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[All_In]

My posts in this thread is a great example of knowing physics and learning gyroplane theory very well.
But most of my knowledge is based on theory and observations because I'm a low time gyro pilot without real experience testing my belief to my current understanding of the theory.

If I had more experience I would have experienced the short time frame of these flaring too high events and not posted my silly belief in physics without taking the actually time frame into account having experienced flaring too high. But I've never flared to high, yet, and do not really have a clue other than observations from the ground.

Those with knowledge of physics and actual experience testing it as a pilot really know the difference.
Once I have flown all the blades in about the same aircraft model you could believe my opinions until them it's just my theory.

 

[Jean Claude]

Hi JC:
My apologies. I must have missed something. Did you post a video link?

Yes Abid. Video link is post #43 (from 2:48)

 

[Abid]

Abid,
First of all sir. I consider you a friend however let’s get a couple of things straight. I was there when Greg test flew my Dad’s new Big blades. They are not the standard DW’s. They are a different airfoil and are heavier. In fact I rode with Greg in your machine and it flew very good on a Disk that was 2 feet smaller. To be quite honest had the personalities of Dad and Greg not clashed I would bet think you all would be flying my dad’s blades. I would really appreciate your opinion of how rotor blades fly and the differences between them if you actually flew gyros. I realize your a high time trike pilot bit that does not translate when Evaluating rotor blade performance. I know there was a disagreement because Dad charged you for adapting your rotor head to his blades. For some reason this was perceived as wrong and that Dad should have eaten the cost of this. I don’t think you guys paying for a set of Teeter towers justified being told that he should pay 250.00 an hour to evaluate the blades for your use. I think the major reason for the negative opinion of the new blades was due to a personality clash more than true performance. It’s all water under the bridge now. Just wanted to set a few things straight. I wish you the best with your product.

Hey Mike. I am flying gyroplanes but yes I did not fly (or fly in the gyro with Greg) those specific blades as only Greg flew them two years ago. I was hoping Ernie would have the sense to allow us to work with them over a few days. In one day, setting them up and flying them is not really enough. I didn't mind or care for the charge for modifying the teeter tower for the needle bearings. That work wasn't much at all. The billet teeter tower itself that was used is more like $700. That's a lot more than what Ernie charged us to modify it for his blades so obviously the amount of money for the work was the least of my concerns.
I don't know what transpired between Greg and Ernie. To me both of them have strong personalities and trust me I know that quite well. Believe me when I tell you the little charge for the teeter tower modification came in one ear and left the other for me and after all I was the one writing the check and I certainly did not ask or expect Ernie to pay $250/hour to test his blades on AR-1. I would happily do it for many hours for free if there was business to be established. That must be a Greg thing and I think I vaguely remember him saying that when Ernie asked him for money for modifying the teeter tower, he asked him for test flying the rotors in a tit fr tat reaction. I think I remember laughing at both Ernie and at Greg at the time. I would have not asked an OEM serious enough to take a $700 part and allowing it to be modified for any money for modification and I would not have asked a rotor blade manufacturer who brought his blades over for test flying time. That's just me. I really am not too concerned about things like that at all. We are not dealing with end users and there is a difference there in establishing business relationships. To be fair to Greg, Greg is a part minority owner but not an employee of SilverLight Aviation. He makes his yearly income money through training, test flying and commissions on sales he is involved in through his company Rotorcraft Unlimited. I do refer students and potential customers to him. So if he wants to charge someone something, I can't really tell him do this or don't. The guy's got to eat.
But sometimes fate does things for a reason. Your dad sold the business to a company that is probably not going to amount to any true market penetration and sounds more of a real estate play company than a gyroplane manufacturing operation. I would have hated to be in the shoes where I would have to deal with them right now.

 

[Abid]

Yes Abid. Video link is post #43 (from 2:48)

Ah I see. Sorry I missed it.
JC that bank angle sustained is not 55 degrees. Its 49 degrees.
For 49 degrees the load factor is 1/cos 49 = 1.52 So if 340 RRPM in 1 G then you should expect (340 x sq.rt 1.52) 420 RRPM there or so and you are getting 390. Not a huge difference and some of it may be measurement error. I don't see how that bank angle can be expected to give you 450 RRPM and I am assuming no dumping of load in that turn which is an assumption since you don't have Gs measured directly. I bet you if you measured Gs directly, that difference would be even less than that

And I still want to understand how Magni rotors which are nose heavy instead of tail heavy also have good hang time though less than Averso. Obviously that can't be explained away by this pitching moment and tail heaviness. Things have to add up so there are some missing pieces here. I can only theorize that inertia is playing a significant role and this small pitching moment in Averso with rigidity of blades is a contributing factor as well.

