R22 Corner
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Sorry kids, but while Lu is entitled to his opinion he is also a crackpot. His ludicrous theories have been rebutted by every genuine expert in the field on this forum, but his ever-wilder gyrations have kept us amused down the years, when he hasn't been banned for extra-crazy behaviour.
Unfortunately he sometimes frightens the kids, so it's necessary every now and then to point out that he is a buffoon with a fixation. He does not respond to logic or common sense (or even ridicule). He knows a little but talks a lot.
The R22 has now been flying for 29 years, and it is one of the safest helicopters ever, with a fatal accident rate better than most fixed-wings - currently 1.4 per 100,000 hours on NTSB statistics. Fly safely, and don't be taken in by Lu Zuckerman.
Unfortunately he sometimes frightens the kids, so it's necessary every now and then to point out that he is a buffoon with a fixation. He does not respond to logic or common sense (or even ridicule). He knows a little but talks a lot.
The R22 has now been flying for 29 years, and it is one of the safest helicopters ever, with a fatal accident rate better than most fixed-wings - currently 1.4 per 100,000 hours on NTSB statistics. Fly safely, and don't be taken in by Lu Zuckerman.
Iconoclast
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Now, I'm not only as nutty as a fruitcake I'm also a crackpot and a buffoon.
To: DrCopter
QUOTE]Can you explain why you think a 90 degree phase angle would make the helicopter 'uncontrollable'.[/QUOTE]
On the Robinson when it is at low pitch the pitch horn is coincident with the cone hinge so if you were to raise the blade pivoting on the cone hinge there would be no pitch flap coupling. However if you were to flap the rotor on the teeter hinge you would get some degree of pitch flap coupling.
With the rotor spinning and the pilot raises the collective the pitch horn/pitch link attachment would raise above the cone hinge. In this case when the blade flaps on either the cone hinge or the teeter hinge you would get pitch flap coupling. In this case the R-22 has a 72-degree pitch horn. If you had a 90-degree pitch horn the pitch horn would extend beyond the cone hinge and it would be coincident with the teeter hinge when the blades are at low pitch. If you were to teeter the blades in this condition you would get minimal pitch flap coupling however with pitch in the blades and if the blades coned you would actually increase the pitch over and above what you had put in with the collective and when the blades flapped about the cone hinge pitch would be input into the blade when it flapped up and removed from the blade when it flapped down. Pitch flap coupling on a conventional rotor system is the opposite. So with a 90-degree pitch horn what ever the pilot put into the blades the input would practically double and instead of having normal pitch flap coupling you would get the opposite.
To: Pat Malone
It seems that history is repeating itself. Ever since I expounded on my theories on the R-22 I was viciously attacked by RW-1 who challenged me on everything I said about the R-22 yet when I challenged him in return to tell me what exactly was wrong with what I was saying he never responded. It seems that you are doing the same thing but instead of a southern accent you are doing it with a Cornish accent. Just like RW-1 you refer to what other people say but never offer your technical opinions as to why I am wrong. Are you talking about my use of the term centrifugal force or, are you referring to my use of the term gyroscopic precession or are you talking about my theories on the R-22? Just what are you taking objections to and please tell me and the others what exactly am I saying that is wrong. I am not saying that I am right as they are theories but you are saying I am wrong.
Well what is wrong with what I have been saying?
Well?
QUOTE]Can you explain why you think a 90 degree phase angle would make the helicopter 'uncontrollable'.[/QUOTE]
On the Robinson when it is at low pitch the pitch horn is coincident with the cone hinge so if you were to raise the blade pivoting on the cone hinge there would be no pitch flap coupling. However if you were to flap the rotor on the teeter hinge you would get some degree of pitch flap coupling.
With the rotor spinning and the pilot raises the collective the pitch horn/pitch link attachment would raise above the cone hinge. In this case when the blade flaps on either the cone hinge or the teeter hinge you would get pitch flap coupling. In this case the R-22 has a 72-degree pitch horn. If you had a 90-degree pitch horn the pitch horn would extend beyond the cone hinge and it would be coincident with the teeter hinge when the blades are at low pitch. If you were to teeter the blades in this condition you would get minimal pitch flap coupling however with pitch in the blades and if the blades coned you would actually increase the pitch over and above what you had put in with the collective and when the blades flapped about the cone hinge pitch would be input into the blade when it flapped up and removed from the blade when it flapped down. Pitch flap coupling on a conventional rotor system is the opposite. So with a 90-degree pitch horn what ever the pilot put into the blades the input would practically double and instead of having normal pitch flap coupling you would get the opposite.
