R22 Corner
Guest
Posts: n/a
TO: HELO TEACHER
“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?
RESPONSE: YOU ARE CORRECT, THE DEGREES OF COUPLING WERE MINE. I WENT BACK TO THE CERTIFICATION DOCUMENT AND I FOUND THAT I MADE A COMMENT ON THE BOTTOM OF THE PAGE. THE SECTION OF THE DOCUMENT STATED THAT THERE SHOULD BE A STANDARDIZE MOTION IN THAT WHEN THE CONTROLS WERE MOVED THE HELICOPTER SHOULD RESPOND IN THE DIRECTION OF CONTROL MOVEMENT. THE DOCUMENT ALLOWED FOR A CERTAIN DEVIATION DUE TO CYCLIC/COLLECTIVE COUPLING BUT NOT ENOUGH THAT THE PILOTS WOULD FIND IT UNCOMFORTABLE. My COMMENT STATED THAT 1-3-DEGREES OF COLLECTIVE/CYCLIC COUPLE WOULD BE ACCEPTABLE BUT NOT 18-DEGREES. I PICJKED UP THE COMMENT AND ADDED TO MY REPORT AS A MEANS OF COMPARING COLLECTIVE/CYCLIC COUPLE AS DESCRIBED IN THE CERTIFICATION DOCUMENT AND MY PREMISE THAT STATED THAT THERE IS AN 18-DEGREE OFFSET REQUIRING THE PILOT TO COMPENSATE FOR THAT OFFSET. THE SECTION THAT DEALS WITH THE SENSE OF DIRECTION IS SECTION 27.779 OF THE FAA NORMAL CATEGORY ROTORCRAFT CERTIFICATION REQUIREMENTS. DOCUMENT NUMBER AC 27.1 CHANGE 2
“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”.
RESPONSE: THE LIMIT OR RESTRICTION AGAINST SIDESLIP AND OUT OF TRIM WAS PLACED IN THE POHs FOR REASONS PREVIOUSLY STATED AND THEY APPLY TO ALL PILOTS NO MATTER WHAT THEIR LEVEL OF EXPERIENCE MIGHT BE.
“Also, can you please explain how the coning hinges prevent a 90 degree lead but allow a 72-degree lead”?
RESPONSE: IF YOU HAVE ACCESS TO A BELL 206 YOU CAN CHECK THE ROTORHEAD AND YOU CAN SEE THAT THE PITCH HORN TERMINATES AT THE TEETER HINGE. IF WHEN THE DISC IS TILTED OR WHEN YOU ARE IN A HOVER THE BLADES ARE DISPLACED FROM THE TIP PATH SELECTED BY THE PILOT THE DISC WILL FLAP IN RELATION TO THE FIXED SWASHPLATE. THIS CAUSES A RELATIVE MOVEMENT BETWEEN THE FIXED PITCH LINK AND THE PITCH HORN. IF THE BLADE FLAPS DOWN IN RELATION TO THE FIXED PITCH LINK THE PITCH WILL INCREASE AND THE OPPOSITE IS TRUE FOR THE OTHER BLADE THAT FLAPS UP. THIS PROVIDES A RESTORING FORCE AND RETURNS THE DISC TO THE COMMANDED POSITION. WHEN THE SWASH PLATE AND ROTOR DISC ARE PARALLEL THE ACTION WILL STOP. IF THE PITCH HORN / PITCHLINK ATTACHMENT ARE COINCIDENT WITH THE TEETER HINGE THERE WILL BE NO PITCH CHANGE IF AN EXTERNAL FORCE DISPLACES THE BLADE. IN THIS CASE THERE MIGHT BE A DISC DISPLACEMENT DUE TO GYROSCOPIC PRECESSION (MAYBE)
NOW, LOOK AT THE ROBINSON HEAD. TRY TO VISUALIZE A 90-DEGREE PITCH HORN. NOW TRY TO VISUALIZE WHAT HAPPENS WHEN THE BLADES CONE UP. WHEN THEY CONE, THE PITCH COUPLING WOULD INCREASE THE PITCH SETTING APPLIED BY THE PILOT TO SUCH AN EXTENT THAT YOU COULD END UP STALLING THE BLADES. IF YOU COULD GET IT OFF THE GROUND, TRY TO VISUALIZE WHAT HAPPENS DUE TO PITCH COUPLING WHEN THE CYCLIC IS DISPLACED AND YOU ADD IN ADDITIONAL PITCH ON THE RETREATING BLADE.
IF YOU COULD GET IT OFF THE GROUND AND YOU HAD THE POWER AND THEN INTRODUCED CYCLIC PITCH YOU WOULD IMMEDIADTELY BE EATING A PLEXIGLAS SANDWICH. THE POSITION OF THE CONE HINGES DICTATES WHERE THE PITCH HORN / PITCHLINK CONNECT POINT MUST BE. UNDER IDEAL CONDITIONS THE PITCH HORN / PITCH LINK WOULD TERMINATE COINCIDENT WITH THE CONE HINGE. FLIGHT MANEUVERING AND PITCH SETTINGS DO NOT ALLOW THIS TO HAPPEN. IN THIS RESPECT, THE ROBINSON HEAD IS JUST LIKE A SIKORSKY HEAD THAT HAS OFFSET HINGES.
NOW, IF YOU UNDERSTAND THIS, YOU WILL ALSO UNDERSTAND WHY I STATED THAT FRANK ROBINSON WAS HANDING OUT A LINE OF BULL WHEN HE INDICATED,THAT HE HAD CONSIDERED THE 90-DEGREE PITCH,HORN EVEN THOUGH HIS ROTOR SYSTEM IN EFFECT HAD AN OFFSET HINGE AS A PART OF THE DESIGN FROM DAY ONE.
YOU MAY HAVE NOTICED THAT I HAVE CHANGED MY STORY A BIT ABOUT WHAT HAPPENS IF YOU HAVE A 90-DEGREE PITCH HORN ON A RIOBINSON HEAD. THIS COMES FROM YOUR INPUT THAT CAUSED ME TO EXAMINE THE PROBLEM FROM A DIFFERENT PERSPECTIVE.
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The Cat
[This message has been edited by Lu Zuckerman (edited 01 January 2001).]
“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?
RESPONSE: YOU ARE CORRECT, THE DEGREES OF COUPLING WERE MINE. I WENT BACK TO THE CERTIFICATION DOCUMENT AND I FOUND THAT I MADE A COMMENT ON THE BOTTOM OF THE PAGE. THE SECTION OF THE DOCUMENT STATED THAT THERE SHOULD BE A STANDARDIZE MOTION IN THAT WHEN THE CONTROLS WERE MOVED THE HELICOPTER SHOULD RESPOND IN THE DIRECTION OF CONTROL MOVEMENT. THE DOCUMENT ALLOWED FOR A CERTAIN DEVIATION DUE TO CYCLIC/COLLECTIVE COUPLING BUT NOT ENOUGH THAT THE PILOTS WOULD FIND IT UNCOMFORTABLE. My COMMENT STATED THAT 1-3-DEGREES OF COLLECTIVE/CYCLIC COUPLE WOULD BE ACCEPTABLE BUT NOT 18-DEGREES. I PICJKED UP THE COMMENT AND ADDED TO MY REPORT AS A MEANS OF COMPARING COLLECTIVE/CYCLIC COUPLE AS DESCRIBED IN THE CERTIFICATION DOCUMENT AND MY PREMISE THAT STATED THAT THERE IS AN 18-DEGREE OFFSET REQUIRING THE PILOT TO COMPENSATE FOR THAT OFFSET. THE SECTION THAT DEALS WITH THE SENSE OF DIRECTION IS SECTION 27.779 OF THE FAA NORMAL CATEGORY ROTORCRAFT CERTIFICATION REQUIREMENTS. DOCUMENT NUMBER AC 27.1 CHANGE 2
“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”.
RESPONSE: THE LIMIT OR RESTRICTION AGAINST SIDESLIP AND OUT OF TRIM WAS PLACED IN THE POHs FOR REASONS PREVIOUSLY STATED AND THEY APPLY TO ALL PILOTS NO MATTER WHAT THEIR LEVEL OF EXPERIENCE MIGHT BE.
“Also, can you please explain how the coning hinges prevent a 90 degree lead but allow a 72-degree lead”?
