Robinson Safety Courses
To Lu Z,
a. The original para (a) was that cyclic application and sideslip are separate issues. You seem to agree here. No question that sideslip will produce flapping loads. See para (b) for discussion on cyclic application, as I purposely separated these issu4es for discussion.
b. Yes, I have an argument here. I am not convinced that the application of cyclic causes high (if any) flapping loads. I am even more skeptical now that you have changed your position by saying it only occurs under zero G. The disc DOES NOT behave differently under zero G. How could it? You know I do not have the POH, so perhaps you could post the bit where it says that “The application of left cyclic only during zero G conditions will cause severe flapping loads”? P.S. Why is it that you quote the POH as an authority here, but your whole argument is that the POH is flawed?
c. Thank you for conceding that >> It is true that the disc does not behave wildly under a zero G condition<< but then you repeat the left cyclic equals flapping argument, and introduce an entirely new (and irrelevant word: frequency. Lets ignore frequency, and go back to the cyclic issue. Once again, please quote the POH, or explain why.
d. Your answer here once again ignores the fundamental question. Talking about which way the cyclic needs to be pushed to go forward is getting off track. Both the Robbie and the Bell teetering head share the same mast bump characteristics in zero G. One of them doesn’t use an 18 degree offset, nor conning hinges, but they both still behave the same way. How can this be other than the conning hinges and offset ARE IRRELEVANT? Did you know that the UH-1H and B205 A1 have tail rotors on opposite sides of the tail boom? This doesn’t affect zero G behaviour either – therefore it is irrelevant too! You know that the blade shape on the uh-1h and 205 A1 are different, but again it is irrelevant to the zero G situation. You need to be able to demonstrate a distinct difference attributable to a component before it can be RELEVANT. So far you have not done that with the conning hinges or offset. Until you can define a behavioural difference your argument is mute. So I ask once again: If a Bell system is vulnerable to mast bump in exactly the same circumstances as a Robbie, and it does NOT have the 18 degree offset, nor the flapping hinges – how can the 18 degree offset or flapping hinges be the culprit??????.
e. Great, you have the statistics on mast separations. Kind of prooves the point that the lack of 18 degree offset and conning hinges have not protected the Bell system doesn’t it?
f. roger that..
g. Lets keep “cyclic causes flapping” to (b). But I would still like your reply to the original questions which I have reproduced here: You then state that :>>If my contention of the 18-degree offset were correct then this would further exacerbate the problem by increasing the roll rate<< Interesting assertion Lu, how do you think the offset increases roll rate? Do you believe this always happens, or only with zero G? If only with zero G, how does the G affect the offset?
a. The original para (a) was that cyclic application and sideslip are separate issues. You seem to agree here. No question that sideslip will produce flapping loads. See para (b) for discussion on cyclic application, as I purposely separated these issu4es for discussion.
b. Yes, I have an argument here. I am not convinced that the application of cyclic causes high (if any) flapping loads. I am even more skeptical now that you have changed your position by saying it only occurs under zero G. The disc DOES NOT behave differently under zero G. How could it? You know I do not have the POH, so perhaps you could post the bit where it says that “The application of left cyclic only during zero G conditions will cause severe flapping loads”? P.S. Why is it that you quote the POH as an authority here, but your whole argument is that the POH is flawed?
c. Thank you for conceding that >> It is true that the disc does not behave wildly under a zero G condition<< but then you repeat the left cyclic equals flapping argument, and introduce an entirely new (and irrelevant word: frequency. Lets ignore frequency, and go back to the cyclic issue. Once again, please quote the POH, or explain why.
d. Your answer here once again ignores the fundamental question. Talking about which way the cyclic needs to be pushed to go forward is getting off track. Both the Robbie and the Bell teetering head share the same mast bump characteristics in zero G. One of them doesn’t use an 18 degree offset, nor conning hinges, but they both still behave the same way. How can this be other than the conning hinges and offset ARE IRRELEVANT? Did you know that the UH-1H and B205 A1 have tail rotors on opposite sides of the tail boom? This doesn’t affect zero G behaviour either – therefore it is irrelevant too! You know that the blade shape on the uh-1h and 205 A1 are different, but again it is irrelevant to the zero G situation. You need to be able to demonstrate a distinct difference attributable to a component before it can be RELEVANT. So far you have not done that with the conning hinges or offset. Until you can define a behavioural difference your argument is mute. So I ask once again: If a Bell system is vulnerable to mast bump in exactly the same circumstances as a Robbie, and it does NOT have the 18 degree offset, nor the flapping hinges – how can the 18 degree offset or flapping hinges be the culprit??????.
e. Great, you have the statistics on mast separations. Kind of prooves the point that the lack of 18 degree offset and conning hinges have not protected the Bell system doesn’t it?
f. roger that..
g. Lets keep “cyclic causes flapping” to (b). But I would still like your reply to the original questions which I have reproduced here: You then state that :>>If my contention of the 18-degree offset were correct then this would further exacerbate the problem by increasing the roll rate<< Interesting assertion Lu, how do you think the offset increases roll rate? Do you believe this always happens, or only with zero G? If only with zero G, how does the G affect the offset?
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To: helmet fire
Let me give you a bit of history and then I will respond to your questions. Back around 1994 the FAA and NTSB became alarmed because of the high number of crashes of R22s and R44s resulting from main rotor separation. The FAA commissioned the University of Georgia Aeronautics department to evaluate the crash data and to develop a computer model that would point out exactly what was causing the problem. Although the report was never fully completed there was enough data to show that under certain maneuvering conditions the rotor system would develop high levels of flapping to the point that the rotor head would contact the mast or a blade would contact the fuselage. As a result of the report the FAA issued a priority letter AD which was issued on 13 January 1995. The FAA and NTSB negotiated with Robinson on what should be done to limit the possibility of flapping excursions. Robinson did two things, they initiated the safety course and an SFAR was issued outlining the safety requirements. They also modified the POH by including the FAA AD however they never put a page number and as such the full impact of the AD was never fully enforced as it took on the guise of only being a suggestion and not a hard requirement. In some cases in the UK the page was not included in the POH. From what I was told by the CAA they were going to rewrite it and make it a safety sensitive requirement.
I don’t know how this requirement is addressed in the safety course nor do I know if it is explained why the changes were made and why the Robinson helicopters are the only helicopters with the stated restrictions.
Response to your post:
A) Does not require a response
B) The POH does not state only during zero G. This is what it says in Safety Notice SN-11: If the pilot attempts to stop the right roll by applying full left cyclic before regaining main rotor thrust, the rotor can exceed its’ flapping limits and cause structural failure of the rotor shaft due to mast bumping or allow blade contact with the airframe. It goes on to say that in recovering from a zero G incident the pilot should gently bring the cyclic aft to regain main rotor thrust before applying lateral cyclic. I would consider the POH to be flawed only if the pilot has to correct for an 18-degree offset in the controls. If this were the case there would be a right bias in the controls so that when the pilot brought the cyclic back he could add to the right roll of the tail rotor. If it is eventually proven that there is no offset then there is no problem in what the POH directs the pilot to do.
