RBS, precession & LZ

[helmet fire]

This thread has begun at the suggestion of Lu (see vote thread).

I have seen many of Lu’s posts, and I believe that his search for understanding needs to start back with first principles, so I will have a go at retreating blade stall whilst (hopefully) demonstrating to Lu that he needs to go back to basics first…………………

To Lu: you need to grasp first aerodynamic POF before you can hope to grasp the explanations offered by so many in various threads. You particularly need to understand how FLAPPING TO EQUALITY, achieves EQUALITY OF LIFT. These concepts were ably explained to you in the last thread by Arm out the window, with almost no acknowledgement from you, but once you understand these basic POF concepts, most of the explanations offered to you will become more easily understood. After all, your stated aim is to understand.

Why am I going down this path? Some examples….

You have persisted with the notion that the rotor disc has different lift in different areas: You said: >> If it were pure aerodynamics the helicopter would roll to the right because of the differential of lift across the disc<<. This is NOT TRUE. The DISSYMETRY OF LIFT (not differential) is equalised by the blades FLAPPING TO EQUALITY, thus we have the steady state situation of lift being equal across the entire disc from entirely aerodynamic processes.

You said: >>When a helicopter is in the flight regime that will result in retreating blade stall the blade does not stall like a wing on an airplane. Most people think that when the blade stalls it drops out of the tip path and strikes the tail boom this is not true. What happens, is the left side of the rotor system although it has higher pitch it is generating less lift than the right side of the disc. This differential of lift will cause the perturbing force to be on the right side and like the rotor on a gyro the disc will tip up over the nose and down over the tail<<.

NOT TRUE

A rotor blade stall is entirely consistent with a wing on an aeroplane that enters a stall. BECAUSE A ROTOR BLADE IS A WING (maybe that’s why they call them “rotary wing” aircraft). The blade does NOT become >>suddenly unstable<< as you have asserted. It does NOT have a higher pitch angle. It does not suddenly fall out of the plane of rotation. It does not even lose all lift. The stall is caused by the blade exceeding its critical angle of attack (AoA), as opposed to pitch angle, due to the airspeed/AoA relationship, just like a fixed wing. As the blade approaches the critical AoA, it is still generating significant lift, but the drag is beginning to increase dramatically. Further increase in the AoA produces the buffet where airflow begins to break its laminar flow over the aerofoil and lift dramatically decreases whilst drag dramatically increases.

At this point in the process, a DISSYMETRY OF LIFT situation is created because of the rapid loss of lift from the retreating blade side and the blade is unable to flap to equality from this situation. Accordingly FOR PURELY AERODYNAMIC reasons, the aircraft will roll toward its retreating blade side. The stalled blade begins to reduce its upward movement (remember the retreating blade is normally climbing), but due to rotation, the airflow changes and the blade quickly becomes unstalled, and resumes its climb toward the highest point of the disc over the tailboom. Because the stall interrupts the blade’s climb, it can no longer reach its pre stall height over the tail boom, hence the tip path plane is lower at the rear when in retreating blade stall. Accordingly, the aircraft will pitch nose up. How gyroscopics applies to this is beyond me. So what the pilot feels and sees is:
A number of blades per rev vibration (ie a two per in a B212, a four per in a S76) rapidly building in severity, a pitch up and roll moment toward the retreating blade side.

By lowering the collective, the pilot can bring the blade out of the stall and recover the aircraft. BUT here is the crunch: when it recovers this way, there is a restoration of flapping to equality and lift is again equalized across the disc and therefore the disc DOES NOT SUDDENLY ROLL BACK TOWARD THE ADVANCING SIDE. So why des the nose try to gently pitch down if there are no GYROSCOPIC roll moments applied? Because the blade again climbs to a higher high point over the tail (the upward movement around the retreating side is no longer disrupted by the stall) and the aircraft will pitch VERY gently nose down (if you are brave enough to let it). IE an aerodynamic situation.

There is more:

You said: >> I won’t challenge your statement that you allude to as pure crap as that would take too much time but I will address one point. I made the comment about the Bell blades not having equal lift when the blades passed over the longitudinal centerline. I caught a lot of flack on that so; I contacted the that showed what causes the two per rev. At approximately 5-7 degrees ahead of the lateral centerline the advancing blade will cause an upward movement. Just like the explanations of Nick and Frank. He explained that this upward movement was the cause of the two per rev. Now as I addressed the movement of the transmission on the 214 it moved not only up, it moved down by the same amount. that if the advancing blade made the transmission move up then what makes it move down. is the blade loses lift at some point and the transmission falls. When the next blade comes around the trannie moves up and this happens at twice the rotor speed. Based on this, I would like to hear some of your opinions.<<

My opinion? You caught a lot of flack because what you are saying is NOT TRUE.
The Facts? See Nick Lappos’ excellent description of the causes of the vibration. If you look back over your statement, you will see the key to understanding what people are trying to tell you……

You said: >>[The]senior aerodynamicist at Bell….sent me some engineering diagrams. I didn’t fully understand the diagrams. My mind tells me. The only thing I can think of.<<

When you don’t understand, you do not ask, you create a theory in your own mind and reject explanations that do not accord with your theory. I believe that if you understood equality of lift as achieved by flapping to equality, you will be equipped with the basic tools you need to help you understand the rest of the discussions presented to you. Good luck in your search for understanding Lu.

For others.....have I grasped retreating blade stall? It has been a long time since I have reached into these memory banks.

AAARRRGGGGHHH my helmet is on fire……………..

[ 04 August 2001: Message edited by: helmet fire ]

[ShyTorque]

I think it's about right!

It needs to be borne in mind that the blade cannot be thought of as a single wing like that of an aeroplane because of the variance of airspeeds seen by the blade from root to tip (very high speed near the tip, very slow near the blade root). That is why the blade is designed with twist and sometimes with profile and size variations along its lentgh.

As soon as the helicopter moves away from the hover, the blade on the retreating side is experiencing a reduction in airspeed and the inner portions / elements will very soon reach a stalled condition folowed by a reversal of airflow i.e. negative airspeed.

To put some simple figures on that (the only type most pilots like):

Rotational velocity = circumference of circle times rotor rpm = 2 x "pi" x R x N

"pi" = 3.142, R = distance from centre of rotor hub and N = rotor rpm.

A blade element 1 foot out sees 14.3 mph

A blade element 2 feet out sees 28.6 mph

A blade element 20 feet out sees 286 mph

It should be seen that the inner part of a rotor may be stalled or very close to it even in the hover! Once the helicopter moves into forward flight the stalled area expands outwards. An area of not only stalled blade but with a reversed airflow follows it outwards from the centre as the forward airspeed increases. Retreating blade stall is very definitely not a sudden phenomena.

It is of even more complicated than this! The airflow is of course modified by the induced flow which affects the angle of attack of each blade element, and at low speeds this is significantly different from "front to back" of the disc with regard to the direction of travel (looks like we are into inflow roll and flap-back next!). :eek:

Just thought I'd remind folks of this.

ShyT

[ 04 August 2001: Message edited by: ShyTorque ]

[helmet fire]

To ShyT:
Thanks for that excellent info. You reminded me that the blade does not stall along its entire length, rather it starts with the hub and expands outwards and fore/aft of the 9 oclock position (American helos) as the stall deepens. Thanks.

To LZ:
RBS is not about precession per se, thats why it was addressed seperately to Dave Jackson's thread. Perhaps the topic title should have excluded it, but it entered this discussion because you attributed the nose up pitch experienced in RBS to gyroscopic precession. Hopefully, I have shown you an alternative explanation.

I note your comments about putting up theories for discussion, but arguing with known principles is not achieving anything. Your stated aim was to gain understanding and I am suggesting the road to that goal. The above explanation of a relatively straight forward situation is intended to help you grasp first principles so that your deeper discussions can be more benefitial to you, and less anoying for others. For example, there is no point discussing the effect of the moon on tidal fluctuations if you do not first accept that the earth is round and the moon orbits the earth. In our case, you need to understand flapping to equality before you can grasp phase lag, delta hinges, 2 per vibrations, flapping in a Bell teetering head, cyclic feathering, etc.

[ 04 August 2001: Message edited by: helmet fire ]

[sling load]

Lu,

Why is it you always start the majority of your posts with a thumbs down?

You can't take it, but you can sure dish it out mate.

You can disagree all you like with me, or I can disagree with you, but you cant fight science, maths and the laws of physics, which you seem to do very well, I endorse the above posts about UNDERSTANDING helicopter priciples of flight.

