Robinson R44
Passion Flying Hobby Science Sponsor Work
Join Date: Apr 2004
Location: Belgium
Age: 68
Posts: 461
Likes: 0
Received 0 Likes
on
0 Posts
SMOUC
I have seen people carry just about anything on those seats: from golfclubs to dogs.
What is the formal instruction that forbids this ?. Is there a differnce between professional and private use ?
What about a dog : on a long trip it is in a cage that just fits in the rear seats and can be kept by the seat belt.
On short trips she just sleeps on a seat, and as she does not use a seatbelt this is probably not OK...
This btw sometimes also makes me hesitate when replying to the question from ATC : how many POB.... do animals count...
Delta3
I have seen people carry just about anything on those seats: from golfclubs to dogs.
What is the formal instruction that forbids this ?. Is there a differnce between professional and private use ?
What about a dog : on a long trip it is in a cage that just fits in the rear seats and can be kept by the seat belt.
On short trips she just sleeps on a seat, and as she does not use a seatbelt this is probably not OK...
This btw sometimes also makes me hesitate when replying to the question from ATC : how many POB.... do animals count...
Delta3
Join Date: Jun 2004
Location: bill's fridge
Posts: 62
Likes: 0
Received 0 Likes
on
0 Posts
delta 3: I think the P in POB is persons, not pets. (Do you have a blue hawian shirt and a KH4?) 
How do the helipods work?
The manual states that the skids are only designed to bear weight from below and to put weight on top of them will be detrimental to the air frame.
So the issue is the baggage coming free over the top of the belt, rather than the quality of the restraints. I guess it will be difficult to maintain control with 20kg of louis vuitton in your lap.
I generally make judicous use of fat straps and infant belts to secure the baggage if it don't quite fit.
How do the helipods work?
The manual states that the skids are only designed to bear weight from below and to put weight on top of them will be detrimental to the air frame.
So the issue is the baggage coming free over the top of the belt, rather than the quality of the restraints. I guess it will be difficult to maintain control with 20kg of louis vuitton in your lap.
I generally make judicous use of fat straps and infant belts to secure the baggage if it don't quite fit.
Join Date: Mar 2002
Location: Queensland Australia
Posts: 267
Likes: 0
Received 0 Likes
on
0 Posts
How do the helipods work? The manual states that the skids are only designed to bear weight from below and to put weight on top of them will be detrimental to the air frame.
Two sets of blades ago I could only use one pod cos when I added the second it caused a vibration so bad it used to turn off the GPS and rattle my fillings loose! (That was with a blade some goose had bent and rebent the tabs so much that even though they were out a bit the engineer wasn't game to try to bend them back anymore in case they broke. Anyway got rid of them and the new ones were fine.
So what I think I proved is that the dissipation IS affected by the pods so I only use them when I need them then take them off - even witht he new smooth blades.
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
You can't get here from there.
Here is another point. Let's say the basic pitch setting on the R-44 measured at the root is 10-degrees (example only). The pilot pulls collective to a hover adding an additional 8-degrees (example only). In order for the helicopter to hover the blades will cone up until the lift is countered by the centrifugal force establishing the cone angle. The pitch coupling adds in an additional 3-degrees, which is added to the collective input giving a total input of 11-degrees (example only). The additional 3-degrees might or might not cause the helicopter to rise. As I stated previously this in itself is not a bad thing.
Now, let’s enter into an auto rotation. The pilot puts the collective full down but because the blades are still coned he can not return the pitch setting to 8-degrees measured at the root. The actual angle is 11-degrees and this may effect autorotation.
Possibly.
On another forum an R-44 pilot stated that you had to fight the helicopter to the ground. Assuming this is a correct statement could it be due to the pitch coupling on the rotor head during coning?
Now, let’s enter into an auto rotation. The pilot puts the collective full down but because the blades are still coned he can not return the pitch setting to 8-degrees measured at the root. The actual angle is 11-degrees and this may effect autorotation.
Possibly.
On another forum an R-44 pilot stated that you had to fight the helicopter to the ground. Assuming this is a correct statement could it be due to the pitch coupling on the rotor head during coning?
Join Date: Jul 2003
Location: Gaithersburg, MD
Posts: 622
Likes: 0
Received 0 Likes
on
0 Posts
When that pilot said he had to, "fight the helicopter to the ground" I think he meant to say he had to actively FLY it to the ground. It was the first time he'd flown an R44 and most of his time was in the smaller Schweizers. He wasn't execting to have to apply so much downward force on the collective (good thing he wasn't flying a B47).
