Robinson R44
Join Date: Mar 2002
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Hydraulic Servo R44
Hi
We have found hydraulic fluid leaking from our RH-FWD hydraulic servo assy (Part D2/2-1). Is it cheaper to service the faulty one or just plain quicker and easier to get a replacement unit?
Our reason beyound the question is the delay in getting parts or service done from the the US every time we need something, not mentioning the mark up charged by the local dealer...Sth East Asia based.
Regards
We have found hydraulic fluid leaking from our RH-FWD hydraulic servo assy (Part D2/2-1). Is it cheaper to service the faulty one or just plain quicker and easier to get a replacement unit?
Our reason beyound the question is the delay in getting parts or service done from the the US every time we need something, not mentioning the mark up charged by the local dealer...Sth East Asia based.
Regards
Join Date: Jul 2004
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Robbo parts
Gday WLM,
In Indo i used to get parts and pieces from our friends at aviall in Singapore and Robbo parts from heliflite in bankstown. Just make sure they send the proper paperwork and mark it as anything but aircraft parts and all should be well. Same deal with the dealer in Indo.....100-150% mark up. However they sharpened their pencil when they found out you can get parts from elsewhere.
Terima kasih banyak,
evod
In Indo i used to get parts and pieces from our friends at aviall in Singapore and Robbo parts from heliflite in bankstown. Just make sure they send the proper paperwork and mark it as anything but aircraft parts and all should be well. Same deal with the dealer in Indo.....100-150% mark up. However they sharpened their pencil when they found out you can get parts from elsewhere.
Terima kasih banyak,
evod
Join Date: Jul 2004
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parts
WLM...Sorry for the delay.
My contact was James someone in Singas for aviall (check the website) Probaly not much help now as it was in my indo days pre Malay. Good luck with heliflite as 10 or 11 gorillas for a servo sounds sedikit mahal (ask peter for translation)
Cheers,
Evod
My contact was James someone in Singas for aviall (check the website) Probaly not much help now as it was in my indo days pre Malay. Good luck with heliflite as 10 or 11 gorillas for a servo sounds sedikit mahal (ask peter for translation)
Cheers,
Evod
Join Date: Oct 2004
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Securing Baggage R44
How do you carry two pax in an R44 with baggage that can not fit under the seat and have the baggage ' secured '. CASA does not approve the seat belt. All our 44s are on floats, so no side pods. Any one know of an EO or something like a net that is approved.
SMO
SMO
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.
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R-44 Rotorhead. Sorry guys I just couldn't help myself.
OH NO, HERE WE GO AGAIN.
I responded that if the pitch horn reached beyond the cone hinge there would be problems related to controllability. It has been brought to my attention that on the R-44 the pitch horn extends beyond the cone hinge by approximately 28mm and this got me thinking. What effect does this have on delta-3 pitch coupling and blade flap?
When the blade flaps on the teeter hinge the up flapping blade would have a pitch decrease and the down flapping blade would have a pitch increase, which is what you would expect. However the blade is capable of flapping on the cone hinges and herein lies a problem.
On the R-44 if the helicopter enters into a loss of control situation and
there are extreme changes in blade position relative to the cone hinges the
pitch changes due to delta-3 will be exacerbated. You would expect that
when a blade flaps up the pitch will decrease due to delta-3 but in this
case it will increase increasing the upward flap. Conversely if the blade
flaps down the pitch decrease will also be exacerbated causing the blade to
flap downward even further. In a loss of control situation this would help speed up the process resulting in rotor incursion, mast bumping and contact with and fracture of the blade tusks.
Here is another example. Let's say the pilot at startup increases blade pitch to say 10+ degrees in order to hover. The blades cone up and in doing so increase the pitch to 12+degrees causing the helicopter to rise. What does the pilot do?
Please tell me I am wrong. Explaining why I am wrong with technical statements and not vitriol.
Original thread is here.
See response by Frank Robinson posted 30th November 2000.
Heliport
Last edited by Lu Zuckerman; 15th Oct 2004 at 20:17.