You however don't. I recall when you tried to comment on the mixing box of the CH-47 a few months ago and got trashed by very experienced pilots and instructors on that aircraft. You tried to pass off your theories off and up until that point you had everyone convinced that you were an expert on the Chinook, then you end the thread by saying, "thats my theory but I could be wrong". You also said that when a pilot is executing an autorotation "The pilot then lowers the collective to effect touchdown"

To which I replied" Please tell us that was a typo Lu"

To which you failed to respond.

You really don't understand fundamental helicopter aerodynamics, so you put theories forward to this forum to make yourself out to be an aerodynamic guru.

Concepts of understanding are way different to what you have been putting forward on your posts, you just don't understand.

If the above posts help other to understand the concepts of helicopter aerodynamics thats great!

Don't throw your stuff off as theories, they are set in concrete, and no matter what keeps you up at night be it a Robinson or an Airbus, your theories don't cut it.

You are not an Engineer,
You are not an Aerodynamicist
You are not a Pilot
You are not involved in rotor design
You are by experience an unlicensed A&P Mechanic, I think you should stick to that.

If you are trying to understand helicopter principles of flight by way of this forum and not expousing your theories, then all the other posts you have made are therefore, by definition, a misunderstanding of helicopter theory.

Thats fine, but don't pass your own theories off as an expert, you definately are not one.

Anyone who reads your posts should understand this.

Anyone whos interested should go to the top of the page, click forums for last 100 days,go to page 8, find the Subject of "Chinook Flying" then click on page 2 and read the stuff from Lu, then read the responses by the experts.

Lu, you just can never accept the experts

[ 05 August 2001: Message edited by: sling load ]

[sling load]

no response as usual

[MrPlod]

SLING LOAD 1

LU ZUCKERMAN 0


Very interesting reading on the Chinook posts

[Too Cloudy]

All this nastiness is making me very upset!!!
Must be time for a group cuddle!!!

[ 08 August 2001: Message edited by: Too Cloudy ]

[sling load]

Lu,
I have never stated I was right, my position is that of Nick Lappos, your position is to argue with everyone, and Im not talking about concepts of understanding, Im talking about theory.

You argue and try to knock theories, or convince people to beleive you are an expert, I have never tried to convince anyone im an expert, you however have.

Im a Helo driver with an ATP and over 3000 hrs m/e ifr sar/ems exp, Mon and Tues i beleive i was at University doing my Aerospace Engineering studies.

Lu, you are obviously trying to impress me with your reliability and maintenance work on the Rolls Royce Tay engine, hey, like i said, stick with what you know, thats great, but don't advise helicopter pilots how to fly if youre not one, and don't tell engineers theyre wrong if youre not one, and if you are trying to pursue a concept of understanding thats good too, if you are trying to be different for the sake of it, you are obviously trying to be noticed.

Trouble is Lu, youre being noticed for the wrong ideas.

All the Chinook drivers and instructors blew you out the water, while you offer your "thats my theory but I could be wrong ", up until that point you tried to convince everyone that you were an expert, sorry mate, you aren't. And neither am I an expert in Chinooks, but I have got quite a deal of flying behind me and some heavy aerodynamics studies ive done, but I AM IN NO POSITION to dish out criticism of a proven rotorhead design like you do, IM NOT QUALIFIED TO DO THAT LU.

[Arm out the window]

Contrary to the opinion expressed by Mr Thumbs Down, it's not a good idea to lower the collective as you're sliding along the ground at the bottom of an auto.

Keep the collective where it was when you finished cushioning on until the aircraft stops moving, then lower it, otherwise you'll probably have the blade flapping all over the place and cause damage to various bits of the airframe.

The thing about the blades stalling out and dropping is a crock!

[Arm out the window]

Lu,

What I was saying was that the collective shouldn't be lowered until all movement stops. This is because at very low RPM such as will be experienced at the bottom of an auto, you don't have much in the way of direct response to your cyclic inputs. Therefore, any blade flapping may lead to exaggerated disc movement and possible contact with parts of the airframe as you are bouncing along.

The collective should be held where it was when you finished cushioning on to the ground, definitely not lowered, as that would increase the likelihood of the blades getting low enough to strike the airframe.

The 'blade stalling and dropping' idea that you expressed above doesn't apply - even though they may not be flying very efficiently at these low speeds, positive pitch on the blades will always help to hold them up until you're ready to lower them (gently).

I was concerned because what you said in the post a few above seems to suggest that the collective should be lowered before the blades get slow enough to stall and drop quickly, allowing them to strike the tailboom or whatever.

That is what I was referring to as being a crock, and instead I would encourage pilots to definitely not lower the collective until all sliding or rocking motion at the bottom of an auto has ceased.

[sling load]

Thanks Arm Out the Window,

I went over this point exactly on another thread after Lu posted this rubbish.

SL

[jayteeto]

I must admit I am not a regular on rotorheads but as a CFS (H) Sqn staff chap with quite a bit of POF experience, I thought the explanation at the top of the page was brill summing RB Stall in one quick post. This chap Lu is WRONG, he says we are all entitled to an opinion, yes we are, he is WRONG however. Gyroscopic Shymoscopic. Let him deny all day, there are people in this world who will not accept they can be WRONG. Don't get stressed and slag him off because he is WRONG, he is entitled to his input. We all make mistakes,don't we?

[sling load]

Jayteeto,

Absolutely agree, you probably missed however, this Lu started a thread name "18 degrees Ask Nick Lappos the ultimate arbitration".

Lu has been bashing the R 22 design for a while, he asked Nick Lappos a highly regarded Sikorsky Test Pilot his opinion, eventually Nick got his point across, but as usual, Lu had to throw in his two cents back, at which point Lu started a slanging match because Nick did not agree, like we all, don't agree that the R-22 is "dangerous". Lu started a thread that went to about 100 posts and Lu decided to remove it, because of the caning he copped I supect, however Lu is still active telling all of us helo pilots that all we know about aerodynamics is really precession, and other "theories".

Go to his old posts, and you will make a judgement probably like the rest of us.

[ 09 August 2001: Message edited by: sling load ]

[RW-1]

I can absolutely guarantee that anyone that is from OZ or the UK or any country allied to them in language and government will say Lu Zuckerman is full of crap and so are his theories. What it appears to me is that all of the individuals that fit into the above nationalistic category say that I am wrong because they (you) believe you are right. I can accept that but it seems that none of you can accept an alternate theory because it conflicts with yours.

Naaah ....

It's pretty much the entire planet, but the ISS astronauts haven't been polled yet, you could hold out for Jim Voss but ...

You haven't accepted anything since this started long ago, you fail to realize that no one will accept an "Alternate theory" that is plain wrong, and is not supported by FACTS. No one here has countered your drivel with a theory, just facts.

Several personnel have tried to prove your theory, something you yourself have refused to do on your own, and they all have reported back: What you predict doesn't happen.

When a theory is not proven, it is discarded.

You are the only one who seems to have a problem with that. But then As I have repeated so many times, if you didn't have that one theory to banter on about endlessly, you would no longer have a reason to be here, for the Robbie Ranting seems to be your only calling.

Your theory is not correct, it has not been proven by numerous people in the know. It has been discarded by everyone but yourself, the only reason it continues here is you.

Your answering everyone else is just from the FACT that you either want to have the last word (which is still meaningless in light of the flawed theories), or from the fact that you still will not accept that you are just plain wrong.

My thought is both, and as in the other threads you have started or busted into, you will now dredge up any number of sorry sad excuses to continue, make other personal observations of me and others (the pond education division theory was a nice try, but just who you kidding here?, no one is falling for it)

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

[Nick Lappos]

Lu Zuckerman said:
I can absolutely guarantee that anyone that is from OZ or the UK or any country allied to them in language and government will say Lu Zuckerman is full of crap and so are his theories.

Nick sez:

Oh well, I really like the US, but considering how I feel on this issue, I guess I have to move to Oz or the UK now. How's the beer, mate? :D

[Arm out the window]

Nick, the beer's nice, cold and tasty. Or, if you're going to the UK, warm and tasty. ;)

I assume Lu's done a comprehensive world survey to support his obviously well-founded claim that he can personally guarantee what everyone in the UK or Aust helicopter fraternities thinks.

[ 09 August 2001: Message edited by: Arm out the window ]

[ShyTorque]

Nick,

Are you sure you want to move? You would be made very welcome but rotor blades go the opposite way over here in UK and even worse, helicopters fly upside down in Oz..