Join Date: Oct 2004
Location: south of France
Posts: 184
Likes: 0
Received 0 Likes
on
0 Posts
What software do you use?
Delta 3 ,
would you have the kindness to tell a scratching-head like me the software you used to perform those charts or from where you got them, please ?
thank you
victor
would you have the kindness to tell a scratching-head like me the software you used to perform those charts or from where you got them, please ?
thank you
victor
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
Once again into the breech....
To: RD Rickster (Nee Reynolds)
I'll accept that it was his first ride in an R-44 however his having to apply more than normal down collective to get it on the ground I go back to my original premise: Do you or anyone else feel that it might be the pitch coupling due to coning that causes a pilot to have to fly the R-44 to the ground.
I also ask you to consider if this pitch coupling has any effect on autorotation since the pilot can't return the blades to basic pitch with the collective all the way down.
When that pilot said he had to, "fight the helicopter to the ground" I think he meant to say he had to actively FLY it to the ground. It was the first time he'd flown an R44 and most of his time was in the smaller Schweizers. He wasn't execting to have to apply so much downward force on the collective (good thing he wasn't flying a B47).
I also ask you to consider if this pitch coupling has any effect on autorotation since the pilot can't return the blades to basic pitch with the collective all the way down.
Passion Flying Hobby Science Sponsor Work
Join Date: Apr 2004
Location: Belgium
Age: 68
Posts: 461
Likes: 0
Received 0 Likes
on
0 Posts
To zeeoo
I basically put al the equations into Matlab (a powerful math solving and simulation package, now common in R&D)
The model adresses
- full dynamics: I checked this with the books of Eric Dick, Gordon Leisman and Wayne Johnson. The equations are similar, but adapted to the specifics of the R44 rotor head. It is not just a linear or first harmonic kind of thing, but the full math.
- airfoils : I assumed a 63015 of which I recalibrated the lift and drag coefficients using XFoil from MIT (freeware). This allows to refine the simple C times v square kind of stuff. Especially in the 0,6 to 0,8 Mach range
- tip losses
- reverse flow
Simplifications
- uniform inflow (I just solve - be it the full- Glauert equation to determine the induced velocity). This is not OK for 0-20 knots transition and during flow reversals such as before entering autorot, but it can be compensated (tdb)
- stiff blades . This I will refine, both bending and twisting, but for that I need to measure the blades otherwise I get GIGO (garbage in and out). I am still puzzled with the famous german film of the rotating blades, so I want to model this and simulate it.
When validating the results I had several 'sleepness nigths' not believing what I saw. After some validation work I am now convinced and 'understand' it better, although some of the stuff is at first very weard (for me at least I am not a Helo-professional).
For those who care about this egg-head stuff an example : total lift per blade plotted as a function of rotation angle, in the following case : R44 level flight (100 knots), fuel fuel, 1 POB, required cyclic and heli pitching.
I show a 'camera type picture as viewed from the front to the rear'. Looking at this I first thought : this can not be It will tip the whole machine, but actually it doesn't....
Delta3
I basically put al the equations into Matlab (a powerful math solving and simulation package, now common in R&D)
The model adresses
- full dynamics: I checked this with the books of Eric Dick, Gordon Leisman and Wayne Johnson. The equations are similar, but adapted to the specifics of the R44 rotor head. It is not just a linear or first harmonic kind of thing, but the full math.
- airfoils : I assumed a 63015 of which I recalibrated the lift and drag coefficients using XFoil from MIT (freeware). This allows to refine the simple C times v square kind of stuff. Especially in the 0,6 to 0,8 Mach range
- tip losses
- reverse flow
Simplifications
- uniform inflow (I just solve - be it the full- Glauert equation to determine the induced velocity). This is not OK for 0-20 knots transition and during flow reversals such as before entering autorot, but it can be compensated (tdb)
- stiff blades . This I will refine, both bending and twisting, but for that I need to measure the blades otherwise I get GIGO (garbage in and out). I am still puzzled with the famous german film of the rotating blades, so I want to model this and simulate it.
When validating the results I had several 'sleepness nigths' not believing what I saw. After some validation work I am now convinced and 'understand' it better, although some of the stuff is at first very weard (for me at least I am not a Helo-professional).
