R22 Corner
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lu
i recon the coning hinges on a robinson would never flap seperately because of the weight from the blades forcing the head to be flat with disc attitude, if no flapping , no lead or lagging??
Iconoclast
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I say tomAto and you say tomAHto.
To: vorticey
The rotor and blades are coincident with each other (flat) only when the collective is full down. When collective is pulled the blades cone up to the point where centrifugal forces on the blades are effected by the aerodynamic lift. In a sense the blades have flapped up and will maintain this relative position unless effected by aerodynamic forces or input of cyclic pitch and then they will flap up and down in relation to each other.
Other things that will influence flapping are:
1) Flapback during translational lift (flapping to equality).
2) Gusting
3) Flying out of trim.
4) Side slip
5) Incorrect recovery from a zero G episode.
The extent of flapping is effected by the extent of the maneuver (3,4 and 5 above). This flapping can range from minor or acceptable levels to severe enough to cause mast bumping or rotor incursion.
Now let’s assume you are correct and there is no flapping which would result in leading and lagging. If this is the case please explain what forces are present in the rotor system to cause the elliptical wear pattern on the cone hinges and to a lesser extent on the teeter hinge.
The rotor and blades are coincident with each other (flat) only when the collective is full down. When collective is pulled the blades cone up to the point where centrifugal forces on the blades are effected by the aerodynamic lift. In a sense the blades have flapped up and will maintain this relative position unless effected by aerodynamic forces or input of cyclic pitch and then they will flap up and down in relation to each other.
Other things that will influence flapping are:
1) Flapback during translational lift (flapping to equality).
2) Gusting
3) Flying out of trim.
4) Side slip
5) Incorrect recovery from a zero G episode.
The extent of flapping is effected by the extent of the maneuver (3,4 and 5 above). This flapping can range from minor or acceptable levels to severe enough to cause mast bumping or rotor incursion.
Now let’s assume you are correct and there is no flapping which would result in leading and lagging. If this is the case please explain what forces are present in the rotor system to cause the elliptical wear pattern on the cone hinges and to a lesser extent on the teeter hinge.
Senis Semper Fidelis
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Tammy,
A Dinky refers to something small, like the dinky you possibly wear on your high heels, or your sense of humour perhaps, and why would Army flyers shout any instruction when flying solo?
A Dinky refers to something small, like the dinky you possibly wear on your high heels, or your sense of humour perhaps, and why would Army flyers shout any instruction when flying solo?
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Hi gang,
I agree with "buitenzorg"(was it...?)
It seems the whole world cracks down on Robinson when one comes down and everything points to the design.
Why do there have to be SN´s from the factory, warning people from overspeeding the rotor on take off? Well R-Drivers know the trick to get off a little easier on a hot day, just override the governor and take off with 106 - 108% rpm. Normally you are off in 5-10 sec and let go on the throttle and the governor do his work. I was surprised to read in the SN, that there are crackheads who actually pull it to 120% !!!!!
It is always the same, for some idiots there are no rules and when something happens it goes back to the factory.
By the way Lu, I believe the Robinson cone hinges are the best invention since the underslung head, they actually take any bending moment caused by coning completely out.
Arguments that the coning hinges do flap work are not valid. If you look up the maintenance manual, you will find that there are precise procedures how to adjust the frictions on the head system. if it is set up right it will work fine. If for any reason the friction values change in one hinge it becomes apparent immediately as a mainrotor vibration. At this time it has to go into the shop to adjust this. No big deal.
If you IGNORE any indications of "out of normal" on ANY HELICOPTER you are bound to get into trouble!! Not just on Robinsons, however I found that the Robinson has an extremly high tolerance on these ocasions and is comparatively inexpensive to fix (ups - repair, I mean...), resulting in little down time. I do not see that on the Bell´s of our competition!
Another feature of the Robinson Rotor is a max lifetime of 2000hrs or 10 years - whatever comes first. That is active safety! No matter how good the blades look - 2000hrs and the go!!
I have been flying Robinsons on the edge for about 4000 hrs now and never had any problems with blades. However I suggest to all Helicopter Schools to do a little sermon now and then on HOW TO NOT ABUSE helicopters!!
3top
I agree with "buitenzorg"(was it...?)