Wait a minute - maybe that's the whole problem. Perhaps gyroscopic precession only works one way round....

ShyT

:D

[Arm out the window]

Lu,

I do believe that aerodynamic forces are largely responsible for the motions of rotor blades in response to pitch and airflow changes, and that the 'gyroscopic precession' explanation is just a convenient teaching tool

However, I also think that because rotors are large heavy whirling masses, I would be a mug to discount entirely the effects of gyroscopic forces on how they behave.

So yes, I subscribe to the 'aerodynamics' school of thought on the subject, but I'm sure it's more complex than any of us can understand or describe.

My two objections to your posts above are:

1. You seemed to be telling people that they should lower the collective after an auto to prevent the blades stalling and dropping suddenly. I strongly believe that is bad advice, for the reasons I gave before, and I know from experience that your reasoning is flawed in regard to that point.

2. Your statement about the aerodynamic vs. gyroscopic theories and how they apply to different countries and groups of people is probably broadly true, in that we tend to repeat the things we were taught, but I didn't want to let your sweeping generalisations go unchallenged.

Read back over your statement - how can you possibly guarantee, as you did, that everyone in those groups think as you say they do?

I like reading some of your stuff, but I don't think it's right to pass off your opinions as fact.

[Mark Six]

LZ, it's not just Oz and UK pilots that disagree with you. Remember the "Just Helicopters" forum? Most of the contributors to that are from North America, and they told you where to go with your theories in no uncertain terms, to the point that you vowed to stop posting. Virtually the next day you popped up on Pprune and started all over again. You got the same reaction, only with a lot less vitriol.

[helmet fire]

Lu,

I, like Arm out the window, believe the aerodynamic theory whilst not entirely discounting gyroscopics because I do not fully understand some of the more complex dynamics. BUT, I note that you have focussed on gyroscopics in this thread, despite the fact that it is an attempt to help you understand RBS. See the original post, and my response to your first post on this thread.

So rather than just go >>on and on<< as you said above, how about reponding to the topic at hand....RBS, and your need to grasp flapping to equality in order to apply fundamental background logic to your theories? If you can describe them in terms of this, you will have many more followers than detractors. I reiterate my above comments on having to understand that the earth is round before discussing tidal fluctuations.

You will never understand any one's reply to you until you grasp flapping to equality.

[heedm]

I'll make one quick observation related to RBS, in reference to helmet fire's originating post.

Good explanation throughout that post. I agree with your theory, but there are some parts where you haven't explained through. For example, you said, "Because the stall interrupts the blade’s climb, it can no longer reach its pre stall height over the tail boom, hence the tip path plane is lower at the rear when in retreating blade stall.".

I agree that interrupting that climb would change the tip path plane, but nothing you said indicates that the disk maintains it's orientation, other than lower at the rear (ie it doesn't tilt to the left or right). It doesn't go on to explain why the tip path rises in the front. I'd almost expect the front to be even lower since the blade starts it's forward sweep from a lower position.

I can answer these questions. The interrupted lift on the left side of the disk acts similiar to inputting aft cyclic. Whatever explanation you want to give at this point will fill in the blanks I have above. I prefer an aerodynamic explanation that talks about rotational dynamics, but I do find the gyroscopic precession explanation legible even though in most rotors it is not completely accurate.


Matthew.

[helmet fire]

Thanks Heedm, good point.
You said: >>The interrupted lift on the left side of the disk acts similar to inputting aft cyclic. Whatever explanation you want to give at this point will fill in the blanks I have above.<<

I agree, it does act similarly (I think) to aft cyclic but I would like to avoid reference to a different cyclic position because it introduces more variables. Perhaps I should have explained it thus:

As the stall causes the blade to reach a reduced high point over the tail, the tip path plane can effectively be now thought of as lower at the rear than the pre stall condition. As the system attempts to align the rotor mast perpendicular to the tip path plane, the lower rear blade position will manifest itself as a fuselage pitch up, i.e. the nose pitches up.

How does that sound?

[sling load]

Lu,
A POSTCARD FROM THE COLONIES

Things down here in the Colony are going well, a woman was burned at the stake for being a witch, and a few thousand arrived by prison hulk for stealing bread.

There was also a public whipping for a guy teaching gyroscopic precession, down here in the colonies, we frown on that.

The kangaroos are causing trouble in the main square and the Koalas fall out of the trees because their gyroscopes don't work well.

We got a letter from the old country and things are still pretty glum there, no talk of precession at all, even in the pubs, only aerodynamics.

At least the beer is cold.

Farewell from the Colony :D

[heedm]

helmet fire, your explanation seems sound.

However, I still don't see how it explains the disk rising at the front. Does the disk rise at the front? I don't know.

Matthew.

[sling load]

Sorry Lu,
We havn't been called a Colony for quite some time

[Chiplight]

Frank Robinson's post explained why the swashplate links are rotated 18 degrees away from where Lu would like them to be in the Robbie.

Lu maintains that a cross coupling exists that will make the R22 rotor tilt in a diferent direction than what it is commanded to do. Ho-Hum we've been through this.

Helicopter pilots understand that the rotor takes 1/4 turn to respond to a cyclic input(90 degrees).
Those with an engineering backround know that this lag can be altered by such things as delta3 or pitch-flap coupling, offset flap hinges, etc. Lu does not buy it.

But here is the kicker:
Let's assume that Lu is right somehow, and the R22, with its 18 degree mis-rigged head will have the rotor tilt slightly left and forward in response to strictly forward stick....

Even if this were true, I believe that the cross coupling error would be a momentary event.
In other words, when the cyclic is moved, the rotor would respond as Lu suggests, but then would quickly wobble around to the correct orientation.
The controls can be rigged with 90, 72, 63 or whatever degrees and the rotor will still follow the plane of the swashplate.

The swashplate tilts exactly in the direction that the cyclic is pointed, right?
The rotor disk must be perfectly parallel to the swashplate or it will see a cyclic pitch change.
If the rotor disk is not parallel to the swashplate, it will re-orient itself until it gets there. If there is a gamma angle of 72 degrees instead of 90, it will take a few revolutions of the rotor for the disk to get settled down, but the rotor will always wind up parallel to the swashplate.

I found ammunition to support this idea at :
http://www.cartercopters.com/pressrel30.html

They have spectacular photos of a prop spinner disintegrating in flight.
Down lower on the page it talks about their delta 3 rotor head and how it has a momentary rotor response in the wrong direction.

Floyd

[ 11 August 2001: Message edited by: Floyd Dan ]

[ 11 August 2001: Message edited by: Floyd Dan ]

[RW-1]

After having it shoved down my throat by so many individuals that didn’t even understand the concept I accepted it with one caveat and that was to have a conversation with Ray Prouty and get his read on the subject.


GET YOUR ACT STRAIGHT OLD MAN.

Yopu announced it as "The ultimate arbitration" intending to get the end all answer from Nick Lappos, and you didn't like his answeer, so you ran to hide behind Ray Prouty, whom you claimed called you out of the blue when in fact you called him.

No one knows just what you told him, but one thing is certain, he wasn't given all the FACTS, and you likely DIDN'T understand his response.

And you have never accepted anything presented to you here. You didn't in the above statement as well, round and round it goes ... Have at it with the rest of them.

I guarentee that it will end up like any other LZ thread ...

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

[RW-1]

No, you didn't. You announced to all "I just received a call from Ray Prouty", someone to whom you have placed disagreements with in the past. You made no mention that you called him, etc.

You ran to him because your arbitrator didn't live up to your expectations,period.

You removed the thread after I made mention to this, that you would never live that thread down, and you still will not.

Plain and simple, the thread was to be your end all, but it didn't go that way, anyone here who read it can be witness, and you needed to give the possible comment from Ray the only weight you had left on that thread, otherwise it was over.

Let's get something straight here, now your arrogance says that the forum will die without you, another demanted theory, did you tell them that at JH before they booted you? JH is still there. Some wish you would fade away and PPRUNE rotorheads will not suffer at all, will not fade away, but can get on with business instead of constantly trying to educate one LZ. Why not do what normal newbies/wannabies do? Lurk. You are close to the ground anyway, it should be normal for you.

When, not if (for reasons given again and again by everyone) you finally decide that you were incorrect, then we all can move on I'm movin on now, for I have some weather flying to do this PM ... But I predict you will still play the semantic game until that has been exhausted as well.

