget the neutrino wind from the sun. You definitely don't want to be on the downwind side of that.
Am I getting warm, Udi???

PS: I was going to mention the magnetic mono-poles, but I don't want to get Ken J. any more riled up than he already is about ethnic slurs.

[C. Beaty]

If you’re going to say rotor rpm/G load, have another beer, Udi.

G load in constant bank angle coordinated turns is also constant. Upwind or downwind.

The excess rpm remaining after rolling out of a tight turn produces a momentary lift increase.

Tailheavy rotorblades also cause some peculiarities.

I think Mr. Hammer might be closer to the mark than anyone else. It’s likely nothing more exotic than instrument lag, assuming all the claims are factually correct.

PS: Al, you might not be another Jack Benny but your shtick ain’t too shabby. Just think what you could do if you had a fiddle.

[Udi]

Sorry guys - not even getting warm. Both of you will hit your foreheads and say 'of course how didn't we think of that' after you'll know what it is. Mark has reported the facts correctly. I am surprised, Chuck, that you don't have this answer ready from your hip, cause I thought you would. I am also surprised you haven't experienced it yourself but apparently you haven't flown in 30 kt winds over a forest. I am surprised Scott has experienced it at the dry lakebed at El Mirage but I suppose that may be due to the relatively high atmospheric instability over the hot dry lakebed. Normally this problem will be less noticeable over bare ground. More hints.

Can I take another beer now?

Udi

[raghu]

Udi, in general most anomalies wrt upwind and downwind ( as you and others have pointed out ) during low flight can be attributed to wind gradients. Energy can be taken out and given out rapidly by moving between layers of wind. Dynamic soaring is a good example of this effect.

More to the point, perhaps your explanation has to do with the height of the aircraft. Gyros are quite tall with a low CG. Hence, at very low altitude, due to wind gradients, it is conceivable that the top of the aircraft is facing a different relative wind to the bottom, resulting in a pitch up moment that increases drag. I suspect you where referring to para-motors as the other aircrafts that are affected more by this effect than gyros.

Anyway, the point is I am not very comfortable speculating on a theory given that we are not entirely sure if the phenomenon exists in the first place until someone instruments and systematically tests the effect.

[birdy]

Now we is getn close.............in one aspect at least.:)

[Udi]

Raghu got it.

Udi, in general most anomalies wrt upwind and downwind ( as you and others have pointed out ) during low flight can be attributed to wind gradients... More to the point, perhaps your explanation has to do with the height of the aircraft. Gyros are quite tall with a low CG. Hence, at very low altitude, due to wind gradients, it is conceivable that the top of the aircraft is facing a different relative wind to the bottom, resulting in a pitch up moment that increases drag. I suspect you where referring to para-motors as the other aircrafts that are affected more by this effect than gyros.
All true, except the part about the pitch up moment that increases drag. It is very simple, really. I have a good paper and some data at work that I can post tomorrow that shows the boundary layer and the wind gradient over trees and over open plains, Raghu, this will make you more comfortable with this theory.

For a gyro that flies low (10-30 meters) above trees during strong wind conditions, it is not out of the question to expect a wind gradient of 5 mph between the rotor and the airframe. This wind gradient is fairly consistent in this alt range, so bobbing up and down does not take you out of the gradient.

The upwind-to-downwind turn under gradient conditions is a little more difficult to understand so I will start with the steady state conditions of upwind flight vs. downwind flight.

Mark said:
Also the flying down wind thing needing more throttle is back on again to, dont know why but it does, about 300 rpm more
This is not the first time people have reported needing more power when flying downwind vs. upwind.

See attached drawing. The pilot is flying at a constant INDICATED airspeed. Due to the wind gradient, when flying upwind, the rotor apparent headwind is higher than the indicated airspeed. But when flying downwind, the rotor apparent headwind is lower than the indicated airspeed.

When flying in the 40-60 mph range, rotor drag goes down with airspeed. IOW, a rotor has less drag at 50 mph than at 40 mph. So, even though the pilot THINKS he is flying at 45 mph, the rotor is actually flying at a different airspeed. This explains very nicely Marks observation that he needed 300 more RPM flying downwind than flying upwind.

Back to the upwind-to-downwind turn discussion. This is a little more difficult to visualize because the gyro doesn't really fly in a "big mass of moving air", like we always like to explain in this kind of discussions. The gyro is flying in layers of moving air. Look at the picture below again. The top gyro, flying at 45 mph and with the rotor flying at 50 mph, is now going to make a 180 degree turn and still fly at 45 mph, BUT, the rotor is now transitioning from a 50 mph headwind to a 40 mph headwind. This is like being hit from the back by a gust of wind that takes away 10 mph from your airspeed. What's going to happen? The gyro is sinking until the pilot has a chance to increase power and pull back on the stick to transition to the new and less efficient rotor airspeed.

That is the whole explanation. Tomorrow I will post a chart that shows the wind gradient over trees and over open planes. Trees create a very significant friction with the wind and that makes for a very significant wind gradient in the first 10-40 meters (depending on wind intensity).

Udi

[Udi]

There is one more aspect to flying in a steep wind gradient that I haven’t mentioned above. When flying upwind, a gyro has a better climb rate than normal because you are constantly climbing into layers of faster head winds. You are getting free energy, if you will.

The opposite is true for flying downwind. When climbing downwind, you are constantly flying into layers of higher BACK winds. This requires much more power to climb than normally because the gyro has to accelerate all the time, in addition to climbing.

This has nothing to do with the downwind turn discussion per-se, but it adds to the pilot’s perception of having more power available flying upwind than downwind. It is harder to make up for lost altitude when flying in a downwind gradient.

Udi

[Al_Hammer]

It sounds convincing, Udi, but when I look at an actual chart of wind gradients, such as this one below, it doesn't add up.

At first glance it looks like the wind goes from 45 mph just over the trees to 65 mph a few ft above that. Actually thats about a 200 ft difference. Plus, the wind isn't normally going to be blowing at 45 mph near the surface.
If you scale everything down to represent actual conditions on a normal day, it looks like you might get a 10 mph gradient in 200 ft. That works out to about 1/4 mph difference in airspeed from rotor to fuselage.
If the gradient were 5 mph in 5 ft, as you suggest; that's 1 mph per ft and the wind would be hundreds of miles per hour by the time you got to pattern altitude on a calm day. This is the only chart I could find for wind gradients over land. http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd028_e.html

[scott heger]

You all had me thinking about these issues. So this afternoon I went and did a little flying to find out a few details. The groundwind in a particular area was 5-10MPH, unusually low for a afternoon around here. I went and did Ron and Chuck's 360's (just yanking you guys a little)without change of power or altitude , just like the book says it should happen. I then moved over to a mountain and canyon area known for higher wind conditions. My estimate the wind was closer to 20MPH with some gust. I only concentrated on the upwind- downwind portions of the flight( not the turn portion) trying to maintain altitude and airspeed only for a given power setting. I did 5 one mile runs back and forth each way at 30MPH ASI. This is obviously slightly behind the power curve and was done on purpose so I could measure power loss more easily.