It seems the whole world cracks down on Robinson when one comes down and everything points to the design.
Why do there have to be SN´s from the factory, warning people from overspeeding the rotor on take off? Well R-Drivers know the trick to get off a little easier on a hot day, just override the governor and take off with 106 - 108% rpm. Normally you are off in 5-10 sec and let go on the throttle and the governor do his work. I was surprised to read in the SN, that there are crackheads who actually pull it to 120% !!!!!
It is always the same, for some idiots there are no rules and when something happens it goes back to the factory.
By the way Lu, I believe the Robinson cone hinges are the best invention since the underslung head, they actually take any bending moment caused by coning completely out.
Arguments that the coning hinges do flap work are not valid. If you look up the maintenance manual, you will find that there are precise procedures how to adjust the frictions on the head system. if it is set up right it will work fine. If for any reason the friction values change in one hinge it becomes apparent immediately as a mainrotor vibration. At this time it has to go into the shop to adjust this. No big deal.
If you IGNORE any indications of "out of normal" on ANY HELICOPTER you are bound to get into trouble!! Not just on Robinsons, however I found that the Robinson has an extremly high tolerance on these ocasions and is comparatively inexpensive to fix (ups - repair, I mean...), resulting in little down time. I do not see that on the Bell´s of our competition!
Another feature of the Robinson Rotor is a max lifetime of 2000hrs or 10 years - whatever comes first. That is active safety! No matter how good the blades look - 2000hrs and the go!!
I have been flying Robinsons on the edge for about 4000 hrs now and never had any problems with blades. However I suggest to all Helicopter Schools to do a little sermon now and then on HOW TO NOT ABUSE helicopters!!
3top
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The Nr Fairy,
Thanks for that link, I wasn't aware of those accidents. But just imagine what peak stresses an R22 with two aboard must undergo during the hard low-level maneuvering of mustering flights. I wonder if a mustering ship has ever been instrumented to record that? Probably not.
Thanks for that link, I wasn't aware of those accidents. But just imagine what peak stresses an R22 with two aboard must undergo during the hard low-level maneuvering of mustering flights. I wonder if a mustering ship has ever been instrumented to record that? Probably not.
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And another one:
Although Robinson is the number 1 in safety - at least in the statistics: I am afraid the relative number of R´s in accidents will increase. There are just so many out there already and getting more everyday, at a high rate. If half the world drives Toyotas, well a lot of Toyotas will be in accidents.
It will still be the safest machine per flighthours!
Besides I think Robinson is very conservative about his helicopters.
Look at the new Raven II, finally we got a max grossweight increase of 100 lb to the new engine! I do not believe that there had to be any structural changes done.
Fly safe!
Although Robinson is the number 1 in safety - at least in the statistics: I am afraid the relative number of R´s in accidents will increase. There are just so many out there already and getting more everyday, at a high rate. If half the world drives Toyotas, well a lot of Toyotas will be in accidents.
It will still be the safest machine per flighthours!
Besides I think Robinson is very conservative about his helicopters.
Look at the new Raven II, finally we got a max grossweight increase of 100 lb to the new engine! I do not believe that there had to be any structural changes done.
Fly safe!
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Last one:
Talking to THE safety course instructor from Robinson about R22 flying, and that man should know, he said he never saw such extreme flying like cattle herding in OZ. I thought I did my share on tuna boats and fumigation with R22. According to the man thats all peanuts compared to the Australian way of cattle mustering!
Out for today!!
Talking to THE safety course instructor from Robinson about R22 flying, and that man should know, he said he never saw such extreme flying like cattle herding in OZ. I thought I did my share on tuna boats and fumigation with R22. According to the man thats all peanuts compared to the Australian way of cattle mustering!
Out for today!!
Iconoclast
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Cone hinges Vs Flapping hinges
To: 3top
Quote:
"By the way Lu, I believe the Robinson cone hinges are the best invention since the underslung head, they actually take any bending moment caused by coning completely out".
"Arguments that the coning hinges do flap work are not valid. If you look up the maintenance manual, you will find that there are precise procedures how to adjust the frictions on the head system. if it is set up right it will work fine. If for any reason the friction values change in one hinge it becomes apparent immediately as a mainrotor vibration. At this time it has to go into the shop to adjust this. No big deal".