You are not worth anyone's time, you have to resort to wind up's to get a response at this point.

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

[helmet fire]

To heedm, you said:
>>However, I still don't see how it explains the disk rising at the front. Does the disk rise at the front?<<

No, the disc does not rise at the front per se, in fact this is the reason I try to avoid comparing the pitch up to aft cyclic. The term “rotor disc” should never be thought of as a solid entity (sorry Lu), rather it should be thought of in terms of individual blades. The term is used purely for simplicity of description and ease of understanding. (I believe this was one of the points you were alluding to in your excellent description of gyroscopic precession.) Accordingly, when the rear blade no longer climbs as high in RBS as it did in the pre stall, there is no corresponding effect on the height of the front blade because the disc/tip path plane is not solid. The effect is that the tip path plane (again not a solid entity as such) is lowered at the rear without being heightened at the front. Hence the aircraft attempts to realign itself with the new tip path plane by pitching nose up.

Hope that helps. Please bear in mind that I am no aerodynamics expert, so I may be going off on a tangent.

[helmet fire]

To Lu,

I note that you continue to avoid discussion on specific points by diverting discussion. Until you can keep it on track, I do not think you will be able to achieve your stated aim of being able to understand some of the POF discussed on the forum. An example?

You said on the “vote” thread, Page 3 post 5: >> Here is the way I would teach it and actually it is the way I teach it<< and then you went on to describe your method.

In post 7 on the same page, I dissected your statement to show you where your understandings are incorrect and in need of flapping to equality/cyclic feathering understanding.

Your response to that was in post 8 on the same page, and I quote:

>>To: Helmet Fire
I do not teach it that way.<<

Lu, can you not see the contradiction from what you said in post 5? Why do you deflect the discussion to irrelevant details such as wether or not you do/don’t teach it that way rather than try and benefit from the explanations offered? You did not acknowledge that any points were even made.

For example, you have avoided any response to my opening posts on RBS, and on which parts of your understanding are flawed. Even in your new explanation of how you “really” teach it you are mixing concepts. You said:

>>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.<<

This is not true Lu. The disc does not raise at the back, the rear blade is just unable to climb as high as it did in the pre stall condition, creating an apparent lowering of the tip path plane at the rear of the disc. Flap back is a completely different phenomena unrelated to this discussion, rather it is applicable to changing of airspeeds over the disc and flapping to equality/cyclic feathering (see explanation by Arm out the window on gyroscopic thread). This use of incorrect terminology is continued in your repeated reference to pitch instead of Angle of Attack, amongst other things. Unfortunately, the incorrect usage hints at a lack of understanding of application, so you might want to tighten up your terminology, and I am using US terminology here.

You continued by saying: >>However it is not instantaneous [ie the stall] so the disc will become unstable and the lift differential will generate a left rolling moment.<<

As stated in the posts above (that you ignored), the disc does NOT become unstable. The disc cannot be thought of as a solid entity. As pointed out above by ShyT, only sections of an individual blade enter and leave the stalled state during its revolution through the retreating side. Perhaps it is semantics, but I would say that even the individual blade is not “unstable” in this condition. It was bought to your attention in previous posts on this thread that the blade does not suddenly drop, etc (you ignored this too).
Lastly, you finish your explanation with:

>>Shortly thereafter the rolling moment will manifest itself by causing the disc to flap back due to gyroscopic precession.<<

Flap back is not related to this discussion, as per above (see Arm out the window’s explanation on flapping to equality/cyclic feathering). I will not go into the gyroscopic bit as I do not full understand the dynamics of gyroscopes, but in my original post, I had a go at describing recovering from RBS. In that description I noted that you get a pitch down in the absence of a rolling moment. I note that you ignored it too.

There is not a difference of opinion being discussed here (Mr Prouty and Ft Rucker teach flapping to equality and cyclic feathering), so please do not divert the conversation by saying its just a difference of opinion. You will never develop in your knowledge if you cannot start from sound first principles.

A disclaimer: I am no expert, and some of you will no doubt see flaws in my explanations, so dig in, I am here to learn too. I need a drink now…..

[sling load]

Lu,
Your reputation has been slaughtered by your own words, your way of understanding is flawed by the fact that you, as an unqualified person, cannot accept PROVEN theory of EXPERTS in their field. You persist with "ive been teaching it this way" and " this is what i was told" and " One guy at so and so said .....".

LU, GIVE IT A REST and get on with your real job, you are reducing this forum to how Just Helicopters is, you tried your rubbish there and got trashed, you are bitter and twisted about something, don't take it out on us, this is the pilots forum............ if the bloody concept doesn't work my guess is that all of the people here at pprune would be dead............


You are a nasty piece of work when you use words like" if Ray Prouty disagrees with Nick you go tell him he is full of crap" some professional you are.

Lu, you are WRONG ACCEPT IT AND GET A LIFE

[ 12 August 2001: Message edited by: sling load ]

[ 12 August 2001: Message edited by: sling load ]

[RW-1]

Round and round ... Now it's the "poor me" speech, geez, you are that sad.

That post made no sense to anyone but you of course, because it is meant as another distraction and diversion.

You made a point, and EVERYONE told you you were wrong, experts and novices alike (not "Two People").

You choose to go into whatever excuse you can dredge up at this point, and you are getting quite far reaching in those, but that seems to be better to you than actually admitting you are incorrect, and finally moving on.

You truly are hopeless, but that was known from the beginning.

By the way the real tower is Babel, but your mispelling is appropriate, for you have babbled your way to a new low.

Again:

It's not a difference of opinion.
It's not a difference in educational methods.
Not a difference in teaching.
You have no "Alternate theory", it is garbage.

Others have placed FACTS to your theory, and it is down in flames.

Deciding that the difference in statements between two EXPERTS telling you you are WRONG, will not change that FACT.

And no matter how many people want to give you differing reasons for it, the key point for YOU to consider is how they all come together to tell you you are wrong. It is no coinsidence, but at this point that's all you have left. Divert away, but I know by now with Sling's post that you don't have anything left in terms of:

credibility.
believabilility.
knowledge base.
professionalism.
sadly I add "Guru status, but to most you never were to begin with.

Realize it, accept it and move on, for all you do now is give more misdirection, insults to those who are the true professionals in the field, and excuses.

Obviously the "Learning" you set out to do is not going to happen, for learning is accepting when you are wrong, and since you cannot do that, then it is impossible for you to move forward. You would rather argue the point, for if not, then you have:

No arguement.
No theory.
No "Alternate" theory (crap excuse), and the fact that you use the FLAWED deductions you come to an apply them to other subjects is what has most here wanting you to shut up, the only danger here is a new person actually believing your crap, that could get them into trouble.
No differing of educational systems.
No more "Robbie is unsafe" rantings.
And a long list of people that you owe apologies to, starting with FR, the FAA, the NTSB investigators, NL, and all of us on this forum who fly and also fly Robbies.

If you read the posts above, you will realize that that would be a step upwards for the level you are at now.

I can truly understand the bind you are in, for if there were no more Robbie rantings and circle misdirections about offsets, you would have nothing else to say here. No direction in life, etc.

You don't have to respond, you are compelled to respond:

I also know that like a 6 year old in an arguement, even when proven wrong you will want to get the last word, you can't shake that either, so have it, but you only serve to ring true everything I have outlined about you, your flawed theories, and your behaviour throughout the period of discussion.

You are an unqualified wannabe who cannot accept that he has placed his foot in mouth too many times. You may feel you are gaining something as it continues, and you are not: your supporter list declines each time.

Well, go ahead with another 2-3 paragraphs that no one will really want to read, for it is full of I have to, I meant to, Ithe manual isn't .. excuses, misdirection, etc.

It will be another diatribe to circumvent previous postings, renew other directions in any attempt to throw the reader fromt he plain facts:

You proposed the same sad theory again here, it was shot down by ... aw heck >Insert anyone's name here< and you run to another excuse, redirection, resupposition, anything you think will cause a failed theory to rise up and smite FACTS you CANNOT UNDERSTAND. Previous examples of this include:

Didn't like the american answer so you run to the UK.
They tell you your'e full of it, and now it's a "Difference in teaching"
THEN you go to america vs Ft. Rucker, and the Rucker CFI's tell you your'e full of it,
Asking A known heli test pilot for the "Ultimate arbitration of this crap, and when he gave you the same answer (any suprise here? Anyone? ) you then go off to Ray Prouty.

