R22 Corner
Guest
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Grey area, I'm still interested in this subject and hope that you DO post some more info (at least one person will read it)- as for gyros and precession I think we can all agree that a helicopter rotor system is an "ineffective" gyro and therefore exibits SOME of a gyro's characteristics. The real thing requires much more mass and a much higher RPM (relatively).
Guest
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Although a rotor disc might 'coincidently' display the 'odd' similar characteristic, it is NOT the same. Even considering them as having some of the same characteristics will only confuse the issue, especially when you try to explain some more complex helicopter effects. Trust me; leave the precession for a GYRO. The rotor disc is a completely different beast.
[This message has been edited by Baque Flip (edited 21 December 2000).]
[This message has been edited by Baque Flip (edited 21 December 2000).]
Guest
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I'm with Baque Flip on this one. The precessive qualities of a gyro stem from the inertial effects of the rotating mass. As has already been said the mass and rpm of a rotor are not sufficient. I once had a formula for the minimum mass/rpm for a gyro which I have (thankfully for most of you) misplaced, but I did use it on a helo rotor system (Lynx [grey]) and fell well short. Incidently it is inertial effects that cock up the phase lag in an offset flapping hinge.
[This message has been edited by Grey Area (edited 21 December 2000).]
[This message has been edited by Grey Area (edited 21 December 2000).]
Guest
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To: Rotorque
Admitting my own ignorance, what is an alpha angle and what does it have to do with this thread? Just asking not attacking. Hopefully this doesn't generate into a discussion based on how you and I were taught the same subject.
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The Cat
Admitting my own ignorance, what is an alpha angle and what does it have to do with this thread? Just asking not attacking. Hopefully this doesn't generate into a discussion based on how you and I were taught the same subject.
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The Cat
Guest
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Lu's answer:
"The mast length on the Robbie like that on the 206 has to be long because of the low rotor blade/rotorhead interlock. It supplies a longer moment arm."
Means:
Long mast required to accomodate CoG range, since 'teetering' rotor heads supply no direct attitude changing moment - the CoG will hang directly under the center of the rotor head in a hover - to keep the angle between mast axis and disc axis small you need a long mast.
(any heads with flapping hinges (or virtual hinges) at a distance make a restoring force which resists attitude differences between helicopter and disc - (less g dependant for attitude control authority) - so they tend to have much shorter masts and have relatively more CoG range)
- I hope I haven't made it worse.
"The mast length on the Robbie like that on the 206 has to be long because of the low rotor blade/rotorhead interlock. It supplies a longer moment arm."
Means:
Long mast required to accomodate CoG range, since 'teetering' rotor heads supply no direct attitude changing moment - the CoG will hang directly under the center of the rotor head in a hover - to keep the angle between mast axis and disc axis small you need a long mast.
(any heads with flapping hinges (or virtual hinges) at a distance make a restoring force which resists attitude differences between helicopter and disc - (less g dependant for attitude control authority) - so they tend to have much shorter masts and have relatively more CoG range)
- I hope I haven't made it worse.
Guest
Posts: n/a
TO ROBINSON LAMEs AND A&Ps
To: LAMEs and A&Ps that work on Robinson Helicopters
In making this post I will make several assumptions;
1) In order to be able to work on the Robinson Helicopters you attended a factory school or, you attended a Robinson sponsored school that was operated by a Robinson distributor.
2) You were taught flight theory as well as how to rig the helicopter.
3) If you were taught in the USA you were told about gyroscopic precession and if you were taught in the UK or OZ you learned it in a different way. (Unless the subject was taught by a Robinson representative).
Although there are variants of the above assumptions it can be assumed that they are correct. If that were the case, I would like to pose these questions.
1) In learning about gyroscopic precession or the same phenomenon as taught in the UK or Oz did they use the Robinson system as a demonstration or, did they use a Bell system as a means of explaining the subject?
The reason I ask this is because there are at least two websites that are the home pages of two Robinson dealers and flight schools. These websites have a very good explanation of how a helicopter flies. They have excellent pictures of Robinson helicopters and the major elements of those helicopters. They show pictures of Bell and Robinson rotorheads and they then go into the subject of gyroscopic precession.
Although the preceding text on the website(s) dealt with a Robinson rotorhead they explained gyroscopic precession by using a Bell system as an example. The two systems are different.
2) In teaching the rigging process how did they explain the differences in the positioning of the Robinson blades as opposed to those of a Bell helicopter and, how did they rectify what they taught about gyroscopic precession as related to the positioning of the blades?
I assume they taught that the precession phase angle was 90 degrees and yet the Robinson blades are disposed 18-degrees from the respective axes during the rigging process. What did they tell you about where the blade disc would dip if the cyclic was pushed forward from the rigged neutral position?