I was not able to fly the downwind portion and keep the same altitude and airspeed without the use of more throttle each time I tried this. The upwind portion was also easier to keep a nearly perfect altitude, yet I had to do more controlling on the downwind to try to stay at level flight . The airspeed indication was as close as I could get in both directions. Not very scientific, but I feel comfortable saying Mark is correct about requiring more power to keep level flight downwind. I just don't know why this would be so at the same airspeed.


Scott Heger,Laguna Niguel,Ca N86SH

[Al_Hammer]

Nice work, Scott. Looks like you've got some convincing data.
I'm personally trying to stay open minded on what might be the reason for what you're seeing.

[bones]

Scott, it is damn frustrating sometimes AYYY, things just dont make sense,,, nil wind i can cruise at 4200rpm at 60 kts, the other day it was howling wind coming home, i was 60kts ASI with a ground speed of 110 mph, and needed 4800 rpm to still level in flight,, go figure

[birdy]

Keep at it Udi, at least theyre listen'n to you.:)
Your rite on the money.

Al, i hear wot your sayn, but you gota remember, Bones is at 5/20', were the GREATEST gradient is.
Once your over 50', you hardly notice the effects of gradient.

[chuter]

Any chance the wind gradient could be causing something like I've drawn here; sort of like rolling out a carpet?

Sort of a miniature wind rotor close to the surface?

[Heron]

Long time ago I asked what would happen in this situation:
Virtual gyro flying with a fan providing the "wind"
Turn off the wind . . .change wind 180 degrees
results?
I guess I will have the answer now and it is pretty close to what I thought then.
thanks
Heron

[C. Beaty]

Al, here’s a link to a site that provides a microview of surface winds.

They also include a spreadsheet which permits a plot of wind gradient with various wind speeds and surface roughness coefficients.

I haven’t had time for more than a casual look but it does seem plausible that if someone was skimming treetops over a heavily wooded area, there would be a detectable difference of performance upwind Vs. downwind.

30 feet above the treetops, the gradient is too slight to make a difference.

http://www.onemetre.net/Design/Gradient/Gradient.htm

[Udi]

Dr. Barry Gardiner of the UK Forestry Commission did a lot of research in the field of atmospheric science. This paper (http://www.bwea.com/pdf/trees/Barry_Gardiner.pdf) (actually a presentation) gives the information we need for this discussion. This is a very interesting reading but if you want to go straight to the most relevant data go to page 30. The graphs on page 30 show the boundary layer and wind profiles over trees and open spaces. As you can see, the wind gradient over trees is greatest in the boundary layer between 10 and 30 meters (meters, Chuck, not feet). The exact shape of the boundary layer depends on many factors but, in general, a stronger wind would result in a thicker (taller) boundary layer. This graph shows that a 5 mph gradient over 2 meters is not out of the question but regardless of the numbers the existence of this phenomenon cannot be disputed.

Udi

[dragonflyerthom]

Udi

I am wondering if when the downwind turn is made if the wind from behind will effect the lift in the rotor area. ie reducing the vacuum on the top side. Some will say that it is unequal pressure. Could be while others will say a vacuum is developed on the top foil.. This could explain why lift is lost also.

[Udi]

The rotor doesn't really see any wind from behind, Thom. The change in flight direction under severe wind gradient conditions results in a change to the relative headwind. It is as if you have slowed down from 50 mph to 40 mph. The rotor is not hit by anything from the back. This change is not instantaneous - it takes time to turn 180 degrees. Only people who fly very low at extreme wind conditions are subject to this problem.

Udi

[C. Beaty]

Udi, I understand there is a wind gradient near the surface that is a function of wind speed and surface roughness. No argument and it’s a plausible explanation for the experiences of Australian cow chasers.

I’ve never experienced it inasmuch as I would never fly at treetop level over heavily wooded terrain. When flying at low level, I always try to provide an escape route if something goes wrong.

But for most people who believe they’ll fall out of the sky when turning downwind, it’s a state of mind. The human mind is a marvelous thing.

Force someone at gunpoint to drink a glass of warm, amber liquid which he believes to be horse urine and he’ll gag and vomit even though it’s only beer.

The Gardner paper seems to be authoritative but there’s an awful lot of stuff to digest.

[scott heger]

Chuck, stay on target here, nobobys thinking about drinking a warm glass of horse pi*s while flying around. Changing the subject"the human mind is a marvelous thing" really is just a way of avoiding what we are observing that does not fit into what you have said as undisputable fact. I did not challange your previous post regarding upwind-downwind thrust (remember the parked car one verus downwind driving one). Unless you can provide a documented test proving a low level gyro thrust pull in each direction in strong wind, I am not buying that either as correct. Yesterday's test I did just reconfirms what Mark and I have been saying all along about needing more power to fly downwind at higher groundwinds in a gyro. I believe there is more to the whole downwind flying/ turn issue than just legend and myth. Most of the time it requires just a minor power adjustment, but in rare circumstances, it can put you in harms way. The most important purpose to continue this discussion is to help pilots realize this could be a trap to fall(litterly) into and aviod splatting themself. Unless the gyro is very high performance, it can easily happen, especially in higher winds and DA's. I keep harping away on this because I have witnessed 3 of these accidents , each one causing major injuries. The easiest way to aviod this is to fly higher as the winds increase, and not become another statistic.


Scott Heger, Laguna Niguel, Ca N86SH

[Al_Hammer]

Udi, the size of the pdf you linked to precludes me from looking at it on this machine, but I went ahead and plugged in some numbers using the formula given on the site where I got the graph in my previous post.


An interesting thing about this formula for wind gradient is that it depends on the ratio of heights. If you are going from 1 ft to 3 ft, thats a three fold increase in height and the gradient will be large. At a higher altitude any change in height will tend to be less important.

The next thing to decide is what coefficient to use. The site say it may vary between 1/2 and 1/7, country to city. I split the difference and used .32
This gives a 4 mph wind speed gradient going from 3 ft to 9 ft- a 6 ft difference corresponding to a gyro mast.

So, yes, the formula does predict a significant gradient at very low altitude over rough terrain. At least your theory is plausible- congratulations!

It does not apply to all downwind flying, of course, just the special case noted above.