 

[Jean Claude]

JC that bank angle sustained is not 55 degrees. Its 49 degrees.
For 49 degrees the load factor is 1/cos 49 = 1.52

Abid, You makes a visual perspective error.
On my video, you can see your self
One turn in less T= 12s, at more 105km/h or V = 29m/s. It is easy of deduce centrifugal force = 2π m*V/ T = m*15.2, while Weight = m*9.8 In other words the load factor is =1.8 ie 56 degrees




The best is to do the measurements yourself with a G meter, since you doubt

 

[Abid]

Abid, You makes a visual perspective error.
On my video, you can see your self
One turn in less T= 12s, at more 105km/h or V = 29m/s. It is easy of deduce centrifugal force = 2π m*V/ T = m*15.2, while Weight = m*9.8 In other words the load factor is =1.8 ie 56 degrees




The best is to do the measurements yourself with a G meter, since you doubt

I will. I stopped your video and measured the angle at a couple of places where the front tube seemed clearly to be at 49 degrees to the horizon.

Any thoughts about why Magni rotors that are nose heavy have way better hang time than say something like Dragon wings? That is the other puzzle that can't explained with this theory.

 

[Vance]

I have found considerable divergence between what appeared to be my angle of bank from a GoPro and what the G meter showed.

I don't pretend to know why.

I found the American Ranger to be very stable and predictable from zero indicated air speed to something over a hundred knots.

I flew steep turn at full throttle increasing the angle of bank until she started to descend faster than I was comfortable with. In the Predator this produces 2.1 Gs. I did not notice what the rotor rpm was.

I did several zoom climbs.

All flying was done two up very near to maximum takeoff weight and in windy conditions.

I did multiple landings replicating the mistakes my clients have made in a fifteen to twenty five knot cross wind and the response to my control inputs were very predictable and progressive.

The American Ranger is a system that works in harmony..

It is fun for me to try to understand why it works so well and less fun to try to imagine why it is not handicapped by what some feel are serious defects.

 

[C. Beaty]

No one has criticized Averso rotor blades, Vance. The intent was to correct the misconception about the effects of rotor blade inertia.

Professionally designed rotor blades have zero pitching moment coefficients with chordwise CG located on the aerodynamic centers whether gyroplane or helicopter, beginning with Juan de la Cierva. If high inertia is required, and it generally is for helicopters, it is always by the use of tip weights because of the weight saving as opposed to uniformly heavy rotor blades.

But even Cierva goofed; early C-30s used rotor blades with a negative pitching moment that resulted in at least one fatality.

 

[Vance]

Thank you Chuck, I misunderstood with your reference to uncommented pitch ups with Sky wheels as a suggestion that the same thing would happen with Averso blades.

When I was landing the American Ranger I found a very direct connection between my control inputs and the response of the aircraft.

I found the American Ranger similar to the Predator with her 30 foot Sport Rotors.

 

[C. Beaty]

And Vance, I’ll bet you mistakenly believed that the high rearward stick force required by your Sportcopter rotrblades was the result of low drag rather than a negative ptching moment.

 

[Vance]

And Vance, I’ll bet you mistakenly believed that the high rearward stick force required by your Sportcopter rotrblades was the result of low drag rather than a negative ptching moment.

I have learned a lot from you Chuck and appreciate your efforts to educate the less educated.

In this case you are wrong Chuck; I just believed the Sport Rotors needed more trim spring than the RAF blades that The Predator came with.

The why of it was not very important to me because I felt at the time Sport Rotors or RAF blades were my two choices for a 1,400 pound machine.

My RAF blades had cracks in the trailing edge and I did not care for the hub bar.

The goal became make the Sport Rotors work as nicely as practical.

I continue to be pleased with my Sport Rotors.

The why of things is interesting to me and that is part of why I am so attentive to your posts. I have also listened to my friend Jonnie Ham many times at great length about how a gyroplane rotor works.