To get a better understanding of what I am asking, log onto the following websites and download the diagrams.
http://205467.homestead.com/diagrams.html
http://pprune.homestead.com/files/rigging.jpg
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The Cat
In making this post I will make several assumptions;
1) In order to be able to work on the Robinson Helicopters you attended a factory school or, you attended a Robinson sponsored school that was operated by a Robinson distributor.
2) You were taught flight theory as well as how to rig the helicopter.
3) If you were taught in the USA you were told about gyroscopic precession and if you were taught in the UK or OZ you learned it in a different way. (Unless the subject was taught by a Robinson representative).
Although there are variants of the above assumptions it can be assumed that they are correct. If that were the case, I would like to pose these questions.
1) In learning about gyroscopic precession or the same phenomenon as taught in the UK or Oz did they use the Robinson system as a demonstration or, did they use a Bell system as a means of explaining the subject?
The reason I ask this is because there are at least two websites that are the home pages of two Robinson dealers and flight schools. These websites have a very good explanation of how a helicopter flies. They have excellent pictures of Robinson helicopters and the major elements of those helicopters. They show pictures of Bell and Robinson rotorheads and they then go into the subject of gyroscopic precession.
Although the preceding text on the website(s) dealt with a Robinson rotorhead they explained gyroscopic precession by using a Bell system as an example. The two systems are different.
2) In teaching the rigging process how did they explain the differences in the positioning of the Robinson blades as opposed to those of a Bell helicopter and, how did they rectify what they taught about gyroscopic precession as related to the positioning of the blades?
I assume they taught that the precession phase angle was 90 degrees and yet the Robinson blades are disposed 18-degrees from the respective axes during the rigging process. What did they tell you about where the blade disc would dip if the cyclic was pushed forward from the rigged neutral position?
To get a better understanding of what I am asking, log onto the following websites and download the diagrams.
http://205467.homestead.com/diagrams.html
http://pprune.homestead.com/files/rigging.jpg
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The Cat
Guest
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Lu Zuckerman wrote:
I assume they taught that the precession phase angle was 90 degrees and yet the Robinson blades are disposed 18-degrees from the respective axes during the rigging process. What did they tell you about where the blade disc would dip if the cyclic was pushed forward from the rigged neutral position?
In a previous posting to this forum (to which you made several replies), Frank Robinson explained the reason for the 18 degree Delta-3 angle that is incorporated into the R22/44 rotor system. It seems that either you simply ignored his explanation, or you are incapable of understanding it.
Numerous pilots with experience flying the Robinsons have stated in this forum that the ship does *not* behave in the manner you claim. Not only do you continue to ignore these statements, but you refuse even the opportunity to gain first-hand knowlege of the situation by actually flying in the ship with an experienced pilot. Somewhat like the clerics who refused to look through Galileo's telescope, you choose to remain blissful in your ignorance.
Perhaps you feel ignorance is bliss. But, if in fact you actually DO understand the effect of Delta-3, why do you believe it is *not* applicable to the behavior of the R22/44 rotor system in the manner that was explained by Mr. Robinson?
Guest
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In this post you make several assumptions:
That this will begin another 100+ thread.
Not going to happen.
My assumption for 2001: Slowly, those who are on the board all the time will tire of endless repostings about the subject, and begin to ignore them.
The only way they will stay in the forum is if you add to them yourself.
Mark561, don't bother trying, he has an answer for everything except why it doesn't follow his predictions.
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Marc
That this will begin another 100+ thread.
Not going to happen.
My assumption for 2001: Slowly, those who are on the board all the time will tire of endless repostings about the subject, and begin to ignore them.
The only way they will stay in the forum is if you add to them yourself.
Mark561, don't bother trying, he has an answer for everything except why it doesn't follow his predictions.
------------------
Marc
Guest
Posts: n/a
To: mark561 and RW-1
First of all, I was trying to solicit responses from mechanics that work on Robinson helicopters as to what they were taught about the rigging of the two helicopters and what they were taught about flight theory. I was not looking for any criticism. Paul Cantrell writes the two web sites I often refer to and Robinson dealers and flight schools sponsor both. Mr. Cantrell addresses the function of various aspects of both the Robinson and Bell dynamic systems and then addresses gyroscopic precession indicating that it is 90-degrees (phase angle) for both the Bell and the Robinson. When he demonstrates the principles of gyroscopic precession he uses a diagram of the Bell control input and response which showed where the input and ultimate responses of the disc tilt were. On the RW-1 website you indicated that you got the information from a US Army flight instruction manual. Well the illustration used by Mr.Cantrell is the same as that used on your website so I can only assume that gyroscopic precession is addressed in your website as being 90-degrees.
In regards to this aspect of the control input Vs response, the Robinson is completely different in that during the rigging procedure the position of the blades during pitch setting are offset by eighteen degrees as opposed to where the Bell Blades are positioned for the same setting.