C) The reason for the high level of flapping is covered in the history paragraph. I personally believe the high flapping loads are generated due to the design of the main rotor and that mast bumping is caused by the design of the main rotor. On other helicopters that incorporate flapping hinges the blades are allowed to flap above and below the static position of the blade at rest. This is allowed by the use of unlocking stops that are centrifugally operated. On the Robinson the blade is restrained from dropping lower than its’ at rest static position by a stop. I believe that when there are large flapping excursions the blade can contact its’ static stop coupling with the main rotor and driving a blade into the fuselage or causing mast bumping.
D) There are no basic differences in cyclic movement between the Bell and the Robinson unless it can be proven that the pilot of the Robinson must compensate for the 18-degree offset. If there is no requirement to compensate then the problem is mooted. The flapping hinges are not the problem (assuming 18-degree offset problems) it is the fact that the flapping hinges and not the flapping action that causes the 18-degree offset. The Bell has a phase angle of 90-degrees and the Robinson has according to Frank Robinson and Nick Lappos a 72-degree phase angle. I believe that the Robinson like other helicopters has a 90-degree phase angle and because of this, the pilot must input right cyclic to fly forward. Nick tried very hard to convince me but I respond to the physical and not the theoretical and as such I hope to perform a test in the next few weeks. The results of that test will be published on these threads no matter which way it goes. If it proves Nick right I will acknowledge that too and will in the process have learned something.
E) It is not the 18-degree offset on the Robinson that causes the problem it is the entry into zero G and improper technique in countering the problem. It is the same for the Bell.
F) No comment
G) As previously stated if there is an 18-degree offset then in the recovery from zero G in accordance with the POH the pilot will add to the right roll thrust caused by the tail rotor. If there is an 18-degree offset in the control input then if the helicopter is flying straightforward and the pilot brings the helicopter to a hover by moving the cyclic straight back with no lateral input then he should move to the right. This will be proven or disproved in the test.
Let me give you a bit of history and then I will respond to your questions. Back around 1994 the FAA and NTSB became alarmed because of the high number of crashes of R22s and R44s resulting from main rotor separation. The FAA commissioned the University of Georgia Aeronautics department to evaluate the crash data and to develop a computer model that would point out exactly what was causing the problem. Although the report was never fully completed there was enough data to show that under certain maneuvering conditions the rotor system would develop high levels of flapping to the point that the rotor head would contact the mast or a blade would contact the fuselage. As a result of the report the FAA issued a priority letter AD which was issued on 13 January 1995. The FAA and NTSB negotiated with Robinson on what should be done to limit the possibility of flapping excursions. Robinson did two things, they initiated the safety course and an SFAR was issued outlining the safety requirements. They also modified the POH by including the FAA AD however they never put a page number and as such the full impact of the AD was never fully enforced as it took on the guise of only being a suggestion and not a hard requirement. In some cases in the UK the page was not included in the POH. From what I was told by the CAA they were going to rewrite it and make it a safety sensitive requirement.
I don’t know how this requirement is addressed in the safety course nor do I know if it is explained why the changes were made and why the Robinson helicopters are the only helicopters with the stated restrictions.
Response to your post:
A) Does not require a response
B) The POH does not state only during zero G. This is what it says in Safety Notice SN-11: If the pilot attempts to stop the right roll by applying full left cyclic before regaining main rotor thrust, the rotor can exceed its’ flapping limits and cause structural failure of the rotor shaft due to mast bumping or allow blade contact with the airframe. It goes on to say that in recovering from a zero G incident the pilot should gently bring the cyclic aft to regain main rotor thrust before applying lateral cyclic. I would consider the POH to be flawed only if the pilot has to correct for an 18-degree offset in the controls. If this were the case there would be a right bias in the controls so that when the pilot brought the cyclic back he could add to the right roll of the tail rotor. If it is eventually proven that there is no offset then there is no problem in what the POH directs the pilot to do.
C) The reason for the high level of flapping is covered in the history paragraph. I personally believe the high flapping loads are generated due to the design of the main rotor and that mast bumping is caused by the design of the main rotor. On other helicopters that incorporate flapping hinges the blades are allowed to flap above and below the static position of the blade at rest. This is allowed by the use of unlocking stops that are centrifugally operated. On the Robinson the blade is restrained from dropping lower than its’ at rest static position by a stop. I believe that when there are large flapping excursions the blade can contact its’ static stop coupling with the main rotor and driving a blade into the fuselage or causing mast bumping.
D) There are no basic differences in cyclic movement between the Bell and the Robinson unless it can be proven that the pilot of the Robinson must compensate for the 18-degree offset. If there is no requirement to compensate then the problem is mooted. The flapping hinges are not the problem (assuming 18-degree offset problems) it is the fact that the flapping hinges and not the flapping action that causes the 18-degree offset. The Bell has a phase angle of 90-degrees and the Robinson has according to Frank Robinson and Nick Lappos a 72-degree phase angle. I believe that the Robinson like other helicopters has a 90-degree phase angle and because of this, the pilot must input right cyclic to fly forward. Nick tried very hard to convince me but I respond to the physical and not the theoretical and as such I hope to perform a test in the next few weeks. The results of that test will be published on these threads no matter which way it goes. If it proves Nick right I will acknowledge that too and will in the process have learned something.
E) It is not the 18-degree offset on the Robinson that causes the problem it is the entry into zero G and improper technique in countering the problem. It is the same for the Bell.
F) No comment
G) As previously stated if there is an 18-degree offset then in the recovery from zero G in accordance with the POH the pilot will add to the right roll thrust caused by the tail rotor. If there is an 18-degree offset in the control input then if the helicopter is flying straightforward and the pilot brings the helicopter to a hover by moving the cyclic straight back with no lateral input then he should move to the right. This will be proven or disproved in the test.
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LU
The Safety Course was not started because of SFAR 73 it was in fact many years before.
The reason for the Safety Course originally was to help low time pilots gain insurance as CFI's.
The Safety Course was not started because of SFAR 73 it was in fact many years before.
The reason for the Safety Course originally was to help low time pilots gain insurance as CFI's.
Lu,
Firstly, thanks for the history, it makes informative reading. I think we are in danger of a consensus about certain matters soon!!
a. We are agreed: Cyclic application and sideslip are separate things.
b. You have neglected to quote from the POH where it contends that cyclic application under zero G creates severe flapping moments. Does it actually say that? Please quote. We will restrict discussion of cyclic causing flapping to para (b) from now to reduce repetition, so I will cover one of your statements in your para (c) : you said >> The reason for the high level of flapping is covered in the history paragraph. I personally believe the high flapping loads are generated due to the design of the main rotor and that mast bumping is caused by the design of the main rotor<<. Firstly, what is a history paragraph? Secondly, I understand that you think the flapping occurs due to the main rotor design but my question still remains HOW?
c. We are agreed that the disc is neither unstable nor wild during zero G maneuvers. We will keep cyclic “flapping” to para (b).
d. I had pointed out that the 90 degree phase angle argument is irrelevant to the topic at hand, so we will ignore it. The topic at hand remains the fact that you need to be able to demonstrate a distinct difference attributable to a component before it can be RELEVANT. So far you have not done that with either the conning hinges or 18 degree offset. The proof, therefore, must be that there are demonstrable differences in the way the aircraft behaves under zero G, and that these differences can be attributed to the components. Merely repeating the recovery theory is not meeting this proof as the same technique is valid for the Bell.
e. You state: >> It is not the 18-degree offset on the Robinson that causes the problem it is the entry into zero G and improper technique in countering the problem. It is the same for the Bell.<< So we are in agreement: the 18 degree offset IS IRRELEVANT to zero G, it is merely a piloting technique that is at fault. IE the Robbo is not dangerous – just the pilot whom mishandles it. The same could be said about the Bell teetering head, the UH-1H lack of tail rotor, or even the stall characteristics of the MU-2 in icing, etc, etc, etc. Nothing bad about the Robbie per se.
f. Settled.
g. You have not attempted to answer the questions which were: Lu, how do you think the offset increases roll rate? Do you believe this always happens, or only with zero G? If only with zero G, how does the G affect the offset? Instead your response indicates that you believe the offset will now >> add to the right roll thrust caused by the tail rotor<<. Although this is a radical change in your theory (left roll rate of the disc increases to now adding to tail rotor roll) could you explain how rather that what please?
h. I will add an (h) in response to your test. Can you outline the test parameters and what are the objective objectives (don’t you love that phrase?!!). That way perhaps the test could be performed by many to give a more realistic outcome.