If you look at the patent application for the three hinge rotor system referenced above Frank Robinson makes the same point about reduction of the bending stresses when compared to a Bell system which has very high bending stresses at the root. Whether the Robinson’s’ cone hinges are the best invention since the underslung rotor is a bit of a stretch. If the cone hinges were not incorporated the rotor system would be so heavy as to minimize any payload for the helicopter.
Adjustment of the friction on the cone hinges preloads the system to minimize any relative movement on the stack-up of the parts in the assembly. The point you made about the change in friction level on one cone hinge causing a vibration is correct however it is also true when there is an imbalance between elastomeric elements in a multi-blade system. For instance if the elastomeric dampers on the Apache differ by more than 5% the aircraft can enter into air resonance and self-destruct. The same is true for hydraulic or friction dampers on other helicopters. The Robinson head is in effect a semi rigid semi articulated rotor system and being semi articulated (free to flap) it is subject to the same forces that generate leading and lagging.
Quote:
"By the way Lu, I believe the Robinson cone hinges are the best invention since the underslung head, they actually take any bending moment caused by coning completely out".
"Arguments that the coning hinges do flap work are not valid. If you look up the maintenance manual, you will find that there are precise procedures how to adjust the frictions on the head system. if it is set up right it will work fine. If for any reason the friction values change in one hinge it becomes apparent immediately as a mainrotor vibration. At this time it has to go into the shop to adjust this. No big deal".
If you look at the patent application for the three hinge rotor system referenced above Frank Robinson makes the same point about reduction of the bending stresses when compared to a Bell system which has very high bending stresses at the root. Whether the Robinson’s’ cone hinges are the best invention since the underslung rotor is a bit of a stretch. If the cone hinges were not incorporated the rotor system would be so heavy as to minimize any payload for the helicopter.
Adjustment of the friction on the cone hinges preloads the system to minimize any relative movement on the stack-up of the parts in the assembly. The point you made about the change in friction level on one cone hinge causing a vibration is correct however it is also true when there is an imbalance between elastomeric elements in a multi-blade system. For instance if the elastomeric dampers on the Apache differ by more than 5% the aircraft can enter into air resonance and self-destruct. The same is true for hydraulic or friction dampers on other helicopters. The Robinson head is in effect a semi rigid semi articulated rotor system and being semi articulated (free to flap) it is subject to the same forces that generate leading and lagging.
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Hi Lu,
unfortunately my theory on helicopter design is rather very limited. I try to argue based more on common sense......
Though I have a mechanical engineering education it just lets me understand the basics what you and guys like Nick Lappos are talking about when the going gets deep...
But I am glad I do not disintegrate in the air when the friction values on the Robinson head change for whatever reason (like those poor guys in their Apaches...).
I had the unfortune to fly one Robinson 44 with one completely lose coning hinge once. It just jumps with one per rev.........
I still could fly it back to the shop.
The unlucky son of a b... of a mechanic did not heed the advice in the maintance manual, that the hinges have to be ABSOLUTELY clean during assembly. Grease - even fat from your own fingers are too much for teflonbased friction bearings. That happens when people (mechanics, pilots, etc.) know it all better than the guys who built the machine and write the manuals!!
3top
PS: Lu, as you are the "one" who started the 18 degree offset discussion: Do you still have all the arguments and responses?
I got to late into PPRUNE to catch that forum. However I would like to read about it. If you can send me an e-mail with some info on that!
Thanks
unfortunately my theory on helicopter design is rather very limited. I try to argue based more on common sense......
Though I have a mechanical engineering education it just lets me understand the basics what you and guys like Nick Lappos are talking about when the going gets deep...
But I am glad I do not disintegrate in the air when the friction values on the Robinson head change for whatever reason (like those poor guys in their Apaches...).
I had the unfortune to fly one Robinson 44 with one completely lose coning hinge once. It just jumps with one per rev.........
I still could fly it back to the shop.
The unlucky son of a b... of a mechanic did not heed the advice in the maintance manual, that the hinges have to be ABSOLUTELY clean during assembly. Grease - even fat from your own fingers are too much for teflonbased friction bearings. That happens when people (mechanics, pilots, etc.) know it all better than the guys who built the machine and write the manuals!!