[C. Beaty]

Scott, I’m not sure what you’re trying to prove with a gyro tied to a parked car in a 30 mph wind but it has nothing whatever to do with wind gradient.

What it does prove is that you’re incapable of understanding that airspeed and ground speed are unrelated, at least out of the boundary layer.

[Udi]

I realize there is a problem that some people may jump on this wagon and say - 'see, we told you all this time a downwind turn was dangerous.' I don't know how to deal with people making logical leaps in places they shouldn't be. That's the nature of a public forum where seatbelt award discussions meet aerodynamics... I don't think we should shy away from in-depth aerodynamics discussions because some people might misunderstand what was said. I think there are quite a few folks around here that can follow the logic without jumping into the wrong conclusions.

Udi

[C. Beaty]

Ever the gentleman, Udi.

But to get back on topic, what you’ve uncovered would be a good subject for a paper on low level flight.

You would have to fit a gyro with a pair of propeller type recording anemometers, one at the top of the mast and one at the keel and then make a series of flights over a forest from treetop level to several hundred feet above.

Maybe Mr. Bird would volunteer to be your test pilot.

[scott heger]

Chuck,I fly by airspeed, nothing else and I have never said different, you keep trying to refer back to groundspeed for both Mark and my statements, we don't care about groundspeed.. Ground reference flying will only get you hurt in the wind. I do understand that if I fly around low in higher groundwinds at the same consistant air speed and throttle settings, I may hit the ground. It has almost happened before. I got it. Maybe you agree with the statements that it may take more power to fly downwind, whatever could be causing this factor. Maybe you disagree that it just is not so and is impossible. But if you believe it is possible, then also the thrust pull would not be the same in both directions either.

I know the parked car upwind verus the driven one downwind I used before is a dramatic example, but more energy is being used driving than being parked to keep the same airspeed of a unpowered gyro. The groundspeed of the vehicle was only referenced to show how fast would be necessary to have the correct airspeed. Groundspeed (again)plays no factor, but the direction of the wind and airspeed sure does. It is the ability to store energy in the blades to fly at a given airspeed and the thrust required to do it. Nothing more. Maybe the example should have been with a small motorcycle. Would the parked motorcycle and it's driver been pulled with the gyro into the sky? No way. The motorcycle would be have to be working at near full power to produce enough HP to pull the gyroglider fast enough downwind to keep it airbourne at the same airspeed as the parked upwind motorcycle. I don't have a real world thrust test(no book formulas allowed) to prove it , but I don't think you do either. My flying experience dictates it takes more engine power downwind; is requiring more thrust pull required from the rope in this example of a gyroglider flying at the same airspeed downwind that much a a jump in logic?



@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Scott's orginal post for those that did not see it:

Udi, you may be right. OK, smarties think about this next example. You are sitting out on that hot lakebed with a vintage unpowered Gyro-glider in 6,000 foot DA"s. The wind is blowing 30MPH, and you have it tied with a long rope to a car bumper while it is parked, engine off. You pat up the blades while it is faced into the wind, and the gyro will fly off the ground with a person onboard. Most of us have seen this done, right? How much H.P is the car/gyro using? None(ok a very small amount of negative thrust to hold it in place,but no engine power). But to get that same 30 MPH airspeed downwind you need to use some of the HP of the engine to get the car going 60MPH(30MPH airspeed). I.e it uses more HP to fly downwind than into the wind. The airspeed is the same, so it flies the same. The gyro does not make a difference, because it has no engine, just using the thrust(HP) of the car. Kindly explain to me how the horsepower used in this case is the same in a downwind verus a headwind. Maybe the thrust pull on the rope is exactly the same, but I doubt it is

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@


Scott heger, Laguna Niguel, Ca N86SH

[Al_Hammer]

Scott, I think it is obvious that it takes additional power to takeoff downwind, since you need to accelerate the mass of the vehicle(s) to the windspeed plus takeoff speed. It takes horsepower to move any ground vehicle.
Once up to flying speed, the tow vehicle will continue to need power to tug the gyro. The tension in the rope will be the same as it is upwind.
The difference is that power is consumed when the vehicle moves over the ground. Power = force (tug on rope) X velocity(groundspeed)

In the upwind situation, the power is force(tug on rope) X zero groundspeed= zero.

In both cases, a certain power is required to fly the gyro. In one case it comes from the ground vehicle pulling the gyro against the air and in the other case the air is forcing itself over the gyro rotors while the gyro itself is tied down. The wind does the work and the wind is caused by heat, which comes from the sun. So the sun does the work. Solar powered gyro.

[Papa Smurf]

Thanks everyone, this is good stuff.

You know if we had 3 accelerometers(X,Y,Z), prop speed, rotor speed, 2 anemometers, and air temp this could probably be plotted exactly.

[Chuck_Ellsworth]

It is impossible to maintain a constant, stable attitude and flight profile when flying in an unstable airmass by reference to airspeed as your sole pitch information.

The inherrent lag in arspeed response will result in pitch occillations as you lag behind the attitude changes.

Chuck E.

[bones]

Bloody hell not even i expected something like this,, this is good reading thanks blokes, keep going ,, you lost me about 2 pages ago..

[Udi]

It is impossible to maintain a constant, stable attitude and flight profile when flying...
Got your hands shaking in the old age, Chuck? Can't maintain your airspeed any longer? :) (never mind, i'll go to pound some salt...)

Bloody hell not even i expected something like this,, this is good reading thanks blokes, keep going ,, you lost me about 2 pages ago..
All you really need to know, Mark, is that your observations were validated by science. Congratulations.

Udi

[scott heger]

Fair enough Al and Chuck(s). Udi, your good.



Scott Heger,Laguna Niguel, Ca N86SH

[birdy]

It only took ten pages too Bones. :)
I gota hand it to ya mate, i'm f%$#@ if i could get anyone to listen to me.;)


You seem to have them convinced that there IS a difference caused by WIND GRADIENTS, thanx mainly Udi's help............................... but STILL noone has asked bout ya prop.
Never mind, at least we know ay;).