Firstly, thanks for the history, it makes informative reading. I think we are in danger of a consensus about certain matters soon!!
a. We are agreed: Cyclic application and sideslip are separate things.
b. You have neglected to quote from the POH where it contends that cyclic application under zero G creates severe flapping moments. Does it actually say that? Please quote. We will restrict discussion of cyclic causing flapping to para (b) from now to reduce repetition, so I will cover one of your statements in your para (c) : you said >> The reason for the high level of flapping is covered in the history paragraph. I personally believe the high flapping loads are generated due to the design of the main rotor and that mast bumping is caused by the design of the main rotor<<. Firstly, what is a history paragraph? Secondly, I understand that you think the flapping occurs due to the main rotor design but my question still remains HOW?
c. We are agreed that the disc is neither unstable nor wild during zero G maneuvers. We will keep cyclic “flapping” to para (b).
d. I had pointed out that the 90 degree phase angle argument is irrelevant to the topic at hand, so we will ignore it. The topic at hand remains the fact that you need to be able to demonstrate a distinct difference attributable to a component before it can be RELEVANT. So far you have not done that with either the conning hinges or 18 degree offset. The proof, therefore, must be that there are demonstrable differences in the way the aircraft behaves under zero G, and that these differences can be attributed to the components. Merely repeating the recovery theory is not meeting this proof as the same technique is valid for the Bell.
e. You state: >> It is not the 18-degree offset on the Robinson that causes the problem it is the entry into zero G and improper technique in countering the problem. It is the same for the Bell.<< So we are in agreement: the 18 degree offset IS IRRELEVANT to zero G, it is merely a piloting technique that is at fault. IE the Robbo is not dangerous – just the pilot whom mishandles it. The same could be said about the Bell teetering head, the UH-1H lack of tail rotor, or even the stall characteristics of the MU-2 in icing, etc, etc, etc. Nothing bad about the Robbie per se.
f. Settled.
g. You have not attempted to answer the questions which were: Lu, how do you think the offset increases roll rate? Do you believe this always happens, or only with zero G? If only with zero G, how does the G affect the offset? Instead your response indicates that you believe the offset will now >> add to the right roll thrust caused by the tail rotor<<. Although this is a radical change in your theory (left roll rate of the disc increases to now adding to tail rotor roll) could you explain how rather that what please?
h. I will add an (h) in response to your test. Can you outline the test parameters and what are the objective objectives (don’t you love that phrase?!!). That way perhaps the test could be performed by many to give a more realistic outcome.
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To: helmet fire
Response to (B)
Safety Notice SN-11 states in part, If the pilot attempts to stop the right roll (experienced during zero G) by applying left cyclic before gaining main rotor thrust, the rotor can exceed its flapping limits and cause structural failure of the rotor shaft due to mast bumping or allow a blade to contact the airframe.
The key word is/are “flapping limits”. As I had indicated in my last post helicopters that have blade flapping capability employ some type of stop that can be unlocked as the rotor comes up to speed which allows the blade to flap above and below the static non rotating position. Therefore, the movement of the blade is virtually un- impeded that is, until the blade comes up on its’ flapping limit stop. If the blade hits this stop during maneuvering the pilot will experience a very heavy beat and he will back off on his control input. In order to hit this stop the pilot would have input excess cyclic. Hitting the stop is not a bad condition as long as the pilot responds in a timely manner. The Robinson on the other hand has the flapping limits set by the static (droop) stop built into the rotorhead. Any coning or flapping will be above this stop. If the flapping level is very high as in an incorrect application of left cyclic in recovering from zero G the blade will flap down until it hits the stop and at that time there is a mechanical linkage between the blade and head and it in a sense is like one half of a Bell blade. If both blades hit their respective stops during rotation the lock up can apply severe bending loads to the blades and the lock up can force the rotor to teeter to the point that it contacts the mast or a blade strikes the fuselage.
Response to (D)
What makes the Robinson head different from a Bell head is that the Robinson head employs coning capability separate from the teetering capability, which is common to both types of rotorheads. The cone hinges were incorporated on the Robinson head to minimize the bending loads on the blades during application of collective or during maneuvering. With the incorporation of the cone hinges the Robinson head further deviated from the design of the Bell rotorhead in that the pitch horns had a 72-degree lead as opposed to the 90-degree lead of the Bell pitch horn.
When the Bell is rigged for fore and aft cyclic the rotor blades are disposed over the lateral axis of the helicopter. Rigging for left and right lateral the blades are placed over the longitudinal axis of the helicopter. On the Robinson when rigging for fore and aft the blades are placed 18-degrees ahead of the right lateral axis of the helicopter with the retreating blade being 18-degrees behind the left lateral axis of the helicopter. This places the pitch horn on the longitudinal axis. Rigging for lateral control the blades are placed in a similar manner in respect to the longitudinal axis. Control input relative to swashplate movement is the same for both the Bell and the Robinson.
Both the Bell and Robinson behave the same relative to zero G but it is the Robinson design which permits flapping that allows the exceedance (SP) of flapping limits as opposed to the Bell which the blades can flap in unison with one going up and the other going down but not at the frequency and range of movement that allows contact with the stops resulting in mast bumping. The Bell system must flap a great deal by comparison before the Bell head hits the mast.
In summary, it is the fact that the blades can flap and that the limiting stops enter into the equation when left cyclic is applied during zero G recovery. Also the same applies to sideslip and out of trim flight which can cause excessive flapping to the point of contact with the stops.
Response to (E)
I believe it is easier to get into zero G difficulties in a Robinson than in a Bell although both are susceptible to mast bumping. This can be due to the weight difference in the respective airframes and the fact that the Robinson blades can flap and hit the stops.
Response to (G)
As previously stated if in fact the 18-degree offset comes into play then this is what happens. Because of the offset the pilot would have to apply right cyclic to compensate for the offset which means that if under this condition the pilot encountered zero G and he effected the recovery by moving the cyclic straight back without inputting any lateral control per the POH instructions he, would in fact, already have a right cyclic bias (for compensation for the offset) and this right cyclic bias would add to the right roll component generated by the tail rotor. This takes a rapid roll and upgrades it to a violent roll.
Response to (H)
First of all I do not know if some of what I propose for the test is possible. With that said, here is what I propose.
All movement in the first two elements of the test are made relative to the rigged neutral position of the cyclic stick with this position noted in the maintenance manual regarding cyclic rigging.