To: Pat Malone
It seems that history is repeating itself. Ever since I expounded on my theories on the R-22 I was viciously attacked by RW-1 who challenged me on everything I said about the R-22 yet when I challenged him in return to tell me what exactly was wrong with what I was saying he never responded. It seems that you are doing the same thing but instead of a southern accent you are doing it with a Cornish accent. Just like RW-1 you refer to what other people say but never offer your technical opinions as to why I am wrong. Are you talking about my use of the term centrifugal force or, are you referring to my use of the term gyroscopic precession or are you talking about my theories on the R-22? Just what are you taking objections to and please tell me and the others what exactly am I saying that is wrong. I am not saying that I am right as they are theories but you are saying I am wrong.
Well what is wrong with what I have been saying?
Well?
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Mr. Malone
Your profile says that you are a publisher. Does your personalized attack have anything to do income, and the advertising that begets it?
Are you suggesting that those who are good at promoting helicopters are better people than those who are promoting good helicopters?
Your profile says that you are a publisher. Does your personalized attack have anything to do income, and the advertising that begets it?
Are you suggesting that those who are good at promoting helicopters are better people than those who are promoting good helicopters?
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lu
i see what you mean, but just looking at the r44 from the ground you can see that the pitch links are closer to the mast slightly than the cone hinges and are closest to the cone hinge at full up collective. lift a blade up (make it teeter) and it donest change angle, maybe reduce pitch slightly as the pitch horn comes away from the centre. as i believe one blade cant flap up without the head teetering to equalization, they cant be affected individualy by your theory.
but all i could understand of the robinson waperwork is that the phase angle was made that way to reduce the cyclic neaded at translation and high forward speed.
ive been wrong before (thought i was wrong but i was right)
but all i could understand of the robinson waperwork is that the phase angle was made that way to reduce the cyclic neaded at translation and high forward speed.
ive been wrong before (thought i was wrong but i was right)
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Lu said,
As an engineer you can diagram this action showing the tip path plane and the flapping of the advancing blade and by definition the retreating blade. If in flying in a helicopter you will note that the tip path is one continuous line interrupted periodically a blade flapping out of the tip path due to gusting and within one rotation it is back in the tip path. If the Robinson in fact has a 72-degree phase angle the tip path will not be one continuous line but it will show distinct deviation from the tip path plane and I would assume a lot of attendant vibration.
I often have trouble following Lu's posts but if I have this one worked it is just plain wrong.
Every time we track and balance blades his statement is shown to be wrong.
For those who may not know how its done:
Stick a dropdown tab on the end of each blade with a vertical reflective line on one and and a horizontal reflective line on the other.
Then - Up to the hover and strobe it and fly off at eighty knots and strobe it (with a strobe in the hand of passenger). The two reflectors are easily visible and various adjustments may or may not be needed to have them track so that the lines appear as a cross.
I have piloted machines for track & balance at least ten times
in the last three or four years and the whole idea is that when you fly it around it DOESN'T deviate from the tip path.
Even in gusts in doesn't deviate much and it comes back in line immediately.
Back to the drawing board, Lu.
As an engineer you can diagram this action showing the tip path plane and the flapping of the advancing blade and by definition the retreating blade. If in flying in a helicopter you will note that the tip path is one continuous line interrupted periodically a blade flapping out of the tip path due to gusting and within one rotation it is back in the tip path. If the Robinson in fact has a 72-degree phase angle the tip path will not be one continuous line but it will show distinct deviation from the tip path plane and I would assume a lot of attendant vibration.
I often have trouble following Lu's posts but if I have this one worked it is just plain wrong.
Every time we track and balance blades his statement is shown to be wrong.
For those who may not know how its done:
Stick a dropdown tab on the end of each blade with a vertical reflective line on one and and a horizontal reflective line on the other.
Then - Up to the hover and strobe it and fly off at eighty knots and strobe it (with a strobe in the hand of passenger). The two reflectors are easily visible and various adjustments may or may not be needed to have them track so that the lines appear as a cross.
I have piloted machines for track & balance at least ten times
in the last three or four years and the whole idea is that when you fly it around it DOESN'T deviate from the tip path.
Even in gusts in doesn't deviate much and it comes back in line immediately.
Back to the drawing board, Lu.
Iconoclast
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You missed the point.
To: RobboRider
First of all what I said was in complete agreement with the above quote. The point I was trying to make has to do with a 72-degree phase angle on the Robinson. If it is in fact 72-degrees then the blade must respond to the maximum pitch input in order to get the maximum blade flap. If this is true then the blade must deviate from the tip path from a point 18-degrees ahead of the lateral axis in order to dip down over the nose with the opposite being true for the retreating blade.