RESPONSE: IF YOU HAVE ACCESS TO A BELL 206 YOU CAN CHECK THE ROTORHEAD AND YOU CAN SEE THAT THE PITCH HORN TERMINATES AT THE TEETER HINGE. IF WHEN THE DISC IS TILTED OR WHEN YOU ARE IN A HOVER THE BLADES ARE DISPLACED FROM THE TIP PATH SELECTED BY THE PILOT THE DISC WILL FLAP IN RELATION TO THE FIXED SWASHPLATE. THIS CAUSES A RELATIVE MOVEMENT BETWEEN THE FIXED PITCH LINK AND THE PITCH HORN. IF THE BLADE FLAPS DOWN IN RELATION TO THE FIXED PITCH LINK THE PITCH WILL INCREASE AND THE OPPOSITE IS TRUE FOR THE OTHER BLADE THAT FLAPS UP. THIS PROVIDES A RESTORING FORCE AND RETURNS THE DISC TO THE COMMANDED POSITION. WHEN THE SWASH PLATE AND ROTOR DISC ARE PARALLEL THE ACTION WILL STOP. IF THE PITCH HORN / PITCHLINK ATTACHMENT ARE COINCIDENT WITH THE TEETER HINGE THERE WILL BE NO PITCH CHANGE IF AN EXTERNAL FORCE DISPLACES THE BLADE. IN THIS CASE THERE MIGHT BE A DISC DISPLACEMENT DUE TO GYROSCOPIC PRECESSION (MAYBE)
NOW, LOOK AT THE ROBINSON HEAD. TRY TO VISUALIZE A 90-DEGREE PITCH HORN. NOW TRY TO VISUALIZE WHAT HAPPENS WHEN THE BLADES CONE UP. WHEN THEY CONE, THE PITCH COUPLING WOULD INCREASE THE PITCH SETTING APPLIED BY THE PILOT TO SUCH AN EXTENT THAT YOU COULD END UP STALLING THE BLADES. IF YOU COULD GET IT OFF THE GROUND, TRY TO VISUALIZE WHAT HAPPENS DUE TO PITCH COUPLING WHEN THE CYCLIC IS DISPLACED AND YOU ADD IN ADDITIONAL PITCH ON THE RETREATING BLADE.
IF YOU COULD GET IT OFF THE GROUND AND YOU HAD THE POWER AND THEN INTRODUCED CYCLIC PITCH YOU WOULD IMMEDIADTELY BE EATING A PLEXIGLAS SANDWICH. THE POSITION OF THE CONE HINGES DICTATES WHERE THE PITCH HORN / PITCHLINK CONNECT POINT MUST BE. UNDER IDEAL CONDITIONS THE PITCH HORN / PITCH LINK WOULD TERMINATE COINCIDENT WITH THE CONE HINGE. FLIGHT MANEUVERING AND PITCH SETTINGS DO NOT ALLOW THIS TO HAPPEN. IN THIS RESPECT, THE ROBINSON HEAD IS JUST LIKE A SIKORSKY HEAD THAT HAS OFFSET HINGES.
NOW, IF YOU UNDERSTAND THIS, YOU WILL ALSO UNDERSTAND WHY I STATED THAT FRANK ROBINSON WAS HANDING OUT A LINE OF BULL WHEN HE INDICATED,THAT HE HAD CONSIDERED THE 90-DEGREE PITCH,HORN EVEN THOUGH HIS ROTOR SYSTEM IN EFFECT HAD AN OFFSET HINGE AS A PART OF THE DESIGN FROM DAY ONE.
YOU MAY HAVE NOTICED THAT I HAVE CHANGED MY STORY A BIT ABOUT WHAT HAPPENS IF YOU HAVE A 90-DEGREE PITCH HORN ON A RIOBINSON HEAD. THIS COMES FROM YOUR INPUT THAT CAUSED ME TO EXAMINE THE PROBLEM FROM A DIFFERENT PERSPECTIVE.
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The Cat
[This message has been edited by Lu Zuckerman (edited 01 January 2001).]
Guest
Posts: n/a
To: 212 Man
What you say is quite true. With a single rotor helicopter like the R22 or, R44 there is minimal interlock between the rotorhead and the mast. As such, the angle of the disc is much greater than that of a multiblade rotor system with offset hinges and a much higher interlock. This would place you in a condition that could degrade into mast bumping. The problem is, the Robinson had to demonstrate this situation in order to get a certification. If the condition that you described above was in fact true and I think it is, then the mast bumping or something approaching mast bumping would have been noted. According to Frank Robinson one of the tests he ran was to fully instrument the rotor to determine flapping angles. If he did, then this too would have uncovered the possibility of mast bumping during a side slip.
However, it is my opinion that Mr. Robinson added his comment about exposed sail area when flying sideways as a red herring.
In my report I questioned both Robinson and the FAA if these tests were actually completed and if they were successful. He never answered.
What it all boils down to is if the tests were required and if they were in fact completed to the satisfaction of the FAA the FAA now says that you can't perform sideslips or fly out of trim.
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The Cat
[This message has been edited by Lu Zuckerman (edited 01 January 2001).]
What you say is quite true. With a single rotor helicopter like the R22 or, R44 there is minimal interlock between the rotorhead and the mast. As such, the angle of the disc is much greater than that of a multiblade rotor system with offset hinges and a much higher interlock. This would place you in a condition that could degrade into mast bumping. The problem is, the Robinson had to demonstrate this situation in order to get a certification. If the condition that you described above was in fact true and I think it is, then the mast bumping or something approaching mast bumping would have been noted. According to Frank Robinson one of the tests he ran was to fully instrument the rotor to determine flapping angles. If he did, then this too would have uncovered the possibility of mast bumping during a side slip.
However, it is my opinion that Mr. Robinson added his comment about exposed sail area when flying sideways as a red herring.
In my report I questioned both Robinson and the FAA if these tests were actually completed and if they were successful. He never answered.
What it all boils down to is if the tests were required and if they were in fact completed to the satisfaction of the FAA the FAA now says that you can't perform sideslips or fly out of trim.
------------------
The Cat
[This message has been edited by Lu Zuckerman (edited 01 January 2001).]
Guest
Posts: n/a
To: RW-1
Hey guy welcome back. I could have sworn that I read a post by you stating that you would never darken these threads again. Oh well, as they say you can’t keep a good guy down.
Regarding the crash of the R22 from Volar Helicopters you may have the scoop on what happened but it is premature to say it was pilot error. The pilot was trying to contend with a catastrophic engine failure and that can be upsetting to any pilot no matter how many hours in type especially if it happens in an R22 with a low inertia rotor system. For all you know her passenger may have become freaked out and possibly hit the controls and now, she had two things to contend with. I don’t care how many of her friends you talked to. That lady had her hands full and she was at a fairly low altitude. I would strongly suggest that you and the pilots friends keep your collective mouths shut and let the NTSB do its’ work. Based on past crash histories of all Robinson crashes it will most likely be listed as pilot error. Then and only then can you and you friends gloat and say we were right. By the way, did you attend her funeral?
Why do you fight me so hard when I ask the pilots to perform a test that will either prove me right or prove me wrong. And why do you constantly tell me I am wrong about delta 3 and its’ effects when I continually ask anyone that believes in what Frank Robinson stated to explain to me what he was talking about. I think I have bent over backwards to explain my views to the point that I have to put my comments into memory so I can extract them when some assbite tells me I am wrong and he doesn’t wish to explain his views. All I get is Frank Robinson said it so it must be true. Don’t just tell me I’m wrong because you think I’m wrong. Prove it. Do what I asked of you in a previous post. Give the questions to your mechanics and get your ass in the R22 and perform the tests. If you don’t want to do that then shut up and stop trying to sharpshoot me from sunny Florida.
If they hadn’t lost the local R22 I would have bought an hour several months ago. I may be going out on a consulting assignment soon and hopefully there will be a Robbie in the neighborhood.
Regarding your use of the term Psychotropic Therapy. It is not in my Webster's dictionary however, my mind is clear enough to recall my science and biology studies at Michigan State.
Psycho=Crazy Tropic=Affinity = Close association with crazy people. Who is crazy? The people I deal with on these threads or is it you because I really like to pull your chain.
Nobody has tried to explain anything except Krillian and he used engineering speak to define pitch coupling and not its’ effect on gyroscopic precession. I challenged everyone to explain what Frank Robinson said in countering my arguments. Nobody responded. You accuse me of being pigheaded in my views even though I believe what I say is true. I however would welcome anybody to tell me why I am wrong without quoting Frank Robinson. I think you are pig headed in not wanting to do what I asked because you might be proved wrong.
The gauntlet has been dropped.
Oh yes, regarding those private emails from participants on these threads that back your opinions the challenge goes out to them as well. You know who you are.
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The Cat
Hey guy welcome back. I could have sworn that I read a post by you stating that you would never darken these threads again. Oh well, as they say you can’t keep a good guy down.
