Time to Vote.

[RW-1]

Matthew,

A year ago when this all started most of us had that same opinion. I no longer do.

His purpose is not to learn anymore, it never was. He refuses to bow to knowledge he hasn't, but would rather endlessly argue about a point that has been proven incorrect, too many times, by numerous people.

His thread topic indicated that this would be it, the "ultimate arbitration" (and since I gladly hang that over him he is more than glad to delete it, because he cannot edit a thread title). Amazing to see how long that arbitration lasted, he ousted nick when he didn't get the answer he wanted to her, he got the truth. He doesn't want the truth, the truth means no more ranting.

There is only one point to his topic: He states he believes the Robbie to be unsafe.

He is wrong, and no amount of explaining from you, or anyone else from any location on the planet will suffice. If he stopped ranting about the Robbie, he would have nothing to say here. I guarentee it. He has not participated in any other topics unless he was able to try to tie it into yet another attempt to make the flawed point again.

He has too much wrapped up into his witchhunt to stop, he loses face (not that he hasn't lost it already).

He periodically deletes the thread's because any new personnel entering will end up finding bias against it, and that would rob him of the arguements he likes to create on this board.

I do not subscribe to this "He generates discussion" nonsense. Again, stay a while and you will see it is a rehash of THE SAME THING. You too will tire of it, I guarentee it.

It is one thing when it becomes a conversation, it never has been, and that is entirely due to LZ. His behaviour when discussing the topic itself is an insult to everyone here, plain as day.

[ 03 August 2001: Message edited by: RW-1 ]

[ShyTorque]

Please don't make the mistake of discounting Lu out of hand. He undoubtedly has a large amount of knowledge from many years of working in the aviation business.

I can see where he is coming from in many of his ideas, but certainly not all of them. I can understand his Robinson thread and recognise some sense in it. I did originally contribute to the early discussion about rigging but dropped out because I don't take part in slanging matches.

There are differences in the way that helicopter theory is taught by different agencies; because of the complicated interactions between the gyroscopics and the aerodynamics some simplifications and generalisations often have to be made in order to put across a theory or an idea.

Some of Lu's theoretical posts contain ideas that are at variance with what I was taught and what still is taught by the UK armed forces and civilian schools alike. When I have tried (very recently and in the past) to put across my understanding as an alternative he does not like it.

As an ex-military QHI and QFI with over twenty years of flying helicopters professionally, I enjoy carrying on a protracted discussion (perhaps sometimes in a masochistic way) but I don't like being treated like an idiot when I put forward an alternative theory or idea.

The latter part of my last sentence is my only gripe at Lu.

I do point out that Lu is not the only one responsible for dishing out the dirt!

ShyT

[Lu Zuckerman]

To: All

Aside from RW-1s ranting about me I would like to make this statement. Discounting my initial inability to comprehend Nicks explanation about pitch flap coupling and how it effects phase angle and my eventual acceptance of the concept although I still feel that many of my detractors didn’t understand it either I would like to propose the following. So that I am not involved in the discussion I would ask one of you to open a thread dealing with gyroscopic precession or aerodynamic precession along with retreating blade stall asking individual participants to define these phenomena and describe what happens and why. I personally believe that the reason many of you side with what RW-1 is that I don’t accept your reasoning.

I don’t know if I get the quote correct but it was once said that a common language separates the English and the Americans. The reason many of you disagree with me is that I am promoting the American viewpoint on these two subject areas and you were trained under an entirely different concept and that concept works for you. Conversely, My concept, which is taught in the USA, works for me. We really should not be arguing our respective points because the other guy will never be persuaded that he is wrong.

If you open the thread you will find out that many of you will disagree with each other on these subjects and many of you will reveal in your postings that you really don’t understand the subjects.

Now, let’s see if RW-1 jumps on this idea.

Regarding my removal of the thread I did it because of the lead post on this thread not because of any other influence or other post.

[ShyTorque]

Lu,

Actually the quote was "we gave you the English language - and look what you did to it!"

[RW-1]

Discus it on another thread, I am not going back to this, my thoughts are as well known as Nick's and those who are done with it.

But you make those of us in that category gag as you are now blaming you inability to understand concepts explained to you by both Brit and American pilots as a difference in language. You continue to stretch the limits of excuses.


>>Regarding my removal of the thread I did it because of the lead post on this thread not because of any other influence or other post.<<

Oh, so you mean my first response, that essentially said if Nick tells you you were full of it (which he did by the 4th posting) you would do exactly what I said you would do? Gee, how would I have predicted that so early on hmm?