Al and Scott, i'v never seen a gyroglider, but your not maken sence. Your both dissagreen, and your both rong.
For a start, its not a good annalogy for a powered gyro.
Scott asked;Kindly explain to me how the horsepower used in this case is the same in a downwind verus a headwind.
Then Al said;I think it is obvious that it takes additional power to takeoff downwind, since you need to accelerate the mass of the vehicle(s) to the windspeed plus takeoff speed. It takes horsepower to move any ground vehicle.
It takes the same amount of power to get a gyro off wether its facing UW or DW, the difference is in the length of ground roll. The energy consumed to accelerate the machine to TO GROUND speed is greater DW, because it takes longer to get to TO ground speed, but the POWER requirement is the same.
Your starting the TO roll with negative airflow, the engine has to accelerate the machine to 30mph ground speed before your at the starting point of a take off into a 15mph headwind. The only thing that would cause a need for more POWER downwind, is the extra friction of rubber on the ground at higher speed, but itd be so minisqual its irrelivant.
Its not till you break ground, and try to climb DOWN WIND, through the gradient, that youll notice the power thing. The good part is, the higher you go, the easier it gets, coz the gradient is weakening.


mmmmm................... i should shaddap, coz this thread was constructive till now.[ watch the flac fly now:)]

[C. Beaty]

Birdy, I’m stunned. I was unaware you had such a good grasp of physics; -the conservation of energy law.

I had composed a reply to Al to point out he had been smitten by a wandering zero but didn’t post it; figuring what the hell, I’d better stay out of this.

[birdy]

Patronizing is hard to pick on a forum Chuck, but i got it.;)

[StanFoster]

This has been a most interesting thread to follow.

What we have here is probably some of the best seat of the pants gyro pilots on the planet knowing what they feel as they are down in the dirty air mustering those rowdy cattle. They are trying their best to describe what they are actually feeling while doing so.


We then have what most of us fall into...the group that is using the age old downwind/upwind argument....and wondering why everyone doesnt understand it.

But my circling the balloon analogy doesnt fit here because it was in "clean" air....or 99% out of any wind gradient that would be noticable.

Then Udi comes along with the excellent explanation and it made a lot of sense.

What further made his post a "home run" was when Chuck Beatty and Al also supported and further refined it. To me personally...without them coming aboard with their analytical minds....then I still have some doubt. Little doubt left when they put their "stamp of approval " on it.

Now I think this is a "grand slam" as we have a very plausible and easy to understand explanation for whats really going on and one that gives Birdy's observations the physics support it needed and was lacking.


Thanks Udi/Chuck/ and Al. :first: Thanks Birdy and Bones for being persistent in trying to get what you knew all along across to us in english.


Stan

[C. Beaty]

Patronizing is hard to pick on a forum Chuck, but i got it.;)
Birdy, I hate to sound patronizing.

I should have said you’re not as dumb as you pretend.

Now you’ll compound the pretending by saying; “i wuznt pretendin.”

[Passin' Thru]

Some of you may be interested in a parallel thread over on the Aussie forum. Especialy post #6 by Lord Arrogance hiz self!
http://www.rotorcraft.com.au/smf/index.php?topic=702.0

[Al_Hammer]

Birdy, I accept the correction. Thanks. I got a little sloppy with my thinking.

[Chuck_Ellsworth]

Mornin Udi :

" Got your hands shaking in the old age, Chuck? Can't maintain your airspeed any longer? "

Fortunately neither my mind nor my hands have started to shake yet due to age.....but maybe soon it will start.

I made the statement regarding use of airspeed as the " only " means of maintaining attitude and recognizing attitude changes as a caution due to the issue of lag.

The inherrent lag in the airspeed response therefore makes it unsuitable as a sole means for accurate flying.

All I was attempting to do is caution people who think the airspeed is dependable for maintaining attitudes, it is not due to lag.

In the modern fly by wire PFD glass panel they have added a trend line presentation next to the airspeed digital readout, however this trend line is only another aid and not something that replaces the laser gyro driven attitude presentation, which is very accurate and stable.

Anyhow I merely wanted to caution pilots in reliance on one indication such as an airspeed indicator for accurate attitude trend information.

What you must rely on is looking at where the thing is going and use all your senses visual and vestibular and sound to drive your machine in the direction and flight path you want to go....not where it wants to go. The airspeed indication is only one of many aids you use to get the job done.

I'm betting that is what those cow herders do.

By the way Udi, how did you remember the pound salt advice? I haven't used that one with you have I?

And that is better than telling someone to go fornicate themselves....that one I only use when I'm serious. :lol:

[scott heger]

Al and Birdy, I realize that I have been shot down in flames on the example on the unpowered gyroglider. But I was not talking about acceleratng up to a given airspeed as using HP. Only the HP/thrust required to maintain the same airspeed both up and downwind. I think the thrust of a rope pull would be easier to measure than some of the other methods. Why would this thrust upwind/downwind not be different if you agree with Mark about requiring more throttle in a downwind graident? This has been a very good subject with alot of excellent input. Thanks all for time to respond and putting up with the questions posed here.


Birdy , here is a picture of a Bensen gyroglider. They weighed about 125 pounds. I have watched them fly in as little as 15- 20 mph groundwinds quite well just tied up to the rear of a parked car with a small pilot onboard.





Scott Heger, Laguna Niguel, Ca N86SH

[Heron]

Does prop efficiency u/w X d/w plays a role here?
Could it be that several factors combined will be the ultimate cause?
thanks
Heron

[bones]

Fellas, i'm just glad that we got to some kind of agreement on this, as i and alot of others would understand that some one whom has just started flying wouldnt be doing the stuff that we do regularly, but i and Birdy had talked about this a few times, and we felt it was important that certain people on this forum that swore black and blue( been a defening silence for awhile on this subject too) that there was NO difference UW to DW be shown that there is a big difference IN SOME CIRCUMSTANCES, and if that new flyer should find him/herself down wind in a marginal machine that it is possible for them to get into trouble, even with holding the same AS, and it would be best to try and face the wind at the first opportunity, IMHO...
Thank you Fellas for persueing this to find a result, even though i dont understand most of the tech talk, i sounds right to me :)
My dad always told me you can learn some thing from ANY ONE if you listen... one of the few things i agreed with him on....

[Chuck_Ellsworth]

bones, now that we have beat the crap out of that subject again, any chance you and Birdy can help us North Americans understand the female mind?

[Aussie_Paul]

bones, now that we have beat the crap out of that subject again, any chance you and Birdy can help us North Americans understand the female mind?


Ah, come on Chuck they are not that bloody clever.:wave:

Aussie Paul. :)

[C. Beaty]

Bones, 99% of the people flying gyros will never encounter the effects of wind gradient in the way that you and some of your cohorts have.

To experience the effects, you need a tall machine and have to fly low over rough terrain in a strong wind.

I doubt if a Brantly helicopter with rotor right on top of the fuselage flying along side of you would have noticed any difference upwind vs. downwind.

[scott heger]

Chuck Said:
"As Ron has said, lots of people fly just fine without understanding why.

A monkey can learn to ride a bicycle without having the foggiest notion of what keeps it from falling over."