Johnnie Ham was born in Lancaster, California, and attended the United States Military Academy at West Point. After completing initial tours of duty in Army Aviation in Command and Staff roles, he then attended Georgia Tech, where he received a Master of Science in AeroSpace Engineering and then attended the United States Naval Test Pilot School at Patuxent River, Maryland. He was assigned as an Experimental Test Pilot at Edwards AFB serving on the RAH66 Comanche Flight Test Team, and as Director of Operations.

I also spent a lot of hours learning from Martin Hollmann before his passing. I know you knew Martin.

I feel fortunate to know you.

I don't have the knowledge base or education to discuss gyroplanes on your level.

I do have a sense of what works and what doesn’t.

 

[C. Beaty]

I also spent a lot of hours learning from Martin Hollmann before his passing. I know you knew Martin.

I knew Martin Hollmann very well; he actually had a degree in aeronautical engineering and worked for Martin Aircraft in Orlando.

Whenever he was in Tampa, he’d stop by my office and argue about rotors, unable to grasp the fact that rotors don’t actually flap, simply rotating about a different axis from the rotorhead axis and producing the illusion of flapping.

When I first showed up at a flyin with a hingeless, floating hub 3-blade rotor and had fired up for the initial flight; Martin gathered up an audience and was explaining to them how it was going to fling itself asunder from lack of drag hinges just as I went motoring sedately past. That was related to me by someone who was present in Martin’s audience.

Martin’s problem was that he was living in the shadow of his father’s fame, a famous physicist before WWII who had developed an early multi-cavity magnetron and was a radar pioneer in Germany: Hans Hollmann.

 

[Abid]

No one has criticized Averso rotor blades, Vance. The intent was to correct the misconception about the effects of rotor blade inertia.

Professionally designed rotor blades have zero pitching moment coefficients with chordwise CG located on the aerodynamic centers whether gyroplane or helicopter, beginning with Juan de la Cierva. If high inertia is required, and it generally is for helicopters, it is always by the use of tip weights because of the weight saving as opposed to uniformly heavy rotor blades.

But even Cierva goofed; early C-30s used rotor blades with a negative pitching moment that resulted in at least one fatality.

I for sure thought and nothing seemed to suggest otherwise that you were absolutely cutting Averso Stella rotors to size and equating their behavior with Skywheels and having been in the gyroplane with both of them side by side on the same day, I couldn't have disagreed more. So far my and Greg's feeling is that overall Averso Stella are the best rotors that work with AR-1 and despite our efforts we have not been able to find a better choice. The proof of the pudding is in the eating, all theories aside. We are working with some rotor manufacturer to offer the choice of composite rotors to our customers who want composite rotors but they have to match or better Averso Stella overall for us to put a stamp of approval on them and it is not easy or simple.

 

[C. Beaty]

As i’ve said repeatedly, owners of light weight gyros raved about the ‘hang’ time of Skywheels rotors, mistakenly believing it was the result of high ‘inertia’.

I also recently posted comments about how Skywheels would suddenly and unpredictably do a violent midair flare on a Dreadhaught class gyro, referring to my encounter with CFI Steve McGowan’s Mazda rotary powered Parson’s Trainer some ~20 years ago.

And of course the angle of attack instability of tail heavy Skywheels shows up on light weight gyros, causing noseup pitching during upward gusts but owners passed that off as “high lift”.

 

[Abid]

As i’ve said repeatedly, owners of light weight gyros raved about the ‘hang’ time of Skywheels rotors, mistakenly believing it was the result of high ‘inertia’.

I also recently posted comments about how Skywheels would suddenly and unpredictably do a violent midair flare on a Dreadhaught class gyro, referring to my encounter with CFI Steve McGowan’s Mazda rotary powered Parson’s Trainer some ~20 years ago.

And of course the angle of attack instability of tail heavy Skywheels shows up on light weight gyros, causing noseup pitching during upward gusts but owners passed that off as “high lift”.