The title of your last thread is something you will never live down, no matter what you want to say as to it's cancellation by you.

You couldn't re-edit the title, and you didn't take it as the "ultimate arbitration": Everyone can make that inferance without knowing anything else about the posts within.

That dog won't hunt.

You have two choices now, you can go to the other thread, actually two, and begin.

Or you can continue to try to answer my accurate observations I just made in this post, which would let everyone know that I am correct as to what is important to you.

Good luck to you, for I see the other two threads ending up as the last one.

[ 04 August 2001: Message edited by: RW-1 ]

[Kyrilian]

ShyTorque,
Not to start an English language debate, but I thought it was "two nations divided by a common language"

[imabell]

to suggest that the theory of helicopter flight could be so different on two continents is a joke, as is inferred by the statement that we speak a different language therefore our concept is different.
are our teaching methods in australia different again. wake up.

[ShyTorque]

Yes, mate, it must be. Your helicopters fly upside down!



ShyT

[Lu Zuckerman]

To: Imabell

What I was implying is that the engineering philosophies in presenting POF are different. I said this many posts ago that if a UK or OZ helicopter instructor were to conduct a course in POF to students in the USA that had previously learned this subject from their instructors they would think the UK or OZ instructor to be daft. It has nothing to do with language it has everything to do with philosophy and concepts. Now, your understanding of the subject may be spot on but it doesn’t fly in the USA at least, in technical and service schools for pilots and mechanics as they for the most part teach gyroscopic precession and phase angles of 90-degrees. The concept is very easy to present when you look at the lead angle of the Bell rotor system of 90-degrees relative to the displacement of the swashplate of 90-degrees ahead in rotation. On all Sikorsky helicopters but with the possible exception it seems of the S-76 the servo positions are displaced at 45-degrees ahead of the desired disc displacement and the pitch horn is placed 45-degrees ahead of the blade. It all adds up to 90-degrees of phase angle.

The blades may move exactly the way that Nick Lappos indicated and for all of the technical reasons he indicated. However to try to teach this engineering concept to pilots and mechanics you would lose your audience at least in the USA.

[Thud_and_Blunder]

Ah, a thumbs-down at the beginning of the post again; it can mean only one thing.

Actually Lu, you're not often right but you're wrong this time. The only people in the audience who'd be lost would be those who can't/won't listen - sound familiar?. None of the exchange QHIs we've had from the States over here (some of whom have been good enough to win the theory and flying prizes, I might add) have had any difficulty grasping the concepts so clearly stated here and elsewhere.

[Lu Zuckerman]

If you studied the subject in a university it would be most likely taught in the same manner it is taught in the UK. All I am saying is that in the factory schools in the states and in most military training schools that I am familiar with, they teach gyroscopic precession because it is easy to understand. Now in some people’s minds this theory is incorrect and does not reflect the world of science and they may be correct. But, until the schools in the United States start to teach it your way. I will have to stick to my story. You may think I’m wrong but as long as I stay on my side of the pond I will not have to argue the point if I get into a discussion with an American pilot or mechanic because most of them learned the subject in the same way I did.

Regarding the thumbs down icon I will repeat what I said when this subject was raised on another thread: The very first post I made I noticed that many of the posts on that thread had thumbs up icons. I simply chose the thumbs down icon simply to be different. Sometimes the icon reflects my comments but it is not to be taken seriously by the individuals I was responding to. I would imagine that if I used the fish icon someone would eventually question me about that.

[RW-1]

Simply another excuse that takes the misunderstanding "off" of LZ and transfers it to the educational system.

Just stick to the new threads, learn to use the Message Icons, the others do work ...

You are not fooling anyone from both continents with such nonsense.

[ 08 August 2001: Message edited by: RW-1 ]

[Lu Zuckerman]

To: RW-1

This material was lifted from your website and it explains GYROSCOPIC PRECESSION in exactly the same way I do yet you keep challenging me on every point. I ask in front of the forum, do you believe in what is posted as a part of your web site? If you don’t then remove it and replace it with a more palatable dogma.

GYROSCOPIC PRECESSION is a phenomenon occurring in rotating bodies in which an applied force is manifested 90 degrees later in the direction of rotation from where the force was applied.

Although PRECESSION is not a dominant force in rotary-wing aerodynamics, it must be reckoned with because turning rotor systems exhibit some of the characteristics of a GYRO. The graphic shows how PRECESSION effects the rotor disk when force is applied at a given point:

The material below was attached to an illustration of what appears to be a Bell swashplate.