It is for this reason that I presented my theory that the blade in fact would dip down 18-degrees to the left of the longitudinal axis (90-degree phase angle). And that in the process of correcting for inflow roll, transverse flow effect and dissymmetry of lift the pilot is moving the cyclic all over the place. And when everything settles down and the helicopter is flying straight the cyclic should be somewhere to the right of the rigged neutral position. To support my theory I have stated that if the cyclic is to the right of the rigged neutral position it may be there for several reasons including compensation for the 18-degree offset. Many of the respondents to my theory will state that this is to compensate for phase angle shift and completely discount the compensation for the offset. If I understand phase angle shift it will be some number of degrees less than the 90-degree phase angle built into the helicopter. If this is the case then the cyclic should be to the left of the rigged neutral position in order to compensate for the phase shift from 90-degrees which would cause the helicopter to fly to the right.
The design guidelines allow for several degrees of cross coupling so it is normal for all helicopters to experience this shift and it is acceptable in the certification process. Getting back to your statement relative to blade tracking I totally agree with you.
Even in gusts in doesn't deviate much and it comes back in line immediately.
It is for this reason that I presented my theory that the blade in fact would dip down 18-degrees to the left of the longitudinal axis (90-degree phase angle). And that in the process of correcting for inflow roll, transverse flow effect and dissymmetry of lift the pilot is moving the cyclic all over the place. And when everything settles down and the helicopter is flying straight the cyclic should be somewhere to the right of the rigged neutral position. To support my theory I have stated that if the cyclic is to the right of the rigged neutral position it may be there for several reasons including compensation for the 18-degree offset. Many of the respondents to my theory will state that this is to compensate for phase angle shift and completely discount the compensation for the offset. If I understand phase angle shift it will be some number of degrees less than the 90-degree phase angle built into the helicopter. If this is the case then the cyclic should be to the left of the rigged neutral position in order to compensate for the phase shift from 90-degrees which would cause the helicopter to fly to the right.
The design guidelines allow for several degrees of cross coupling so it is normal for all helicopters to experience this shift and it is acceptable in the certification process. Getting back to your statement relative to blade tracking I totally agree with you.
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Mr Jackson:
Lu and I are old sparring partners. I used to post on the forum under the name of Tain't Natural, and Lu and I had some fine old ding-dongs which I'm sure shed an enormous amount of light on this debate.
I have thought for some time that the camouflage of anonymity led me to say glib things about which I might be more circumspect if I were unable to hide, so I decided to post under my own name. Now I have to be extremely sure of my ground when I say Lu is a fixated monomaniac with a fetish, and 30 years of history, every truly expert opinion in the helicopter world and enough ridicule to kill a buffalo isn't going to change that.
But every so often he tries out his drivel on a new batch of ppruners, and there's a danger that some of them might be taken in.
Your notion of Robinson simply being good at promoting helicopters rather than promoting good helicopters is specious. I've followed your posts down the years and I have great respect for you. You usually do better than that.
None of my magazines have ever taken advertising from Robinson.
Lu and I are old sparring partners. I used to post on the forum under the name of Tain't Natural, and Lu and I had some fine old ding-dongs which I'm sure shed an enormous amount of light on this debate.
I have thought for some time that the camouflage of anonymity led me to say glib things about which I might be more circumspect if I were unable to hide, so I decided to post under my own name. Now I have to be extremely sure of my ground when I say Lu is a fixated monomaniac with a fetish, and 30 years of history, every truly expert opinion in the helicopter world and enough ridicule to kill a buffalo isn't going to change that.
But every so often he tries out his drivel on a new batch of ppruners, and there's a danger that some of them might be taken in.
Your notion of Robinson simply being good at promoting helicopters rather than promoting good helicopters is specious. I've followed your posts down the years and I have great respect for you. You usually do better than that.
None of my magazines have ever taken advertising from Robinson.
Iconoclast
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The mask is removed but the face is still the same.
To: Pat Malone ex t'aint natural
I couldn’t believe that there were two of you. From your profile you have a PPL (H) which means most of your helicopter time is in R-22s and you in no way would ever admit that there might be a problem in the design. A famous comedian once said that Denial is not just a river in Egypt.
You have a very low opinion of me as reflected in your comments in the above posts. I think every time you see my name on these forums you become apoplectic. Would it surprise you that I don’t even have any feelings one way or another when I see either your pseudonym or your real name. To me it is a game.