For those who care about this egg-head stuff an example : total lift per blade plotted as a function of rotation angle, in the following case : R44 level flight (100 knots), fuel fuel, 1 POB, required cyclic and heli pitching.
I show a 'camera type picture as viewed from the front to the rear'. Looking at this I first thought : this can not be It will tip the whole machine, but actually it doesn't....
Delta3
Last edited by delta3; 26th Oct 2004 at 21:27.
Rotational dynamics (def):
The dynamics resulting from a Zukerman quest for clarification or understanding, that when fully explained or answered, results in yet another example of his point without any form of acknowledging the original responses. Hence, around we go again, thus the term "rotational".
Example: Lu asks/states the R44 has a dangerously unstable rotorhead design. Delta3 kindly maths models the solution, explains it in depth, and comes up with proof that Lu's statement is unsupported. Lu reacts not by acknowledging the explaination, questioning the maths model, nor even the assumptions. Instead he replies..
Rotational Dynamics at it's very best.
The dynamics resulting from a Zukerman quest for clarification or understanding, that when fully explained or answered, results in yet another example of his point without any form of acknowledging the original responses. Hence, around we go again, thus the term "rotational".
Example: Lu asks/states the R44 has a dangerously unstable rotorhead design. Delta3 kindly maths models the solution, explains it in depth, and comes up with proof that Lu's statement is unsupported. Lu reacts not by acknowledging the explaination, questioning the maths model, nor even the assumptions. Instead he replies..
Here is another point.
Join Date: Oct 2004
Location: south of France
Posts: 184
Likes: 0
Received 0 Likes
on
0 Posts
to Delta 3
great thanks, i ll follow your posts here..i ll try to get more about to simulate my own design ( i m not eng)
i tried Xfoil but every time i tried to make it perform the charts, i got a runtime error, so thought it was bugged...
the soft looks great, can you simulate special blade-tips ?
(BTW im looking for a complete doc about berp tips)
i really appreciate someone helping me to acquire some knowledge. Dave jackson also helped a lot
(dave you met another
..that's it ?, what has he better than me ? 
ok i suppose i ll have to live ith that 
)
thanks again delta 3
great thanks, i ll follow your posts here..i ll try to get more about to simulate my own design ( i m not eng)
i tried Xfoil but every time i tried to make it perform the charts, i got a runtime error, so thought it was bugged...
the soft looks great, can you simulate special blade-tips ?
(BTW im looking for a complete doc about berp tips)
i really appreciate someone helping me to acquire some knowledge. Dave jackson also helped a lot
(dave you met another
..that's it ?, what has he better than me ? ok i suppose i ll have to live ith that )thanks again delta 3
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
Checks your PMs. Frank Robinsong is giving his thanks for sticking up for him.
To: helmet fire
You must be spring loaded in the pissed off position relative to anything I post and I think it is clouding your vision.
First of all I never stated that the R-44 has a dangerously unstable rotor system. What I stated that if the R-44 ever entered into a situation where there were extreme flapping on both the teeter and cone hinges I postulated that the delta 3 might exacerbate the flapping by increasing the pitch on an upward flapping blade and decreasing the pitch on a downward.
This is contrary to what Delta-3 is intended for.
Secondly I don't have the engineering background to understand Delta-3s graphs and I can only assume that many of the members of this forum are in the same boat. In a private3 communication from Delta-3 he indicated that in his investigation he determined that the phase angle on the R-44 was 108-degrees. At least that is what I thought he said. I asked him to explain how he arrived at this conclusion and he explained in engineering speak which went over my head.
This is what I stated in my first post. Maybe I should have added in "not with complex graphs". That way we can all understand the problem.
All of my comments on this subject are based on the kinematics of the R-44 rotorhead and are based on a graph provided by Delta-3. Maybe he can include the graph and we can go from there.
You must be spring loaded in the pissed off position relative to anything I post and I think it is clouding your vision.
Example: Lu asks/states the R44 has a dangerously unstable rotorhead design. Delta3 kindly maths models the solution, explains it in depth, and comes up with proof that Lu's statement is unsupported. Lu reacts not by acknowledging the explaination, questioning the maths model, nor even the assumptions. Instead he replies..
This is contrary to what Delta-3 is intended for.
Secondly I don't have the engineering background to understand Delta-3s graphs and I can only assume that many of the members of this forum are in the same boat. In a private3 communication from Delta-3 he indicated that in his investigation he determined that the phase angle on the R-44 was 108-degrees. At least that is what I thought he said. I asked him to explain how he arrived at this conclusion and he explained in engineering speak which went over my head.