******************************************

Do you guys need the banana peels cleaned out so you don't slip and fall on your words? I hope you keep a slightly more open mind next time to the experiences of others. You dismissed what we all had to say time and again like we were idiots. Mark and I originally presented a situation that has caused some serious injuries to pilots before that have fallen into this trap, and you wrote the whole thing off to ground referencing. My experiences were right on, the reasons why it was happening left me seeking the advice of others, not to be called a fool, in so many words. Low level flight seperates the men from the boys. The flying herders(I say that with true respect) from Down Under know how to do it far better than most, or they don't last-read live. Theory alone can get them killed, true experience is what keeps us alive while flying. Thanks again to all for the time you took to explore this corner of the flight envelope. Hopefully those that have not experienced this low level downwind problem have learned something here, and will be very careful as the wind speed increases if flying near the ground.
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@\
Scott said:


"I never make steep angle downwind turns in stronger wind conditions. The sink happens when there is plenty of groundwind, straight and level, downwind after the turn maybe one out of 100 or 200 times. Airspeed is normal and conditions don't have to be gusty for it to happen"

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@


Again Chuck, what if it only happens every now and then, under certain field conditions? It is still a area you want to aviod, because you can not predict WHEN it is going to occur. In maybe 99 percent of the time, the sink will be minor and hardly noticeable. The other one percent of the time it can be dramatic and will get you very seriously hurt if low to the ground. I am just glad that you and others have taken the time to discuss these issues, agree or not. If you fly in a low level enviorment beware!! The downwind turn "myth" is fact and can bite you.

Scott Heger,Laguna Niguel, Ca N86SH

[groundhog]

now that's why I love this forum,guys from all over the world "hashing it out"
It appears you guys have solved something that hasn't been accepted as possible before now
Mr beatty you never cease to impress me, a wealth of knowledge, an open mind,and a sense of humour
Twice I tried to bait you over to the "bridge effect" thread,ah come on

[C. Beaty]

Groundhog, I expect you own a box fan.

The air exiting the fan has a well-defined slipstream.

The inlet air does not, being drawn in from all directions.

If you were to place your box fan with outlet end near the wall and the floor was slippery, the pressure increase would push it away (ground effect).

Flipped around so inlet side was near the wall, the fan wouldn’t suck itself toward the wall unless very close.

I’ve flown under power lines but never under a bridge so don’t have any firsthand knowledge of what the effect would be but I imagine it would work about like the box fan.

Speaking of helicopters, of course. Gyros with comparatively low disc loading don’t have very strong slipstreams.

[Udi]

...The downwind turn "myth" is fact and can bite you...
See, that's what I was afraid of. Scott - in my opinion, 90% or more of the downwind turn accidents are due to ground reference and NOT due to wind gradient. I don't think that many gyro pilots that fly low use their ASI to maintain airspeed in a turn - they fly by visual reference.

People who fly low at high wind conditions should be aware of the possibility of a wind gradient and maintain extra airspeed going into and thru the turn -- maintaining extra airspeed is a good idea anyway when flying low under turbulent air conditions.

Udi

[groundhog]

I was lead to believe that ground effect was caused by reduction of drag when tip vortices were disturbed (blocked) not by pressure increase,which means it would work above.
now that's a highjack,wish you had re-opened the other thread

[bones]

bones, now that we have beat the crap out of that subject again, any chance you and Birdy can help us North Americans understand the female mind?

CHUCK, bloody hell ,,, crap ,,,, can we look at this down wind thing again its got to be easier to work out :peace: :humble: :whip: :Cry:

Your on your own on the one buddy, dont ask me about them, my track record on this subject is worse than my flying one :boom:

[groundhog]

women are all about sincerity, once you can fake that...

[C. Beaty]

Me: “But that’s what he said, Sweetie.”

Sweetie: “But that’s not what he meant, Stupid.”

Sorry, Udi, for corrupting your thread but it’s about played out anyhow. All that remains is for you to write your scientific paper and get it published in something prestigious.

I’m serious. I don’t believe this subject has ever been discussed in an aviation-related publication.

The sail boat racers apparently have awareness, designing exotic sail shapes to take advantage of wind gradients.

[PW_Plack]

Great thread!

Now, just about the time you thought you could start drafting equations, Heron has touched on a small corner of another factor.

If you're flying in a wind gradient, turning 180 will affect not only the effective airspeed of the rotor, but the effective pitch, and therefore efficiency of the prop. Hmmm...

Chuck, to understand the female mind, you'd first have to understand the female endocrine system. Fat chance.

Hmm? What, Honey? No! I didn't say you looked fat...

[Chuck_Ellsworth]

I'm still waiting for Birdy to give his thoughts on how the female mind works.

Reading the Aussie forum a year or so ago I got the feeling birdy knows how to out fox e'm and he uses that cunning talent to out fox his gyro.

[scott heger]

Udi, in all three downwind crashess I was at, I was directly looking at the gyros from the ground. All were on hot windy days. One was a low airspeed steep turn at under 20 feet. Probably as you say ,a ground reference mistake. The other two were what should have been high enough altitude with enough airspeed to pull out, but they went full power into the ground. I can't put myself in the pilots seat and see what the ASI was reading to second guess these accidents, but you can't either. What I can tell you is that whatever effect it is that can cause this sinking, airspeed alone will not save you. More altitude is better than more airspeed in this case. I have experienced it myself, I am a believer. It only takes once of this happeneing first hand and you will understand what this is all about. If you don't fly in high wind conditions closer to the ground, and possibly higher DA's you will probably never see it. Lets just leave it at the potential exist for this to happen, ok? Now I need to go to the store, they just got a new banana shipment in.

Now the most important instrument we need to help out , is a wife-o-meter. It gives your a warning like a barometer. It tells you if the day is going to be sunny, or a pending hurricane is just around the corner. It gives the owner plenty of advance warning, so that he can go to the pub and ride the storm out.


Scott Heger,Laguna Niguel, Ca N86SH

[Chuck_Ellsworth]

Scott, the main thing to remember is.

"man who fight with wife all day will have no piece at night "

[scott heger]

Chuck E, I don't think this forum has enough bandwidth the tackle that subject, but you did a good job of narrowing down the final outcome.