3top
PS: Lu, as you are the "one" who started the 18 degree offset discussion: Do you still have all the arguments and responses?
I got to late into PPRUNE to catch that forum. However I would like to read about it. If you can send me an e-mail with some info on that!
Thanks
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lu
i think that the examples of "flapping" you gave are not realy flapping but teetering. the only way the flapping hinges move is by changing the load on the disc either with weight or high 'g' movements.
for example when flap back occures the head tilts back with the disc, not just the blade swiping past the nose.
are you sure that the elipticle holes arent just wear caused by coning under power? this would let the blades lag a bit behind their original line.
what do you recon?
for example when flap back occures the head tilts back with the disc, not just the blade swiping past the nose.
are you sure that the elipticle holes arent just wear caused by coning under power? this would let the blades lag a bit behind their original line.
what do you recon?
Iconoclast
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In response
To: 3top
The Apache example was a bit extreme. The point I was trying to make is that rotor systems are balanced both statically and dynamically and if some thing goes out of balance a vibration will ensue. In the case of the Robinson head if the friction is not the same on both sides you will get a vibration.
To: vorticey
If I understand you correctly you are saying that the only movement on the cone bushes is when the pilot pulls collective and the blades cone up taking on the weight of the helicopter with this upward movement being balanced out by centrifugal loading on the blades. In your explanation you state from that point the blades do not move when cyclic is applied and at that point the rotor system is just like a Bell.
If the increased lift on the blades when lifting off is sufficient to overcome the friction on the cone hinges then it is also possible for the changing aerodynamic loads on the blade due to cyclic pitch changes to be sufficient also to overcome the friction on the cone hinges.
The flapping due to improper control input is also sufficient to overcome the friction to the point that the tusk can strike the stop and fracture either itself or the stop.
Your statement about the loads stemming from coning being the cause of the wear on the cone hinges is true. Even though the head is underslung like a Bell the coning or flapping can cause a difference between the driven axis and the driving axis when cyclic is pushed and at this point the forces of conservation of angular momentum take over and you get leading and lagging. Using Nicks’ explanation this results in edgewise bending which cyclically loads the blade root and the cone hinges causing (I assume) the cracking of the blade spar and the wear on the cone and teeter hinges.
The Apache example was a bit extreme. The point I was trying to make is that rotor systems are balanced both statically and dynamically and if some thing goes out of balance a vibration will ensue. In the case of the Robinson head if the friction is not the same on both sides you will get a vibration.
To: vorticey
If I understand you correctly you are saying that the only movement on the cone bushes is when the pilot pulls collective and the blades cone up taking on the weight of the helicopter with this upward movement being balanced out by centrifugal loading on the blades. In your explanation you state from that point the blades do not move when cyclic is applied and at that point the rotor system is just like a Bell.
If the increased lift on the blades when lifting off is sufficient to overcome the friction on the cone hinges then it is also possible for the changing aerodynamic loads on the blade due to cyclic pitch changes to be sufficient also to overcome the friction on the cone hinges.
The flapping due to improper control input is also sufficient to overcome the friction to the point that the tusk can strike the stop and fracture either itself or the stop.
Your statement about the loads stemming from coning being the cause of the wear on the cone hinges is true. Even though the head is underslung like a Bell the coning or flapping can cause a difference between the driven axis and the driving axis when cyclic is pushed and at this point the forces of conservation of angular momentum take over and you get leading and lagging. Using Nicks’ explanation this results in edgewise bending which cyclically loads the blade root and the cone hinges causing (I assume) the cracking of the blade spar and the wear on the cone and teeter hinges.
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for an effective way to show a stude the remarkable fact that the r22 does what it does - show them it in bits in the workshop! to think that when all those fragile little bits do what they do when bolted together might just let some realise the fragility of it.
Personally, you wouldn't get me in one, but that is another story
Personally, you wouldn't get me in one, but that is another story
Iconoclast
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The other side of the coin.
To: STANDTO
Along the same line I would suggest that you let a Robbie pilot either high or low time look at a disassembled head that is going in for a 2000 hour check. If you really want to scare the crap out of them have them look at a rotor head removed from a cattle mustering helicopter for its’ 2000 hour check (assuming it lasted that long).