If the Robinson blades are offset by 18-degrees during rigging then the maximum pitch input on advancing blade is decreased to the maximum and the retreating blade which is also offset by 18-degrees and it is at its’ maximum pitch change then please explain to me the following. How in hell will the Robinson rotor system defy the laws of physics governing gyroscopic precession and tilt down over the nose and up over the tail. If you refer to what Frank Robinson said in his reply I will tell you both that you are full of S**t and so is he.
Listen to what I am about to say and then go out and look at the Robinson rotorhead. Frank Robinson stated that they evaluated the benefits of a 90-degree pitch horn Vs a 72-degree pitch horn and determined that the 72-degree pitch horn would solve a problem relating to transverse flow effect. He implied that the 72-degree pitch horn would eliminate this problem that effected the Bell with its’ 90-degree pitch horn. That is pure bull crap. RW-1 what happens to your R22 when you speed up from a hover to say around 20-30 Knots. Do you encounter transverse flow effect? If you do, then what Mr. Robinson stated about his choice of a 72-degree pitch horn and why it was selected is wrong.
Another point I have made regarding the rotorhead design is that from the very beginning, Frank Robinson incorporated cone hinges on his rotorhead. This was not done to counter the effects of transverse flow it was done to minimize the bending moments of the blade and to minimize the transmission of flapping (coning) moments so the design could never incorporate a 90-degree pitch horn.
He also stated that the delta 3 effect would make up for the 18-degree offset and result in a 72-degree phase angle and allow the blade disc to tilt down over the nose when the cyclic was pushed forward. This too is bull crap. The delta 3-effect causes pitch to be removed or added to the blade when it flaps due to external aerodynamic forces. If the blade flaps up pitch is removed and if it flaps down pitch is added. Just like on a tail rotor. However this can only happen if the pitch horn / pitch link attachment is above or below the cone hinge. If the two points are coincident then there is no pitch coupling. Explain this, if the points are coincident when forward cyclic is pushed then which way will the disc tilt? Will it tilt down over the nose or, will it tilt down left of the longitudinal centerline. You can’t have it both ways and state that it will tilt in one way or the other if you use the explanation used by Frank Robinson.
RW-1 here is something you can demonstrate since you like flying on the edge. Lift off with your cyclic in the rigged neutral position. Do not move it laterally. Push it forward and fly through the transverse flow effect. The helicopter should roll to the right but don’t move the cyclic. When you are through the transverse flow effect, let me know which direction the helicopter is flying.
This is for mark561.
According to your Bio, you are most likely working at the Lazy B but then again there are a lot of places in your area that employ engineers. Your Bio also indicates that you fly model helicopters.
I don’t know what kind of engineering training you have (ME, AE or, EE) but I assume that you learned the theory of gyroscopic precession and that barring any mechanical or, friction problems the gyroscopic phase angle is always 90-degrees. If you downloaded my diagrams especially the one that Helidrvr put on this thread you can see the difference between a Robinson blade and a Bell blade during the rigging process. The relative positions of the blade sets are the point that they have the maximum perturbing force and according to the laws of physics the blade disc will react 90-degrees later in the direction of rotation. It is my contention that there will be a left roll component added when the reaction takes place. Regarding the demonstration I asked RW-1 to perform, two pilots on this thread performed the test and their conclusions were that I was correct.
When the Robinson accelerates forward the pilot will counter the transverse flow effect by adding left cyclic. This is in addition to the left roll caused by the 18-degree offset. When he passes through the transverse flow effect he moves his cyclic to the right. In doing this he is reestablishing the helicopter in forward flight as opposed to rolling left. Is there a possibility that in the process of moving the cyclic to the right he is not only recovering from the transverse flow effect he is also countering the effect of the left roll induced by the offset? This is why I asked if in the certification process they used a stick plotting board, then they would have noted this problem.
This is also for mark561. You seem to have taken a stand based solely on what Frank Robinson said in regards to my postings and not from a detailed understanding of the mechanics of the Robinson Helicopters. If this is an incorrect assumption then I stand corrected. I stated this in a previous post, if Frank Robinson makes a counter statement to my postings it doesn’t mean it is true. He is not Jesus making his Sermon on the Mount and he is not God in the form of a burning bush giving the Ten Commandments to Moses. He is an engineer and businessman that will say anything to protect his interests and if you are a pilot that buys the farm in a Robinson Helicopter then he will be your survivors’ worst enemy.