Here was yeterday's flying conditions in the desert, think we get a little wind ?

time temp wdir winds vis
15 Sep 3:50 pm 71 45 39 WSW 21G25 10.00 CLR 1008.0 29.82 27.186 OK
15 Sep 2:50 pm 70 46 42 WSW 18G31 10.00 CLR 1008.6 29.84 27.205 OK
15 Sep 1:50 pm 71 44 38 WSW 21G33 10.00 CLR 1008.5 29.84 27.205 OK
15 Sep 12:50 pm 71 43 36 WSW 24G31 10.00 CLR 1008.4 29.83 27.196 OK
15 Sep 11:50 am 70 42 36 SW 23G30 10.00 CLR 1008.5 29.84 27.205 OK
15 Sep 10:50 am 69 40 35 WSW 22G32 10.00 CLR 1008.3 29.83 27.196 69 56 OK
15 Sep 9:50 am 67 40 37 WSW 20 10.00 CLR 1007.6 29.81 27.177 OK
15 Sep 8:50 am 63 44 50 SW 21G24 10.00 CLR 1007.5 29.81 27.177 OK
15 Sep 7:50 am 59 46 63 SW 21 10.00 CLR 1007.5 29.80 27.168 OK
15 Sep 6:50 am 57 47 69 SW 20 10.00 CLR 1006.9 29.78 27.149 OK
15 Sep 5:50 am 58 47 67 SW 20 10.00 CLR 1006.1 29.77 27.140 OK
15 Sep 4:50 am 57 50 77 SW 13 10.00 CLR 1006.6 29.79 27.158 60 57 OK
15 Sep 3:50 am 58 50 75 SW 16G22 10.00 CLR 1006.5 29.79 27.158 OK
15 Sep 2:50 am 58 51 78 WSW 17G24




Scott Heger,Laguna Niguel,Ca N86SH

[birdy]

Especialy post #6 by Lord Arrogance hiz self!
Geez, i bin called alota things befor, but never lord. :)

[I]I should have said you’re not as dumb as you pretend.
Im a SCG Chuck, not a DCG.;)

I realize that I have been shot down in flames on the example ............
Not compleatly Scott, iv stuffed up there too.
I forgot to mention that, with the strongest part of the windgradient startn at ground level, your taken off in the strongest part, so as your accelerating down wind, the machine has to gain slightly more AS AND ground speed coz the rotors are in slightly faster wind.
Like i said, iv never seen a gyroglider in the flesh, and dont know wot the average blade loading would be. But id imagine itd be pretty low, and considern me powered ferel can hold alt with the ASI on 0, that dont supprise me a glider can float on 15/20mph brezzes.

I doubt if a Brantly helicopter with rotor right on top of the fuselage flying
Hmmmmm, just wen i thought we had him agree'n.;)
Chuck, theres a big difference between helis and gyros. That be'n the source of propusion.
The gyro gets it from the prop, which is lower than the flyn surface, haven it in a different level of the wind gradient.
The heli's source of propulsion is at the same level as its flyn surface, so theyre in the same air, and wind gradient isnt a factor. [ i'll get shot twice for this:)]

I don't think that many gyro pilots that fly low use their ASI to maintain airspeed in a turn
I gota agree Udi, most down wind spills would be caued by ground referancing misstakes.
I never look at my ASI, dont need to, i can FEEL it.
If you ignore the ground speed, feel the air, AND the stick pressure, [ and know wot its tryn to tell you], theres no reason you would get into trouble.

I'm still waiting for Birdy to give his thoughts on how the female mind works.
Thats easy Chuck E., It dont:).

All that remains is for you to write your scientific paper and get it published in something prestigious.
I’m serious. I don’t believe this subject has ever been discussed in an aviation-related publication
With due respect Chuck, I dont think we're [ all forum users] are anyway near conclusion on this subject.
We'v only agreed on just one of a few things that can make a gyro want to dive wen turning DW. And this is the obviose one.
I'll wait till its been digested before i'll hint bout the others.

If you're flying in a wind gradient, turning 180 will affect not only the effective airspeed of the rotor, but the effective pitch, and therefore efficiency of the prop. Hmmm...
Hang on Paul, one thing at a time mate, or this excellant construtive and ON TOPIC thread will explode into sh!t.

Then agin, maybe i'll get my mate Bones to do it for me, coz then it may just have a chance of be'n noticed for wot is written, not for wots written between the lines.[ RON]


I'd never consider meself a spert on any aspect of gyros. I'v only, like a few others, have done a few hours in varying degrees of crappy air, do'n manouvers close to the ground, below treetop level, do'n a ground based job.
IOW, if you try to go past your understanding of your and your machines capabilities, your go'n in. Symple.
And see'n as i'm interested, i try to understand HOW, and WHY.
I come up with me own ideas, like any inquisitive mind would.
The difference be'n, once i'v figured sumthn out, i'll try my theory out............IN THE REAL WORLD.
Its only in the real world that you can truly test your theorys, coz if its rong, the mess ona ground will convince you that you'v neglected sum miner detail. Neglect only one minre detail in any theory, and the answer is not worth sh1t.

Like i said, i'm no spert, but i have tryed all my UNDERSTANDINGS with real world tests, and im still ere, so i must be getn sumthn right, no?

For one instance, this subject, the wind gradient thingy, i'v known it for years, and coz i'v known it, i can do as tight a turn DW as UW, coz i know how to counter the windgradient.[ among other things]. If i didnt understand wind it, i wouldnt be able to do it, would I?

[Chopper Reid]

I'm nominating Bones as chief spokesperson !!!
You have done very well.

"Lord Arrogence" Lord Birdy, has a lovely ring to it :) Actually, "Sir" Birdy sounds a lot more respectable!!! :)

[Heron]

C´mon . . .stop the confetti already!
Is it possible to monitor rrpm all the way in a turn?
I can´t pry my mind from the notion that wind from opposite directions will cause opposite reactions.
At least for a moment that in cases is enough to cause the sink.
Pilot input will correct but what about a locked stick and power setting?
thanks
\heron

[C. Beaty]

The downside to your wind gradient hypothesis, Udi, as you’ve already mentioned, is that some individuals will use it as reinforcement for their misconceptions about “downwind turns.”

Most gyro pilots will never encounter severe wind gradients since they don’t fly 20 feet above areas strewn with house size boulders or dense forests in gale force winds. Or even in 20-mph winds.

From the plot below: http://www.onemetre.net/Design/Gradient/Gradient.htm

Over a smooth surface (water, no waves) the steepest wind gradient is between the surface and 2 meters. The plot is for wind speeds from 2 m/s through 10 m/s. (1 m/s ~ 2.2 mph)

And Birdy, thanks for informing me that helicopters don’t have propellers.

I think most of the wind gradient discrepancy comes from increased fuselage drag rather than from a reduction of propeller thrust. Propeller thrust does decrease with increasing airspeed but it’s not very significant going from say 40-45 mph. Besides, Udi was only able to find a difference of 5 mph over a height difference of 6 feet. Most propellers are less than 6 feet below the rotor.