With the helicopter on the ground and the rotor turning up to speed move the cyclic gently forward and on a line with the rigged neutral position and observe the movement of the disc. Does it tip down over the nose or, does it tip down and to the left?
Lift the helicopter up several feet and trying not to compensate for cg shift or propeller effect move the cyclic forward on a line with the rigged neutral cyclic position and hover taxi at a slow speed. Does the helicopter fly forward or to the left? Propeller effect may cause left movement so note the disc position (see above) to see if it is tipped down over the nose or, down and to the left.
Noting the rigged neutral position of the cyclic bring the helicopter up to speed where you have passed through inflow roll and you have compensated for blow back. Note the position of the cyclic stick relative to the rigged neutral position. Is it on a line with the rigged neutral lateral position or, is it to the right of that position.
Response to (B)
Safety Notice SN-11 states in part, If the pilot attempts to stop the right roll (experienced during zero G) by applying left cyclic before gaining main rotor thrust, the rotor can exceed its flapping limits and cause structural failure of the rotor shaft due to mast bumping or allow a blade to contact the airframe.
The key word is/are “flapping limits”. As I had indicated in my last post helicopters that have blade flapping capability employ some type of stop that can be unlocked as the rotor comes up to speed which allows the blade to flap above and below the static non rotating position. Therefore, the movement of the blade is virtually un- impeded that is, until the blade comes up on its’ flapping limit stop. If the blade hits this stop during maneuvering the pilot will experience a very heavy beat and he will back off on his control input. In order to hit this stop the pilot would have input excess cyclic. Hitting the stop is not a bad condition as long as the pilot responds in a timely manner. The Robinson on the other hand has the flapping limits set by the static (droop) stop built into the rotorhead. Any coning or flapping will be above this stop. If the flapping level is very high as in an incorrect application of left cyclic in recovering from zero G the blade will flap down until it hits the stop and at that time there is a mechanical linkage between the blade and head and it in a sense is like one half of a Bell blade. If both blades hit their respective stops during rotation the lock up can apply severe bending loads to the blades and the lock up can force the rotor to teeter to the point that it contacts the mast or a blade strikes the fuselage.
Response to (D)
What makes the Robinson head different from a Bell head is that the Robinson head employs coning capability separate from the teetering capability, which is common to both types of rotorheads. The cone hinges were incorporated on the Robinson head to minimize the bending loads on the blades during application of collective or during maneuvering. With the incorporation of the cone hinges the Robinson head further deviated from the design of the Bell rotorhead in that the pitch horns had a 72-degree lead as opposed to the 90-degree lead of the Bell pitch horn.
When the Bell is rigged for fore and aft cyclic the rotor blades are disposed over the lateral axis of the helicopter. Rigging for left and right lateral the blades are placed over the longitudinal axis of the helicopter. On the Robinson when rigging for fore and aft the blades are placed 18-degrees ahead of the right lateral axis of the helicopter with the retreating blade being 18-degrees behind the left lateral axis of the helicopter. This places the pitch horn on the longitudinal axis. Rigging for lateral control the blades are placed in a similar manner in respect to the longitudinal axis. Control input relative to swashplate movement is the same for both the Bell and the Robinson.
Both the Bell and Robinson behave the same relative to zero G but it is the Robinson design which permits flapping that allows the exceedance (SP) of flapping limits as opposed to the Bell which the blades can flap in unison with one going up and the other going down but not at the frequency and range of movement that allows contact with the stops resulting in mast bumping. The Bell system must flap a great deal by comparison before the Bell head hits the mast.
In summary, it is the fact that the blades can flap and that the limiting stops enter into the equation when left cyclic is applied during zero G recovery. Also the same applies to sideslip and out of trim flight which can cause excessive flapping to the point of contact with the stops.
Response to (E)
I believe it is easier to get into zero G difficulties in a Robinson than in a Bell although both are susceptible to mast bumping. This can be due to the weight difference in the respective airframes and the fact that the Robinson blades can flap and hit the stops.
Response to (G)
As previously stated if in fact the 18-degree offset comes into play then this is what happens. Because of the offset the pilot would have to apply right cyclic to compensate for the offset which means that if under this condition the pilot encountered zero G and he effected the recovery by moving the cyclic straight back without inputting any lateral control per the POH instructions he, would in fact, already have a right cyclic bias (for compensation for the offset) and this right cyclic bias would add to the right roll component generated by the tail rotor. This takes a rapid roll and upgrades it to a violent roll.
Response to (H)
First of all I do not know if some of what I propose for the test is possible. With that said, here is what I propose.
All movement in the first two elements of the test are made relative to the rigged neutral position of the cyclic stick with this position noted in the maintenance manual regarding cyclic rigging.
With the helicopter on the ground and the rotor turning up to speed move the cyclic gently forward and on a line with the rigged neutral position and observe the movement of the disc. Does it tip down over the nose or, does it tip down and to the left?
Lift the helicopter up several feet and trying not to compensate for cg shift or propeller effect move the cyclic forward on a line with the rigged neutral cyclic position and hover taxi at a slow speed. Does the helicopter fly forward or to the left? Propeller effect may cause left movement so note the disc position (see above) to see if it is tipped down over the nose or, down and to the left.
Noting the rigged neutral position of the cyclic bring the helicopter up to speed where you have passed through inflow roll and you have compensated for blow back. Note the position of the cyclic stick relative to the rigged neutral position. Is it on a line with the rigged neutral lateral position or, is it to the right of that position.
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Lu: Sorry I haven't replied earlier - I don't look at pprune as often as I used to, largely because I'm sick of reading your preposterous drivel. You're what's known here in the UK as a crackpot, a fixated monomaniac consumed by some nuthouse maunderings dressed up as aeronautical theory. You know enough to gull the biddable, you've got an over-developed opinion of your own abilities, and no matter how often your credibility is destroyed by people who, unlike yourself, have a background in helicopter design and piloting, you keep coming back with your stale old mantra. I can usually get along with people like you, except for one thing - whenever one of your key points is hopelessly undermined, you simply stop mentioning it. Some theoriser you are.
One word of advice: Just because you don't want something to be true doesn't mean it isn't.
Unlike you, an aviation consultancy here in the UK has studied the accident statistics in great depth. I hate to rise to your bait, and I know that trying to give you real information is like bouncing eggs off an outhouse wall, but I'll say this... the R22 flew 46.46 percent of all civil single-engined helicopter hours in the UK between 1995 and 2000. (That's almost half, I feel you'll agree.) During that time it was involved in three of the 15 fatal accidents involving single-engined helicopters. (That's one in five, or 20 percent). The fatal accident rate, as I said in my previous post, was one per 115,213 hours. By comparison the fatal accident rate for the 206 was one per 39,903 hours. The rate for the Hughes 269/Schweizer 300 is one fatal per 30,939 hours over the same period. That makes the R22 three times safer than the 300 over the last five years.
When you consider the treatment the R22 is subjected to in training, and by low-time pilots, it puts this whole thing into its proper context.
Do us a favour, get off your hobby horse and find something useful to do in your retirement... I've suggested before that all you've got to do is build a better helicopter than Frank Robinson - I'm sure he'll let you steal all of his design except for the bits that you're hung up on - and if it's flyable, I'll be first in line to buy it.
I'm sure you'll reply, but forgive me if I don't get back to it for a couple of weeks.
One word of advice: Just because you don't want something to be true doesn't mean it isn't.