If you want to play the game you must play by the rules. The first rule is you do not have to accept what I say as fact but if you disagree you must counter my statement with a technical fact that proves me wrong. Rule number two is that you must not rely on other peoples statements about me relative to technical accuracy and making these statements to be fact (even if they are) instead you must prove me wrong by stating a technical fact.
If you do not want to play by the rules you can continue with your caustic comments and prove to the newbies to this thread that I am not to be trusted. You will also be proven to be another RW-1 but with an English accent. However, if you continue this way Heliport may jump you.
I couldn’t believe that there were two of you. From your profile you have a PPL (H) which means most of your helicopter time is in R-22s and you in no way would ever admit that there might be a problem in the design. A famous comedian once said that Denial is not just a river in Egypt.
You have a very low opinion of me as reflected in your comments in the above posts. I think every time you see my name on these forums you become apoplectic. Would it surprise you that I don’t even have any feelings one way or another when I see either your pseudonym or your real name. To me it is a game.
If you want to play the game you must play by the rules. The first rule is you do not have to accept what I say as fact but if you disagree you must counter my statement with a technical fact that proves me wrong. Rule number two is that you must not rely on other peoples statements about me relative to technical accuracy and making these statements to be fact (even if they are) instead you must prove me wrong by stating a technical fact.
If you do not want to play by the rules you can continue with your caustic comments and prove to the newbies to this thread that I am not to be trusted. You will also be proven to be another RW-1 but with an English accent. However, if you continue this way Heliport may jump you.
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Another clash of the Titans?
Could there be another Clash of the Titans in the near future? Stay tuned boys and girls... same Bat Time... same Bat Channel!
Honorable "Ah-Dee-Rik-Stah"
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Lu,
What you spend most of your time doing is exhorting an explanation and then saying therefore lots of bad things must be happening.
Lets pretend for a minute that we have a scientific outlook to a situation.
First make an observation. THEN try and explain it.
Quote L.Z.
If the Robinson in fact has a 72-degree phase angle the tip path will not be one continuous line but it will show distinct deviation from the tip path plane and I would assume a lot of attendant vibration.
Real life situation:
Blades do not show distinct deviation and do not have a lot of attendant vibration.
Quote L.Z.
It is for this reason that I presented my theory that the blade in fact would dip down 18-degrees to the left of the longitudinal axis (90-degree phase angle). And that in the process of correcting for inflow roll, transverse flow effect and dissymmetry of lift the pilot is moving the cyclic all over the place.
Real Life Situation:
The cyclic does not need to be moved all over the place.
So now from observation we need to develop a theory Not the other way round.
What you spend most of your time doing is exhorting an explanation and then saying therefore lots of bad things must be happening.
Lets pretend for a minute that we have a scientific outlook to a situation.
First make an observation. THEN try and explain it.
Quote L.Z.
If the Robinson in fact has a 72-degree phase angle the tip path will not be one continuous line but it will show distinct deviation from the tip path plane and I would assume a lot of attendant vibration.
Real life situation:
Blades do not show distinct deviation and do not have a lot of attendant vibration.
Quote L.Z.
It is for this reason that I presented my theory that the blade in fact would dip down 18-degrees to the left of the longitudinal axis (90-degree phase angle). And that in the process of correcting for inflow roll, transverse flow effect and dissymmetry of lift the pilot is moving the cyclic all over the place.
Real Life Situation:
The cyclic does not need to be moved all over the place.
So now from observation we need to develop a theory Not the other way round.
Iconoclast
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Cart and horse Dilemma. Which comes first?
To: RobboRider
I stated that if in fact there were a 72-degree phase angle there would be a significant deviation from the tip path plane. I further stated in so many words that if there were in fact a 90-degree phase angle like in other helicopters the blades would dip down left of the nose with forward cyclic.
You stated: The cyclic does not need to be moved all over the place.
Now, I have a question. When you lift off do you make a cyclic correction to compensate for tail rotor translation? When you lift off single pilot do you make a correction to compensate for lateral CG displacement? When you are entering translational lift do you make any cyclic correction to compensate for transverse flow effect? When passing through translational lift do you make any cyclic corrections for dissymmetry of lift and attendant blowback?
I would assume that you answered yes to several of the above questions if not all. If you answered yes then the cyclic is being moved to compensate for the above conditions. Is there just a small possibility that you are also compensating for an 18-degree offset (if it exists) and you are totally unaware of it because at the end you are flying straight ahead?