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R-44 Rotorhead. Sorry guys I just couldn't help myself.
Would not the coning angle remain the same? ,providing the mrrpm are correct. If this is not the case, would one assume that the coning angle on this type of head , alters depending on the gross weight of the machine.
Iconoclast
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Coning angle.
To: NIGINOO
QUOTE]Would not the coning angle remain the same? ,providing the mrrpm are correct. If this is not the case, would one assume that the coning angle on this type of head , alters depending on the gross weight of the machine.[/QUOTE]
The coning angle is a function of gross weight. If the helicopter only has a pilot the coning angle would reflect that weight and would be a very shallow angle. If the helicopter had a full load the coning angle would be greater.
Using assumed numbers if it took ten degrees of increased pitch to get the helicopter to hover with one person aboard the delta-3 connection would increase by say 2-degrees giving a total pitch of 12-degrees causing the helicopter to rise from the hover. By the same token if it took twelve degrees to hover with a full load the delta-3 connection would increase the collective pitch to say 14-degrees causing the helicopter to rise.
What does the pilot do to maintain the hover? If he decreases collective pitch he will go below the original pitch input to hover and end up back on tera firma. At least I think so.
I believe the problem would go away after passing through translational lift.
QUOTE]Would not the coning angle remain the same? ,providing the mrrpm are correct. If this is not the case, would one assume that the coning angle on this type of head , alters depending on the gross weight of the machine.[/QUOTE]
The coning angle is a function of gross weight. If the helicopter only has a pilot the coning angle would reflect that weight and would be a very shallow angle. If the helicopter had a full load the coning angle would be greater.
Using assumed numbers if it took ten degrees of increased pitch to get the helicopter to hover with one person aboard the delta-3 connection would increase by say 2-degrees giving a total pitch of 12-degrees causing the helicopter to rise from the hover. By the same token if it took twelve degrees to hover with a full load the delta-3 connection would increase the collective pitch to say 14-degrees causing the helicopter to rise.
What does the pilot do to maintain the hover? If he decreases collective pitch he will go below the original pitch input to hover and end up back on tera firma. At least I think so.
I believe the problem would go away after passing through translational lift.
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won't the coning angle increase gradually?
As you say, the helicopter will not come to a four foot hover, then all of a sudden the coning angle increases increasing aoa and lift.
The effect is present incrementally throught the motion as so is adjusted for continuosly. There's no up and down with the lever malarchy.
(last time i tried contributing to anything like this is was plainly clear i'd have trouble finding my a*se with both hands.)
As you say, the helicopter will not come to a four foot hover, then all of a sudden the coning angle increases increasing aoa and lift.
The effect is present incrementally throught the motion as so is adjusted for continuosly. There's no up and down with the lever malarchy.
(last time i tried contributing to anything like this is was plainly clear i'd have trouble finding my a*se with both hands.)
Iconoclast
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I had time to think it over.
To: 4ero
After giving it some thought it would seem that as the blades cone the pitch in the blades is greater than the collective input and the pilot can lift off to a hover with less collective input and if this is the case it is a good thing. However if the helicopter enters a situation where there is excessive flapping on the cone hinges (pitching over, sideslip, excessive cyclic input) when the blade flaps up the pitch will increase exacerbating the situation. The same is true when the blade flaps down pitch is further decreased and this could lead to loss of control.
After giving it some thought it would seem that as the blades cone the pitch in the blades is greater than the collective input and the pilot can lift off to a hover with less collective input and if this is the case it is a good thing. However if the helicopter enters a situation where there is excessive flapping on the cone hinges (pitching over, sideslip, excessive cyclic input) when the blade flaps up the pitch will increase exacerbating the situation. The same is true when the blade flaps down pitch is further decreased and this could lead to loss of control.
