R22 Corner
Guest
Posts: n/a
bad week for r22's
Join Date: Dec 2000
Location: Ask the voices!
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
How very sad.
It is so easy to see how Robinsons get such a bad name/reputation.
I cannot help but wonder, if the Robinson was not around would another aircraft have such mis-fortune?
Frank Robinson has filled a niche in the small rotorcraft market, and over all I think he has done it very well. I believe that if the Robinson was not in existance, and another type was used in it's place (H300 for example) it would have as bad a reputation.
"Some days you are the pigeon, some days you are the statue!"
It is so easy to see how Robinsons get such a bad name/reputation.
I cannot help but wonder, if the Robinson was not around would another aircraft have such mis-fortune?
Frank Robinson has filled a niche in the small rotorcraft market, and over all I think he has done it very well. I believe that if the Robinson was not in existance, and another type was used in it's place (H300 for example) it would have as bad a reputation.
"Some days you are the pigeon, some days you are the statue!"
HeliFirst
Join Date: Jan 2001
Location: Lincoln & Norwich
Posts: 225
Likes: 0
Received 0 Likes
on
0 Posts
Please do not put the S300 (Hughes269) + variants in the same group as the Robbo.
The R22 really is a lightweight helicopter and it's great in its own way but not in the same league as the S300!!!
Safe flying is all about knowledge....
topilot or to pprune
nullbut
The R22 really is a lightweight helicopter and it's great in its own way but not in the same league as the S300!!!
Safe flying is all about knowledge....
topilot or to pprune
nullbut
Join Date: Dec 2000
Location: Ask the voices!
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
Please don't get me wrong, I am not placing anything in the same group as anything.
I was simply trying to simulate a Robinson free world. The H300 is a sturdy beast, and is still very popular for training etc..
Both the robbo and Hughes have their own valuable place in aviation, with their own qualities
I was simply trying to simulate a Robinson free world. The H300 is a sturdy beast, and is still very popular for training etc..
Both the robbo and Hughes have their own valuable place in aviation, with their own qualities
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
Posts: 2,132
Likes: 0
Received 0 Likes
on
0 Posts
To: HeliEng
A variant of the Hughes 300 was used for years as a basic helicopter trainer by the US Army and they had their fair share of accidents caused by low time pilots. The 300and its’ variants still have their fair share of accidents caused by low time pilots or idiot high time pilots. The one thing that they do not suffer from is mast bumping and rotor separation or fuselage incursion. If by chance one or two have suffered rotor incursion it was because they were flown way outside of the envelope. If they suffered total rotor loss it was because of mechanical error and if they lost a blade it was due to fatigue or higher than normal stress levels. Whether this would cause a bad reputation is up for speculation.
A variant of the Hughes 300 was used for years as a basic helicopter trainer by the US Army and they had their fair share of accidents caused by low time pilots. The 300and its’ variants still have their fair share of accidents caused by low time pilots or idiot high time pilots. The one thing that they do not suffer from is mast bumping and rotor separation or fuselage incursion. If by chance one or two have suffered rotor incursion it was because they were flown way outside of the envelope. If they suffered total rotor loss it was because of mechanical error and if they lost a blade it was due to fatigue or higher than normal stress levels. Whether this would cause a bad reputation is up for speculation.
Join Date: Dec 2000
Location: Ask the voices!
Posts: 435
Likes: 0
Received 0 Likes
on
0 Posts
Lu,
Understood. I have worked on Robinsons, and I have to say that my experience of them has been good, and the only accidents I know of have been through pilot error.
I understand the issues of blade separation etc..
Still such a shame that innocent people are being killed, and in my opinion no-one deserves to die like that.
Understood. I have worked on Robinsons, and I have to say that my experience of them has been good, and the only accidents I know of have been through pilot error.
I understand the issues of blade separation etc..
Still such a shame that innocent people are being killed, and in my opinion no-one deserves to die like that.
PPRuNe Enigma
Join Date: Feb 2001
Location: Scotland
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
More Robinsons in the air at any one time than any other helicopter. Hence the occasional cluster.
No conspiracy theory. No design flaw. Very very sad but just random chance.
For goodness sake Lu don't get started.