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The Cat
First of all, I was trying to solicit responses from mechanics that work on Robinson helicopters as to what they were taught about the rigging of the two helicopters and what they were taught about flight theory. I was not looking for any criticism. Paul Cantrell writes the two web sites I often refer to and Robinson dealers and flight schools sponsor both. Mr. Cantrell addresses the function of various aspects of both the Robinson and Bell dynamic systems and then addresses gyroscopic precession indicating that it is 90-degrees (phase angle) for both the Bell and the Robinson. When he demonstrates the principles of gyroscopic precession he uses a diagram of the Bell control input and response which showed where the input and ultimate responses of the disc tilt were. On the RW-1 website you indicated that you got the information from a US Army flight instruction manual. Well the illustration used by Mr.Cantrell is the same as that used on your website so I can only assume that gyroscopic precession is addressed in your website as being 90-degrees.
In regards to this aspect of the control input Vs response, the Robinson is completely different in that during the rigging procedure the position of the blades during pitch setting are offset by eighteen degrees as opposed to where the Bell Blades are positioned for the same setting.
If the Robinson blades are offset by 18-degrees during rigging then the maximum pitch input on advancing blade is decreased to the maximum and the retreating blade which is also offset by 18-degrees and it is at its’ maximum pitch change then please explain to me the following. How in hell will the Robinson rotor system defy the laws of physics governing gyroscopic precession and tilt down over the nose and up over the tail. If you refer to what Frank Robinson said in his reply I will tell you both that you are full of S**t and so is he.
Listen to what I am about to say and then go out and look at the Robinson rotorhead. Frank Robinson stated that they evaluated the benefits of a 90-degree pitch horn Vs a 72-degree pitch horn and determined that the 72-degree pitch horn would solve a problem relating to transverse flow effect. He implied that the 72-degree pitch horn would eliminate this problem that effected the Bell with its’ 90-degree pitch horn. That is pure bull crap. RW-1 what happens to your R22 when you speed up from a hover to say around 20-30 Knots. Do you encounter transverse flow effect? If you do, then what Mr. Robinson stated about his choice of a 72-degree pitch horn and why it was selected is wrong.
Another point I have made regarding the rotorhead design is that from the very beginning, Frank Robinson incorporated cone hinges on his rotorhead. This was not done to counter the effects of transverse flow it was done to minimize the bending moments of the blade and to minimize the transmission of flapping (coning) moments so the design could never incorporate a 90-degree pitch horn.
He also stated that the delta 3 effect would make up for the 18-degree offset and result in a 72-degree phase angle and allow the blade disc to tilt down over the nose when the cyclic was pushed forward. This too is bull crap. The delta 3-effect causes pitch to be removed or added to the blade when it flaps due to external aerodynamic forces. If the blade flaps up pitch is removed and if it flaps down pitch is added. Just like on a tail rotor. However this can only happen if the pitch horn / pitch link attachment is above or below the cone hinge. If the two points are coincident then there is no pitch coupling. Explain this, if the points are coincident when forward cyclic is pushed then which way will the disc tilt? Will it tilt down over the nose or, will it tilt down left of the longitudinal centerline. You can’t have it both ways and state that it will tilt in one way or the other if you use the explanation used by Frank Robinson.
RW-1 here is something you can demonstrate since you like flying on the edge. Lift off with your cyclic in the rigged neutral position. Do not move it laterally. Push it forward and fly through the transverse flow effect. The helicopter should roll to the right but don’t move the cyclic. When you are through the transverse flow effect, let me know which direction the helicopter is flying.
This is for mark561.
According to your Bio, you are most likely working at the Lazy B but then again there are a lot of places in your area that employ engineers. Your Bio also indicates that you fly model helicopters.
I don’t know what kind of engineering training you have (ME, AE or, EE) but I assume that you learned the theory of gyroscopic precession and that barring any mechanical or, friction problems the gyroscopic phase angle is always 90-degrees. If you downloaded my diagrams especially the one that Helidrvr put on this thread you can see the difference between a Robinson blade and a Bell blade during the rigging process. The relative positions of the blade sets are the point that they have the maximum perturbing force and according to the laws of physics the blade disc will react 90-degrees later in the direction of rotation. It is my contention that there will be a left roll component added when the reaction takes place. Regarding the demonstration I asked RW-1 to perform, two pilots on this thread performed the test and their conclusions were that I was correct.
When the Robinson accelerates forward the pilot will counter the transverse flow effect by adding left cyclic. This is in addition to the left roll caused by the 18-degree offset. When he passes through the transverse flow effect he moves his cyclic to the right. In doing this he is reestablishing the helicopter in forward flight as opposed to rolling left. Is there a possibility that in the process of moving the cyclic to the right he is not only recovering from the transverse flow effect he is also countering the effect of the left roll induced by the offset? This is why I asked if in the certification process they used a stick plotting board, then they would have noted this problem.