Regarding the crash of the R22 from Volar Helicopters you may have the scoop on what happened but it is premature to say it was pilot error. The pilot was trying to contend with a catastrophic engine failure and that can be upsetting to any pilot no matter how many hours in type especially if it happens in an R22 with a low inertia rotor system. For all you know her passenger may have become freaked out and possibly hit the controls and now, she had two things to contend with. I don’t care how many of her friends you talked to. That lady had her hands full and she was at a fairly low altitude. I would strongly suggest that you and the pilots friends keep your collective mouths shut and let the NTSB do its’ work. Based on past crash histories of all Robinson crashes it will most likely be listed as pilot error. Then and only then can you and you friends gloat and say we were right. By the way, did you attend her funeral?
Why do you fight me so hard when I ask the pilots to perform a test that will either prove me right or prove me wrong. And why do you constantly tell me I am wrong about delta 3 and its’ effects when I continually ask anyone that believes in what Frank Robinson stated to explain to me what he was talking about. I think I have bent over backwards to explain my views to the point that I have to put my comments into memory so I can extract them when some assbite tells me I am wrong and he doesn’t wish to explain his views. All I get is Frank Robinson said it so it must be true. Don’t just tell me I’m wrong because you think I’m wrong. Prove it. Do what I asked of you in a previous post. Give the questions to your mechanics and get your ass in the R22 and perform the tests. If you don’t want to do that then shut up and stop trying to sharpshoot me from sunny Florida.
If they hadn’t lost the local R22 I would have bought an hour several months ago. I may be going out on a consulting assignment soon and hopefully there will be a Robbie in the neighborhood.
Regarding your use of the term Psychotropic Therapy. It is not in my Webster's dictionary however, my mind is clear enough to recall my science and biology studies at Michigan State.
Psycho=Crazy Tropic=Affinity = Close association with crazy people. Who is crazy? The people I deal with on these threads or is it you because I really like to pull your chain.
Nobody has tried to explain anything except Krillian and he used engineering speak to define pitch coupling and not its’ effect on gyroscopic precession. I challenged everyone to explain what Frank Robinson said in countering my arguments. Nobody responded. You accuse me of being pigheaded in my views even though I believe what I say is true. I however would welcome anybody to tell me why I am wrong without quoting Frank Robinson. I think you are pig headed in not wanting to do what I asked because you might be proved wrong.
The gauntlet has been dropped.
Oh yes, regarding those private emails from participants on these threads that back your opinions the challenge goes out to them as well. You know who you are.
------------------
The Cat
Guest
Posts: n/a
To: RW-1
This was lifted off of your website. The only thing missing is the diagram. The missing diagram shows the control inputs and gyroscopic precession results. The illustration is of a Bell swashplate. This is the same diagram that is on the two Robinson websites. Do you believe in gyroscopic precession and, if you do, please explain to me and all of the other participants how gyroscopic precession phase angle of 90-degrees applies to a Robinson helicopter that has the same control inputs as a Bell Helicopter.
Gyroscopic precession is a phenomenon occurring in rotating bodies in which an applied force is manifested 90 degrees later in the direction of rotation from where the force was applied.
Although precession is not a dominant force in rotary-wing aerodynamics, it must be reckoned with because turning rotor systems exhibit some of the characteristics of a gyro. The graphic shows how precession affects the rotor disk when force is applied at a given point:
A downward force applied to the disk at point A results in a downward change in disk attitude at point B, and an upward force applied at Point C results in an upward change in disk attitude at point D
.
Forces applied to a spinning rotor disk by control input or by wind gusts will react as follows:
This behavior explains some of the fundamental effects occurring during various helicopter maneuvers. For example, the helicopter behaves differently when rolling into a right turn than when rolling into a left turn. During roll into a left turn, the pilot will have to correct for a nose down tendency in order to maintain altitude. This correction is required because precession causes a nose down tendency and because the tilted disk produces less vertical lift to counteract gravity. Conversely, during a roll into a right turn, precession will cause a nose up tendency while the tilted disk will produce less vertical lift. Pilot input required to maintain altitude is significantly different during a right turn than during a left turn, because gyroscopic precession acts in opposite directions for each.
Return to Dynamic Aerodynamics!
Return to Dynamic Flight
Copyright Š1999-2000 Dynamic Flight, Inc. All rights reserved.
------------------
The Cat
This was lifted off of your website. The only thing missing is the diagram. The missing diagram shows the control inputs and gyroscopic precession results. The illustration is of a Bell swashplate. This is the same diagram that is on the two Robinson websites. Do you believe in gyroscopic precession and, if you do, please explain to me and all of the other participants how gyroscopic precession phase angle of 90-degrees applies to a Robinson helicopter that has the same control inputs as a Bell Helicopter.
Gyroscopic precession is a phenomenon occurring in rotating bodies in which an applied force is manifested 90 degrees later in the direction of rotation from where the force was applied.
Although precession is not a dominant force in rotary-wing aerodynamics, it must be reckoned with because turning rotor systems exhibit some of the characteristics of a gyro. The graphic shows how precession affects the rotor disk when force is applied at a given point:
A downward force applied to the disk at point A results in a downward change in disk attitude at point B, and an upward force applied at Point C results in an upward change in disk attitude at point D
.
Forces applied to a spinning rotor disk by control input or by wind gusts will react as follows:
This behavior explains some of the fundamental effects occurring during various helicopter maneuvers. For example, the helicopter behaves differently when rolling into a right turn than when rolling into a left turn. During roll into a left turn, the pilot will have to correct for a nose down tendency in order to maintain altitude. This correction is required because precession causes a nose down tendency and because the tilted disk produces less vertical lift to counteract gravity. Conversely, during a roll into a right turn, precession will cause a nose up tendency while the tilted disk will produce less vertical lift. Pilot input required to maintain altitude is significantly different during a right turn than during a left turn, because gyroscopic precession acts in opposite directions for each.
Return to Dynamic Aerodynamics!
Return to Dynamic Flight
Copyright Š1999-2000 Dynamic Flight, Inc. All rights reserved.
------------------
The Cat
Guest
Posts: n/a
To: RW-1
Either you are spring loaded to the pissed off position or, your “G” spot is very easily stimulated. Also, calling me a “Dumb MF” on an open forum doesn’t speak well for your own level of intelligence. How are you going to function as an EMS pilot? According to many posts on Just Helicopters it was stated that the Pilot of an EMS helicopter must bend over backwards to accommodate the ideas of his associates. They also stressed CRM. If you carry the same attitudes displayed on this forum into an EMS environment I doubt if you will last very long.
You stated that I need to prove my theory. That is not a true statement. What I am asking, is that you or any of my detractors disprove my theory by performing the test and to provide the list of questions (above) to the mechanics that maintain your aircraft.
What others have told me is basically a repeat of what Frank Robinson stated in his reply to my comments. That does not constitute criticism it is simply the parroting of what FR said. It can be likened to a man that claims to have twenty one years of experienc but under examination it was determined that he had one years experience at twenty one jobs.
Another point you seemed to have missed is that the statements I made in my report, which is what prompted these various threads, have changed. This is due to the back and forth of these threads that forced me to reevaluate and reformulate my theories.
Although the theories have changed the basic premise of the 18-degree offset has not changed.
When I stated that when the pilot pushed forward cyclic from the rigged neutral position I did not consider transverse flow effect. In encountering transverse flow effect the helicopter will roll to the right. To counter this, the pilot will introduce left cyclic which will counter the right roll. It stands to reason that once the helicopter is through the transverse flow effect the helicopter will roll to the left if the cyclic is not moved to the right. Now, for once don’t jump up and down saying no-no-no and try to visualize what I am trying to say. I stated that the 18-degree offset would introduce a left roll or at least cause the helicopter to move in a leftward direction. The pilot inputting left cyclic to counter the right roll is masking this whole phenomenon. Is it even a bit possible that in moving the cyclic to the right after transiting the transverse flow effect that the pilot has also corrected for the left roll caused by the 18-degree offset?
Another question you have not responded to is your explanation of how the 90-degree phase angle that is described in your website can relate to a Bell or any other helicopter and not to the Robinson R22 or the R44. Use your own words and not what Frank Robinson said. You stated that other things effect phase angle. Just what other things are you alluding to? Again, use your own words.
Regarding my attending MS, I went there because they accepted all of my credits from NW Michigan College in Traverse City. I really wanted to go to U of M but I didn’t have enough math credits. How do you feel about UCLA? I attended UCLA in order to get my teaching credentials in four subject areas. One of those subjects was Aircraft and Aerospace Technology.