No conspiracy theory. No design flaw. Very very sad but just random chance.
For goodness sake Lu don't get started.
Join Date: Nov 2000
Location: Sunrise, Fl. U.S.A.
Posts: 467
Likes: 0
Received 0 Likes
on
0 Posts
One of your mishaps was due to the tail rotor contacting the ground during an approach.
One of the others I have seen news stories emerge in which some say they believe that the couple had clipped a power line or other wire obstacle prior to the mishap.
If those are true, then until we hear about the remaining one that is unexplained, the figures are not as bad as they sound.
I will say that I am interested in trying the 300, I am told it is much more forgiving than the robbie in auto's, perhaps it has a more comfortable envelope, but flown as it should be the robbie poses no threat. and therein lies the key for any helicopter, period.
One of the others I have seen news stories emerge in which some say they believe that the couple had clipped a power line or other wire obstacle prior to the mishap.
If those are true, then until we hear about the remaining one that is unexplained, the figures are not as bad as they sound.
I will say that I am interested in trying the 300, I am told it is much more forgiving than the robbie in auto's, perhaps it has a more comfortable envelope, but flown as it should be the robbie poses no threat. and therein lies the key for any helicopter, period.
PPRuNe Enigma
Join Date: Feb 2001
Location: Scotland
Posts: 427
Likes: 0
Received 0 Likes
on
0 Posts
RW's right - without knowing the details of the incidents it's pointless to speculate.
Am I right that wire strikes are still #1 cause of accidents or close to it for all makes of rotorcraft ?
Am I right that wire strikes are still #1 cause of accidents or close to it for all makes of rotorcraft ?
Join Date: Nov 2000
Location: Sunrise, Fl. U.S.A.
Posts: 467
Likes: 0
Received 0 Likes
on
0 Posts
Grainger,
I would think unintentional contacts with anything (wires, obstacles, etc. ) likely would lead that list.
Seconded (IMO) by "continued flight into IMC conditions".
I would think unintentional contacts with anything (wires, obstacles, etc. ) likely would lead that list.
Seconded (IMO) by "continued flight into IMC conditions".
Join Date: May 2001
Location: UK
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
I have seen 2 R22 (in the UK) in the last month, the one is now short enough to change the pitch links without a ladder and the second is tail-less– both were training accidents, none mechanical failure, and everybody involved walk away
As for the 3 one that’s a mystery to me
[ 12 November 2001: Message edited by: SouthXross ]
As for the 3 one that’s a mystery to me
[ 12 November 2001: Message edited by: SouthXross ]
Join Date: May 2001
Location: UK
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
R44 Technical Q & A
Without trying to open a can of worms I have a question of which the answer seem to elude me. It is not in reference to the pitch link offset to the rotor mast not being 90 degree (I think we all remember that on), but its is almost in the same arena.
The Question then: At the point where the pitch-link and the horn meets (directly opposite the coning hinges) on the R22 I have noticed the R44’s is almost and inch offset closer to the rotor shaft and not inline with the coning hinge. Would this not lead to an increase in pitch when the blade flaps up? Or is there another reason why?
SX
The Question then: At the point where the pitch-link and the horn meets (directly opposite the coning hinges) on the R22 I have noticed the R44’s is almost and inch offset closer to the rotor shaft and not inline with the coning hinge. Would this not lead to an increase in pitch when the blade flaps up? Or is there another reason why?
SX
Join Date: Nov 2000
Location: Vancouver, BC, Canada
Posts: 452
Likes: 0
Received 0 Likes
on
0 Posts
SouthCross
You raise an interesting point. The pitch will increase as the cone/flap angle increases, just as you said.
The normal configuration on main rotors is to have the pitch link to pitch horn connection located outboard of the cone/flap hinge. This gives positive pitch-flap coupling and any upward flapping is opposed by a downward change in pitch. It results in an aerodynamic spring.
In the arraignment that you are describing, it appears that teetering up will reduce pitch, whereas coning up will increase pitch.
Perhaps it is done to give a stronger opposition to heaving. Perhaps tail rotors use this negative pitch-flap coupling. Perhaps others will give a better answer.
[ 19 November 2001: Message edited by: Dave Jackson ]
You raise an interesting point. The pitch will increase as the cone/flap angle increases, just as you said.