This same material also appears on Robinson sponsored websites.

A downward force applied to the disk at point A results in a downward change in disk attitude at point B, and an upward force applied at Point C results in an upward change in disk attitude at point D.


Forces applied to a spinning rotor disk by control input or by wind gusts will react as follows:
This behavior explains some of the fundamental effects occurring during various helicopter maneuvers.

For example;

The helicopter behaves differently when rolling into a right turn than when rolling into a left turn.
During the roll into a left turn, the pilot will have to correct for a nose down tendency in order to maintain altitude. This correction is required because PRECESSION causes a nose down tendency and because the tilted disk produces less vertical lift to counteract gravity.
Conversely, during the roll into a right turn, PRECESSION will cause a nose up tendency while the tilted disk will produce less vertical lift.
Pilot input required to maintain altitude is significantly different during a right turn than during a left turn, because GYROSCOPIC PRECESSION acts in opposite directions for each.

[imabell]

rubbish lz, i trained at el monte on enstroms with dean cayot in 77 and on the first production robbie at pacific wing and rotor with tim tucker on long beach airport.

i was the first person from australia to do so.

i learnt the american way. basically no aerodynamic theory at all.

i have been teaching theory for twenty years and have never heard so much inane comment by you about "different concepts of the theory of flight".

there are of course arguments about how it
works and that's good fun. newtons third law of every action etc, and it just beats the crap out of the air, but the notion that things work differently at different positions on the earth is ludicrous.

the fact is that designers create machines that work using the theory or fact that exists on the day. if they don't work they design it better.

if it is designed against that concept there is a pretty good chance that it will fail.

one of the ideas that i try to get through to students is that if you don't understand how helicopers work you won't be able to make them work properly and i have managed to train some pretty good ones over the years.

sanity and logic must prevail in the long run.

it could be assumed that you write purely to antagonise and that is your only motive. if this is the right concept that i and others have then you are immensly successful.

it seems that you cannot see that you are usually the only one out of step in the whole army.

[Lu Zuckerman]

To: imabell

I too have taught POF to both mechanics and pilots and I believe they accepted what I put out in these classes. I would well imagine that if you locked my students and your students in a room they would be having the same argument that you and I are having. The basic argument stems from the differing philosophies relative to POF. There are differences in the teaching of POF and the major differences exist between the UK and OZ collectively and my methodology which deals with pure gyroscopic precession as the moving force and the aerodynamic forces that are involved in initiating gyroscopic precession.

I am not saying that you or the guys from the UK are wrong because the theory you teach is more closely allied with what Nick has said because it teaches the engineering principles involved in moving the blades from one point of the disc tip path to another. It is just that my philosophy is more easily understood by US Army mechanics and Warrant officers that were in most cases not better educated than the mechanic students.

Here is the way I would teach it and actually it is the way I teach it. Most likely you will say it is wrong. I say it can be accepted as an alternative theory. I first posted this on Just helicopters last year.

Try to visualize this, or better still, pick up a pencil and paper and draw a picture of a circle. Cut the circle into four equal parts. On the circumference of the circle where one line meets, write the letter N for North. Now, label the other lines East, West and South. North is the direction the helicopter is flying. The existing way of teaching helo aerodynamics is to say that the blade is stalled over West and because the blades have a precession angle of 90 degrees the effect will take place 90 degrees later or, over South. That sounds reasonable, but can you picture a blade that has a tip speed near the speed of sound flying from an in track position at West to a stalled position over the tail cone at South. Now, try and picture that same blade flying from that low position over South to an in track position over the right side at East. Then, because the pilot has the cyclic in a forward position, that same blade, because of precession, will be flying low over the nose or, North and back up to an in track position over West and then, it starts all over again at the rate of say 250 or more times a minute. Try to visualize the vibratory forces involved if the blade in fact acted as an individual unit.

I would suggest that you stop thinking of individual blades flying in a circle. Instead, think of the blades as a solid disc just like the rotor on a gyroscope. If you apply a force to a gyro that is on gimbals, the gyro because of precession will react 90 degrees later in the direction of rotation. The same is true on a helicopter. Cyclic input will change the pitch relationship across the disc and will result in an imbalance of forces. If the pilot pushes the stick forward, the greater force is over the West side of the disc. This upward force (due to precession) will cause the disc to raise over South and drop over North. Aerodynamics plays a minimal part in this action. The change in disc position was caused
by the change in lift forces but the actual movement was caused by the gyroscopic characteristics of the spinning disc.
Blades do not fly to a position, the are moved by gyroscopic forces. If you want to call it blade stall that’s OK. When you enter the realm of blade stall there are ways of getting out of it but once it happens, individual blade do not stall. They simply change the balance of forces across the disc and physics does the rest.