On your website you stated that you were associated with six different helicopters and one fixed wing aircraft. All of this according to your Bio was in a SAR capacity. Just what was it that you did in performing you duties that gave you such exposure and I assume your wide technical knowledge that allows you to be so critical of my ideas and theories. One other point, I didn't know that the US Navy used the HH-65. I was under the impression that the USCG was the only military force that used this helicopter. If I'm wrong, I stand corrected.
Regarding the acceptance of my theories, how about this? For two years, I managed a training program for the US Army. As a part of my duties, I taught helicopter flight theory and the flight control systems on three different helicopters. I also taught rigging procedures. I taught a class in flight theory at Fredrick Junior College A&P program and, I taught the same class at Ivy Tech State College in Indiana. Nobody questioned my presentation nor did they say I was wrong.
At Fredrick Junior College they had a Bell model 47 as their training aircraft. It just so happened that it was hangered with an R22. This allowed me to put both helicopters side-by-side and explain the differences between the two. I showed them the 18-degree offset and they fully understood what I was talking about. Why can’t you understand?
Oh yes,when you were two years old pointing your finger towards the sky and saying,"Jet" I was manager of technical assistance for Bell Heicopter International overseeing the product support of over 900 helicopters and fixed wing aircraft.
Please respond but without vulgarities.
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The Cat
[This message has been edited by Lu Zuckerman (edited 02 January 2001).]
[This message has been edited by Lu Zuckerman (edited 02 January 2001).]
[This message has been edited by Lu Zuckerman (edited 02 January 2001).]
Either you are spring loaded to the pissed off position or, your “G” spot is very easily stimulated. Also, calling me a “Dumb MF” on an open forum doesn’t speak well for your own level of intelligence. How are you going to function as an EMS pilot? According to many posts on Just Helicopters it was stated that the Pilot of an EMS helicopter must bend over backwards to accommodate the ideas of his associates. They also stressed CRM. If you carry the same attitudes displayed on this forum into an EMS environment I doubt if you will last very long.
You stated that I need to prove my theory. That is not a true statement. What I am asking, is that you or any of my detractors disprove my theory by performing the test and to provide the list of questions (above) to the mechanics that maintain your aircraft.
What others have told me is basically a repeat of what Frank Robinson stated in his reply to my comments. That does not constitute criticism it is simply the parroting of what FR said. It can be likened to a man that claims to have twenty one years of experienc but under examination it was determined that he had one years experience at twenty one jobs.
Another point you seemed to have missed is that the statements I made in my report, which is what prompted these various threads, have changed. This is due to the back and forth of these threads that forced me to reevaluate and reformulate my theories.
Although the theories have changed the basic premise of the 18-degree offset has not changed.
When I stated that when the pilot pushed forward cyclic from the rigged neutral position I did not consider transverse flow effect. In encountering transverse flow effect the helicopter will roll to the right. To counter this, the pilot will introduce left cyclic which will counter the right roll. It stands to reason that once the helicopter is through the transverse flow effect the helicopter will roll to the left if the cyclic is not moved to the right. Now, for once don’t jump up and down saying no-no-no and try to visualize what I am trying to say. I stated that the 18-degree offset would introduce a left roll or at least cause the helicopter to move in a leftward direction. The pilot inputting left cyclic to counter the right roll is masking this whole phenomenon. Is it even a bit possible that in moving the cyclic to the right after transiting the transverse flow effect that the pilot has also corrected for the left roll caused by the 18-degree offset?
Another question you have not responded to is your explanation of how the 90-degree phase angle that is described in your website can relate to a Bell or any other helicopter and not to the Robinson R22 or the R44. Use your own words and not what Frank Robinson said. You stated that other things effect phase angle. Just what other things are you alluding to? Again, use your own words.
Regarding my attending MS, I went there because they accepted all of my credits from NW Michigan College in Traverse City. I really wanted to go to U of M but I didn’t have enough math credits. How do you feel about UCLA? I attended UCLA in order to get my teaching credentials in four subject areas. One of those subjects was Aircraft and Aerospace Technology.
On your website you stated that you were associated with six different helicopters and one fixed wing aircraft. All of this according to your Bio was in a SAR capacity. Just what was it that you did in performing you duties that gave you such exposure and I assume your wide technical knowledge that allows you to be so critical of my ideas and theories. One other point, I didn't know that the US Navy used the HH-65. I was under the impression that the USCG was the only military force that used this helicopter. If I'm wrong, I stand corrected.
Regarding the acceptance of my theories, how about this? For two years, I managed a training program for the US Army. As a part of my duties, I taught helicopter flight theory and the flight control systems on three different helicopters. I also taught rigging procedures. I taught a class in flight theory at Fredrick Junior College A&P program and, I taught the same class at Ivy Tech State College in Indiana. Nobody questioned my presentation nor did they say I was wrong.
At Fredrick Junior College they had a Bell model 47 as their training aircraft. It just so happened that it was hangered with an R22. This allowed me to put both helicopters side-by-side and explain the differences between the two. I showed them the 18-degree offset and they fully understood what I was talking about. Why can’t you understand?
Oh yes,when you were two years old pointing your finger towards the sky and saying,"Jet" I was manager of technical assistance for Bell Heicopter International overseeing the product support of over 900 helicopters and fixed wing aircraft.
Please respond but without vulgarities.
------------------
The Cat
[This message has been edited by Lu Zuckerman (edited 02 January 2001).]
[This message has been edited by Lu Zuckerman (edited 02 January 2001).]
[This message has been edited by Lu Zuckerman (edited 02 January 2001).]
Guest
Posts: n/a
Doing some reading and thinking aerodynamically, and I thought I'd pass on a couple items for thought.
(1)
With reference to the rigged neutral position on the R22 being right of center, a quote from "Rotary Wing Flight" talking about design features intended to overcome tranlating tendency [tail-rotor drift]:
^flight control rigging may be designed so the rotor disc is tilted slightly left when the cyclic conrol is centered^
(2)
as regards transverse flow effect, i find it hard to beleive the robbie ever gets going fast enough to stop seing the effects of this. as a result, it is quite likely that the left cyclic that would be required is being fed in by the notorious 18 degree offset (left component with forward cyclic movement).
(3)
how on earth did the whole delta-three thing start? what i've been reading about these hinges doesn't seem to apply at all??? it looks like a teeter and standard coning hinges to me.
(4)
the nose down tendency resulting from rolling into a left turn will be countered again by the notorious . 1 . 8 (sounds like a rap band). again this tends to explain why, in the cockpit, the aircraft behaves quite normally and not objectionably to the pilot. worth a thoughth.
(5)
found a good explanation of stick plots as well, and the typical plot was quite a zig-zag related to airspeed.
anyway, thought i'd pass it along, just the instructor in me, i can't let an incomplete explanation alone :-)
(1)
With reference to the rigged neutral position on the R22 being right of center, a quote from "Rotary Wing Flight" talking about design features intended to overcome tranlating tendency [tail-rotor drift]:
^flight control rigging may be designed so the rotor disc is tilted slightly left when the cyclic conrol is centered^
(2)
as regards transverse flow effect, i find it hard to beleive the robbie ever gets going fast enough to stop seing the effects of this. as a result, it is quite likely that the left cyclic that would be required is being fed in by the notorious 18 degree offset (left component with forward cyclic movement).
(3)
how on earth did the whole delta-three thing start? what i've been reading about these hinges doesn't seem to apply at all??? it looks like a teeter and standard coning hinges to me.
(4)
the nose down tendency resulting from rolling into a left turn will be countered again by the notorious . 1 . 8 (sounds like a rap band). again this tends to explain why, in the cockpit, the aircraft behaves quite normally and not objectionably to the pilot. worth a thoughth.
(5)
found a good explanation of stick plots as well, and the typical plot was quite a zig-zag related to airspeed.
anyway, thought i'd pass it along, just the instructor in me, i can't let an incomplete explanation alone :-)
Guest
Posts: n/a
To: Helo Teacher
Point 1) What you stated about the rigging of a helicopter to counter translating tendency is correct. On some helicopters this is built into the mixing unit so that when the pilot pulls collective there is a left bias on the swashplate causing the disc to tip left. On others, the pilot must move the cyclic left to counter the movement of the helicopter. On the Robinson however the Helicopter has a 2-degree left bias on the mast to do the same thing. When the Robbie is rigged, the helicopter is leveled so that the rotorhead is level and the helicopter is leaning 2-degrees to the right. In this position the swashplate is adjusted to conform to a specific setting which in effect makes it parallel to the disc when it is rotating. In this condition the cyclic is placed slightly right of center of the longitudinal centerline of the aircraft. The control linkages are adjusted to obtain this relationship. In the process of setting blade angles the blades are disposed 18-degrees ahead of the respective axes. On a Bell undergoing the same settings the blades are disposed directly over the respective axes. If a Bell has a phase angle of 90-degrees the blade disc will tilt down over the nose. Assuming the Robinson conforms to the laws of physics the disc will tilt down and to the left when the cyclic is pushed forward from the rigged neutral position.