This is also for mark561. You seem to have taken a stand based solely on what Frank Robinson said in regards to my postings and not from a detailed understanding of the mechanics of the Robinson Helicopters. If this is an incorrect assumption then I stand corrected. I stated this in a previous post, if Frank Robinson makes a counter statement to my postings it doesn’t mean it is true. He is not Jesus making his Sermon on the Mount and he is not God in the form of a burning bush giving the Ten Commandments to Moses. He is an engineer and businessman that will say anything to protect his interests and if you are a pilot that buys the farm in a Robinson Helicopter then he will be your survivors’ worst enemy.
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The Cat
Guest
Posts: n/a
To: RW-1
The reason I became so belligerent is because of your attitude in responding to my posts. It is obvious that you and I will never agree on this point so do two things. Perform the test I described and tell me the results and the second is please refrain from participating on this particular forum as I am trying to elicit responses from mechanics that work on Robinson helicopters and not try to defend my ideas.. Oh yes, a third thing, please talk to the mechanics at Volar and pose the same questions I asked on this post.
YOU NEVER SEEM TO ANSWER THE QUESTIONS DIRECTED AT YOU. HOW ABOUT THE QUESTIONS POSED ABOVE BY CRAB?
AND HOW ABOUT THIS WHICH I COPIED FROM A POST ABOVE. PLEASE REPLY.
When the Robinson accelerates forward the pilot will counter the transverse flow effect by adding left cyclic. This is in addition to the left roll caused by the 18-degree offset. When he passes through the transverse flow effect he moves his cyclic to the right. In doing this he is reestablishing the helicopter in forward flight as opposed to rolling left. Is there a possibility that in the process of moving the cyclic to the right he is not only recovering from the transverse flow effect he is also countering the effect of the left roll induced by the offset? This is why I asked if in the certification process they used a stick plotting board, then they would have noted this problem.
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The Cat
[This message has been edited by Lu Zuckerman (edited 31 December 2000).]
The reason I became so belligerent is because of your attitude in responding to my posts. It is obvious that you and I will never agree on this point so do two things. Perform the test I described and tell me the results and the second is please refrain from participating on this particular forum as I am trying to elicit responses from mechanics that work on Robinson helicopters and not try to defend my ideas.. Oh yes, a third thing, please talk to the mechanics at Volar and pose the same questions I asked on this post.
YOU NEVER SEEM TO ANSWER THE QUESTIONS DIRECTED AT YOU. HOW ABOUT THE QUESTIONS POSED ABOVE BY CRAB?
AND HOW ABOUT THIS WHICH I COPIED FROM A POST ABOVE. PLEASE REPLY.
When the Robinson accelerates forward the pilot will counter the transverse flow effect by adding left cyclic. This is in addition to the left roll caused by the 18-degree offset. When he passes through the transverse flow effect he moves his cyclic to the right. In doing this he is reestablishing the helicopter in forward flight as opposed to rolling left. Is there a possibility that in the process of moving the cyclic to the right he is not only recovering from the transverse flow effect he is also countering the effect of the left roll induced by the offset? This is why I asked if in the certification process they used a stick plotting board, then they would have noted this problem.
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The Cat
[This message has been edited by Lu Zuckerman (edited 31 December 2000).]
Guest
Posts: n/a
YOU NEVER SEEM TO ANSWER THE QUESTIONS DIRECTED AT YOU. HOW ABOUT THE QUESTIONS POSED ABOVE BY CRAB?
In the post, I answered twice.
You can be belligerent, I have nothing I have to prove, I do it everytime I fly it.
You have the burden of proof, not I, not FR, not anyone else, not the rotor gods that be.
Just you. Again, you haven't made it.
You should really get off you hang up on gyro precession, you're like an 11 year old I know on another forum who believes he knows all, but hasn't touched an aircraft.
I certainly don't know all, but I know enough that you are not correct in your assertions and your hangup on GP is what keeps you from seeing the whole picture.
You have already been told, not informed, that the cyclic doesn't respond as you predict, and why. But noooooo, you know more than the designer, other engineers, phd's, aerodynamicists, the rotor gods, etc. .... not!
You need to go drive over to a R-22 and get in it, and perform the test I outlined: and then you would be silent. Why can I ask that? Because. (that's a good Lu answer. Because.)
It's as simple as that!
In the post, I answered twice.
You can be belligerent, I have nothing I have to prove, I do it everytime I fly it.
You have the burden of proof, not I, not FR, not anyone else, not the rotor gods that be.
Just you. Again, you haven't made it.
You should really get off you hang up on gyro precession, you're like an 11 year old I know on another forum who believes he knows all, but hasn't touched an aircraft.
I certainly don't know all, but I know enough that you are not correct in your assertions and your hangup on GP is what keeps you from seeing the whole picture.
You have already been told, not informed, that the cyclic doesn't respond as you predict, and why. But noooooo, you know more than the designer, other engineers, phd's, aerodynamicists, the rotor gods, etc. .... not!
You need to go drive over to a R-22 and get in it, and perform the test I outlined: and then you would be silent. Why can I ask that? Because. (that's a good Lu answer. Because.)