Hope all you want, you will NOT change a flawed theory into FACT by repeated preaching and misdirection.

Just isn't going to happen.


So, in short, either discuss the points being made without any other ties to this failed, flawed theory of yours (everyone else seems to be able to discuss the points involved, you never do unless you have a way of bringing it back to ... etc. etc.) or just admit that you have no other agenda than trying once again to push something that has been proven on all populated continents to be crap.

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

[Dave Jackson]

Lu; You're going to love this.

Direct quote from 'Helicopter Flight Dynamics: The Theory and Application of Flying Qualities and Simulation Modeling', 1999, by Gareth D. Padfield, page 417.

"Pitch-roll and roll-pitch cross-couplings can be powerful and insidious. The natural source of both are the gyroscopic and aerodynamic moments developed by the main rotor and, in dynamic maneuvers with large amplitude excursions, the uncommanded and sometimes unpredictable off-axis motion can require continuous attention by the pilot."


Have a good day.

[RW-1]

THEN AGAIN THERE ARE PEOPLE LIKE RW-1 WHO CRITICIZE MY EVERY STATEMENT BUT HE HAS YET IN THE HISTORY OF HIS POSTINGS OFFERED A CONCRETE RESPONSE AS TO WHY I AM WRONG. HE HAS NEVER POSTED A SINGLE RESPONSE TO ANY TECHNICAL MATTER OTHER THAN TO SAY I AM WRONG. OK RW-1 LET EVERYBODY KNOW WHY YOU FEEL I AM WRONG BY EXPOUNDING ON YOUR THEORY REGARDING GYROSCOPIC PRECESSION AND RETREATING BLADE STALL. I AND THE OTHER PARTICIPANTS AWAIT YOUR ANSWER.

You poor ignorant sod.

You have the burden of proof here, not I.

Do you really think that everyone here hasn't figured out that you can dish out garbage, but can't be told anything? It's a reocurring pattern with you, and your asking lowly I for an explaination that you have refused from those with FAR GREATER KNOWLEDGE AND EXPERIENCE only serves 2 things:

Lowers you believability and credability again. (Yet ANOTHER LZ wind up excuse)
Insults those who are in the industry.

Everyone here has at some point proven your flawed theory for what it is. People I might add that have way more experience than I.
and SINCE THEY HAVE DONE SO, I have no reason to argue the aero, you cannot change FACTS, no matter how you want to preach.

By the way, they are not statements you make anymore, but either wind ups designed to illicit response; or excuses for you not to face what all on both sides of the pond have shown you, etc.

Therefore this quoted para above is just another excuse for you not to face the facts.

Now you are saying that everything everyone else has said means nothing unless I can explain it to you, well, sorry sparky, what makes you think that you would admit you are wrong to me all of a sudden, when you have insulted and refused everyone else on the planet?

That dog won't hunt either, but nice try ... It was one of the last excuses you had left for your arguement, you have used it, so lets not try that again.

Just about what I said previously in a prediction of your responses, thank you for validating my observations about you, you only serve to add reliability to my observations about your upcoming actions/statements. :D

[RW-1]

To Lu Excuseman,

I havent "attacked" any other poster here because they show the capability of accepting when they are incorrect.

Refer back to above and previous posts so I don't have to retype all of it. :D

You don't get pissed, you are too ignorant to get pissed, your method of dealing with it is to just assume they have not the knowledge of the great LZ, so you ignore it. Too bad, so sad.

And I'm not pissed, for facts are facts.

Yet another posting by you that serves nothing but to delay the inevitable ...

You can say anything you want about me, I could care less, at least coming from you, that would be the LEAST of my worries, you poor sod.

as I know that they are made out of ignorance of the facts or a false perception of the facts. Tell me that you understand the technical intricacies of the subjects being discussed and offer sound technical reasons why I am wrong. At that point I might gain a bit of respect for you.

Gee, another repeat, I covered this above. Others have covered it with you, I have no need to do so. And as for gaining respect of someone at your level, who has annoyed and ticked off most of the working professionals int he industry, geez, that's just another arrogant statement, you thinking I want or need your respect. Well Lu, you are not above ground on the totem pole, remember to take yourself off that pedestal you placed yourself. I have no need of your respect, nor want it. And taking the thread in that direction serves only what I have been saying all along, you just can't stay on topic, you are compelled to answer.

Make your next statement, prove to all here that you CANNOT stay on track, and discuss the topic. If you are not the 6 year old i have proposed, then you will have no issues at all in ignoring this and moving on, but you and I both KNOW you cannot.

Now, if for some miraculous reason you manage to keep on topic and not give the same sorry excuses you have been doing, then, and ONLY then shall I not make further observations.

You have a good day now, and remember to take your afternoon nappy, right after cookies and milk. I've some flying to do. :D

This about sums it up: http://www.dynamicflight.com/lz.gif

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

[Arm out the window]

Got to be a bit cautious about getting caught in the crossfire between Lu and RW-1 here!

Lu - I put a post about aerodynamic flapping on one of the other threads.

What you're talking about in your last post, the disc flapping back with forward speed, is simply called 'flapback' in UK/Aust speak.

It's a pretty straightforward idea, which if you will indulge me I'll expound a bit about here, to clarify it. As I said on the other thread, if you already know about this, excuse me telling you how to suck eggs.

As you tilt the cyclic forward, the control orbit, ie the path that the rotating part of the swash plate follows also tilts forward. The disc quickly aligns itself with that plane (aerodynamically, I reckon, but obviously we may differ on that point!).

As the helicopter moves forward, the advancing blade has a greater airspeed and generates more lift, and this lift is at a maximum on your right (anticlockwise when viewed from above direction of rotation).

If the blades were rigidly attached, the helicopter would roll left. However, they are free to flap to a position of equilibrium between lift (pushing them up)and rotational forces (throwing them out and down towards the horizontal).

Now, the key to understanding aerodynamic flapping is that where the lift force is greatest, the blades will flap up at the maximum rate; therefore directly on our right, they are flapping up fastest.

However, at any point on the advancing side, there is more lift being generated than there was before, so when a steady state is reached, the blades will flap up (compared to their previous path) all the way round the advancing side, reaching a peak at the front, and will flap down all the way round the retreating side.

The net result is that the disc has now repositioned itself so that it has 'flapped back' with respect to the control orbit, and to keep the forward motion going as you wanted, you will have to put more forward cyclic in.

You can easily see the effect if you transition forward from the hover, get the aircraft accellerating forward, and then hold the cyclic steady in the fore-and-aft plane. The aircraft will pitch up due to flapback, and you will soon have to introduce more forward cyclic to hold the nose where you want it.

That's about it - not trying to convert you, just make the aerodynamic theory a bit clearer.

[RW-1]

Well said Arm !

Oh and to that other person, your students wondering will cease when they get in the heli (something all here will note you still have not done for yourself ...) so stop hypothasizing aboutwhat they are thinking (it's what you are thinking) at any point in their training.

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

[RW-1]

HH-65, Coast Guard detachment Gauntanamo Bay Flew with 'em on my weekends off.
And the Coasties in New Orleans.

Another wind up from the Queen.

Why not tell us all here of your hands on flying experience, not theory, not Walter Mitty LZ Dreams, not something you were involved in, or pondered from your cubicle, but FLEW, your hands on the sticks, for more than until you likely got banned from the cockpit for an offhand comment to the flight crew (that if on the CH-53E would reduce you to being given the relief tube to use as the intercom ....)

I (let alone any plain student!) certainly am not subject to your telling me what I should do, for you certainly have demonstrated far worse need of needing actual flight experience Mr. "lower the collective at the bottom of the autorotation" :D

Never in my life has there been a person more in need of an hour of dual actual flight instruction...

For you see while you can wonder away in your cube, pilots everyday are pushing cyclic, getting summed forces and the tip path tilts in the direction it was asked of it by us pilots. End of story, end of theory.

You should get your butt in a Robbie, unless of course you feel it is too much heli for you ...

Or are you over the 240 Lb seat crush limit ?

Now that excuse for not trying it is one I could buy without hesitation :D

Geez, this still not done? well, I've better things to do with my time ...

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

[Nick Lappos]

Lu,
Your facination with the swashplate is really something. Why do you always get into confusing discussions about the swashplate and horn angles? Do you have some more pet theories about how some designer made a mistake that happened when you went to the toilet during the design phase of the program?