Unlike you, an aviation consultancy here in the UK has studied the accident statistics in great depth. I hate to rise to your bait, and I know that trying to give you real information is like bouncing eggs off an outhouse wall, but I'll say this... the R22 flew 46.46 percent of all civil single-engined helicopter hours in the UK between 1995 and 2000. (That's almost half, I feel you'll agree.) During that time it was involved in three of the 15 fatal accidents involving single-engined helicopters. (That's one in five, or 20 percent). The fatal accident rate, as I said in my previous post, was one per 115,213 hours. By comparison the fatal accident rate for the 206 was one per 39,903 hours. The rate for the Hughes 269/Schweizer 300 is one fatal per 30,939 hours over the same period. That makes the R22 three times safer than the 300 over the last five years.
When you consider the treatment the R22 is subjected to in training, and by low-time pilots, it puts this whole thing into its proper context.
Do us a favour, get off your hobby horse and find something useful to do in your retirement... I've suggested before that all you've got to do is build a better helicopter than Frank Robinson - I'm sure he'll let you steal all of his design except for the bits that you're hung up on - and if it's flyable, I'll be first in line to buy it.
I'm sure you'll reply, but forgive me if I don't get back to it for a couple of weeks.
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To: T'aint natural
Your opinion of me as a person or a technician really doesn’t matter because I will never have to come to you for a position. The English consultancy that you referenced most likely dealt with accident data published by your CAA or some other organizations. The point I made dealt with rotor loss or rotor incursion accidents and not fatal accidents in general. As I indicated there have been several in the UK and two in the USA in the years since that study was made. If you reference the rotor loss / rotor incursion accidents against the number of hours flown you will see that the Robinson accident rate is much higher than any other helicopter. I would suggest you refer to the statistics compiled by the NTSB and you will find that it is supportive of my statements
regarding the overall safety of the Robinson design.
If I am allowed to expound on my personal views I believe that the design of the rotorhead on the R22 and R44 is the major contributor (high flapping loads and the static droop stops) that lead to the high accident rate (rotor loss / rotor incursion). I believe that the restrictions placed on the flight envelope (out of trim and sideslip) are also related to the rotor design.
Now you can call me an idiot or whatever you want but I will continue on this quest until the testing of my theories is either proven or disproved. That hopefully will take place in the next several weeks.
The loss of a rotor or rotor incursion is comparable to the loss of a wing on a fixed wing aircraft. In some cases wing loss can result from maneuvering stress well in excess of design loads or improper maintenance but it does happen but it doesn’t happen at the frequency recorded by the Bell and Robinson designs.
What it all boils down to is safety is not design related it is how well the pilot follows the instructions. The problem is, the instructions are there to cover up a design flaw.
See you in a few weeks.
Your opinion of me as a person or a technician really doesn’t matter because I will never have to come to you for a position. The English consultancy that you referenced most likely dealt with accident data published by your CAA or some other organizations. The point I made dealt with rotor loss or rotor incursion accidents and not fatal accidents in general. As I indicated there have been several in the UK and two in the USA in the years since that study was made. If you reference the rotor loss / rotor incursion accidents against the number of hours flown you will see that the Robinson accident rate is much higher than any other helicopter. I would suggest you refer to the statistics compiled by the NTSB and you will find that it is supportive of my statements
regarding the overall safety of the Robinson design.
If I am allowed to expound on my personal views I believe that the design of the rotorhead on the R22 and R44 is the major contributor (high flapping loads and the static droop stops) that lead to the high accident rate (rotor loss / rotor incursion). I believe that the restrictions placed on the flight envelope (out of trim and sideslip) are also related to the rotor design.
Now you can call me an idiot or whatever you want but I will continue on this quest until the testing of my theories is either proven or disproved. That hopefully will take place in the next several weeks.
The loss of a rotor or rotor incursion is comparable to the loss of a wing on a fixed wing aircraft. In some cases wing loss can result from maneuvering stress well in excess of design loads or improper maintenance but it does happen but it doesn’t happen at the frequency recorded by the Bell and Robinson designs.
What it all boils down to is safety is not design related it is how well the pilot follows the instructions. The problem is, the instructions are there to cover up a design flaw.
See you in a few weeks.
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T'aint natural,
Hang in there. Your opinions are shared by many, perhaps all of us regarding the drivel. I hope all have figured him out by now.
The Robinson is a machine, not an evil entity, and Frank Robinson did a pretty good job, considering all the challenges that he faced making a small, economic, capable machine. For all that, he deserves better enemies than Lu, or at least he deserves a gadfly who makes sense!
Keep reading, keep posting, and try (as I have to continually try) to keep from rising to the bait.
Hang in there. Your opinions are shared by many, perhaps all of us regarding the drivel. I hope all have figured him out by now.
The Robinson is a machine, not an evil entity, and Frank Robinson did a pretty good job, considering all the challenges that he faced making a small, economic, capable machine. For all that, he deserves better enemies than Lu, or at least he deserves a gadfly who makes sense!
Keep reading, keep posting, and try (as I have to continually try) to keep from rising to the bait.
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Lu
Sounds interesting.
What have you got planned Lu?
.......... I will continue on this quest until the testing of my theories is either proven or disproved. That hopefully will take place in the next several weeks.
What have you got planned Lu?
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To: Heliport
I have contacted a member of this forum who is an instructor on R22 and R44 and I am awaiting his response. In a personal email
he indicated that the cyclic is to the right of center in normal flight. That was demonstrated using a stick plotting board.
If he does perform the test, it will put this matter to rest. Proving Nick Lappos correct or proving my theory to be correct.
[ 03 November 2001: Message edited by: Lu Zuckerman ]
I have contacted a member of this forum who is an instructor on R22 and R44 and I am awaiting his response. In a personal email
he indicated that the cyclic is to the right of center in normal flight. That was demonstrated using a stick plotting board.
If he does perform the test, it will put this matter to rest. Proving Nick Lappos correct or proving my theory to be correct.
[ 03 November 2001: Message edited by: Lu Zuckerman ]
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Here I go rising to the bait (can I stop myself?)
The stick will go to the right in a helicopter with 18 degrees of Delta 3 coupling, so it will go to the right on the Robinson. That proves nothing, LU. It goes to the right on an S-76 for the SAME reason, about 1.5 inch out of the 5 inches from center for the 145 knot cruise.
Please don't answer this post, LU. Please.
The stick will go to the right in a helicopter with 18 degrees of Delta 3 coupling, so it will go to the right on the Robinson. That proves nothing, LU. It goes to the right on an S-76 for the SAME reason, about 1.5 inch out of the 5 inches from center for the 145 knot cruise.
Please don't answer this post, LU. Please.
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To: Nick Lappos
Since the fish has risen to the bait the only thing to do is reel him in. Actually, I would like you to explain the reason for the right movement of the cyclic on both the Robinson and the S-76.
If on both helicopters you were flying at speed and you brought the helicopter to a hover with out moving the stick laterally what would the disc be doing relative to its’ rotational plane?
You mentioned an 18-degree delta 3 angle. Is that the same as the 18-degree offset? It was my understanding from your previous posts that the fact that there was an 18-degree offset it did not matter because of the pitch /flap coupling would cause the disc to tilt down over the nose as opposed to dipping down and to the left. I was wondering if this is true, why does the stick have to be displaced to the right at speed? Is this an aerodynamic phenomenon that is common to some helicopters? Is it possible that on the S-76 the engineers didn’t get it totally right in designing the flight control system to compensate for the position of the servos and that there is a similar offset on the S-76 that has to be compensated for?