Try this: The next time you go flying have your mechanic show you where the rigged neutral position is on the cyclic. In this position the swashplate is not tilted. Make note of the cyclic position. In forward flight keep the cyclic in the forward-displaced position and move the cyclic laterally to the rigged neutral position. If I am right the helicopter will fly to the left. If it doesn't deviate from the flight direction I am wrong and I will shut up. It is a simple test and could take all of 15 seconds.
Or, try this:
At your next start up place the cyclic in the rigged neutral position.
With the blades turning at 100% pull a slight amount of collective to get the blades to cone slightly. Move the cyclic forward from the rigged neutral position. Note what the blade disc does. Does it tip down over the nose or does it tip to the left. Another fifteen second test neither of which will place you or the helicopter in danger.
Am I right or, am I wrong? Take the time to prove your point and discount mine.
I stated that if in fact there were a 72-degree phase angle there would be a significant deviation from the tip path plane. I further stated in so many words that if there were in fact a 90-degree phase angle like in other helicopters the blades would dip down left of the nose with forward cyclic.
You stated: The cyclic does not need to be moved all over the place.
Now, I have a question. When you lift off do you make a cyclic correction to compensate for tail rotor translation? When you lift off single pilot do you make a correction to compensate for lateral CG displacement? When you are entering translational lift do you make any cyclic correction to compensate for transverse flow effect? When passing through translational lift do you make any cyclic corrections for dissymmetry of lift and attendant blowback?
I would assume that you answered yes to several of the above questions if not all. If you answered yes then the cyclic is being moved to compensate for the above conditions. Is there just a small possibility that you are also compensating for an 18-degree offset (if it exists) and you are totally unaware of it because at the end you are flying straight ahead?
Try this: The next time you go flying have your mechanic show you where the rigged neutral position is on the cyclic. In this position the swashplate is not tilted. Make note of the cyclic position. In forward flight keep the cyclic in the forward-displaced position and move the cyclic laterally to the rigged neutral position. If I am right the helicopter will fly to the left. If it doesn't deviate from the flight direction I am wrong and I will shut up. It is a simple test and could take all of 15 seconds.
Or, try this:
At your next start up place the cyclic in the rigged neutral position.
With the blades turning at 100% pull a slight amount of collective to get the blades to cone slightly. Move the cyclic forward from the rigged neutral position. Note what the blade disc does. Does it tip down over the nose or does it tip to the left. Another fifteen second test neither of which will place you or the helicopter in danger.
Am I right or, am I wrong? Take the time to prove your point and discount mine.
Last edited by Lu Zuckerman; 18th Apr 2004 at 16:33.
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Lu,
L.Z.
Left cyclic to compensate for tail rotor translation?
RR
Yes left lateral cyclic . But by your explanation I should be using foreward cyclic.
L.Z.
lift off single pilot … to compensate for lateral CG displacement?
R.R.
Yes lateral left cyclic and also forward cyclic because it hangs tail low when solo (but not when with Passenger). By your explanation I should be using foreward to compensate for the lateral CG and right for the tail low rearward drift
L.Z.
When you are entering translational lift .. any cyclic correction to compensate for transverse flow effect?
R.R.
Don’t recall any but I’d have to do it and take notice.
L.Z.
When passing through translational lift do you make any cyclic corrections for dissymmetry of lift
R.R.
Not that I recall but I’ll have to try and take notice.
L.Z.
and attendant blowback?
R.R.
Yes. Nose will pitch up noticeably if you don’t keep the cyclic forward. (Not to the right as your theory would suggest)
R.R.
Are there any helicopters (rigged in any way) that don’t have all these effects. I thought these were characteristics of pretty much all rotor discs. The cyclic movements aren't "all over the place" as your post would suggest.
I'll try it later in the week. I will try and get photos or video.
RR
L.Z.
Left cyclic to compensate for tail rotor translation?
RR
Yes left lateral cyclic . But by your explanation I should be using foreward cyclic.
L.Z.
lift off single pilot … to compensate for lateral CG displacement?
R.R.
Yes lateral left cyclic and also forward cyclic because it hangs tail low when solo (but not when with Passenger). By your explanation I should be using foreward to compensate for the lateral CG and right for the tail low rearward drift
L.Z.
When you are entering translational lift .. any cyclic correction to compensate for transverse flow effect?
R.R.
Don’t recall any but I’d have to do it and take notice.
L.Z.
When passing through translational lift do you make any cyclic corrections for dissymmetry of lift
R.R.
Not that I recall but I’ll have to try and take notice.
L.Z.
and attendant blowback?
R.R.