[heedm]

Lu,

Have you read my long description of gyroscopic precession? If you follow through it, you should find that the blade flying to position theory and gyroscopic precession are the same, under certain conditions.

Most rotor systems don't meet those conditions precisely, so I don't think gyroscopic precession is an accurate general description of helicopter dynamics, but it is true in some cases and close in others.

I do, however, believe it is a good subject to introduce so students can understand thru visuals how rotational dynamics isn't intuitive.

Matthew.

[helmet fire]

Lets look at this yet again. I have added my input to your quote below Lu. I have added it in capitals to distinguish it from your words, the capitals are not intended to be “shouting”. I presume that you are talking about a disc in forward flight.
Lu, you said: >>Try to visualize this, or better still, pick up a pencil and paper and draw a picture of a circle. Cut the circle into four equal parts. On the circumference of the circle where one line meets, write the letter N for North. Now, label the other lines East, West and South. North is the direction the helicopter is flying. The existing way of teaching helo aerodynamics is to say that the blade is stalled over West NO IT IS NOT TAUGHT LIKE THIS AT FT RUCKER, NOR IN OZ/UK TO MY KNOWLEDGE. SEE FLAPPING TO EQUALITY. and because the blades have a precession angle of 90 degrees the effect will take place 90 degrees later or, over South. That sounds reasonable, but can you picture a blade that has a tip speed near the speed of sound flying from an in track position at West to a stalled position over the tail cone at South. THIS IS NOT AT ALL TRUE. SEE FLAPPING TO EQUALITY. Now, try and picture that same blade flying from that low position over South to an in track position over the right side at East. Then, because the pilot has the cyclic in a forward position, that same blade, because of precession, will be flying low over the nose or, North and back up to an in track position over West and then, it starts all over again at the rate of say 250 or more times a minute. Try to visualize the vibratory forces involved if the blade in fact acted as an individual unit. IF THE BLADE WERE INDIVIDUAL YOUR HELICOPTER WOULD BE MASSIVELY OUT OF BALANCE AND YOUR FORWARD CYCLIC WOULD BE THE LEAST OF YOUR CONCERNS.
You also say >> blade flying from that low position over South to<< and then say: >> that same blade, because of precession, will be flying low over the nose or, North<< .
Think about it Lu, this would mean that front and back would be low……..so tell me how we fly in a direction?
If you are teaching this, your teaching qualification needs to be examined.
If you want to keep it simple, use gyroscopic precession as it neatly explains everything simply, as per Ft Rucker. BUT, if you want to teach reality, it is more accurate to use aerodynamic precession. See Heedm’s excellent explanations, But either way, stop teaching the above…it is not true.

[Lu Zuckerman]

To: Helmet Fire

I do not teach it that way. The entire text was in response to those individuals that believe that when the blade stalls over the left side it drops down because of the stalling. The way I teach it is as follows;

In order for a helicopter to fly the rotor must generate equal lift across the disc otherwise there would be a rolling moment and subsequent pitching of the disc. In a retreating blade stall condition the right side of the disc is generating more lift than the left side. It is this differential of lift that causes the disc to raise 90-degrees later and the disc flaps back. However it is not instantaneous so the disc will become unstable and the lift differential will generate a left rolling moment. Shortly thereafter the rolling moment will manifest itself by causing the disc to flap back due to gyroscopic precession.

In order for you or anyone else to accept that theory you must accept gyroscopic precession and the lift equality/Lift inequality concept. If you don’t, then the last few minutes on the keyboard were in vain.

A similar condition exists in the inflow roll/transverse flow effect. There is a lift differential resulting in gyroscopic precession causing a rolling moment. The reason the roll is not as violent as retreating blade stall is that you are moving at about 20-Knots and not the speeds required to induce retreating blade stall.

I shall now retreat to the bomb shelter.

[RW-1]

No, you need to learn and accept flapping to equality.

[collective bias]

RW-1 and Helmetfire,
Please guys; I started this thread to encourage this to be dropped.
RW-1 you know as well as the rest of us that no amount of typing will ever change Lu's mind and that is his perogative. Still its your time but my opinion is just don't reply. You just supply more ammo.
RW1 sorry for not replying....I have been busy moving hemispheres.
Regards CB