You don’t have to answer me but maybe there are others on this forum that would like to know.
Since the fish has risen to the bait the only thing to do is reel him in. Actually, I would like you to explain the reason for the right movement of the cyclic on both the Robinson and the S-76.
If on both helicopters you were flying at speed and you brought the helicopter to a hover with out moving the stick laterally what would the disc be doing relative to its’ rotational plane?
You mentioned an 18-degree delta 3 angle. Is that the same as the 18-degree offset? It was my understanding from your previous posts that the fact that there was an 18-degree offset it did not matter because of the pitch /flap coupling would cause the disc to tilt down over the nose as opposed to dipping down and to the left. I was wondering if this is true, why does the stick have to be displaced to the right at speed? Is this an aerodynamic phenomenon that is common to some helicopters? Is it possible that on the S-76 the engineers didn’t get it totally right in designing the flight control system to compensate for the position of the servos and that there is a similar offset on the S-76 that has to be compensated for?
You don’t have to answer me but maybe there are others on this forum that would like to know.
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Here I go Lu:
The gamma rigging change of 18 degrees is there to KEEP the cyclic in proper phase so that forward stick is forward tilt. That is what happens on the Robinson, and the S-76. Period. The disk tilts forward when the stick goes forward. Got that? Do you? Have you learned ANYTHING in the interminable posts that you have sparked??
The stick does travel at an angle as you advance in speed, so when you get to cruise, it is a bit to the right. That is the STATIC TRIM position of the stick. Repeat that slowly, Lu. STATIC TRIM. That has NOTHING to do with which way the disk tilts when the stick is pushed forward. NOTHING TO DO WITH STICK PHASING. NOTHING. repeat that, Lu.
The delta 3 coupling of the rotor is on almost every tail rotor in existence. EVERY TAIL ROTOR. Repeat that, Lu. It is not some mysterious problem of the Robinson, Lu. It is not unusual, Lu. It does not make rotors fly off, or aircraft crash, Lu. All main rotors that have elastomeric bearings have some delta 3, Lu. ALL.
OK, what did we learn? 1) The static stick position does not relate to the control phasing. 2) The S-76 and the Robinson fly nicely with forward stick making the rotor tilt forward. 3) Lu is fishing around for some way to prove he is "right" about some crackpot theory that he discovered some bibical truth about Robinsons. 4) I rose to the bait.
What a way to start the day!
The gamma rigging change of 18 degrees is there to KEEP the cyclic in proper phase so that forward stick is forward tilt. That is what happens on the Robinson, and the S-76. Period. The disk tilts forward when the stick goes forward. Got that? Do you? Have you learned ANYTHING in the interminable posts that you have sparked??
The stick does travel at an angle as you advance in speed, so when you get to cruise, it is a bit to the right. That is the STATIC TRIM position of the stick. Repeat that slowly, Lu. STATIC TRIM. That has NOTHING to do with which way the disk tilts when the stick is pushed forward. NOTHING TO DO WITH STICK PHASING. NOTHING. repeat that, Lu.
The delta 3 coupling of the rotor is on almost every tail rotor in existence. EVERY TAIL ROTOR. Repeat that, Lu. It is not some mysterious problem of the Robinson, Lu. It is not unusual, Lu. It does not make rotors fly off, or aircraft crash, Lu. All main rotors that have elastomeric bearings have some delta 3, Lu. ALL.
OK, what did we learn? 1) The static stick position does not relate to the control phasing. 2) The S-76 and the Robinson fly nicely with forward stick making the rotor tilt forward. 3) Lu is fishing around for some way to prove he is "right" about some crackpot theory that he discovered some bibical truth about Robinsons. 4) I rose to the bait.
What a way to start the day!
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To: Nick Lappos
The gamma rigging change of 18 degrees is there to KEEP the cyclic in proper phase so that forward stick is forward tilt. That is what happens on the Robinson, and the S-76. Period. The disk tilts forward when the stick goes forward. Got that? Do you? Have you learned ANYTHING in the interminable posts that you have sparked??
Response:
Are you saying that when Frank Robinson determined that in order to keep the blades from breaking off and to get the helicopter to fly straight with forward cyclic he placed the cone hinges where he did? By placing the cone hinges in their present place he ended up with an 18-degree offset. That is one hell of an engineering job especially when you consider the helicopter was designed in his living room. Which came first, the chicken or the egg. Did he select a blade design and build the rotorhead to accommodate that design or, did he design the blade to accommodate the rotorhead with its’ 18-degree offset in order to get the disc to move down over the nose when pushing forward cyclic?
The stick does travel at an angle as you advance in speed, so when you get to cruise, it is a bit to the right. That is the STATIC TRIM position of the stick. Repeat that slowly, Lu. STATIC TRIM. That has NOTHING to do with which way the disk tilts when the stick is pushed forward. NOTHING TO DO WITH STICK PHASING. NOTHING. repeat that, Lu.
Response:
If I remember correctly the certification document for normal category rotorcraft states that disc movement must be in the same sense as cyclic input. They do allow a few degrees mismatch due to pitch coupling. That means that what you refer to as static trim means that if the stick is displaced to the right then the rotor disc is following suit. Now this may reflect the aerodynamic loading on the disc but in any case it ends up that the disc is moved in the same direction as cyclic displacement.
Maybe this is the case for the S-76 but I still believe until the test tells me different that the right displacement on the Robinson is to compensate for the 18-degree offset in the rotor system. Please don’t blow a gasket.
The delta 3 coupling of the rotor is on almost every tail rotor in existence. EVERY TAIL ROTOR. Repeat that, Lu. It is not some mysterious problem of the Robinson, Lu. It is not unusual, Lu. It does not make rotors fly off, or aircraft crash, Lu. All main rotors that have elastomeric bearings have some delta 3, Lu. ALL.
Response:
I am well aware of the mechanics and the reason behind the delta hinge effect on both tail rotors and main rotors. However I don’t believe I mentioned anything about pitch flap coupling on this thread. I would strongly suggest that you acquaint yourself with the design of the Robinson rotorhead both on the outside and the inside. My comments about rotor loss are based both on the tendency for the Robinson rotor system to demonstrate severe flapping loads with certain maneuvers and how those loads are reacted by the internal droop stops inside of the rotorhead. If a flapping blade contacts one of the stops the kinetic energy of the blade will turn the rotorhead into a lever forcing it down pivoting on the teeter hinge. This in itself can cause mast bumping or rotor incursion however, if in turning the head into a lever it causes the other blade to contact the static stop it will cause severe bending loads in that blade as well as the heavy bending loads in the first blade. All of this can cause mast bumping, rotor incursion or, loss of a blade all of, which will cause the helicopter to crash.
OK, what did we learn? 1) The static stick position does not relate to the control phasing. 2) The S-76 and the Robinson fly nicely with forward stick making the rotor tilt forward. 3) Lu is fishing around for some way to prove he is "right" about some crackpot theory that he discovered some biblical truth about Robinsons. 4) I rose to the bait.