Please tell me I am wrong. Explaining why I am wrong with technical statements and not vitriol.
All of my comments on this subject are based on the kinematics of the R-44 rotorhead and are based on a graph provided by Delta-3. Maybe he can include the graph and we can go from there.
Join Date: Feb 2003
Location: Harwich
Age: 65
Posts: 777
Likes: 0
Received 0 Likes
on
0 Posts
Delta3, would you be able to post a similar graph for a 206? This might give us something to compare.
Looking at the graph, it seems assymmetric - though exactly what is assymetric I'm not sure - lift? And if it is lift, why isn't the aircraft rolling left?
Looking at the graph, it seems assymmetric - though exactly what is assymetric I'm not sure - lift? And if it is lift, why isn't the aircraft rolling left?
Join Date: Oct 2002
Location: Bristol UK
Posts: 47
Likes: 0
Received 0 Likes
on
0 Posts
Is MR coning not a function of rotor thrust as opposed to gross weight, so in auto configuration the total rotor thrust is massively reduced, thus reducing coning.
That said I didn't really understand Lu's question in the first place.
I'll get me coat.....
That said I didn't really understand Lu's question in the first place.
I'll get me coat.....
Passion Flying Hobby Science Sponsor Work
Join Date: Apr 2004
Location: Belgium
Age: 68
Posts: 461
Likes: 0
Received 0 Likes
on
0 Posts
Over our head
To Lu
I must admit it sometimes goes over my head, but then again that is the challenge/charm of helo's it can keep you buzzy for a while.
I really want to try to make sense, but this is perhaps even more challenging then trying to understand it myself.
Fase lags :
gyroscopic precession=flywheel=simple zero excentricity rotor turning in outer space=90°='resonant system'
Real world=not always simple rotors=damping=not resonant
Real world=aerodynamic side effects=not inertial
So fase of a real world rotor is not always 90.
Examples:
For a typical stiff rotor (large excentricity or ridgid joints) the lag will be less
For the R44 (low excentricity non ridgid) with coning and wind it is more
Concerning the coning delta3
It is a dynamic system indeed Lu, but I showed a step responce that is extremely well behaved and fast (less than one rev) , so for all normal disturbances no negative side effects on dynamic behaviour.
I come up with another idea why this could be there : Robinson certainly knows how to reduce designs to the essence, which I would call good engineering practice (Lu you know a lot about maintainability, if I see what a steel plants some of the other rotor systems are...). May be it is by wanting a simple flapping delta3 system he introduced a coning delta3, just because of geometric simplicity, reducing the number of moving parts etc. But this coning delta3 just is an amplifier which can be simply taken care off be adapting the other mechanical (or hydraulic) amplifiers in the overall collective pitch link system. So it is a good approach to simplify mechanically the design.
Continuing to try to make sense....
Delta3
To Hilico
Yes I most likely can, but need to have precise enough data. I don\'t have a 206, but at the heliport I can get the data. Give me some time (2-3 weeks I have to dose the time for this hobby...) Any material is well come (mechanical design drawings of hub, measures, weights, profile, blade twist, this must be reasonably precise, otherwise GIGO)
As far as the assymetry of lift is concerned I worked out an explanation but allow me (sadistically I admit..) to let you guys come up with an explanation (or rebutal..).
Some extra material : the dynamic lift distribution in this case as looked from the front and the right rear (rotor without tip losses) looks like
I may try to find a way to have 3d quicktime pictures published on the net (this is what I get, and is very help full when looking into the proposed solutions)
Delta3
To Whirlycopter
you are right about the coning it is a function of trust. In autorot this is however not massively reduced, oyherwise we would fall out of the sky.
Delta3
I must admit it sometimes goes over my head, but then again that is the challenge/charm of helo's it can keep you buzzy for a while.
I really want to try to make sense, but this is perhaps even more challenging then trying to understand it myself.
Fase lags :
gyroscopic precession=flywheel=simple zero excentricity rotor turning in outer space=90°='resonant system'
Real world=not always simple rotors=damping=not resonant
Real world=aerodynamic side effects=not inertial
So fase of a real world rotor is not always 90.