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R44 nets
Nets are available. I have used nets that when in the stowed position are rolled up across the back of the front seats , when they're in use they unroll and clip to the top hard point of the rear seat belts. Not really a viable answer for pax and bags but they work really nice for loading the back right up with cargo
Cool as a moosp
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I don't know of a system that has been approved for the '44 (and I supect that Frank has never authorised one, so this will have to be an in country civil aviation authorisation) but the principle is the same as "in seat cargo" that has been used in the fixed wing world for many years.
What you need is a bag that "looks" as though it is nine g strong with loops to take the shoulder and lap straps. It should fit onto the seat looking like an overweight pax with no legs. Then get your local friendly Authority Airworthiness rep to have a look at your system.
If it looks sensible they will probably allow it on some kind of local agreement. It is highly unlikely that they will require a crash test of your machine with the bag in place, unless you operate in certain countries of which we all know...
The ones I remember years ago in airline work were heavy canvas like a mail bag, but cut in a pear shape. The volume was surprisingly large, and you had to be careful to check the mass of the stuff in it.
Try giving your CASA rep a call. Most of them are remarkably approachable on such subjects, and although they cannot legally suggest a solution, they will often give you a good idea of what might be approved if you presented it to them.
FWIW
What you need is a bag that "looks" as though it is nine g strong with loops to take the shoulder and lap straps. It should fit onto the seat looking like an overweight pax with no legs. Then get your local friendly Authority Airworthiness rep to have a look at your system.
If it looks sensible they will probably allow it on some kind of local agreement. It is highly unlikely that they will require a crash test of your machine with the bag in place, unless you operate in certain countries of which we all know...
The ones I remember years ago in airline work were heavy canvas like a mail bag, but cut in a pear shape. The volume was surprisingly large, and you had to be careful to check the mass of the stuff in it.
Try giving your CASA rep a call. Most of them are remarkably approachable on such subjects, and although they cannot legally suggest a solution, they will often give you a good idea of what might be approved if you presented it to them.
FWIW
Passion Flying Hobby Science Sponsor Work
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The answer of an egg-head
Delta3, gyroscopic precession.
Lu,
I think the answers can be found in the following results
(sorry guys this is from an egg-head-pilot)
First (you never know) To the pilots : DISCLAIMER
The data is only approximative, precise enough to illustrate
the discussion points, but not to be used to plan flights.
The author declines all responsabilities.
-------------------------------------------------------------------------------------------
In the last year I have read a number of heated discussions
concerning the R-44 rotor. As I am mathematically inclined I decided
to make a detailed blade element dynamic model of the rotor
in order to investigate its behaviour. The model is pretty detailed
and even takes viscous fluid, mach, reynolds numbers etc into account.
I have 3-D animations but cannot publish this on the net.
I do want to share some curves concerning
the flapping angle of the rotor calculated for two scenarios:
1. sudden wind gust (with and without delta3)
2. sudden cyclic forward (with and without delta3)
The math shows that the rotor stays perfectly aligned thanks to delta 3
and illustrates the remarks Frank Robinson made a long time ago concerning
- right blow back because of coning (wind)
- wee-waa or zig-zag in case of cyclic transient
Image 1. Sudden 50 knts gust : R44 rotor blows back but stays aligned.
See legend to see what curves mean. The X-axis is in number of rotations.
Remark how fast rotors react to disturbances (1,5 revolutions)
Image 2. Same without delta3 : rotor blows to the right (blade at the left is higher)
Image 3. No wind but sudden 2degree forward cyclic: Rotor moves forward fully align both during and after the transient
Image 4. Same without delta3 : since there is no wind the rotor is aligned after transient, but tilts to the right during the transient (blade is higher at the left during the firs 180 degrees)
With respect to the question in this thread: the possive coning delta3 provoques no instabilities (wind,cyclic, collective inputs). It just increases coning to a design angle.
Removing this delta3 has only one effect : coning angle decreases.
SORRY ... (edited october 22)
The following paragraphs are wrong : the lift increased in the experiment because coning delta3 increased blade pitch
START OF ERROR
So I assume the following design choice were made:
1. the coning is determined by the precise lift distribution and centrifugal forces along the blade (these are fully detailed in the used model).