Point 2) According to the documentation transverse flow effect diminishes after about 20 Knots. But on the other hand if you are correct in you assumption about the 18-degree offset countering the transverse flow effect at speeds higher than 20 knots then my argument goes out the window. However, my source on the transverse flow effect is the FAA Rotorcraft handbook and it says that transverse flow effect stops around 20 Knots.
Point 3) Frank Robinson brought it up in his response on the Robbie certification thread. He said it was the delta 3 effect that caused the rotor disc to tip down over the nose even though it defied the laws of physics, (90-degrees of precession). I said the 18-degree offset would cause the disc to tip left because that is what the laws of precession would dictate. He said the delta 3-hinge effect would cause the disc to tip down over the nose.
Point 4) this was taken from the website of RW-1. I never discussed this phenomenon in my threads nor, was it discussed in my report to the NTSB.
Point 5) regarding the stick plotting board what you say is true. My reference to the plotting board was in reference to the 18-degree offset and what it recorded when the cyclic was pushed forward.
Thanks for responding.
------------------
The Cat
Point 1) What you stated about the rigging of a helicopter to counter translating tendency is correct. On some helicopters this is built into the mixing unit so that when the pilot pulls collective there is a left bias on the swashplate causing the disc to tip left. On others, the pilot must move the cyclic left to counter the movement of the helicopter. On the Robinson however the Helicopter has a 2-degree left bias on the mast to do the same thing. When the Robbie is rigged, the helicopter is leveled so that the rotorhead is level and the helicopter is leaning 2-degrees to the right. In this position the swashplate is adjusted to conform to a specific setting which in effect makes it parallel to the disc when it is rotating. In this condition the cyclic is placed slightly right of center of the longitudinal centerline of the aircraft. The control linkages are adjusted to obtain this relationship. In the process of setting blade angles the blades are disposed 18-degrees ahead of the respective axes. On a Bell undergoing the same settings the blades are disposed directly over the respective axes. If a Bell has a phase angle of 90-degrees the blade disc will tilt down over the nose. Assuming the Robinson conforms to the laws of physics the disc will tilt down and to the left when the cyclic is pushed forward from the rigged neutral position.
Point 2) According to the documentation transverse flow effect diminishes after about 20 Knots. But on the other hand if you are correct in you assumption about the 18-degree offset countering the transverse flow effect at speeds higher than 20 knots then my argument goes out the window. However, my source on the transverse flow effect is the FAA Rotorcraft handbook and it says that transverse flow effect stops around 20 Knots.
Point 3) Frank Robinson brought it up in his response on the Robbie certification thread. He said it was the delta 3 effect that caused the rotor disc to tip down over the nose even though it defied the laws of physics, (90-degrees of precession). I said the 18-degree offset would cause the disc to tip left because that is what the laws of precession would dictate. He said the delta 3-hinge effect would cause the disc to tip down over the nose.
Point 4) this was taken from the website of RW-1. I never discussed this phenomenon in my threads nor, was it discussed in my report to the NTSB.
Point 5) regarding the stick plotting board what you say is true. My reference to the plotting board was in reference to the 18-degree offset and what it recorded when the cyclic was pushed forward.
Thanks for responding.
------------------
The Cat
Guest
Posts: n/a
To RW-1
I apologize sincerely for having deleted several of your posts here, but you leave me little choice. I have received several complaints about the level of vitriol and I agree.
You must understand that this a civilized forum where we debate even contentious issues such as the R22 certification with courtesy. Please accept that PPRuNe works very differently from the other major helicopter forum and conduct yourself accordingly.
I apologize sincerely for having deleted several of your posts here, but you leave me little choice. I have received several complaints about the level of vitriol and I agree.
You must understand that this a civilized forum where we debate even contentious issues such as the R22 certification with courtesy. Please accept that PPRuNe works very differently from the other major helicopter forum and conduct yourself accordingly.
Guest
Posts: n/a
helidrvr,
no problem here.
Lu:
Your quals mean squat. Period. Sandcrab (look that one up, it's an affectionate Navy term)
You come here making your predictions and asking everyone to go fly it and do your tests.
Engineer - > do the tests yourself, as it should have been done for your report.
Funny how you want to rely on others to perform tests, are you sure they will report it right? What if everyone did the test you describe and it doesn't live up to your expectations?
Boy, I can see the responses now "Oh you failed to do it right, or you forgot to do it in a particular manner."
There is no answer you can give that would be acceptable to any rational human being, let alone a pilot or another engineer for this. Get your own test data yourself and present it as it should have been done.
You made the report, you need to back it up with flight test data, we, the R-22 pilots who fly it all the time, don't have to do anything, one way or another.
If you can't understand that concept, then I really feel sorry for you.
RW-1 is off this topic. As for the last word, you might have one here, but I have it as the R-22's will continue to fly, fly well, and likely continue the trend of being the most widely sold heli in the world.
------------------
Marc
no problem here.
Lu:
Your quals mean squat. Period. Sandcrab (look that one up, it's an affectionate Navy term)
You come here making your predictions and asking everyone to go fly it and do your tests.
Engineer - > do the tests yourself, as it should have been done for your report.
Funny how you want to rely on others to perform tests, are you sure they will report it right? What if everyone did the test you describe and it doesn't live up to your expectations?
Boy, I can see the responses now "Oh you failed to do it right, or you forgot to do it in a particular manner."
There is no answer you can give that would be acceptable to any rational human being, let alone a pilot or another engineer for this. Get your own test data yourself and present it as it should have been done.
You made the report, you need to back it up with flight test data, we, the R-22 pilots who fly it all the time, don't have to do anything, one way or another.
If you can't understand that concept, then I really feel sorry for you.
RW-1 is off this topic. As for the last word, you might have one here, but I have it as the R-22's will continue to fly, fly well, and likely continue the trend of being the most widely sold heli in the world.
------------------
Marc
Guest
Posts: n/a
To: RW-1 and all
You keep insisting that you are never going to darken these threads and then you come back as if you were attached by a bungee cord. Either stay away or stick with it and we can exchange ideas. We may not agree but it helps stimulate the dialog for others to join in.
I figured this part was going to be a private email conversation between RW-1 and myself. This is related to RW-1s comments about my qualifications not meaning squat. He sent me an email telling me how he operated under extreme conditions and had among other things been suspended under a Huey while strapped to another person. If you read his website he states that he was involved in SAR activities. In his email to me he stated that he had done it for 9 years in the US Navy. I sent him an email describing my experiences in the US Coast Guard that were at least equal if not greater than his and, I did it in 6 years. He also stated that since I was not a pilot I should have no say on a forum such as this. In my email to him I stated that I had 1400 hours as a flight engineer and many other hours as a flight mechanic on helicopters. I told him that I flew every aircraft that I was assigned to and that although I didn’t say it I had more stick time than he did.
Now, we get back to RW-1s comments in this thread. I told him repeatedly that if I had direct access to an R22 I would conduct the tests to determine if there was actually an 18-degree coupling. He constantly refers to what a good engineer would do and that is, to perform the tests himself to verify the findings in my report.
Two points, 1) since I didn’t perform the tests to prove I was correct then, as a good engineer why doesn’t RW-1 perform the test to prove I was incorrect and 2) the report itself.
The report was written and submitted to the NTSB to question the design of the R22 and the R44. I made certain technical statements as to my feelings about the design. I referenced each point to the FAA Certification of Normal Category Rotorcraft Advisory Circular (AC-27-1). At the end of the report I posed a series of questions that were directed to the FAA and Robinson. It was these questions that would have supplied the answers I seek. It was not my intent to get plastered by everybody that did or thought that they knew more than I did on these threads. When I offered a copy of the report to the NTSB, it was my intent to get both Robinson and the FAA to explain how and why the R22 was certified.
In answering the first question on these forums I exposed myself to individuals like RW-1 that totally disagreed with my point of view yet when I asked him (them) to give me an explanation that did not parrot Frank Robinsons’ words they themselves were at a loss for words. The questions in the report were in some cases couched to get a further explanation and not to expose my ignorance on the subjects being questioned. For those of you that have never read the report here are those questions. RW-1 how many of these questions can you answer?