Yes. Nose will pitch up noticeably if you don’t keep the cyclic forward. (Not to the right as your theory would suggest)
R.R.
Are there any helicopters (rigged in any way) that don’t have all these effects. I thought these were characteristics of pretty much all rotor discs. The cyclic movements aren't "all over the place" as your post would suggest.
I'll try it later in the week. I will try and get photos or video.
RR
Last edited by RobboRider; 19th Apr 2004 at 10:23.
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Now we are getting somwhere.
To: RobboRider
The Robinson so I have been told has a very sensitive cyclic input
so moving the cyclic all over the place may be an over statement. However on most helicopters the movement is significant enough to be noticed (that is if your are looking for it).
On compensation for tail rotor translation I was not inferring that the cyclic would be moved forward.
Regarding rearward drift I would assume that you would compensate with forward cyclic. QUOTE: By your explanation I should be using forward to compensate for the lateral CG and right for the tail low rearward drift. UNQUOTE
I think your explanation is backwards. Forward for rear drift and lateral for CG placement.
Regarding for compensation for blowback: QUOTE Yes. Nose will pitch up noticeably if you don’t keep the cyclic forward. (Not to the right as your theory would suggest) UNQUOTE
I was addressing only the forward movement of the cyclic and not compensation for the offset. That is a problem in itself. The purpose of my post was to point out that the cyclic is under constant movement to compensate for the aerodynamic input into the rotor system.
[QUOTE]Are there any helicopters (rigged in any way) that don’t have all these effects. I thought these were characteristics of pretty much all rotor discs. The cyclic movements aren't "all over the place”, as your post would suggest. UNQUOTE
According to Frank Robinson the R-22 is not very susceptible to most of these conditions because it has a 72-degree phase angle
and according to him there is no phase angle shift. At least that is what I got out of his posting.
I will post on phase angle shift and perchance it will either enlighten some and infuriate others.
The Robinson so I have been told has a very sensitive cyclic input
so moving the cyclic all over the place may be an over statement. However on most helicopters the movement is significant enough to be noticed (that is if your are looking for it).
On compensation for tail rotor translation I was not inferring that the cyclic would be moved forward.
Regarding rearward drift I would assume that you would compensate with forward cyclic. QUOTE: By your explanation I should be using forward to compensate for the lateral CG and right for the tail low rearward drift. UNQUOTE
I think your explanation is backwards. Forward for rear drift and lateral for CG placement.
Regarding for compensation for blowback: QUOTE Yes. Nose will pitch up noticeably if you don’t keep the cyclic forward. (Not to the right as your theory would suggest) UNQUOTE
I was addressing only the forward movement of the cyclic and not compensation for the offset. That is a problem in itself. The purpose of my post was to point out that the cyclic is under constant movement to compensate for the aerodynamic input into the rotor system.
[QUOTE]Are there any helicopters (rigged in any way) that don’t have all these effects. I thought these were characteristics of pretty much all rotor discs. The cyclic movements aren't "all over the place”, as your post would suggest. UNQUOTE
According to Frank Robinson the R-22 is not very susceptible to most of these conditions because it has a 72-degree phase angle
and according to him there is no phase angle shift. At least that is what I got out of his posting.
I will post on phase angle shift and perchance it will either enlighten some and infuriate others.
and I thought reality tv was the most boring thing on Earth. Iconoclast
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Phase angle and phase angle shift
To: Anyone that will listen
The design requirements of the FAA dictate that the blades shall respond in the same sense as cyclic movement. It further states that even with the best design you are allowed to have several degrees of cross coupling. I would assume that this would be due to control geometry or aerodynamic influences (phase angle shift).
All helicopters have a design phase angle. This angle is 90-degrees. There is one exception and that according to Nick Lappos is the S-76 and it is not 90-degrees. You will have to get him to explain why. Also since I have no information on the BK series I can’t address the phase angle on those helicopters so we are stuck with Bell, Aerospatial and Sikorsky.
Now my definitions may be wrong but you will have to accept them as everything is predicated on these explanations.
Phase angle: The designed in control geometry that results in an angle of 90-degrees
Phase angle shift: The deviation from the 90-degree phase angle resulting from outside influences such as blade loading, air density, speed and any one of several other outside influences. This shift will result in the decrease of the 90-degrees to some figure less than 90-degrees.
Sikorsky helicopters have a 90-degree phase angle. The servos lead the direction of cyclic input by 45-degrees and the pitch horn leads the blade by 45-degrees. 45 + 45 = 90-degrees.
On two blade Bell helicopters the pitch horn leads or follows the blade by 90-degrees and the swashplate is displaced 90-degrees ahead of the blade.