2. if blades have extra tip weight coning is reduced
3. a 2-3 degree coning is wished
4. the coning delta3 increases coning in this case by approx 0,5 degrees.
I could also model the R22, which I did not yet, but my guess is that the original R22 blades were lighter with less tip weight, so rotor coned enough without coning delta3.....
""(END of ERROR)
CORRECTED VERSION :
After introduction of coning delta3 the collective needs to be lowered to achieve the same trust level. So I guess this delta3 primarily acts as a simple linear (quasi non dynamic) amplifier on the collective handle. I still maintain the conclusions about the stability
END OF CORRECTION
Delta3
A very hypothetical case
Suddenly introduce the coning delta3 to a rotor.
It would in practice take a very advanced servo to achieve this,
but this mathematical scenario can help clarify a stability
question : suddenly introduce the control law in the
system and look what happens:
not oscillations, just an increase in coning angle
Delta3
Lu,
I think the answers can be found in the following results
(sorry guys this is from an egg-head-pilot)
First (you never know) To the pilots : DISCLAIMER
The data is only approximative, precise enough to illustrate
the discussion points, but not to be used to plan flights.
The author declines all responsabilities.
-------------------------------------------------------------------------------------------
In the last year I have read a number of heated discussions
concerning the R-44 rotor. As I am mathematically inclined I decided
to make a detailed blade element dynamic model of the rotor
in order to investigate its behaviour. The model is pretty detailed
and even takes viscous fluid, mach, reynolds numbers etc into account.
I have 3-D animations but cannot publish this on the net.
I do want to share some curves concerning
the flapping angle of the rotor calculated for two scenarios:
1. sudden wind gust (with and without delta3)
2. sudden cyclic forward (with and without delta3)
The math shows that the rotor stays perfectly aligned thanks to delta 3
and illustrates the remarks Frank Robinson made a long time ago concerning
- right blow back because of coning (wind)
- wee-waa or zig-zag in case of cyclic transient
Image 1. Sudden 50 knts gust : R44 rotor blows back but stays aligned.
See legend to see what curves mean. The X-axis is in number of rotations.
Remark how fast rotors react to disturbances (1,5 revolutions)
Image 2. Same without delta3 : rotor blows to the right (blade at the left is higher)
Image 3. No wind but sudden 2degree forward cyclic: Rotor moves forward fully align both during and after the transient
Image 4. Same without delta3 : since there is no wind the rotor is aligned after transient, but tilts to the right during the transient (blade is higher at the left during the firs 180 degrees)
With respect to the question in this thread: the possive coning delta3 provoques no instabilities (wind,cyclic, collective inputs). It just increases coning to a design angle.
Removing this delta3 has only one effect : coning angle decreases.
SORRY ... (edited october 22)
The following paragraphs are wrong : the lift increased in the experiment because coning delta3 increased blade pitch
START OF ERROR
So I assume the following design choice were made:
1. the coning is determined by the precise lift distribution and centrifugal forces along the blade (these are fully detailed in the used model).
2. if blades have extra tip weight coning is reduced
3. a 2-3 degree coning is wished
4. the coning delta3 increases coning in this case by approx 0,5 degrees.
I could also model the R22, which I did not yet, but my guess is that the original R22 blades were lighter with less tip weight, so rotor coned enough without coning delta3.....
""(END of ERROR)
CORRECTED VERSION :
After introduction of coning delta3 the collective needs to be lowered to achieve the same trust level. So I guess this delta3 primarily acts as a simple linear (quasi non dynamic) amplifier on the collective handle. I still maintain the conclusions about the stability
END OF CORRECTION
Delta3
A very hypothetical case
Suddenly introduce the coning delta3 to a rotor.
It would in practice take a very advanced servo to achieve this,
but this mathematical scenario can help clarify a stability
question : suddenly introduce the control law in the
system and look what happens:
not oscillations, just an increase in coning angle
Delta3
Last edited by delta3; 20th Oct 2004 at 08:17.