Examples:
For a typical stiff rotor (large excentricity or ridgid joints) the lag will be less
For the R44 (low excentricity non ridgid) with coning and wind it is more
Concerning the coning delta3
It is a dynamic system indeed Lu, but I showed a step responce that is extremely well behaved and fast (less than one rev) , so for all normal disturbances no negative side effects on dynamic behaviour.
I come up with another idea why this could be there : Robinson certainly knows how to reduce designs to the essence, which I would call good engineering practice (Lu you know a lot about maintainability, if I see what a steel plants some of the other rotor systems are...). May be it is by wanting a simple flapping delta3 system he introduced a coning delta3, just because of geometric simplicity, reducing the number of moving parts etc. But this coning delta3 just is an amplifier which can be simply taken care off be adapting the other mechanical (or hydraulic) amplifiers in the overall collective pitch link system. So it is a good approach to simplify mechanically the design.
Continuing to try to make sense....
Delta3
To Hilico
Yes I most likely can, but need to have precise enough data. I don\'t have a 206, but at the heliport I can get the data. Give me some time (2-3 weeks I have to dose the time for this hobby...) Any material is well come (mechanical design drawings of hub, measures, weights, profile, blade twist, this must be reasonably precise, otherwise GIGO)
As far as the assymetry of lift is concerned I worked out an explanation but allow me (sadistically I admit..) to let you guys come up with an explanation (or rebutal..).
Some extra material : the dynamic lift distribution in this case as looked from the front and the right rear (rotor without tip losses) looks like
I may try to find a way to have 3d quicktime pictures published on the net (this is what I get, and is very help full when looking into the proposed solutions)
Delta3
To Whirlycopter
you are right about the coning it is a function of trust. In autorot this is however not massively reduced, oyherwise we would fall out of the sky.
Delta3
Last edited by delta3; 27th Oct 2004 at 17:12.
Join Date: Apr 2003
Location: Vancouver, BC, Canada
Posts: 1,635
Likes: 0
Received 0 Likes
on
0 Posts
First things first
To evaluate the Robinson rotorhead, the first requirement will be to determine whether the two outer hinges are coning hinges (rotate in unison) or flapping hinges (rotate independently).
Is there a venturesome pilot who would be willing to;
~ Remove a coning/flapping hinge bolt, then stick it through a piece of white cardboard and then replace it on the rotor head.
~ Remove the cotter pin from the nut on the other coning/flapping bolt and replace the cotter pin with the innards of a BIC pen.
~ Bend the tip end of the pen so that it's ball is touching the cardboard.
~ Fly the hell out of the helicopter.
If there is a straight line on the cardboard pointing toward the bolt that is holding the cardboard in place; then they are coning hinges.
If the pen has randomly scrawled on the cardboard; then they are flapping hinges.
If the cardboard, the pen, and the nut are missing; then thank the almighty, whoever she may be, for a safe return.
If the missing nut is the pilot who tried this ridiculous experiment; then the prayers to the almighty must be modified slightly.
Anonymous
I've got to get a real job.
Is there a venturesome pilot who would be willing to;
~ Remove a coning/flapping hinge bolt, then stick it through a piece of white cardboard and then replace it on the rotor head.
~ Remove the cotter pin from the nut on the other coning/flapping bolt and replace the cotter pin with the innards of a BIC pen.
~ Bend the tip end of the pen so that it's ball is touching the cardboard.
~ Fly the hell out of the helicopter.
If there is a straight line on the cardboard pointing toward the bolt that is holding the cardboard in place; then they are coning hinges.
If the pen has randomly scrawled on the cardboard; then they are flapping hinges.
If the cardboard, the pen, and the nut are missing; then thank the almighty, whoever she may be, for a safe return.
If the missing nut is the pilot who tried this ridiculous experiment; then the prayers to the almighty must be modified slightly.
Anonymous
I've got to get a real job.
Join Date: Feb 2003
Location: Harwich
Age: 65
Posts: 777
Likes: 0
Received 0 Likes
on
0 Posts
Delta 3
Please don't spend a couple of weeks of effort! I don't have a 206 either, nor any access to the data you require. It was curiosity pure and simple (I am a very curious chap). I once tried a course in modelling fluid flows - perhaps after this I'll go back to it, as it looked a lot easier.
Please don't spend a couple of weeks of effort! I don't have a 206 either, nor any access to the data you require. It was curiosity pure and simple (I am a very curious chap). I once tried a course in modelling fluid flows - perhaps after this I'll go back to it, as it looked a lot easier.