It's as simple as that!
Guest
Posts: n/a
To: RW-1
Do you want to shut me up? If so, please do the following
Ask these three questions of the R22 mechanics at Volar. Then, come back on to this thread.
Better still, print the questions and hand them to the mechanics. That way there will be no confusion or no influence by you in phrasing the questions.
1) In learning about gyroscopic precession or the same phenomenon as taught in the UK or Oz did they use the Robinson system as a demonstration or, did they use a Bell system as a means of explaining the subject?
The reason I ask this is because there are at least two websites that are the home pages of two Robinson dealers and flight schools. These websites have a very good explanation of how a helicopter flies. They have excellent pictures of Robinson helicopters and the major elements of those helicopters. They show pictures of Bell and Robinson rotorheads and they then go into the subject of gyroscopic precession.
Although the preceding text on the website(s) dealt with a Robinson rotorhead they explained gyroscopic precession by using a Bell system as an example. The two systems are different
.
2) In teaching the rigging process how did they explain the differences in the positioning of the Robinson blades as opposed to those of a Bell helicopter and, how did they rectify what they taught about gyroscopic precession as related to the positioning of the blades?
3)
I assume they taught that the precession phase angle was 90 degrees and yet the Robinson blades are disposed 18-degrees from the respective axes during the rigging process. What did they tell you about where the blade disc would dip if the cyclic was pushed forward from the rigged neutral position?
Please provide your thoughts on this following paragraph.
When the Robinson accelerates forward the pilot will counter the transverse flow effect by adding left cyclic. This is in addition to the left roll caused by the 18-degree offset. When he passes through the transverse flow effect he moves his cyclic to the right. In doing this he is reestablishing the helicopter in forward flight as opposed to rolling left. Is there a possibility that in the process of moving the cyclic to the right he is not only recovering from the transverse flow effect he is also countering the effect of the left roll induced by the offset? This is why I asked if in the certification process that they used a stick plotting board, then they would have noted this problem.
Please perform the following test (Providing it does not compromise flight safety).
RW-1 here is something you can demonstrate since you like flying on the edge. Lift off with your cyclic in the rigged neutral position. Do not move it laterally. Push it forward and fly through the transverse flow effect. The helicopter should roll to the right but don’t move the cyclic. When you are through the transverse flow effect, let me know which direction the helicopter is flying. Or, try this. With the cyclic in the rigged neutral position lift off in a hover and hover taxi the helicopter by moving the cyclic straight forward on the rigged neutral centerline. Do not move it off of the rigged neutral centerline.
If after accomplishing the above please let me know the results. This also goes for the rest of you R22/R44 pilots participating on this forum and on this thread.
One final note. Instead of constantly referring to what Frank Robinson said in his reply why don’t you respond to the points I made in disproving his statements about the 90-degree Vs 72-degree pitch horns? You seem to completely ignore my points and simply say that I am wrong because I disagree with what Mr. Robinson stated in his reply. I called them Bull S**t and you said I was a Bull S****er
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The Cat
Do you want to shut me up? If so, please do the following
Ask these three questions of the R22 mechanics at Volar. Then, come back on to this thread.
Better still, print the questions and hand them to the mechanics. That way there will be no confusion or no influence by you in phrasing the questions.
1) In learning about gyroscopic precession or the same phenomenon as taught in the UK or Oz did they use the Robinson system as a demonstration or, did they use a Bell system as a means of explaining the subject?
The reason I ask this is because there are at least two websites that are the home pages of two Robinson dealers and flight schools. These websites have a very good explanation of how a helicopter flies. They have excellent pictures of Robinson helicopters and the major elements of those helicopters. They show pictures of Bell and Robinson rotorheads and they then go into the subject of gyroscopic precession.
Although the preceding text on the website(s) dealt with a Robinson rotorhead they explained gyroscopic precession by using a Bell system as an example. The two systems are different
.
2) In teaching the rigging process how did they explain the differences in the positioning of the Robinson blades as opposed to those of a Bell helicopter and, how did they rectify what they taught about gyroscopic precession as related to the positioning of the blades?
3)
I assume they taught that the precession phase angle was 90 degrees and yet the Robinson blades are disposed 18-degrees from the respective axes during the rigging process. What did they tell you about where the blade disc would dip if the cyclic was pushed forward from the rigged neutral position?
Please provide your thoughts on this following paragraph.
When the Robinson accelerates forward the pilot will counter the transverse flow effect by adding left cyclic. This is in addition to the left roll caused by the 18-degree offset. When he passes through the transverse flow effect he moves his cyclic to the right. In doing this he is reestablishing the helicopter in forward flight as opposed to rolling left. Is there a possibility that in the process of moving the cyclic to the right he is not only recovering from the transverse flow effect he is also countering the effect of the left roll induced by the offset? This is why I asked if in the certification process that they used a stick plotting board, then they would have noted this problem.