I got that and I told you its because they are made like a flex noodles not maintaining any shape in chord twist or span wise. Even Dragon wings the way they are constructed if taken to 8.5 chord will do weird stuff because their rigidity would be too compromised to maintain stable airfoil and stable angle of attack. Try it even with Dragon Wing airfoil and construction method and tell me what you find. This is no different than what we find in airplane wings not structurally engineered properly and that do not pass the load tests for torsional rigidity. In flight tests they are divergent as one goes faster and faster.
Has there ever been a light Dragon wing blades for 8 inch plus chord? Does anyone have any experience with any of them. I heard they were tried once some years back and put the fear of God in the customer. I would bet they were divergent as well. Can't make them without torsional rigidity and control to keep the right shape while flying..
I will try and verify your theory of this "collective pitch effect" on landing with direct measurement of G and rotor RPM and let you know how much is really that giving us the hang time and how much is "NOT" that or is inertia of high inertia rotors.
You have given me no sound explanation of why Magni which you say is nose heavy rotor also has significant hang time compared to low inertia Dragon wings, both I have first hand flight experience in as well as in Averso of course. Things have to add up correctly if your theory is to hold.
You say high inertia rotors on flare will fall through because they will not increase RRPM. Well they don't on Magni. You say Averso Stella don't increase RRPM but don't fall through because of this "collective pitch effect" because they are tail heavy. Ok will see for sure. Your theory basically says Dragon wings should have hang time because they increase RRPM because they are low inertia and not fall through. Well Dragon wings with light inertia don't hold a candle in the respect of hang time to Averso Stella or Magni rotors. Your theory and statements are not adding up in real life to me. I am sorry. Something is very much missing.

 

[C. Beaty]

The basic problem with Skywheels was the result of tail heaviness; torsionally stiffening them via a honeycomb core would delay the onset of divergence but would not eliminate it.

What is so strange about correct chordwise CG location?

Flexibility in a flapwise direction is necessary for durability.

 

[C. Beaty]

Hobbycopters have always been an undertaking largely the domain of by guess and by gosh designers and make believe engineers.

The currently popular Eurotub style was originated by Vittorio Magni, a helicopter mechanic who learned how to design gyros from having built a Bensen. Magni purchased a license for the blades and rotorhead of his gyro from Jukka Tervanaki, a real engineer who had interned at Bensen.

Magni’s low slung Italian sports car styling converted a flying lawn chair into something that many people found attractive.

The Spanish firm ELA produced a copy of a Magni and raised the seating position in an effort to decrease the CG/thrustline offset.

The German firm AutoGyro built ELAs under license for several years until going off on their own.

There have been a number of copies of AutoGyro designs but they’re all about the same.

The lesson is that when copying someone else’s design, copy something that is already commercially successful.

It is all the fault of Igor Bensen, an engineer at GE who started it all, playing with a British Rotachute.

 

[Jean Claude]

Any thoughts about why Magni rotors that are nose heavy have way better hang time than say something like Dragon wings? That is the other puzzle that can't explained with this theory.

I have no idea, Abid. I have no quantified data of the feel of landing ease of one rotor over another. In my humble opinion, three things work here:
- rotary inertia
- collective pitch effect by heavy tail
- low pitch setting for keep rotative energy more longtime

 

[eddie]

Actually Jukka designed, the MT-7 for magni in the mid 80'S,he also was the one that tried to sell the fact that the lack of a tail section was the instability problem not

the high thrust line,of course here in this country nobody listened, Magni did and the rest or Europe also did,so all of the really good gyros were

made in Europe until the AR line of gyros came into being here in this country. It appears that Abid has payed attention and has produced a line of Gyros that

have raised the standard in quality,flight performance and handling. I personally will never have the money for one of his machines but that wont keep me from

admiring them.

 

[Abid]

The basic problem with Skywheels was the result of tail heaviness; torsionally stiffening them via a honeycomb core would delay the onset of divergence but would not eliminate it.

What is so strange about correct chordwise CG location?

Flexibility in a flapwise direction is necessary for durability.

Well yeah. Of course beyond a certain speed every airplane will also be divergent because many high performing fast airplanes have pretty good pitching moment on their wings and the tail is designed to balance that to a certain point. Design and construction always has a criteria and specs to stay within and beyond those, they can all behave erratically. Goes without saying.

Flexibility in span is ok but not like what Skywheels have. Have you ever put an assembled set of large Skywheels on saw horses and seen them droop. They are way beyond AutoGyro, Averso, Magni and many other rotors of similar span.