[Udi]

I is interesting, Chuck ,that the boundary layer in the wind over water graph is so different from the boundary layer in the wind over open space in Dr. Gardiner's paper (the blue line below). I wonder if it has something to do with hills, distance from a forest, etc.

I am not sure which discrepancy you are referring to in your last post.

Birdy – I can’t take the suspense… What other factors, other than wind gradient, have you found for DW/UW dissymmetry?

Udi

[mceagle]

See, that's what I was afraid of. Scott - in my opinion, 90% or more of the downwind turn accidents are due to ground reference and NOT due to wind gradient.

The downside to your wind gradient hypothesis, Udi, as you’ve already mentioned, is that some individuals will use it as reinforcement for their misconceptions about “downwind turns.”

These are probably the two most important conclusions to come out of this thread.
There is no substitute for flying correctly, and that includes flying safely low over suspect terrain in windy conditions.

Udi, everybody knows water is slipprier than dirt.

[C. Beaty]

Udi, maybe I’m dense or to use Birdy’s favorite expression, simple, but I don’t understand the Gardner plot.

Using an eyeball scale, the blue line, RH plot, shows a steeper gradient upwind of the forest than over the forest.

The blue line shows a variance of 15 m/s in the first 10 meters. (For people who only think in English units, that’s a difference of 33 mph in the first 33 feet.)

The red line shows a variance of 2 m/s in the first 10 meters.

On second thought, perhaps it does make sense; the boundary layer is thinner over open areas so the variation is greater nearer the ground.

Taking the Gardner plot literally, it would be more dangerous to make ‘downwind” turns in the open area upwind of the forest than over it.

Where am I going wrong? At least the overwater plots look rational.

“Discrepancy” was a poor choice of words. I should have said differences with and without wind gradient.

ps: Before anything is chiseled in stone, we ought to make some gyro specific measurements.

I’ll make the mechanical stuff if we can get electric Al to handle the electricity. A pair of propeller wind meters sensed by photo interrupters.

Al, what would be required to record the outputs on flash memory? I’ll even donate a USB thumb drive so the recorded data can be loaded into a computer.

[Chuck_Ellsworth]

O.K. gang it's time I introduced you to my Chief Pilot.

http://i43.photobucket.com/albums/e353/ChuckEllsworth/P1010671.jpg

Wilbur has been flying since he was 52 days old and is wise beyond beliefe.

He told me to tell you guys not to fly beyond your comfort level and never fly low when there is a high wind.

He says a dog has to know his limitations.

[dragonflyerthom]

Good lookin Pooch

Like his wardrobe too

Thom

[Udi]

Chuck - I think the low gradient over the first 10 meters in the forest (red line) is due to the height of the trees. The steep gradient (which is conversely depicted by a shallow slope - typical English) starts right over the trees, but the interesting thing is that it stays steep mach longer than blue line. The red line between ~15 meters and 40 meters is pretty much parallel to the red line between ~2 and 10 meters.

I agree that it would be very beneficial having some hard data to support this theory, hopefully with the help of our friends from Down Under. I have no doubt about the validity of the principle; I just don't have a good feel for what is the real world range of wind gradient.

Why do you want to use mechanical wind meters? Why not use pitot tubes? I thought maybe use two pitot tubes connected to a water manometer? All you need is 10-15 ft of clear tubing and 2 pitot tubes. It can be easily calibrated.

Udi

[birdy]

Birdy – I can’t take the suspense..................
Its logical Udi, i bet nearlty every one of those pretty graphs you n Chuck are postn are in controled conditions. They are only an indicater of the general way wind reacts, in controled conditions.
If you take into account, or should i say, throw into the equasion, horisontal wind gradients, dead spots[ calm air masses on windy days], thermal influences, venturie effects, dust devls,............just to name a few.
Then facter in the effects of the different forces incorperated in the machine its self, like torque roll, prop gyroscopic effect .................. .

Wot i'm tryn to say is, your only go'n to get answers to very symplistic questions, coz the scope of possable variants is so limited.
All you'll get is a rough idea of wots go'n to happen to a gyro if its flyn over the same conditions in the test setup.


Wots needed is a better understanding of the air itself, symple.

Till then, everybody should stay out of the low level stuff, and He told me to tell you guys not to fly beyond your comfort level

never fly low when there is a high wind.
I never fly high Chuck, so ill never fly in high winds;).

[Chuck_Ellsworth]

Birdy, when I said never fly low when there are high winds I meant it as a caution to those unfamiliar with flying in those conditions...

..but you already knew what I meant didn't you? :peace:

How do you like my Chief Pilot?

[scott heger]

Birdy, and all.....those charts shown and are a great visual and taken from measurements somewhere. The problem we all face as pilots, all those nasty little wind related problems you mentioned do happen(I would include flying in high DA's to compounding lack of power), and some can not be predicted till they are happening real time. What would normally be a routine low level downwind flight, can have you running out of altitude and power before recovery is possible. If you have a high performance gyro and lots of experience, you have more room to get away with low level flight, but most of us don't have both. Easy solution, fly higher than you would on a calm day.

I can say without hesitation, El Mirage has been the sight of more gyro crashes and fatalites than anyplace in the world over the last 50 years. Why is this? Most of these are low time pilots, but it has also caused injury and death to high time gyro pilots and CFI's. This little 6 mile by 2 mile chunk of earth, has caused this happen for a variety of reasons. Some of these incidents are because it serves as a training area, and it has poor landmark and ground/altitude reference from the unchanging dirt color. Not everybody has full instruments to determine height when flying out here. Other factors are mechanical, and running into poles and wires from flying low. Some pilots choose to fly out here because they have no license/medical, and the FAA is not going to catch them if they can walk away from the crash,most of the non-injury ones are never reported. One fatality was caused by a glider tow rope being dropped by a plane from above and hitting the flying gyro. But many of the problems can be traced to wind related issues some of which Birdy stated above. The dust devils are predictable, but the rest can be happening also, nearby, or 5 minutes before. That is the kind of wind conditions which if flying higher can be delt with. If you are a few feet off the ground and at the lower end of the flying airspeed range, you can get nailed into the ground. The weather conditions can change very fast and without much warning. Again the charts that have been presented are great for explaining the issues involved, but in the real world the conditions can be much, much more severe. I lost over 200 feet in a sink at full power with good airspeed. Was it wind shear, wind gradient, thermals, etc? Who the hell knows, but it happened to me, so try to make sure it does not happen to you by giving yourself some extra altitude if you choose to fly in high wind conditions. I am not trying to tie this in to a standard downwind/airspeed/ground reference problem, just be aware that other wind factors can play a significant role at certain locations more than others. I fly in stronger winds all the time, most of the "surprises" dealing with the wind have been at El Mirage.