The normal configuration on main rotors is to have the pitch link to pitch horn connection located outboard of the cone/flap hinge. This gives positive pitch-flap coupling and any upward flapping is opposed by a downward change in pitch. It results in an aerodynamic spring.
In the arraignment that you are describing, it appears that teetering up will reduce pitch, whereas coning up will increase pitch.
Perhaps it is done to give a stronger opposition to heaving. Perhaps tail rotors use this negative pitch-flap coupling. Perhaps others will give a better answer.
[ 19 November 2001: Message edited by: Dave Jackson ]
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
Posts: 2,132
Likes: 0
Received 0 Likes
on
0 Posts
To: SouthXross
First of all if you have flapping capability and the blade flaps upward and there is an increase in the pitch setting made by the pilot then there is a major flaw in the design. If I understand your description, the pitch link is not inline with the cone axis but lies ahead of it in relation to the blade. So that when the R-44 blade flaps up it will have a higher increase in pitch than the R-22 if it flapped to the same angle.
The whole purpose of the flapping is to equalize the lift on the disc. So, when the blade flaps up pitch will decrease and the aerodynamics will bring the blade into the rotational plane. The opposite is true when the blade flaps down the pitch will increase. This is called pitch coupling and it is exactly like on the tail rotor. When the tail rotor teeters the advancing blade depending on the design will flap inward and the retreating blade flaps outward. The advancing blade looses pitch and the retreating blade gains pitch thus equalizing the aerodynamic forces on the tail rotor.
The further outward the pitch link is relative to the cone axis the greater the pitch coupling. Understand this one point on the Robinson rotorhead the pitch link can never be mounted so that it is behind the cone axis. If this were true then your thoughts would be correct in that when the blade flaps up the pitch would increase.
If what you observed is true then Frank and his designers wanted the difference between the two rotorheads as he needed the extra pitch coupling +/- on the R-44 head for aerodynamic reasons. What those reasons are, I don’t have a clue.
Here is another point. Go out to your R-22 and R-44 and check if the R-44 pitch link is at an angle relative to the swashplate connection and the pitch horn connection. If it is then this will have an effect on the phase angle. If it is straight up and down like on the R-22 then the offset angle is greater than on the R-22, which has an 18-degree offset. I may have this backwards but if it is straight up and down as opposed to angled then the control geometry is different between the two helicopters.
[ 20 November 2001: Message edited by: Lu Zuckerman ]
[ 20 November 2001: Message edited by: Lu Zuckerman ]
[ 20 November 2001: Message edited by: Lu Zuckerman ]
First of all if you have flapping capability and the blade flaps upward and there is an increase in the pitch setting made by the pilot then there is a major flaw in the design. If I understand your description, the pitch link is not inline with the cone axis but lies ahead of it in relation to the blade. So that when the R-44 blade flaps up it will have a higher increase in pitch than the R-22 if it flapped to the same angle.
The whole purpose of the flapping is to equalize the lift on the disc. So, when the blade flaps up pitch will decrease and the aerodynamics will bring the blade into the rotational plane. The opposite is true when the blade flaps down the pitch will increase. This is called pitch coupling and it is exactly like on the tail rotor. When the tail rotor teeters the advancing blade depending on the design will flap inward and the retreating blade flaps outward. The advancing blade looses pitch and the retreating blade gains pitch thus equalizing the aerodynamic forces on the tail rotor.
The further outward the pitch link is relative to the cone axis the greater the pitch coupling. Understand this one point on the Robinson rotorhead the pitch link can never be mounted so that it is behind the cone axis. If this were true then your thoughts would be correct in that when the blade flaps up the pitch would increase.
If what you observed is true then Frank and his designers wanted the difference between the two rotorheads as he needed the extra pitch coupling +/- on the R-44 head for aerodynamic reasons. What those reasons are, I don’t have a clue.
Here is another point. Go out to your R-22 and R-44 and check if the R-44 pitch link is at an angle relative to the swashplate connection and the pitch horn connection. If it is then this will have an effect on the phase angle. If it is straight up and down like on the R-22 then the offset angle is greater than on the R-22, which has an 18-degree offset. I may have this backwards but if it is straight up and down as opposed to angled then the control geometry is different between the two helicopters.