The horn contribution to the swashplate phasing gets the reader all confused, as it confuses you, too. What would happen if I wrapped a pitch horn twice around the swashplate, so the horn angle was 720 degrees? Whould you then claim that the swashplate was 2 rebolutions ahead of the blade? How absurd can you be?

The horn angle and the swashplate angle are both summed when talking about the swashplate phase angle, which we call gamma. Why don't you stop all this confusing drivel, and get back to the basics?

The swashplate angle of virtually all helicopters is matched to the need of the blade to flap properly and give the pilot the tip path tilt that he demanded with his cyclic. I cringe when you start with the "Sikorsky has 45 degrees and shmidlap has 90 degrees" when it is all really the same!!

This whole string of threads started when you tried to yet again assert that the Robinson was off by 18 degrees, and that is why it is (in your eyes) such a poor helicopter.

Give it a rest, please.

To those who read Lu's seemingly curious questions and claimed facts:

He is mostly wrong in his facts, and very mostly wrong in his explanations. If you wish to learn something about helos, try to simply ignore his poor math and poorer explanations.

I have been the chief R&D test pilot of a major helicopter company, have written many technical papers on these subjects, hold a number of patents on helicopter controls, and I get the willies when I read yet another Lu Zuckerman explanation for some poor unsuspecting student pilot.

I get further steamed when he blows this hot air, then backtracks waffles and then finally blames those who he says taught him the stuff he spouts.

Sorry for the venting, but please take what I say to heart. I know Lu is only trying to help, but the only ray of light I can see is that Lu has not offered any advice on brain surgery, as this is a quicker way to get hurt than following his aviation advice.

[Arm out the window]

What?! You mean there is no tooth fairy?!

Lu, as you said, the advancing blade is flapping down with respect to the horizontal when you're in forward flight.

However, as I said, flapback alters the path that the blades would otherwise follow, so the 'maximum rate of flapping up' mentioned above is with respect to the original, 'unflapped' tip path.

Regarding your comment about retreating blade stall; yes, the advancing blade will be producing high lift, but as the name implies, blade stall is all about stalling, and the subsequent loss of lift;

i.e. the retreating blade loses so much airspeed due to your high forward speed, and is already at a high angle of attack because of the power and blade pitch you have in to maintain that speed that it stalls like any other wing, loses a good degree of its lift, and there you have it.

[Arm out the window]

Well in keeping with the rotary nature of this forum, we're certainly going round and round!

Lu, it's true that in some aircraft the swash plate tilts a different direction to the disc, but as Nick says, it's all the same in the end.

Whatever happens, a blade needs to be getting its 'maximum fly down' pitch input about 90 degrees before the desired lowest point on the disc.

If your swash plate tilts down 30 degrees prior to the forward direction of the longitudinal axis, then the pitch change mechanism that follows that swash plate must lead the blade that it controls by about 60 degrees. In the case of the Bell UH-1, the swash plate tilts in the same direction as the disc because pitch commands go to the stab bar, which leads the blades by 90 degrees.

It seems that your basic conception of the rotor 'disc' is a cause of confusion. All smoke screens aside, a rotor blade is just a wing - lift, drag, stalling, angle of attack, relative airflow - all these things are as per any wing.

So flapback, flapping to equality, retreating blade stall and so on can all be fairly easily described in these terms, and it is a misinterpretation to say that some effects are because the blades make up a 'disc' and some are because they must be treated as individual elements.

If you understand the basic concepts of aerodynamic lift and drag, and how airflow behaves over a wing approaching and during the stall, then you won't have any trouble understanding how they apply to a rotary wing.

[sling load]

Lu Zuckerman,

Here we go again about the Robinson, You know, you are about an inch away from copping a defamation suit, surely you are intelligent enough to realise that this forum is public, Ill say it again Lu, PUBLIC, you may want to know that this forum is not protected from any legal action from any person, you really are a bitter and twisted person when it comes to sound engineering advice and sound test piloting advice. You always post so called advice, as if you are the only person in the world who knows! I GOT A NEWS FLASH FOR YOU LU, there are helicopters all over the world that fly sucessfully everyday, and a lot of them Robinsons. In fact I flew one in NZ In the mountains in shocking turbulence, hey Lu Im still alive. Your life really has to be miserable when you, an unlicensed A&P Mechanic, sit in judgement of Professionals Like Mr Nick Lappos. He doesn't have to do
your research on the Robinson, HE DOES NOT HAVE TO LU, He is an engineer and test pilot, he is very much aware of helicopter rotor head design, YOU ARE NOT!

The subject is closed, the people here do not have to answer to your whinings that keep you up at night, ringing bells, burning insence, or reading Harry Potter books, or whatever it is keeps you awake, mate you gotta get out and breathe some fresh air, it is very obvious to all on this forum that you have no grasp of aerodynamics whatever, and I have no problem with that given your background, but as I said before, you are in no position to question others, or pass yourself off as a helicopter aerodynamics whiz, that you aren't Lu. Your grasp of basic physics and mathmatics is not very good.

All this rubbish about fixing helicopters before Nick was born is nothing but pathetic. You really are scraping the bottom of the river with that crap.

I suppose you invented the internet too Lu.

You really are doing yourself alot of damage to your reputation, I suspect you don't tell the people whose Gulfstream you are working on that you are posting this rubbish.


Concepts of Understanding are different from theories Lu, and you can't even understand that.

Your so called findings are based on "so and so told me this" " another fellow told me that". Findings!, theyre nothing but hearsay,inconclusive,and the result of an obsession. Get over it Lu. IT WORKS.

My guess is that Nick Lappos has been training a lot more than you, and I feel you really have not done much training at any serious level at all.

Judging by your previous posts, you should be winning the state lottery every week, you know everything else.

[ 16 August 2001: Message edited by: sling load ]

[JohnJ]

Lu
just an idea... if you can't accept or understand the numerous replies, what about actually attending the Robinson Factory Course? No offence to anyone else that's been replying to the endless challenge to provide the answer you want to hear, but where better to get a audience with Robinson 'experts'. AND you get to fly with one of the factory test pilots as well. When I was there I flew with Doug Thomkins the chief experimental test pilot, started with Robinson in 1982, ask for him or Tim Tucker, I'm sure either could demonstrate "anything" the robbie is capable of. And then there's Pat Cox who takes the maintenance side of things, knows his stuff inside out, and willing to talk about any subject at any level. If he can decipher my explanation of a mag failure and then explain to me what it was in such layman's terms that I knew exactly what he meant then he's a pro. And then whilst you're there Lu, you can personally discuss your opinions with Frank (and Tim Tucker etc.) at the same time... Just an idea ?

[RW-1]

Poor poor Lu,

Well since you don't wish to heed what I and Nick have said, let's just keep it to the rest of the planet ...

Heed Sling loads and john's postings above, oh yes, here you could go to the Robbie Factory school, and sleep through the same sections you must have at those supposed 6 Sikorsky schools and the supposed 13 more.

So in essance you have stated you have ZERO flying skills what so ever, notice how you gave a great big "I'm just being attacked" para without directly answering the question of stick time ...

AGAIN: Never in my life has there been a person more in need of an hour of dual actual flight instruction...

You have made large mistakes in recalling a lot of things, but you have NOT corrected them, it goes round and round with you and therein lies the reason this hasn't ended, not for anyone else's part.

No, FR response made sense to anyone who UNDERSTOOD ALL the principles behind it.

YOU DIDN"T, and therefore to you it is crap.
(Heed slings comments again, I don't see why FR doesn't slap a lawsuit on you anyway, that certainly would server to both prove the design AGAIN, and embarrass you both financially and professionaly.)

Arrogant is the person with no experience who asks all to prove him right.
Ignorant is the person who cannot accept that they are wrong, when proven so.

You are both in a huge way.

So I don't have to say it again, just re-read EVERYTHING Sling Load stated, for it rings true. Aww heck, I will say it again:

You are not the professional, your course attendance does not give you any right to say "Well prove me wrong" to the true professionals here, they have explained it, your FAILURE to understand the answer does not make the facts invalid, nor raise your flawed thinking of the topic to a theory level. Period.

Proof: you repeatedly return to the same stupid, proven wrong misunderstanding on FTE and EOL, and you believe you are right based only on what others say to you (which leads to your misunderstandings again) and what you have read.

You have NO practical experience to be making the claims that you do here on the Robbie issue, to be giving aero advice, and certainly as I have stated many many many many many many many many times:

People don't have to prove you wrong, you have to prove you are right. You will not do that on the basis of misdirection, third party comments, what you read somewhere etc. GET IN A HELICOPTER AND GENERATE DATA.