Addressed to: Question:
Robinson / FAA If the certification procedure requires that normal category rotorcraft demonstrate the capability of flying at side slip angles of ten to ninety degrees, why are the R-22 and R-44 helicopters restricted from flying at any side slip angle and why must the pilot keep the aircraft trimmed at all times? What problems would manifest themselves if a side slip angle were introduced? If a problem does exist, how did the R-22 and R-44 successfully meet these certification requirements?
Robinson / FAA Is there any restriction as to what forward speed the pilot can apply full right or left cyclic? If such a restriction exists, what is the reason/justification for the restriction? In the application of full left or right lateral cyclic, what would happen if the pilot introduced an aft component to the left lateral or a forward component to right lateral (assuming the maximum forward speed at which the application of left or right lateral cyclic input can be made)?
Robinson / FAA The pilots handbook advises that when countering a "Zero G" situation the pilot must be careful to pull the cyclic straight back. The pilot is told not to try to counter the right roll induced by the tail rotor. What would happen if in pulling the cyclic back the pilot introduced a heavy right roll component?
Robinson / FAA At what forward speed would the pilot be cautioned not to pull the cyclic straight back? If such a restriction exists, what is the justification? If the pilot can pull the stick rearward, what would happen if in doing so the pilot introduced a right roll component? What would happen when the pilot performs a cyclic flare during auto rotation and he/she introduces a right roll component?
Robinson / FAA How much of a pitch angle (collective) must be introduced to stall the main rotor (assuming gross weight and air density are within acceptable limits)? Assuming high collective and maximum cyclic application, at what point would both blades or one blade stall? Assuming the pitch angle at stall could be measured, where would that measurement be taken (blade station)? Does this stall angle vary at different altitudes and gross weights?
Robinson What is the purpose of tail rotor precone?
Robinson What are the demonstrated MTBFs on the following:
1. Main rotor flapping bearings?
2. Main rotor teeter bearings?
3. Tail rotor pitch bearings?
a) inboard
b) outboard
4. Main rotor bearing packs?
What are the modes of these failures?
Robinson What percentage of main rotor heads reach their design life? Of those that are removed, what are the primary modes of failure and which components have the highest rates of failure?
Robinson What can happen if the high and/or low swash plate adjustments are exceeded?
Robinson / FAA Why are two bladed rotor systems susceptible to "Zero G" maneuvers and three or more rotor blade systems are not? Why was a two bladed system selected over a multi-blade system for use on a helicopter that would be operated by pilots who have minimal "stick" time or students learning to fly helicopters?
Robinson / FAA What was the rationale for designing a rotor system that has offset flapping hinges along with a "teeter hinge"? What are the advantages and disadvantages of this design over a system that can flap and not teeter or a system that can teeter but not flap. How are lead-lag loads reacted during rotor flap? Do these in-plane loads cause premature wear-out of the "teeter" bushings or high cycle torque reversals on the main rotor shaft and rotor "teeter" through bolt? Can these oscillatory loads cause bending of the blade and induce a tucking of the blade tip?
Robinson / FAA According to AC-27-1 and CFR-14.21.16, the design of the R-22 rotor head is "novel or unusual" which requires very special care in the certification process to verify the efficacy of the design. Was this very special care exercised during the certification process?
Did the FAA note that the design of the rotor system precludes the helicopter from being sideslipped because of very high flapping loads which could result in blow back and/or fuselage strike? Did Robinson instrument the rotor per certification requirements and, if so, did the R-22 and/or the R-44 pass the sideslip test? If they did pass the test, why are both aircraft restricted from being side slipped?
Robinson / FAA Why are the degrees of blade twist different between the R-22 and R-44, where the R-44 blade is longer and the tip speeds are almost the same?
Robinson / FAA What would happen to the swash plate assembly, if during certain cyclic applications, the "uniball" bearing were placed in a bind?
Robinson / FAA Are the cyclic stop plates the same on all R-22 models? If they are, how can you get different cyclic angles on the Alpha and Beta models if the control "throws" are the same as those used on the R-22 and R-22 HP models?
Robinson / FAA Why was the seventy-five percent point selected to measure pitch angle? Why are blade angles averaged instead of setting an optimum low collective blade angle for both blades and use the stops to control the range for cyclic control? Why was the system selected over adjustable stops that are used to limit over control of pre-established rigged ranges? In other words, why is the Robinson design different from every other helicopter?
FAA Why did the FAA certify the "novel or unusual" rotor head design, when at some point in the certification process, it would have been determined that the rotor could not meet the requirements of the certification process?
RW-1 if you are out there, I am waiting for your response.
------------------
The Cat
[This message has been edited by Lu Zuckerman (edited 03 January 2001).]
[This message has been edited by Lu Zuckerman (edited 03 January 2001).]
You keep insisting that you are never going to darken these threads and then you come back as if you were attached by a bungee cord. Either stay away or stick with it and we can exchange ideas. We may not agree but it helps stimulate the dialog for others to join in.
I figured this part was going to be a private email conversation between RW-1 and myself. This is related to RW-1s comments about my qualifications not meaning squat. He sent me an email telling me how he operated under extreme conditions and had among other things been suspended under a Huey while strapped to another person. If you read his website he states that he was involved in SAR activities. In his email to me he stated that he had done it for 9 years in the US Navy. I sent him an email describing my experiences in the US Coast Guard that were at least equal if not greater than his and, I did it in 6 years. He also stated that since I was not a pilot I should have no say on a forum such as this. In my email to him I stated that I had 1400 hours as a flight engineer and many other hours as a flight mechanic on helicopters. I told him that I flew every aircraft that I was assigned to and that although I didn’t say it I had more stick time than he did.
Now, we get back to RW-1s comments in this thread. I told him repeatedly that if I had direct access to an R22 I would conduct the tests to determine if there was actually an 18-degree coupling. He constantly refers to what a good engineer would do and that is, to perform the tests himself to verify the findings in my report.
Two points, 1) since I didn’t perform the tests to prove I was correct then, as a good engineer why doesn’t RW-1 perform the test to prove I was incorrect and 2) the report itself.
The report was written and submitted to the NTSB to question the design of the R22 and the R44. I made certain technical statements as to my feelings about the design. I referenced each point to the FAA Certification of Normal Category Rotorcraft Advisory Circular (AC-27-1). At the end of the report I posed a series of questions that were directed to the FAA and Robinson. It was these questions that would have supplied the answers I seek. It was not my intent to get plastered by everybody that did or thought that they knew more than I did on these threads. When I offered a copy of the report to the NTSB, it was my intent to get both Robinson and the FAA to explain how and why the R22 was certified.
In answering the first question on these forums I exposed myself to individuals like RW-1 that totally disagreed with my point of view yet when I asked him (them) to give me an explanation that did not parrot Frank Robinsons’ words they themselves were at a loss for words. The questions in the report were in some cases couched to get a further explanation and not to expose my ignorance on the subjects being questioned. For those of you that have never read the report here are those questions. RW-1 how many of these questions can you answer?
Addressed to: Question:
Robinson / FAA If the certification procedure requires that normal category rotorcraft demonstrate the capability of flying at side slip angles of ten to ninety degrees, why are the R-22 and R-44 helicopters restricted from flying at any side slip angle and why must the pilot keep the aircraft trimmed at all times? What problems would manifest themselves if a side slip angle were introduced? If a problem does exist, how did the R-22 and R-44 successfully meet these certification requirements?
Robinson / FAA Is there any restriction as to what forward speed the pilot can apply full right or left cyclic? If such a restriction exists, what is the reason/justification for the restriction? In the application of full left or right lateral cyclic, what would happen if the pilot introduced an aft component to the left lateral or a forward component to right lateral (assuming the maximum forward speed at which the application of left or right lateral cyclic input can be made)?
Robinson / FAA The pilots handbook advises that when countering a "Zero G" situation the pilot must be careful to pull the cyclic straight back. The pilot is told not to try to counter the right roll induced by the tail rotor. What would happen if in pulling the cyclic back the pilot introduced a heavy right roll component?
Robinson / FAA At what forward speed would the pilot be cautioned not to pull the cyclic straight back? If such a restriction exists, what is the justification? If the pilot can pull the stick rearward, what would happen if in doing so the pilot introduced a right roll component? What would happen when the pilot performs a cyclic flare during auto rotation and he/she introduces a right roll component?
Robinson / FAA How much of a pitch angle (collective) must be introduced to stall the main rotor (assuming gross weight and air density are within acceptable limits)? Assuming high collective and maximum cyclic application, at what point would both blades or one blade stall? Assuming the pitch angle at stall could be measured, where would that measurement be taken (blade station)? Does this stall angle vary at different altitudes and gross weights?