[ 20 November 2001: Message edited by: Lu Zuckerman ]
[ 20 November 2001: Message edited by: Lu Zuckerman ]
[ 20 November 2001: Message edited by: Lu Zuckerman ]
Join Date: Feb 2000
Location: UK (Wilts)
Posts: 118
Likes: 0
Received 0 Likes
on
0 Posts
Nice desciption of Delta 3 / Liaison K chaps. Bear in mind that the Robinson head (if memory serves correct) has 3 hinges despite being a 2 blader and therefore emulates both articulated and teetering heads in varying degrees - it could be that in this case the delta 3 effect remains due to the common "teetering" hinge? 
It is true that a negative delta 3 effect would produce unacceptable handling characteristics.
It is true that a negative delta 3 effect would produce unacceptable handling characteristics.
Join Date: Nov 2000
Location: Vancouver, BC, Canada
Posts: 452
Likes: 0
Received 0 Likes
on
0 Posts
Lu
I don't think that we are in any position to comment on the merits of the R-44 rotorhead. All we can do, (for now), is derive some pleasure and knowledge by trying to understand the operation of the rotor.
The pitch link's upper joint location can be inboard or outboard of the coning hinge and still provide an 18-degree offset. The requirement for an 18-degree offset is that this joint's location be 18-degrees off the teetering hinge's axis (if the teetering hinge axis is normal to the blade span). In other words; it does not mater if this joint is 1" or 1 mile from the center of the mast.
Can the control phase angle discussion be excluded, for now?
_____________
Grey Area
Based upon SouthXross' quick description, it appears that the rotorhead configuration will enhance collective input (negative coupling), and diminish cyclic input (positive coupling).
Perturbations will result in
I don't think that we are in any position to comment on the merits of the R-44 rotorhead. All we can do, (for now), is derive some pleasure and knowledge by trying to understand the operation of the rotor.
The pitch link's upper joint location can be inboard or outboard of the coning hinge and still provide an 18-degree offset. The requirement for an 18-degree offset is that this joint's location be 18-degrees off the teetering hinge's axis (if the teetering hinge axis is normal to the blade span). In other words; it does not mater if this joint is 1" or 1 mile from the center of the mast.
Can the control phase angle discussion be excluded, for now?
_____________
Grey Area
Based upon SouthXross' quick description, it appears that the rotorhead configuration will enhance collective input (negative coupling), and diminish cyclic input (positive coupling).
Perturbations will result in
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
Posts: 2,132
Likes: 0
Received 0 Likes
on
0 Posts
To: Dave Jackson
If you have followed many of my previous postings you may have noted that I stated that the pitch horn can not (and I emphasize the word not) cross the cone hinge. If it does then when the blade flaps up the coupling will cause an increase in pitch angle and when the blade flaps down it will result in a decreased pitch angle. So it is imperative that in a proper design that the pitch link attach point be in line with the cone or flapping hinge. The Ideal place for the connection is to be coincident with the cone / flap axis. This is true on most helicopters when the blades are at low pitch. With the application of collective, the pitch will increase and the connect point is no longer coincident with the cone /flap axis so when the blades flap up or down from this position there will be a pitch change which is known as pitch coupling. If the connection is not in line with the cone /flap axis on the R-44 then it is by design and it increases the amount of pitch change per degree of flap as opposed to the R-22.
If you have followed many of my previous postings you may have noted that I stated that the pitch horn can not (and I emphasize the word not) cross the cone hinge. If it does then when the blade flaps up the coupling will cause an increase in pitch angle and when the blade flaps down it will result in a decreased pitch angle. So it is imperative that in a proper design that the pitch link attach point be in line with the cone or flapping hinge. The Ideal place for the connection is to be coincident with the cone / flap axis. This is true on most helicopters when the blades are at low pitch. With the application of collective, the pitch will increase and the connect point is no longer coincident with the cone /flap axis so when the blades flap up or down from this position there will be a pitch change which is known as pitch coupling. If the connection is not in line with the cone /flap axis on the R-44 then it is by design and it increases the amount of pitch change per degree of flap as opposed to the R-22.