Since you are unable/unwilling to get into a heli to do so, it's done.

You state a differing answer from Ray, well to tell the truth, to all here, it is more likely you didn't understand or again misinterpreted the answer given to you, for to do that leave you room to uselessly argue the matter, whereas if you did, then the answer is the same and Nick's, Mine, Sling's, Arm out the window's, FR's, the rotor gods themselves, and the rest of the planet. Something that would spell "END OF THREAD for LZ."

THE MATTER IS CLOSED.

Now, that said, for all these supposed "Attacks" that have been made on you from I, tell us without excuse why SO many people out there from different parts of the planet;
taught in different manners(according to you)
Flying a vast range of machines (where you fly NONE)
Test pilots (whom you are not)
Designers (where you are not)
Commercial pilots (that you are not)
Would ALL come to the same conclusion that you are full of sh*t?

And we are not talking about your Robbie bashing, we are talking about the same conclusion that Sling came to in his last post, he certainly didn't start out that way, he was a supporter of seeing if you were right, JUST HOW did that happen?

Hmmm ?

I end this with the best thing that Sling pointed out to you, you do need to study it, for it busts the "Well I got a different theory (you don't) or I heard form another person" line of crap:

Concepts of Understanding are different from theories Lu, and you can't even understand that.

Your so called findings are based on "so and so told me this" " another fellow told me that". Findings!, they're nothing but heresay, inconclusive,and the result of an obsession. Get over it Lu. IT WORKS.


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

[RW-1]

Ooooh! Nerve hit successful ! :)

Oh, oh, oh ... he's making fun of my name ... You really are a child in most respects LZ, and terribly easy to predict, you must overcome this tendancy, maybe by growing up, losing the obsession, arrogance, and ignorance that stems from your brain, to your hands, then into your posts.

Once again you have shot your mouth off about something you have no knowledge of.

That would be like you talking aerodynamics here on the forum .... (See ALL previous comments to you on this fact, and not only by me ... ) :D

And based upon your irritating nature here I doubt there is ANY pilot willing to have you in their cockpit for any length of time ...

Don't fret Sparky, you can attack me all you want to defer from the fact that just about everyone else here ALSO thinks you are full of S**t . I'm a man, I can take it, especiually when we all know the source:

An old, obsessed, ignorant, arrogant old man, with no life who is nothing more than a wannabe guru here. ;)

The difference between us is that you try and try and try to present yourself as Mr. Know-it-all, every day.

I have made no such claims to fame, and that certainly means that any one with 1 hour in a heli still seems to know more than you do, with WHATEVER you care to post as a resume to back it up. I also understand the difference between a concept, a theroy, and fact, something that you with ALL your immemense experience have not grasped yet.
(I say yet, for there is always hope, even for you)

THAT has to eat you up, ALL these other TRUE PROFESSIONALS aggreeing with me ...
and not you ...
Not LZ ...
How dare they with all you know? :D

Well crow hurts when it has to be eaten,'bout time you eat it like a man, and move on.

Resumes are nothing, your actions and statements are what makes for the meat of the thread, and the evidence YOU yourself have contributed says you slept through your classes.

And I didn't even say that until now, gee, how did all the others come to that conclusion? (refer back to attacking me comment, I can take it, go ahead, attack me and not answer the question.)

This is another round of the immature LZ trying to prove he is something he isn't, and the evidence has been given BY YOU to the contrary. Please go back to basics school, go get some dual in something CURRENT, and then come back here and discuss aero.

The issue at hand is that you know not what you speak, and presume that you do. That's sad.

You are not a wannabe. You are THE WANNABE.

However, you still haven't answered the following, Mr. Know-it-all:

For all these supposed "Attacks" that have been made on you from I, tell us, without excuse, why SO many people out there from different parts of the planet:

taught in different manners(according to you)
Flying a vast range of machines (where you fly NONE)
Test pilots (whom you are not)
Designers (where you are not)
Commercial pilots (that you are not)

Would ALL come to the same conclusion that you are full of sh*t?

And we are not talking about your Robbie bashing, we are talking about the same conclusion that Sling came to in his post, he certainly didn't start out that way, he was a supporter of seeing if you were right, JUST HOW did that happen?

Hmmm ?

You are SAD, just terribly sad .... we're done with you.

You will now continue to make it a LZ vs RW-1 (or insert anyones name here) BECAUSE to do otherwise is to end the thread that has been covered and closed.

So by now going just to me it would seem you have now have ran out of further excuses to make on your end. Plain and simple.

You have a nice day now! I'm going flying this evening, adn I shall enjoy it.

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

[Dave Jackson]

RW-1

>No, FR response made sense to anyone who UNDERSTOOD ALL the principles behind it.,

I understand very little about helicopters. It is the desire to learn that is a primary reason for participating in this and other related threads.

Thanks to Frank Robinson's posting, and some subsequent reading, things have cleared up a little. For instance, it appears that his use of the word "Wee-wa" probably stands for 'small washout'. Do you agree?

It can be assumed that Frank Robinson does not have the time, or the requirement, to publish a thesis on PPRuNe about helicopter rotorheads. Unfortunately, he addressed delta3, which is relatively common. He did not address the Robinson's unique feature. That being, the reasoning behind the combined use of a teetering hinge plus two flap/cone hinges.


In my limited capacity, I see nothing wrong with the Robinson's rotor. What I do see as wrong is threads that are intended to be technical and informative turning into personalized attacks on individuals or companies.

____________

Lu

You, me and probably most of the world, believe that the association between 'gyroscopic precession' and '90-degrees' is a fact.

Hopefully, the following excerpt on gyroscopic precession should be of interest.

But first, we must agree that a helicopter's rotor does not rotate as fast as a gyroscope and that the rotor's relative mass is not as great as a gyroscope's relative mass.

".............. Otherwise the motion of the gyroscope is much more complicated, as you might observe in an actual experiment where the rotation of the rotor slows down over time. We can see that as the rotor slows, the precessional frequency increases. At some point when the precessional frequency exceeds a critical value, the gyroscope will begin to wobble and eventually tumble in its gimbals." [My change to bold].

[ 16 August 2001: Message edited by: Dave Jackson ]

[helmet fire]

Lu,

I will repeat something I said 2 pages ago:

>>Why do you deflect the discussion to irrelevant details such as wether or not you do/don’t teach it that way rather than try and benefit from the explanations offered? You did not acknowledge that any points were even made.
For example, you have avoided any response to my opening posts on RBS, and on which parts of your understanding are flawed. Even in your new explanation of how you “really” teach it you are mixing concepts.<<

You have still not addressed ONE point. You had asked for specific examples/specific explanations to your theories, and I have seen them repeatedly offered to you by various (heedm, Arm out the window, Nick Lappos, sling load, etc) yet you answer only Dave Jackson, as per above. Is it because Dave does not question aspects of your theory?

How about you go back to the subject (RBS), look at the explanations offered to you in this thread, and talk specifics. Otherwise you may never grasp the fundamentals.

Perhaps the detailed gyroscopic discussions could be posted on Dave Jackson's excellent thread?

[Arm out the window]

I have to agree, helmet fire.

I liken a series of posts to a conversation, where a number of people discuss an issue - you have disagreement, interjections and so on, but the basic gist of it goes on, and people either come to some accord, or agree to disagree in the end. Far from what's been happening here!

Lu's posts have been good in that they certainly spark discussion, probably more so than if we all sat around calmly pontificating, but I've had enough of addressing points he raises and then having him spear off on some random tangent.

Compromise ain't on the agenda, by the look of things, so see you all on some other thread!

;)

[Dave Jackson]

Lu

>I’m sorry I can’t agree. <

Thanks for the above statement. As I read it, you are not saying that my position is right or wrong. You are saying that you, personally, are not willing to accept it. (At least not accept it yet. :)

>Even the proverbial bicycle wheel which is considerably lighter than a gyro rotor of the same diameter and rotates at a speed maybe 1 100th of that of a gyro rotor will exhibit rigidity in space and precession. <

Remember that, unlike the helicopter rotor, this bicycle wheel has just about all its mass at the rim (tip). I would suggest that the bicycle wheel is a lot closer to the gyroscope then it is to the helicopter rotor.

>However the stored energy in a helicopter rotor is capable of exerting rigidity in space and precession. <

This may not be a fair analogy but; the spinning gyroscopic toy will maintain orientation for say 1/2 a minute. With the helicopter, you can kiss autorotation goodbye, if you don't do something within a few seconds.