Along the same line I would suggest that you let a Robbie pilot either high or low time look at a disassembled head that is going in for a 2000 hour check. If you really want to scare the crap out of them have them look at a rotor head removed from a cattle mustering helicopter for its’ 2000 hour check (assuming it lasted that long).
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Lu,
Remove a mustering heli's head for a 2000hr check............but it's only just been run in
Robinson's like any ac can and will bite. It is a testament to the ac's strength when you see what ringers put them through in the australian cattle industry.
One unfortunate accident with loss of life involved a blade seperating at the root. ATSB investigation revealed the ac had overflown hour in the order of of 5-6000hrs ABOVE the 2000hr overhaul
Must admit I do like the R22 one up
Remove a mustering heli's head for a 2000hr check............but it's only just been run in
Robinson's like any ac can and will bite. It is a testament to the ac's strength when you see what ringers put them through in the australian cattle industry.
One unfortunate accident with loss of life involved a blade seperating at the root. ATSB investigation revealed the ac had overflown hour in the order of of 5-6000hrs ABOVE the 2000hr overhaul
Must admit I do like the R22 one up
Iconoclast
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Flying cowboys
To: Hone22
At the height of my making posts on this forum regarding the restrictions placed on the R-22 and R-44 relative to FAA AD 95-26-04 I had the pleasure of watching a Discovery channel program about cattle mustering in Oz. I was absolutely amazed at the close in maneuverability of the R-22. I had seen many of them flying but not in that way. However what I saw amazed me in the fact that 90% of the flying was in total violation of the AD and its’ attendant restrictions.
I had previously mentioned seeing an R-22 rotorhead that exhibited very strange wear patterns on the cone bushes and the teeter bushes. I saw this rotorhead at Geneva Aviation in Everett, Washington and was told that it was off of an Australian R-22.
At the height of my making posts on this forum regarding the restrictions placed on the R-22 and R-44 relative to FAA AD 95-26-04 I had the pleasure of watching a Discovery channel program about cattle mustering in Oz. I was absolutely amazed at the close in maneuverability of the R-22. I had seen many of them flying but not in that way. However what I saw amazed me in the fact that 90% of the flying was in total violation of the AD and its’ attendant restrictions.
I had previously mentioned seeing an R-22 rotorhead that exhibited very strange wear patterns on the cone bushes and the teeter bushes. I saw this rotorhead at Geneva Aviation in Everett, Washington and was told that it was off of an Australian R-22.
Hone :
Can you confirm that, please. You're saying the blade was run for about 7,000 hours ?
****ty death ! No disrespect, but if someone knew about that, why the bloody hell didn't it get stopped ?
Can you confirm that, please. You're saying the blade was run for about 7,000 hours ?
****ty death ! No disrespect, but if someone knew about that, why the bloody hell didn't it get stopped ?
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Yes Lu, those mustering machines can be worked hard. But this is not the only cause of the wear in the hub and other parts of the helicopter. The red dust which is prevalent in most Aussie mustering locations also adds to wear. This dust, usually called ‘bulldust’, is as fine as talcum powder and gets into every nook and cranny of these machines. I suspect the wear you saw had its fair share of visible scoring. Its just a part of outback life.
Maybe Frank should manufacture a dedicated mustering machine. He could use the R44 engine/powertrain and rotors (with the hydraulics of course) in an R22 airframe.
LU agree,
About twelve years ago I found a crack on the underside of an R22 blade. The crack was about three and a half inches long and about 24 inches out from the spindle area.
It had started in a small dent caused by an ejected shell from an SLR. The dent had been there (according to the pilot) for eight months. Yet the pilot had not reported any increase in vibration.
Maybe Frank should manufacture a dedicated mustering machine. He could use the R44 engine/powertrain and rotors (with the hydraulics of course) in an R22 airframe.
LU agree,
In some cases even massive cracks in a blade do not manifest themselves in vibration.
It had started in a small dent caused by an ejected shell from an SLR. The dent had been there (according to the pilot) for eight months. Yet the pilot had not reported any increase in vibration.
Me thinks that it is you that missed the whole point of that window
Verbally-calling-out "...turning left and signing off!"