Robinson What is the purpose of tail rotor precone?
Robinson What are the demonstrated MTBFs on the following:
1. Main rotor flapping bearings?
2. Main rotor teeter bearings?
3. Tail rotor pitch bearings?
a) inboard
b) outboard
4. Main rotor bearing packs?
What are the modes of these failures?
Robinson What percentage of main rotor heads reach their design life? Of those that are removed, what are the primary modes of failure and which components have the highest rates of failure?
Robinson What can happen if the high and/or low swash plate adjustments are exceeded?
Robinson / FAA Why are two bladed rotor systems susceptible to "Zero G" maneuvers and three or more rotor blade systems are not? Why was a two bladed system selected over a multi-blade system for use on a helicopter that would be operated by pilots who have minimal "stick" time or students learning to fly helicopters?
Robinson / FAA What was the rationale for designing a rotor system that has offset flapping hinges along with a "teeter hinge"? What are the advantages and disadvantages of this design over a system that can flap and not teeter or a system that can teeter but not flap. How are lead-lag loads reacted during rotor flap? Do these in-plane loads cause premature wear-out of the "teeter" bushings or high cycle torque reversals on the main rotor shaft and rotor "teeter" through bolt? Can these oscillatory loads cause bending of the blade and induce a tucking of the blade tip?
Robinson / FAA According to AC-27-1 and CFR-14.21.16, the design of the R-22 rotor head is "novel or unusual" which requires very special care in the certification process to verify the efficacy of the design. Was this very special care exercised during the certification process?
Did the FAA note that the design of the rotor system precludes the helicopter from being sideslipped because of very high flapping loads which could result in blow back and/or fuselage strike? Did Robinson instrument the rotor per certification requirements and, if so, did the R-22 and/or the R-44 pass the sideslip test? If they did pass the test, why are both aircraft restricted from being side slipped?
Robinson / FAA Why are the degrees of blade twist different between the R-22 and R-44, where the R-44 blade is longer and the tip speeds are almost the same?
Robinson / FAA What would happen to the swash plate assembly, if during certain cyclic applications, the "uniball" bearing were placed in a bind?
Robinson / FAA Are the cyclic stop plates the same on all R-22 models? If they are, how can you get different cyclic angles on the Alpha and Beta models if the control "throws" are the same as those used on the R-22 and R-22 HP models?
Robinson / FAA Why was the seventy-five percent point selected to measure pitch angle? Why are blade angles averaged instead of setting an optimum low collective blade angle for both blades and use the stops to control the range for cyclic control? Why was the system selected over adjustable stops that are used to limit over control of pre-established rigged ranges? In other words, why is the Robinson design different from every other helicopter?
FAA Why did the FAA certify the "novel or unusual" rotor head design, when at some point in the certification process, it would have been determined that the rotor could not meet the requirements of the certification process?
RW-1 if you are out there, I am waiting for your response.
------------------
The Cat
[This message has been edited by Lu Zuckerman (edited 03 January 2001).]
[This message has been edited by Lu Zuckerman (edited 03 January 2001).]
Guest
Posts: n/a
Either helicopter mechanics don't read these threads or maybe they are frightened by all of the animosity and or bull crap they see on this threads.
If you are out there, please respond.
And, yes before some one accuses me of posting to keep this thread alive they are right. I want some feed back from mechanics and not from pilots.
------------------
The Cat
[This message has been edited by Lu Zuckerman (edited 05 January 2001).]
If you are out there, please respond.
And, yes before some one accuses me of posting to keep this thread alive they are right. I want some feed back from mechanics and not from pilots.
------------------
The Cat
[This message has been edited by Lu Zuckerman (edited 05 January 2001).]
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Lu,
In answer to your first post on this thread, starting with your assumptions:
1. I am not aware of any requirement to attend a Robinson factory course just for the purpose of being able to maintain them. I believe that this requirement only gives the company that the AME works for, the right to call itself an approved Robinson Service Centre. (Correct me if I am wrong)
2. Yes we are taught flight theory, but as a basic subject. After talking to a couple of maint. Engineers who had attended Robinson maint. courses, they said flight theory was not on the agenda on those courses. The courses were strictly based on the maintenance manual content.
3. Cannot confirm or deny if we learnt about gyroscopic precession in a different way to the yanks, but the reference material I can remember came from USA and UK. A couple of books that come to mind, on top of the ones you have mentioned on other threads are ‘Helicopter Design & Data Manual” by S.J.Dzik (USA) and ‘The Helicopter” History, Piloting and How it Flies by John Fay (UK). Prouty was another one
Your Questions:
1. When I learnt about Gyroscopic Precession the Robinson helicopter did not exist.
The Fay description is very basic (one small paragraph) and in its last sentence, basically states that some rotors can be said to behave like a gyroscope in that their phase-lag is 90 deg.
That is how I have always understood gyroscopic precession!
No helicopter types are used as an example on that subject but several types (pre-Robinson) appear as examples throughout the book.
The Dzik description: (again, pre Robinson) has more detailed explanation of the phenomenon but ultimately says that on a spinning disc, the reaction is approximately 90 degrees in direction of rotation from the input force.
I think that all helicopter engineers/AMEs understand this principal as well as the pilots. You just have to be able to interpret the different terminologies for the same things. There is no reference to the different types of helo’s, as to the effects after the helicopter is in flight.
2. I believe the rigging process is taught as per the MM with little or no explanation on the GP principles as the subject is covered in basic pre-licensing exams. I also do not think any other manufacturer would have an agenda to re-teach what is considered a basic subject for maintenance personnel.
One point: After looking at a Robbo rotor head, I can see a delta 3 effect in the R22 head between the ‘teetering hinge’, and the pitch horn and maybe a slight coupling effect between the coning hinge and the pitch horn, depending on the collective setting at any given moment, ie; whether the pitch horn/rod attachment is below, level or above the centreline of the coning hinge.
How it all works in flight? …… I have you, Frank Robinson and all the other contributors to this subject to draw on.
As far as understanding any helicopter for the purpose of maintaining them, I can only go by what the manufacturers officially tell us.
A question I have: Is comparing rotors to discs when explaining gyroscopic precession truly correct? …. Even when the rotors are in the shape of a constantly changing cone when in flight?
Lu, I have not personally attended any Robbo Maintenance courses but a couple of fellow maint. Engineers have. (Over 10 years ago).
The last R22 that I worked on was over 10 years ago
------------------
sprocket: .. No standards? Nooo problems!
[This message has been edited by sprocket (edited 07 January 2001).]
In answer to your first post on this thread, starting with your assumptions:
<font face="Verdana, Arial, Helvetica" size="2">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.</font>
<font face="Verdana, Arial, Helvetica" size="2">2) You were taught flight theory as well as how to rig the helicopter.</font>
<font face="Verdana, Arial, Helvetica" size="2">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).</font>
Your Questions:
<font face="Verdana, Arial, Helvetica" size="2">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?</font>
The Fay description is very basic (one small paragraph) and in its last sentence, basically states that some rotors can be said to behave like a gyroscope in that their phase-lag is 90 deg.
That is how I have always understood gyroscopic precession!
No helicopter types are used as an example on that subject but several types (pre-Robinson) appear as examples throughout the book.
The Dzik description: (again, pre Robinson) has more detailed explanation of the phenomenon but ultimately says that on a spinning disc, the reaction is approximately 90 degrees in direction of rotation from the input force.
I think that all helicopter engineers/AMEs understand this principal as well as the pilots. You just have to be able to interpret the different terminologies for the same things. There is no reference to the different types of helo’s, as to the effects after the helicopter is in flight.
<font face="Verdana, Arial, Helvetica" size="2">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?</font>
One point: After looking at a Robbo rotor head, I can see a delta 3 effect in the R22 head between the ‘teetering hinge’, and the pitch horn and maybe a slight coupling effect between the coning hinge and the pitch horn, depending on the collective setting at any given moment, ie; whether the pitch horn/rod attachment is below, level or above the centreline of the coning hinge.
How it all works in flight? …… I have you, Frank Robinson and all the other contributors to this subject to draw on.
As far as understanding any helicopter for the purpose of maintaining them, I can only go by what the manufacturers officially tell us.
A question I have: Is comparing rotors to discs when explaining gyroscopic precession truly correct? …. Even when the rotors are in the shape of a constantly changing cone when in flight?
Lu, I have not personally attended any Robbo Maintenance courses but a couple of fellow maint. Engineers have. (Over 10 years ago).
The last R22 that I worked on was over 10 years ago
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sprocket: .. No standards? Nooo problems!
[This message has been edited by sprocket (edited 07 January 2001).]