Please perform the following test (Providing it does not compromise flight safety).
RW-1 here is something you can demonstrate since you like flying on the edge. Lift off with your cyclic in the rigged neutral position. Do not move it laterally. Push it forward and fly through the transverse flow effect. The helicopter should roll to the right but don’t move the cyclic. When you are through the transverse flow effect, let me know which direction the helicopter is flying. Or, try this. With the cyclic in the rigged neutral position lift off in a hover and hover taxi the helicopter by moving the cyclic straight forward on the rigged neutral centerline. Do not move it off of the rigged neutral centerline.
If after accomplishing the above please let me know the results. This also goes for the rest of you R22/R44 pilots participating on this forum and on this thread.
One final note. Instead of constantly referring to what Frank Robinson said in his reply why don’t you respond to the points I made in disproving his statements about the 90-degree Vs 72-degree pitch horns? You seem to completely ignore my points and simply say that I am wrong because I disagree with what Mr. Robinson stated in his reply. I called them Bull S**t and you said I was a Bull S****er
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The Cat
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Lu, for myself, I have never tried to contradict your assertion that there is a 72 not 90 degree offset in the rigging. The only fact I have disputed with you about is your original assertion that the R22 should not have been certified for a couple reasons:
1> the stick will not move in the correct sense to aircraft movement.
...several times we have stated that it does perform in a sense that is NOT objectionable to the pilot. I would like to note that the 1-2 degree difference you reference several times, near as I can tell, is your own number.
2> the flight manual restriction against sideslip means the certification sideslip could not be performed.
...Lu, all aircraft are required to perform during certification some procedures that are NOT normal procedures. The Bell 206 has a limiting crosswind component. This limit is less than .6 VNE. Does this mean that the 206 could not pass the certification test? Absolutely not. Is is capable of performing the test, but it is NOT a normal procedure.
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I have wondered many times if you are reading my posts with the intent of learning from them. Obviously not. You asked another pilot to perform a test, lifting into a hover with the cyclic in the rigged neutral position, not moving it laterally and then accelerating forward. Lateral cyclic is required to maintain position against tail-rotor drift, left cyclic. I told you this before.
I have learned a good bit of information from your posts about the R22 rigging, accident statistics, and general perception of the aircraft, but I am tempering that with my own experience. When I get a chance to fly one again (sson I hope) I will try to answer some of my own questions, but I still find that I must contend that the primary assertion in your paper to the NTSB questioning the R22 certification is flawed in its most basic logic.
That is the point I tried to address, and I'll post a single response here vice the many other R22 threads to avoid dredging them up from the void.
1> the stick will not move in the correct sense to aircraft movement.
...several times we have stated that it does perform in a sense that is NOT objectionable to the pilot. I would like to note that the 1-2 degree difference you reference several times, near as I can tell, is your own number.
2> the flight manual restriction against sideslip means the certification sideslip could not be performed.
...Lu, all aircraft are required to perform during certification some procedures that are NOT normal procedures. The Bell 206 has a limiting crosswind component. This limit is less than .6 VNE. Does this mean that the 206 could not pass the certification test? Absolutely not. Is is capable of performing the test, but it is NOT a normal procedure.
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I have wondered many times if you are reading my posts with the intent of learning from them. Obviously not. You asked another pilot to perform a test, lifting into a hover with the cyclic in the rigged neutral position, not moving it laterally and then accelerating forward. Lateral cyclic is required to maintain position against tail-rotor drift, left cyclic. I told you this before.
I have learned a good bit of information from your posts about the R22 rigging, accident statistics, and general perception of the aircraft, but I am tempering that with my own experience. When I get a chance to fly one again (sson I hope) I will try to answer some of my own questions, but I still find that I must contend that the primary assertion in your paper to the NTSB questioning the R22 certification is flawed in its most basic logic.
That is the point I tried to address, and I'll post a single response here vice the many other R22 threads to avoid dredging them up from the void.
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To: Helo Teacher
Point 1) the certification requirements dictate that a stick plotting board is used to determine that the helicopter will move in the same sense as cyclic stick displacement. The certification standards indicate that the displacement of the helicopter could be up to 2-degrees from cyclic stick displacement and could be attributed to pitch coupling. It is not intended to be up to the pilot to determine if the stick displacement is objectionable or not. It states that under ideal conditions if you moved the cyclic forward from the rigged neutral position the helicopter would fly straightforward. If it deviates from that sense of movement the difference can be no greater than +/- 2-Degrees.