Response:
Let’s say that you eventually get promoted to be the head of flight test. You are aware that the engineers have been developing a new design. I know that you would be involved in that design but for the sake of argument, you are not. You have a great deal of faith and respect for the engineering staff but one day they come to you and tell you that they have just run the prototype out into the hangar and the techs are correcting all of the manufacturing crabs. Then they tell you that it is not necessary to flight test the helicopter because engineering has thought of everything and that the helicopter will perform to spec. With your background and education will you accept the fact that your department will not be able to proof the helicopter to determine that in fact it will meet all of the specs?
I have a great deal of respect for you for your experience and education and maybe the engineers were correct in stating that no tests were required or that according to you my theories are incorrect. Well I want to prove that I am correct but I will also accept that I am wrong and the only way I can make that determination is to perform the test.
Please bear with me.
The gamma rigging change of 18 degrees is there to KEEP the cyclic in proper phase so that forward stick is forward tilt. That is what happens on the Robinson, and the S-76. Period. The disk tilts forward when the stick goes forward. Got that? Do you? Have you learned ANYTHING in the interminable posts that you have sparked??
Response:
Are you saying that when Frank Robinson determined that in order to keep the blades from breaking off and to get the helicopter to fly straight with forward cyclic he placed the cone hinges where he did? By placing the cone hinges in their present place he ended up with an 18-degree offset. That is one hell of an engineering job especially when you consider the helicopter was designed in his living room. Which came first, the chicken or the egg. Did he select a blade design and build the rotorhead to accommodate that design or, did he design the blade to accommodate the rotorhead with its’ 18-degree offset in order to get the disc to move down over the nose when pushing forward cyclic?
The stick does travel at an angle as you advance in speed, so when you get to cruise, it is a bit to the right. That is the STATIC TRIM position of the stick. Repeat that slowly, Lu. STATIC TRIM. That has NOTHING to do with which way the disk tilts when the stick is pushed forward. NOTHING TO DO WITH STICK PHASING. NOTHING. repeat that, Lu.
Response:
If I remember correctly the certification document for normal category rotorcraft states that disc movement must be in the same sense as cyclic input. They do allow a few degrees mismatch due to pitch coupling. That means that what you refer to as static trim means that if the stick is displaced to the right then the rotor disc is following suit. Now this may reflect the aerodynamic loading on the disc but in any case it ends up that the disc is moved in the same direction as cyclic displacement.
Maybe this is the case for the S-76 but I still believe until the test tells me different that the right displacement on the Robinson is to compensate for the 18-degree offset in the rotor system. Please don’t blow a gasket.
The delta 3 coupling of the rotor is on almost every tail rotor in existence. EVERY TAIL ROTOR. Repeat that, Lu. It is not some mysterious problem of the Robinson, Lu. It is not unusual, Lu. It does not make rotors fly off, or aircraft crash, Lu. All main rotors that have elastomeric bearings have some delta 3, Lu. ALL.
Response:
I am well aware of the mechanics and the reason behind the delta hinge effect on both tail rotors and main rotors. However I don’t believe I mentioned anything about pitch flap coupling on this thread. I would strongly suggest that you acquaint yourself with the design of the Robinson rotorhead both on the outside and the inside. My comments about rotor loss are based both on the tendency for the Robinson rotor system to demonstrate severe flapping loads with certain maneuvers and how those loads are reacted by the internal droop stops inside of the rotorhead. If a flapping blade contacts one of the stops the kinetic energy of the blade will turn the rotorhead into a lever forcing it down pivoting on the teeter hinge. This in itself can cause mast bumping or rotor incursion however, if in turning the head into a lever it causes the other blade to contact the static stop it will cause severe bending loads in that blade as well as the heavy bending loads in the first blade. All of this can cause mast bumping, rotor incursion or, loss of a blade all of, which will cause the helicopter to crash.
OK, what did we learn? 1) The static stick position does not relate to the control phasing. 2) The S-76 and the Robinson fly nicely with forward stick making the rotor tilt forward. 3) Lu is fishing around for some way to prove he is "right" about some crackpot theory that he discovered some biblical truth about Robinsons. 4) I rose to the bait.
Response:
Let’s say that you eventually get promoted to be the head of flight test. You are aware that the engineers have been developing a new design. I know that you would be involved in that design but for the sake of argument, you are not. You have a great deal of faith and respect for the engineering staff but one day they come to you and tell you that they have just run the prototype out into the hangar and the techs are correcting all of the manufacturing crabs. Then they tell you that it is not necessary to flight test the helicopter because engineering has thought of everything and that the helicopter will perform to spec. With your background and education will you accept the fact that your department will not be able to proof the helicopter to determine that in fact it will meet all of the specs?
I have a great deal of respect for you for your experience and education and maybe the engineers were correct in stating that no tests were required or that according to you my theories are incorrect. Well I want to prove that I am correct but I will also accept that I am wrong and the only way I can make that determination is to perform the test.
Please bear with me.
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Lu,
You post is so full of misguided assertions it is hopeless to respond. The fact that you cannot tell the difference between the trimmed cyclic position and the response to a stick input shows that explaining all this to you is truly hopeless. I only hope the readers have the sense to consider that when you make the points you do.
As you put it "the only way I can make that determination is to perform the test."
The thought of you determining something useful from your "test" is a joke, right?
You say "let's say you get promoted to the head of flight test...." Lu, I was the head of flight test, in fact the head of all test at Sikorsky!
[ 04 November 2001: Message edited by: Nick Lappos ]
You post is so full of misguided assertions it is hopeless to respond. The fact that you cannot tell the difference between the trimmed cyclic position and the response to a stick input shows that explaining all this to you is truly hopeless. I only hope the readers have the sense to consider that when you make the points you do.
As you put it "the only way I can make that determination is to perform the test."
The thought of you determining something useful from your "test" is a joke, right?
You say "let's say you get promoted to the head of flight test...." Lu, I was the head of flight test, in fact the head of all test at Sikorsky!
[ 04 November 2001: Message edited by: Nick Lappos ]
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To: Nick Lappos
Your post is so full of misguided assertions it is hopeless to respond. The fact that you cannot tell the difference between the trimmed cyclic position and the response to a stick input shows that explaining all this to you is truly hopeless. I only hope the readers have the sense to consider that when you make the points you do.
Response:
I asked if the static trim position of the cyclic had anything to do with the direction in which the disc would tilt. I referenced the FAA document, which stated that disc movement is in the same sense of cyclic movement. If the cyclic is right of the rigged neutral longitudinal axis then which way is the disc tilted if it is tilted any way other than down over the nose.
As you put it "the only way I can make that determination is to perform the test."
The thought of you determining something useful from your "test" is a joke, right?
Response:
The test when performed will be accomplished by a CFI with high time in both the R-22 and R-44. I will document the test to be performed and he will evaluate those instructions to determine if the test is doable. If the test can be performed without endangering the pilot or the helicopter the test will be performed. The individual is familiar with test and development requirements and he will fully document the test and the results will be published on this forum.
You say "let's say you get promoted to the head of flight test...." Lu, I was the head of flight test, in fact the head of all test at Sikorsky!
Response:
Now that you have told everybody about how important you are and what you have accomplished please answer the question. How would you respond to the engineering department when they told you that testing was unnecessary?
I used that analogy to point out why I have been so hardheaded. Especially since you make statements without being familiar with the design of the Robinson rotorhead and the complications arising from that design.
Another point is that you did not respond to my other comments in the response dealing with delta hinge effect and what I perceive as a design problem with the rotorhead that contributes to mast bumping and / or fuselage incursion.