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If you park an R44 and a 206 next to each other you will quickly see there is very little height difference. The Robinson appears to have a longer mast because it does not have a turbine engine and its associated cowlings mounted atop the fuselage.
If you compare the distance from the fuselage where the payloads go to the rotor you will find little difference. It just looks different because the R44 has its engine in the back of the fuselage instead of on top taking up space between the rotor and fuselage.
[This message has been edited by helisphere (edited 23 January 2001).]
If you compare the distance from the fuselage where the payloads go to the rotor you will find little difference. It just looks different because the R44 has its engine in the back of the fuselage instead of on top taking up space between the rotor and fuselage.
[This message has been edited by helisphere (edited 23 January 2001).]
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One of the less known reasons for the length of a mast is torsional flexibility.
I touched on the two beats per rev vibration for two bladed rotor systems on another thread. Torsional flexibility helps to reduce the effect. In that way, the mast is continually flexing about its own axis as drag increase and decreases across the disc. I hope that this does not scare the readers...! If it were made shorter it would be less flexible and suffer much more stress.
There is a good explanation of torsional flex. in Shawn Coyle's book.
I touched on the two beats per rev vibration for two bladed rotor systems on another thread. Torsional flexibility helps to reduce the effect. In that way, the mast is continually flexing about its own axis as drag increase and decreases across the disc. I hope that this does not scare the readers...! If it were made shorter it would be less flexible and suffer much more stress.
There is a good explanation of torsional flex. in Shawn Coyle's book.
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To: All
When asked why her legs were so long the girl replied they are this long in order to keep my ass off the ground. That is the first reason for the long mast on a teetering rotorhead. It keeps the blades from hitting the tail cone when flying aft or when making a cyclic flare. Everything else is secondary. When Sikorsky first designed the S 55 the tail cone was straight. After a rotorblade incursion on a Chicago Airways S 55 they came up with a mod drooping the tail cone. This was incorporated when they upgraded from the R 1340 to the R 1300 engine.
On several other helicopters with articulated rotorheads they had to incorporate a mast extension in order to raise the blades from the fuselage. This was done to eliminate the compressive drumming sound as the blades passed over the canopy.
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The Cat
When asked why her legs were so long the girl replied they are this long in order to keep my ass off the ground. That is the first reason for the long mast on a teetering rotorhead. It keeps the blades from hitting the tail cone when flying aft or when making a cyclic flare. Everything else is secondary. When Sikorsky first designed the S 55 the tail cone was straight. After a rotorblade incursion on a Chicago Airways S 55 they came up with a mod drooping the tail cone. This was incorporated when they upgraded from the R 1340 to the R 1300 engine.
On several other helicopters with articulated rotorheads they had to incorporate a mast extension in order to raise the blades from the fuselage. This was done to eliminate the compressive drumming sound as the blades passed over the canopy.
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The Cat
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Lu, it's funny that this question should raise itself again. I actualy forgot that I posted my comment on it ages ago.
Where the alpha angle thingy came from is when I was doing my BK117 ground school the engineer was teaching us about the Mast Moment Indicator. This instrument, unique to this breed of helicopter, literally lets you know how much bending of the mast you have, especially on the ground if you try to lead with the cyclic (If you fly any Bells you know what I mean). Sounds scary but it's true.
Anyway the engineer was talking about the alpha angle with respect to why we have small masts on more rigid type systems compared to long masts on teetering type systems. Very much a design discussion because supposedly you can make a much thinner and lighter mast with a small 'alpha angle', whilst you need a short (and therefore strong) mast for larger alpha angles.
Having said all that - I have no idea what it actually is.
The engineer sounded very convincing at the time and I do remember understanding it, but hey you can teach monkeys to fly these things but they may not remember it later.
P.S - Someone was trying to explain or ask about the 45 degree etc phase angle in Helimutt's thread (pg 5 I think). It sounded very close to this alpha angle thing.
Where the alpha angle thingy came from is when I was doing my BK117 ground school the engineer was teaching us about the Mast Moment Indicator. This instrument, unique to this breed of helicopter, literally lets you know how much bending of the mast you have, especially on the ground if you try to lead with the cyclic (If you fly any Bells you know what I mean). Sounds scary but it's true.
Anyway the engineer was talking about the alpha angle with respect to why we have small masts on more rigid type systems compared to long masts on teetering type systems. Very much a design discussion because supposedly you can make a much thinner and lighter mast with a small 'alpha angle', whilst you need a short (and therefore strong) mast for larger alpha angles.
Having said all that - I have no idea what it actually is.
The engineer sounded very convincing at the time and I do remember understanding it, but hey you can teach monkeys to fly these things but they may not remember it later.
P.S - Someone was trying to explain or ask about the 45 degree etc phase angle in Helimutt's thread (pg 5 I think). It sounded very close to this alpha angle thing.
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To: Rotorque
The way you describe it, the Alpha Angle must have something to do with the bending moment on the shaft or, the overturning moment imparted from the rotor to the fuselage caused by the very strong couple between the head and the shaft. You also indicated that the ability to read this Alpha Angle Indicator was very important especially when you were on the ground.
The Cheyenne H-56 rigid rotor had such a strong couple that the cyclic was locked out while you were on the ground. If the cyclic could be moved on the ground you could roll the helicopter over. I think it was unlocked by a squat switch on the landing gear. To maneuver on the ground you would use the propeller on the tail for forward motion and the tail rotor for ground directional control or, you would have to hover taxi to get from one spot to an other.
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The Cat
The way you describe it, the Alpha Angle must have something to do with the bending moment on the shaft or, the overturning moment imparted from the rotor to the fuselage caused by the very strong couple between the head and the shaft. You also indicated that the ability to read this Alpha Angle Indicator was very important especially when you were on the ground.
The Cheyenne H-56 rigid rotor had such a strong couple that the cyclic was locked out while you were on the ground. If the cyclic could be moved on the ground you could roll the helicopter over. I think it was unlocked by a squat switch on the landing gear. To maneuver on the ground you would use the propeller on the tail for forward motion and the tail rotor for ground directional control or, you would have to hover taxi to get from one spot to an other.
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The Cat
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To: Rotorque
It seems that your instructor was wrong in addressing Alpha Angle and I too was wrong in my interpertation of your post. Here is the explanation of Alpha Angle straight from the "Horses Mouth", MBB in Germany.
"Generally, alpha angle - the angle of attack - is defined as the angle
between an airflow (relative wind)
and the reference chord (a line drawn between the leading and trailing
edges) of an airfoil.
This airfoil may be a wing or a rotor blade.
Alpha is a major factor of lift, the greater alpha, the greater the lift
produced, but - everything has limits -
typically at angles of attack around 20°, the airflow stalls and lift
decreases again.
On many fixed wing aircraft alpha is measured by a little hinged surface
mounted in the nose area
which alignes with the airflow. This angle is indicated on a gauge in the
cockpit.
Alpha is not indicated on helicopters, because the airflow pattern through a
rotor is pretty complicated
and changes constantly. Other values are easier to measure and are displayed
instead.
Hope this is what Your were asking for!
Best regards from Munich!
Diethelm Berndt
Test Pilot
Eurocopter Deutschland GmbH
Phone:+49 89 6000 6065
Mobile:+49 171 7341699
Fax: +49 89 6000 6622
E-mail: [email protected]
-----Ursprüngliche Nachricht-----
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The Cat
It seems that your instructor was wrong in addressing Alpha Angle and I too was wrong in my interpertation of your post. Here is the explanation of Alpha Angle straight from the "Horses Mouth", MBB in Germany.
"Generally, alpha angle - the angle of attack - is defined as the angle
between an airflow (relative wind)
and the reference chord (a line drawn between the leading and trailing
edges) of an airfoil.
This airfoil may be a wing or a rotor blade.
Alpha is a major factor of lift, the greater alpha, the greater the lift
produced, but - everything has limits -
typically at angles of attack around 20°, the airflow stalls and lift
decreases again.
On many fixed wing aircraft alpha is measured by a little hinged surface
mounted in the nose area
which alignes with the airflow. This angle is indicated on a gauge in the
cockpit.
Alpha is not indicated on helicopters, because the airflow pattern through a
rotor is pretty complicated
and changes constantly. Other values are easier to measure and are displayed
instead.
Hope this is what Your were asking for!
Best regards from Munich!
Diethelm Berndt
Test Pilot
Eurocopter Deutschland GmbH
Phone:+49 89 6000 6065
Mobile:+49 171 7341699
Fax: +49 89 6000 6622
E-mail: [email protected]
-----Ursprüngliche Nachricht-----
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The Cat