On four blade Bells the pitch horn leads or trails the blade by 45-degrees and the swashplate displacement is 45-degrees. 45 + 45 = 90-degrees
On Aerospatial helicopters the pitch horn leads the blades by 60-degrees and the swashplate displacement is 30-degrees. 60 + 30 = 90-degrees. This may vary from model to model but the resultant is still 90-degrees
The Apache is much like the Sikorsky system.
The blades follow the swashplate movement in all cases and blade movement is as a result of Gyrodynamic Precession or Aeroscopic precession.
The Cheyenne was designed like the Sikorsky (45 + 45 =90-degrees) but the blades due to their aerodynamic shape and their stiffness never worked as designed. They got severe phase angle shift and the disc would not only move in a direction not commanded but they would diverge from the tip path plane and in certain cases would result in blade incursion. It took several years of design to get the blades to behave. This resulted in a sensing system being utilized to detect uncommanded movement and input was made to the main servo to make the blade move in the commanded position of the cyclic.
A similar system was incorporated on the Lynx. The Lynx is somewhat like the Robinson in that when rigging the helicopter the blade pitch is set with the blade 15-degrees ahead of the lateral axis. Without the protection of the black box the blades would dip down 15-degrees past the longitudinal axis when the cyclic was moved forward and because of the inherent stiffness in the rotor system this movement would be immediate.
Now, we get to the Robinson. Like the Lynx the blades have an offset but unlike the Lynx the Robinson is not effected like the Lynx. The Lynx has a 15-degree offset but a 90-degree phase angle. The black box adjusts the servo input so that when the cyclic is moved forward the servo input is adjusted to give 15-degree compensation to the right. The Robinson has an 18-degree offset but unlike the Lynx it has a 72-degree phase angle and according to Frank Robinson there is no need to make compensation for the offset. My god, that man is a genius.
So if the 15-degree offset is recognized by Westland and they compensate for it electronically then why doesn't the same apply to the R--22 and the 18-degree offset being compensated for by cyclic input.
It's Goose and Gander stuff the way I see it.
The design requirements of the FAA dictate that the blades shall respond in the same sense as cyclic movement. It further states that even with the best design you are allowed to have several degrees of cross coupling. I would assume that this would be due to control geometry or aerodynamic influences (phase angle shift).
All helicopters have a design phase angle. This angle is 90-degrees. There is one exception and that according to Nick Lappos is the S-76 and it is not 90-degrees. You will have to get him to explain why. Also since I have no information on the BK series I can’t address the phase angle on those helicopters so we are stuck with Bell, Aerospatial and Sikorsky.
Now my definitions may be wrong but you will have to accept them as everything is predicated on these explanations.
Phase angle: The designed in control geometry that results in an angle of 90-degrees
Phase angle shift: The deviation from the 90-degree phase angle resulting from outside influences such as blade loading, air density, speed and any one of several other outside influences. This shift will result in the decrease of the 90-degrees to some figure less than 90-degrees.
Sikorsky helicopters have a 90-degree phase angle. The servos lead the direction of cyclic input by 45-degrees and the pitch horn leads the blade by 45-degrees. 45 + 45 = 90-degrees.
On two blade Bell helicopters the pitch horn leads or follows the blade by 90-degrees and the swashplate is displaced 90-degrees ahead of the blade.
On four blade Bells the pitch horn leads or trails the blade by 45-degrees and the swashplate displacement is 45-degrees. 45 + 45 = 90-degrees
On Aerospatial helicopters the pitch horn leads the blades by 60-degrees and the swashplate displacement is 30-degrees. 60 + 30 = 90-degrees. This may vary from model to model but the resultant is still 90-degrees
The Apache is much like the Sikorsky system.
The blades follow the swashplate movement in all cases and blade movement is as a result of Gyrodynamic Precession or Aeroscopic precession.
The Cheyenne was designed like the Sikorsky (45 + 45 =90-degrees) but the blades due to their aerodynamic shape and their stiffness never worked as designed. They got severe phase angle shift and the disc would not only move in a direction not commanded but they would diverge from the tip path plane and in certain cases would result in blade incursion. It took several years of design to get the blades to behave. This resulted in a sensing system being utilized to detect uncommanded movement and input was made to the main servo to make the blade move in the commanded position of the cyclic.
A similar system was incorporated on the Lynx. The Lynx is somewhat like the Robinson in that when rigging the helicopter the blade pitch is set with the blade 15-degrees ahead of the lateral axis. Without the protection of the black box the blades would dip down 15-degrees past the longitudinal axis when the cyclic was moved forward and because of the inherent stiffness in the rotor system this movement would be immediate.