Regarding the so-called 18-degree offset, it has absolutely no connection with mast bumping or fuselage incursion. If the offset exists and the pilot has to compensate for it then you could have a problem in zero G recovery. The problem with the R22/44 is that you can easily induce high flapping loads and the design of the rotorhead couples up with these loads and kills people. The Robinson helicopters are the only helicopters that are restricted from out of trim flight and sideslip at all speeds. Violate these SUGGESTIONS and you get high flapping loads as a result. Why don’t you comment on these facts?
Here is another question. On the various Sikorsky designs you are familiar with what is the +/- flapping range in relation to the static droop stops? I will assume that there is a +/- range on all of them but on the Robinson there is a + range but there is no negative range. Do you see any potential problems with that under high flapping excursions?
One of the reasons I feel so strongly about the 18-degree offset is that the Lynx helicopter has the same problem. Its’ offset is 15-degrees and the Lynx is rigged just like the Robbie in that the blade is offset during the rigging procedure just like the Robbie. On the Lynx from what I understand they have some type of stabilizing black box that reads cyclic input and adjusts the servo input to compensate for the 15-degree offset. If the black box fails the input of forward cyclic or any other direction the helicopter will roll 15-degrees after the direction of cyclic input. It is because of this that I believe the Robbies have the same problem even though you state that they don’t.
[ 05 November 2001: Message edited by: Lu Zuckerman ]
Your post is so full of misguided assertions it is hopeless to respond. The fact that you cannot tell the difference between the trimmed cyclic position and the response to a stick input shows that explaining all this to you is truly hopeless. I only hope the readers have the sense to consider that when you make the points you do.
Response:
I asked if the static trim position of the cyclic had anything to do with the direction in which the disc would tilt. I referenced the FAA document, which stated that disc movement is in the same sense of cyclic movement. If the cyclic is right of the rigged neutral longitudinal axis then which way is the disc tilted if it is tilted any way other than down over the nose.
As you put it "the only way I can make that determination is to perform the test."
The thought of you determining something useful from your "test" is a joke, right?
Response:
The test when performed will be accomplished by a CFI with high time in both the R-22 and R-44. I will document the test to be performed and he will evaluate those instructions to determine if the test is doable. If the test can be performed without endangering the pilot or the helicopter the test will be performed. The individual is familiar with test and development requirements and he will fully document the test and the results will be published on this forum.
You say "let's say you get promoted to the head of flight test...." Lu, I was the head of flight test, in fact the head of all test at Sikorsky!
Response:
Now that you have told everybody about how important you are and what you have accomplished please answer the question. How would you respond to the engineering department when they told you that testing was unnecessary?
I used that analogy to point out why I have been so hardheaded. Especially since you make statements without being familiar with the design of the Robinson rotorhead and the complications arising from that design.
Another point is that you did not respond to my other comments in the response dealing with delta hinge effect and what I perceive as a design problem with the rotorhead that contributes to mast bumping and / or fuselage incursion.
Regarding the so-called 18-degree offset, it has absolutely no connection with mast bumping or fuselage incursion. If the offset exists and the pilot has to compensate for it then you could have a problem in zero G recovery. The problem with the R22/44 is that you can easily induce high flapping loads and the design of the rotorhead couples up with these loads and kills people. The Robinson helicopters are the only helicopters that are restricted from out of trim flight and sideslip at all speeds. Violate these SUGGESTIONS and you get high flapping loads as a result. Why don’t you comment on these facts?
Here is another question. On the various Sikorsky designs you are familiar with what is the +/- flapping range in relation to the static droop stops? I will assume that there is a +/- range on all of them but on the Robinson there is a + range but there is no negative range. Do you see any potential problems with that under high flapping excursions?
One of the reasons I feel so strongly about the 18-degree offset is that the Lynx helicopter has the same problem. Its’ offset is 15-degrees and the Lynx is rigged just like the Robbie in that the blade is offset during the rigging procedure just like the Robbie. On the Lynx from what I understand they have some type of stabilizing black box that reads cyclic input and adjusts the servo input to compensate for the 15-degree offset. If the black box fails the input of forward cyclic or any other direction the helicopter will roll 15-degrees after the direction of cyclic input. It is because of this that I believe the Robbies have the same problem even though you state that they don’t.
[ 05 November 2001: Message edited by: Lu Zuckerman ]
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Lu,
Can you go somewhere else and do your I hate Robinson helicopters crusade. You are starting to annoy me as well as others I am sure.
I posted a question and you have hijacked the thread with the same old whinge you spend your life pushing forward.
Perhaps you and the Guvnor could lock yourselves in the same toilet and bullsh!t each other to death.
Now back to the original question. It looks like I will be visiting the factory next year and plan to do the course there rather than here in the UK.
[edited because I can't type]
[ 05 November 2001: Message edited by: Vortex what? ]
Can you go somewhere else and do your I hate Robinson helicopters crusade. You are starting to annoy me as well as others I am sure.
I posted a question and you have hijacked the thread with the same old whinge you spend your life pushing forward.
Perhaps you and the Guvnor could lock yourselves in the same toilet and bullsh!t each other to death.
Now back to the original question. It looks like I will be visiting the factory next year and plan to do the course there rather than here in the UK.
[edited because I can't type]
[ 05 November 2001: Message edited by: Vortex what? ]
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Vortex
A very good decision. Whilst in Torrance should you wish to fly a little around the local area I highly recommend looking up Rainbow Air in Long Beach.
www.rainbowair.com
Dave Parsons will look after you well.
A very good decision. Whilst in Torrance should you wish to fly a little around the local area I highly recommend looking up Rainbow Air in Long Beach.
www.rainbowair.com
Dave Parsons will look after you well.
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To: Nick Lappos
"Lu,
You couldn't see a fact if it hit you in the head. You are hung up on your crackpot theories, and are beyond redemption.
Your posts are a waste of electrons".
Nick:
You have a wonderful way of displaying your superior intellect by the use of personal attack. Please tell me why you do not respond to the technical facts that I place on this forum regarding the design of the Robinson rotorhead. Is it because you don’t understand the design or, that I may be correct? Forget about the 18-degree offset. Even with your assessment of the aerodynamics that allow a 72-degree phase angle to react like a 90-degree phase angle the design does not change.
Now I would believe that a person in your position would seek the truth and not close your mind to the facts. Perchance I am wrong on this point too. At least you could prove it on a public forum.
To those of you that object to this material being on this thread I will gladly take it to another thread but at least I would like Nick to respond on a technical basis as opposed to personal attacks.
"Lu,
You couldn't see a fact if it hit you in the head. You are hung up on your crackpot theories, and are beyond redemption.
Your posts are a waste of electrons".
Nick:
You have a wonderful way of displaying your superior intellect by the use of personal attack. Please tell me why you do not respond to the technical facts that I place on this forum regarding the design of the Robinson rotorhead. Is it because you don’t understand the design or, that I may be correct? Forget about the 18-degree offset. Even with your assessment of the aerodynamics that allow a 72-degree phase angle to react like a 90-degree phase angle the design does not change.
Now I would believe that a person in your position would seek the truth and not close your mind to the facts. Perchance I am wrong on this point too. At least you could prove it on a public forum.
To those of you that object to this material being on this thread I will gladly take it to another thread but at least I would like Nick to respond on a technical basis as opposed to personal attacks.