________________

Correct me if I am wrong, but it has been mathematically proven and I think we can agree on the fact that aerodynamic 'precession' can be less then 90-degrees.

My previous posting did not go into the mathematics of gyroscopic precession. Its intent was simply to show that gyroscopic precession can be less than 90-degrees, as well.

In other words; both gyroscopic precession and aerodynamic precession can be, under certain circumstances, less than 90-degrees.

If you agree with this then we can try to determine what these circumstances are.

[ 17 August 2001: Message edited by: Dave Jackson ]

[PPRuNe Towers]

Tempers have been getting very frayed over the last couple of pages.

Many of you have seen what this has done to other sites. We won't have that here.

Attack the argument and not the person.

Rob Lloyd

[ 17 August 2001: Message edited by: PPRuNe Towers ]

[RW-1]

Attack the argument

With all due respect Rob, this has been done, many many times.

It's the person in question who cannot accept that fact.

Misdirection, inability to remain on topic, various excuses for his misunderstang of basic principles, then returning to the same issues already asked and answered.

It is no longer an arguement, has not been for over a year and a half, but a broken record:

The tune (thread) changes by some degree, but the song itself is ALWAYS the same. The 18 Degree offset concept (not theory, not fact) is dead.

If he cannot accept the answers he gets to the questions he poses to the very people he insults, then you can plainly see where the issue lies.

Helmet and Arm are spot on again.

EVERYTHING I stated in my last posting rings truer than the Liberty Bell (if rung).

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

[RW-1]

Lu Sez:

Blah blah blah ....

The Liberty Bell like many of your arguments has a big crack in it.

You mean like that I must have a lot of company in those CORRECT observations that you still HAVEN'T ADDRESSED?

You have made most of the personal attacks here, you have no Alternate Theory at all, just a misguided interpretation that you contnually try to apply to other things going on with the rotor, with flawed results because you started with a bad concept.

THERE IS NO ALTERNATE THEORY. AGAIN THE BROKEN RECORD...

I refer you back to Sling Load:
Concepts of Understanding are different from theories Lu, and you can't even understand that.
Your so called findings are based on "so and so told me this" " another fellow told me that". Findings!, they're nothing but heresay, inconclusive,and the result of an obsession. Get over it Lu. IT WORKS.


This is tiresome.

LU Zuckerman, the wannabe, all your posts are nothing more than questions asked so that you can continue to tell people that the answers given are incorrect and you are the one who knows all. They have NOTHING to do with learning, or to instruct, but whether your 18 deg concept is correct or not, so that you may continue to bash robbies. You have always had only this one track on your tiny little mind, you are not kidding anyone here.

The following is not an attack, but a correct observation, made prior to me saying it by many many others:

You are an arrogant, ignorant, wind up.

You really seem to get off thinking you are some kind of guru, that must be it. By continuing to just tell people that you have determined they are off, that they must be off, you could never be further than the truth.

You have never, NEVER given anyone a response that aggrees with them without a if and or but that allows you to continue this totally useless ranting.

Again this is no arguement, no alternate theory crap, nothing more than a continuation of your obsession with the Robinson.

AND FOR THE LAST TIME GET OFF THAT DIFFERENCE IN TRAINING GARBAGE, both sides of the pond have told you you are off, it is just another excuse.

You also take 5 responses in JH and tailor then to suit you, not the way it was said TO you.
(Not to mention the mispelling of gyroscopic in the thread title ...)

So now you presume to tell people what they formulated?

Nope, they formed it by BOTH instruction AND FLYING, something YOU STILL HAVE NOT DONE !

This is WHY pilots do BOTH.

And you still have not answered the following (and when you do lets not make if's and s or but's, nor other excuses):


For all these supposed "Attacks" that have been made on you from I, tell us, without excuse, why SO many people out there from different parts of the planet:

taught in different manners(according to you)
Flying a vast range of machines (where you fly NONE)
Test pilots (whom you are not)
Designers (where you are not)
Commercial pilots (that you are not)

Would ALL come to the same conclusion that you are full of sh*t?

And we are not talking about your Robbie bashing, we are talking about the same conclusion that Sling came to in his post, he certainly didn't start out that way, he was a supporter of seeing if you were right, JUST HOW did that happen?


You cannot answer that one huh ?

You will continue to piss off / annoy others, continue to go round and round, excuse after excuse, and eventually you will have no one to converse with. Maybe then you will realize what everyone has told you is true.

For over a year and a half PPRuNer's have been subjected to your crap concept, you have brought forth NOTHING NEW to your end of the so called "arguement."

You needlessly waste everyone's time with the same sad pattern of excuses, redirection, misinterpretation, tailoring what IS said to you to what you WANT to hear, etc.

After all that time the 18 deg issue is still dead wrong, it will continue to be dead wrong, and remain dead wrong. For as it has been pointed out, you cannot make a mistake a fact by preaching.

Basically this thread has gone in the same direction as ALL your others here. And I didn't even get involved with it until you strayed off track, you stray off track because you don't like the 18 deg concept dead station the train heads into each and every time it's discussed.

Quite frankly you are a bitter old man with an obsession that you will take with you to the grave, and even then it will be unproven. (BTW that is not an attack, it is a fact, submitted by plenty others on this forum prior to my saying so, evidence submitted, look at all the other posts here, anyone ...)

Well, it is the weekend, I shall be out flying.

Say something stupid Lu, make another childish comment towards me while I'm out doing something you seemingly cannot handle, flying a Robinson. Whatever it takes to avoid the issue of your refusal to know when you are done.

Just a bitter old man ... I need not say more on the subject, you do a better job of illustrating what I stated previously about you for the last two years ... :D

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

[JohnJ]

Lu

I know I'm repeating myself but that seems to be an accepted thing in these threads. Cut out all the middle men, go to the source, go to the Robinson factory. Don't call someone/anyone, go there, do one of the factory courses. You have a choice of pilot or maintenance course. I guarantee you'll get a very good explanation as to why things are done as they are.

[Mark Six]

Lu, I read your post on Just Helicopters on 14th August, asking pilots what they were taught in relation to blade movement and gyroscopic precession. With regard to the responses you received you stated that "...although they were differing all were taught that the blades move due to gyroscopic precession." There were only 5, (mostly confused and confusing) responses, and only one actually said that he was taught as you stated. He then went on to say that he now realises that this was wrong. You appear to have interpreted the responses to suit your argument.

[Heliport]

Well Lu, you certainly keep Rotorheads lively!

We are all entitled to our views even when we are wrong! But, it is quite helpful to know a little of the background, qualifications and experience etc of the person expressing views, especially when they appear to be controversial.
Why not post details of your qualifications and experience in the industry as suggested by a number of contributors?

Most contributors know something of Nick Lappos' position and standing in the industry. For those who don't .......

http://www2.gdi.net/~nlappos/jobsite.jpg

Nick Lappos is Sikorsky's Assistant Chief Test Pilot. A former U.S. Army Warrant Officer and a combat veteran of Vietnam, he flew Cobra attack helicopters in D Troop, 1st Squadron, 1st Cavalry.
An Aerospace Engineering graduate of Georgia Tech, he came to Sikorsky Aircraft in 1973. Since then, he has flown in the YUH-60 Black Hawk program, flown the first flight and structural shakedown of the S-76, the "Shadow" cockpit research aircraft, the adaptive fuel control experimental aircraft, and the "Fantail" fan-in-fin demonstrator.
He is now assigned to the RAH-66 Comanche project, where he is part of the pilot team flying the shakedown and envelope expansion. In 1988, the Society of Experimental Test Pilots awarded Nick their Tenhoff Award for the most outstanding paper at the Annual Symposium.
The American Helicopter Society awarded Nick their Feinberg award as most outstanding pilot for his contribution to the understanding of maneuverability in 1989 and again in 1998 (as part of the Comanche Team), and in 1994 he was named a Fellow of the Society. He was a member of the American Helicopter Society's Handling Qualities committee and AGARD Working Group #19 (Functional Agility), and is currently a member of the NASA/FAA Air Traffic Management R&D Executive Steering Committee. Nick has written a number of technical papers, and articles for magazines such as "Rotor and Wing," "Interavia," and "Defense Helicopter." He holds 15 U.S. and a number of foreign patents on flight and engine controls and cockpit displays.

Thanks for your contributions, Nick!