Point 2) The certification requirements dictate that the helicopter demonstrate sideslip at .6 VNE by pushing hard to the stops on the pedals. First one pedal and returning to neutral and then on the other pedal. The helicopter must comply with this requirement as well as to demonstrate flying out of trim. Now you have to think on two planes at once. 1) The restrictions were placed on the sideslipping and out of trim flight because it was determined that in doing so you could induce severe flapping loads to the point of causing mast bumping and loss of the rotor. 2) If it was determined that these two actions would result in mast bumping then what happened when these same actions were demonstrated in order to gain certification. My premise about the Robinson not being certifiable stems from the facts above. If the Helicopters were presented for certification with the restrictions against sideslipping and out of trim flight they could not pass the certification requirement requiring demonstration of these flight maneuvers. It is not to say that they could not do these maneuvers because the OZ pilots do it all the time. However the fact remains that if you do these maneuvers and something happens it is your fault because the AD and the POH tell you not to do them.
Regarding the crosswind component on the Bell 206 this limitation was established during the sideslip demonstration during the certification trials. The test sets the maximum outer limits that can be obtained by the specific design. On the Bell it just happened that because of the test it was determined that the restriction be put in place for certification. I am assuming this because of what you said in your post.
Regarding what you said about lateral cyclic having to be used to counter the propeller effect of the tail rotor, I was under the Impression that there is a left tilt of 2-degrees on the mast to counter this effect. Regarding the report, if I had it to do all over again I would have made some changes. These changes would have been prompted by what I have learned from the postings of others including your self which caused me to look deeper into the subject. The most illuminating of all of those changes of mind occurred when I reread the rigging procedures and I found out the following. http://pprune.homestead.com/files/rigging.jpg
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The Cat
Point 1) the certification requirements dictate that a stick plotting board is used to determine that the helicopter will move in the same sense as cyclic stick displacement. The certification standards indicate that the displacement of the helicopter could be up to 2-degrees from cyclic stick displacement and could be attributed to pitch coupling. It is not intended to be up to the pilot to determine if the stick displacement is objectionable or not. It states that under ideal conditions if you moved the cyclic forward from the rigged neutral position the helicopter would fly straightforward. If it deviates from that sense of movement the difference can be no greater than +/- 2-Degrees.
Point 2) The certification requirements dictate that the helicopter demonstrate sideslip at .6 VNE by pushing hard to the stops on the pedals. First one pedal and returning to neutral and then on the other pedal. The helicopter must comply with this requirement as well as to demonstrate flying out of trim. Now you have to think on two planes at once. 1) The restrictions were placed on the sideslipping and out of trim flight because it was determined that in doing so you could induce severe flapping loads to the point of causing mast bumping and loss of the rotor. 2) If it was determined that these two actions would result in mast bumping then what happened when these same actions were demonstrated in order to gain certification. My premise about the Robinson not being certifiable stems from the facts above. If the Helicopters were presented for certification with the restrictions against sideslipping and out of trim flight they could not pass the certification requirement requiring demonstration of these flight maneuvers. It is not to say that they could not do these maneuvers because the OZ pilots do it all the time. However the fact remains that if you do these maneuvers and something happens it is your fault because the AD and the POH tell you not to do them.
Regarding the crosswind component on the Bell 206 this limitation was established during the sideslip demonstration during the certification trials. The test sets the maximum outer limits that can be obtained by the specific design. On the Bell it just happened that because of the test it was determined that the restriction be put in place for certification. I am assuming this because of what you said in your post.
Regarding what you said about lateral cyclic having to be used to counter the propeller effect of the tail rotor, I was under the Impression that there is a left tilt of 2-degrees on the mast to counter this effect. Regarding the report, if I had it to do all over again I would have made some changes. These changes would have been prompted by what I have learned from the postings of others including your self which caused me to look deeper into the subject. The most illuminating of all of those changes of mind occurred when I reread the rigging procedures and I found out the following. http://pprune.homestead.com/files/rigging.jpg
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The Cat
Guest
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My mistake, in reading your report I got the impression the 1-2 degree sense of direction allowance was yours. What I would really like to read at this point is the report that established these limits. You wouldn't happen to have a link would you?
I still feel, from my experiences with the aircraft, is that the biggest threat in a sideslip in the R22 is overcontrolling by the pilot. The limit being there to prevent inexperienced pilots from getting into trouble.
Also, can you please explain how the coning hinges prevent a 90 degree lead but allow a 72 degree lead??
I still feel, from my experiences with the aircraft, is that the biggest threat in a sideslip in the R22 is overcontrolling by the pilot. The limit being there to prevent inexperienced pilots from getting into trouble.
Also, can you please explain how the coning hinges prevent a 90 degree lead but allow a 72 degree lead??
Guest
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Surely the mast bumbing that can occur with large sideslip is due to the aerodynamic effects of trying to fly a fueselage sideways at great speed? rather than in its normal 'clean' sense. Hence the different effect of fixed floats etc.
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Another day in paradise
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Another day in paradise