Now, we get to the Robinson. Like the Lynx the blades have an offset but unlike the Lynx the Robinson is not effected like the Lynx. The Lynx has a 15-degree offset but a 90-degree phase angle. The black box adjusts the servo input so that when the cyclic is moved forward the servo input is adjusted to give 15-degree compensation to the right. The Robinson has an 18-degree offset but unlike the Lynx it has a 72-degree phase angle and according to Frank Robinson there is no need to make compensation for the offset. My god, that man is a genius.
So if the 15-degree offset is recognized by Westland and they compensate for it electronically then why doesn't the same apply to the R--22 and the 18-degree offset being compensated for by cyclic input.
It's Goose and Gander stuff the way I see it.
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Has anyone considered the human physiology aspect of this, and as such did FR come to the 18 degrees offset based on what felt "right" rather than any other design criteria. It cannot be contested that the offset is not a problem to pilots under normal circumstances.
It is some time since I flew a R22 but I remember that holding the cyclic with the left hand made control difficult. This is in marked contrast to my Enstrom which is often flown left handed with no difficulty, whilst adjusting mixture, radios etc. (Enstrom flown from left seat - no offset).
My point is , does the offset fit in with the natural movement of the shoulder and elbow joint of the right arm to make it feel right even though the disk is not moving in the same plane as the cyclic? Does the unique T bar control have any effect?
As we are keen on tests, get a protractor set up facing away from you. move your arm fore and aft not holding anything, resting on your knee, at 90 degrees to your body. Both joints must move. Then try moving it with 20 degrees offset and watch the joints. Which feels more natural?
Robinson don't rely on servos and electronics to nullify the offset. The pilots brain is trained to do it - until you try it left handed.
Could everybody be right?
FR may not like to admit that 18 degrees was arrived at by trial and error. That probably would not have convinced the FAA at the design stage.
Just a thought.
It is some time since I flew a R22 but I remember that holding the cyclic with the left hand made control difficult. This is in marked contrast to my Enstrom which is often flown left handed with no difficulty, whilst adjusting mixture, radios etc. (Enstrom flown from left seat - no offset).
My point is , does the offset fit in with the natural movement of the shoulder and elbow joint of the right arm to make it feel right even though the disk is not moving in the same plane as the cyclic? Does the unique T bar control have any effect?
As we are keen on tests, get a protractor set up facing away from you. move your arm fore and aft not holding anything, resting on your knee, at 90 degrees to your body. Both joints must move. Then try moving it with 20 degrees offset and watch the joints. Which feels more natural?
Robinson don't rely on servos and electronics to nullify the offset. The pilots brain is trained to do it - until you try it left handed.
Could everybody be right?
FR may not like to admit that 18 degrees was arrived at by trial and error. That probably would not have convinced the FAA at the design stage.
Just a thought.
Cool as a moosp
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Gaseous you have a good point.
There is also the change in flight feel when switching to the left seat in a Robbo. If you just look at the cyclic geometry on the ground you'd think that it would operate in exactly the same way, but when you try to fly from the left seat for the first few times it is a very different machine.
Perhaps the 18 degree offset is the reason.
There is also the change in flight feel when switching to the left seat in a Robbo. If you just look at the cyclic geometry on the ground you'd think that it would operate in exactly the same way, but when you try to fly from the left seat for the first few times it is a very different machine.
Perhaps the 18 degree offset is the reason.
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Moosp
I can't say I had noticed left seat problems in R22. If you do try left handed, maybe do it with another pilot onboard. Scared the sh1t out of me the first time I tried it. (hovering)
I can't say I had noticed left seat problems in R22. If you do try left handed, maybe do it with another pilot onboard. Scared the sh1t out of me the first time I tried it. (hovering)
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I think the reason it feels weird is just the fact that it attaches in between the seat. On the right side you feel all the friction on your left side cause that is where the cyclic is rigged. When you move to the left side you feel all the friction on the right side cause that is where the cyclic is rigged. "friction" may not be the best word but you get the idea. My opinion (which doesnt mean much)
Lu-Ill try your experiment tomorrow. I know the rigged position is already right of center on the 22 to compensate for translating tendency and I know if forward flight the cyclic is still off to the right of center, dont know if it is more or less though.
Lu-Ill try your experiment tomorrow. I know the rigged position is already right of center on the 22 to compensate for translating tendency and I know if forward flight the cyclic is still off to the right of center, dont know if it is more or less though.