Scott Heger,Laguna Niguel,Ca N86SH

[C. Beaty]

Unless I made a mistake in arithmetic, Udi, airspeeds of 40 and 45 mph represent a pitot pressure difference of 0.2 inches of water.

Objects moving through the air are preceded by a pressure field that is not easy to predict.

Conventional airspeed indicators, a diaphragm or bellows driving a gear train are subject to friction, backlash and hysteresis.

Propeller wind meters do not respond to pressure and any desired resolution is easily obtained. The output is compatible with digital recording.

Birdy, wind interacting with the Earth’s surface is always chaotic, but you’d never understand anything if you didn’t wipe out the noise.

In the early years of aviation, windtunnels were turbulent and the airfoil data was worthless. With modern windtunnels, extraordinary care is taken to eliminate turbulence.

[Heron]

So . . .there is more in between heavens and down wind turns that can be perceived by our vain phylosophy?
Post #178 by Scott Heger brings us to the point where moving air masses (or the lack thereoff) will change flying patterns.
Question? Will a tractor gyro behave the same?
Rotor, airframe and prop are constantly been hit by different kinds of air all the time.
Maybe the good pilots are doing things (built in reflexes) and not been aware of this corrections.
thanks
Heron

[raghu]

Raghu got it.

Udi

Udi, perhaps the reason I guessed your hypothesis was that I had heard it before. In an earlier thread started by Birdy (Attn. Meteorologists) birdy had proposed the same hypothesis (see below) , and I recall thinking about its plausibility then . In fact, in the same thread you said Birdie's theory was the most plausible thus far. So, I found the subsequent challenge and revelation of your theory quite amusing.


To quote birdy from the thread Attn. meteorologists:


..... How would i know, i'v only flown gyros n trikes.
When i realised this little mistake it sorta reenforced my line o thinkn.
"Trikes n gyros, the only thing remotely simmilar of the two is the 'gap' between craft and lifting surface."
...... ................Fly'n upwind, your rotor, which is about 4/6' higher ,is in slightly stronger wind relitive to the rest of the machine, and prop, minutely leveling the disc= less disc drag.

[Udi]

You have good memory, Raghu. I remembered that someone has previously suggested that flying downwind requires more power than flying upwind but I didn't remember when. Yes, Birdy's explanation was spot on but for some reason it didn't "catch" back then. I hope that after this discussion we'll remember to include wind gradient in other discussions where it may be pertinent.

Since I have such a poor memory I decided to search the forum for any previous posts that may have suggested a connection between the "dreaded downwind turn" and wind gradient. Although I couldn't find any discussions that came up with the full explanation of how wind gradient might affect lift in a downwind turn, I found the following post in a discussion back in December 2003 (the earliest I could find):

I have a basic problem, Ken, with any argument that claims dissymmetry between downwind and upwind turns.

I believe in the fish-in-a-bowl/fly-in-a-box/butterfly-in-a-car type analogy. I don't see any reason why there should be any dissymmetry between downwind turns and upwind turns. You are flying in a moving body of air. The velocity of the air, and your gyro, relative to the ground is irrelevant.

The only reason for any kind of loss of lift dissymmetry in a turn, in my humble opinion, is when the air itself isn't symmetrical. This could be due to altitude dependent wind gradient or gusts. Otherwise, there is no "wind" in the sky...

As you can see, I was replying to a post by Ken Rehler, RIP, who was pretty adamant about the existence of loss of lift in downwind turns. We understood back then there has to be some cause for uw/dw dissymmetry, but we weren't able to put out finger on it, until now.

It's interesting reading thru past threads. You can see how much, or how little, progress we made, and read posts by some of our friends who are no longer with us.

Udi

[Udi]

Unless I made a mistake in arithmetic, Udi, airspeeds of 40 and 45 mph represent a pitot pressure difference of 0.2 inches of water.

Objects moving through the air are preceded by a pressure field that is not easy to predict.

Conventional airspeed indicators, a diaphragm or bellows driving a gear train are subject to friction, backlash and hysteresis.

Propeller wind meters do not respond to pressure and any desired resolution is easily obtained. The output is compatible with digital recording.
Thanks, Chuck. These are convincing arguments.

Udi

[raghu]

Good post Udi!
You have good memory, Raghu. I remembered that someone has previously suggested that flying downwind requires more power than flying upwind but I didn't remember when.
Udi

I am not sure about my memory. In fact at the time of posting my reply to your challenge, I did not consciously remember Birdie's prior hypothesis (I would have mentioned it otherwise). But I am sure it was deep in my subconscious and guided me to the solution. It is only in subsequent searching that I found Birdies post today.

As for the hypothesis that the rotor sees a slightly faster relative wind than the airframe below due to wind gradients, I would still caution against buying wholly into it. It certainly is plausible, but there are/may(see next para) be problems and without measurement it is hard to be sure.

One problem with the model may be the effects of the prop on the relative wind. As you are no doubt aware one half of the acceleration given by the prop to the slipstream occurs ahead of the prop. This acceleration could be significant and could mean that the lower part of the gyro in fact may have a higher(faster) relative wing than the rotor. Obviously this acceleration is the same upwind/downwind, but if it is large enough (it certainly is larger than the 5mph difference in gradient) it would mask the airframe drag variation between upwind and downwind. We could place the pitot high up on the mast and fly by the airspeed it indiacated. It would then be hard to perceive any variation in drag upwind versus downwind.

In addition, there may be other problems. We need to think more deeply before accepting it as fact.

The effect of varrying wind gradient on different parts of the aircraft has been observed on sailplanes(with their long wings) during moderate/steep banked turn from base to final. I recall reading in Derrick Piggot's book on gliding of one such incident.

[C. Beaty]

It is also obvious the machine configuration will affect its response to wind gradient.

Tall machines with low cabin pods like RAFs will be more strongly affected than close coupled machines like Dominators.

A Bensen gyro, where the pilot can hold the rotor while seated, should be hardly affected.

[birdy]

To quote birdy from the thread Attn. meteorologists:
Thanks Raghu, i did mention it earlier, but never gave a link, coz it was obviosly thought of as bunkm then, probably coz i started the thread.
[ no dout everyone woulda thought it was just another of my 'instability dilusions' :)]

Wheres Jim Byrd?
I think the only ones who did show any inteligent interest were Udi and Jim.

[Canadian Rhino]

I think the only ones who did show any inteligent interest were Udi and Jim.

Well Birdy, the rest of us tried!:violin: My thoughts came from the way that wind drops coming on to a lake and then kind of pushes up on the other side coming off of the lake.
We feel that alot up here with the float planes:noidea: