20 degree cant on CH-53 and HH-60
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20 degree cant on CH-53 and HH-60
Nick,
In another post you mentioned the 20 degree cant on the CH-53 and the HH-60 assisting with increased lift and cog. In these aircraft, is tail rotor roll compensated in the main rotor shaft, or does the cant assist with this effect? It appears the tail rotor is mounted at approximately the same height as the rotor head. Would this be the reason why they are mounted that way?
Thanks
S L
In another post you mentioned the 20 degree cant on the CH-53 and the HH-60 assisting with increased lift and cog. In these aircraft, is tail rotor roll compensated in the main rotor shaft, or does the cant assist with this effect? It appears the tail rotor is mounted at approximately the same height as the rotor head. Would this be the reason why they are mounted that way?
Thanks
S L
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Sling Load asked:
Nick,
In another post you mentioned the 20 degree cant on the CH-53 and the HH-60 assisting with increased lift and cog. In these aircraft, is tail rotor roll compensated in the rotor shaft, or does the cant assist with this effect? It appears the tail rotor is mounted at approximately the same height as the rotor head. Would this be the reason why they are mounted that way?
Nick sez:
The canted tail rotor really has no extra roll effect due to its cant, the affect is purely in pitch, since left pedal makes the nose tuck a little, and right pedal the opposite. With a canted tail rotor, we mix the cyclic with some yaw so left pedal puts a little aft cyclic.
All high tail rotors give some roll effect, due to the lateral force they produce acting on the center of gravity (not the rotor head as you have guessed). The right thrusting force of the tail rotor would cause a right roll of the airframe in a hover, but it is countered by the right translation this force causes, and the concurrent need to put in left roll to stop translating. The translating left roll is the dominant factor. All American helicopters hover left skid/wheel low, but if the tail rotor is low, near the vertical CG, the effects don't cancel and the roll attitude is more pronounced. As a rule of thumb, the typical high tail rotor helo hovers about 3 to 4 degrees left wheel low, and a low tail rotor helo hovers about 5 to 6 degrees left wheel low.
Nick,
In another post you mentioned the 20 degree cant on the CH-53 and the HH-60 assisting with increased lift and cog. In these aircraft, is tail rotor roll compensated in the rotor shaft, or does the cant assist with this effect? It appears the tail rotor is mounted at approximately the same height as the rotor head. Would this be the reason why they are mounted that way?
Nick sez:
The canted tail rotor really has no extra roll effect due to its cant, the affect is purely in pitch, since left pedal makes the nose tuck a little, and right pedal the opposite. With a canted tail rotor, we mix the cyclic with some yaw so left pedal puts a little aft cyclic.
All high tail rotors give some roll effect, due to the lateral force they produce acting on the center of gravity (not the rotor head as you have guessed). The right thrusting force of the tail rotor would cause a right roll of the airframe in a hover, but it is countered by the right translation this force causes, and the concurrent need to put in left roll to stop translating. The translating left roll is the dominant factor. All American helicopters hover left skid/wheel low, but if the tail rotor is low, near the vertical CG, the effects don't cancel and the roll attitude is more pronounced. As a rule of thumb, the typical high tail rotor helo hovers about 3 to 4 degrees left wheel low, and a low tail rotor helo hovers about 5 to 6 degrees left wheel low.
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To: Nick Lappos
On older Sikorsky helicopters there was a built in bias in the mixing units to compensate for the right translation caused by the tail rotor. Several models did not have this facility so the pilot had to apply left cyclic in a hover. At full collective the swashplate would be tilted 7-degrees to the left and the mast was tilted 3-degrees forward of vertical, which made the helicopter, tilt to the left and hang tail low. On those helicopters equipped with ASE the ASE black box was placed in a position to reflect the 7-degree tilt to the left and 3-degree tail low and the output signals were nulled out then the black box was placed back on its’ attachments to the airframe. On those helicopters equipped as SONAR dippers the signal generated by the cable pick-offs were also nulled out to compensate for the left tilt-tail low condition so that the helicopter was only subjected to movement caused by the water currents that displaced the SONAR cable.
My question is this. On the UH-60 and the S-76 is there the built in bias in the mixing unit or, does the pilot have to move the stick to the left in a hover?
On older Sikorsky helicopters there was a built in bias in the mixing units to compensate for the right translation caused by the tail rotor. Several models did not have this facility so the pilot had to apply left cyclic in a hover. At full collective the swashplate would be tilted 7-degrees to the left and the mast was tilted 3-degrees forward of vertical, which made the helicopter, tilt to the left and hang tail low. On those helicopters equipped with ASE the ASE black box was placed in a position to reflect the 7-degree tilt to the left and 3-degree tail low and the output signals were nulled out then the black box was placed back on its’ attachments to the airframe. On those helicopters equipped as SONAR dippers the signal generated by the cable pick-offs were also nulled out to compensate for the left tilt-tail low condition so that the helicopter was only subjected to movement caused by the water currents that displaced the SONAR cable.
My question is this. On the UH-60 and the S-76 is there the built in bias in the mixing unit or, does the pilot have to move the stick to the left in a hover?
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Lu you are yet again confusing a simple subjsct, perhaps because you really don't understand it. The controls on most Sikorsky's are mixed to compensate for the aerodynamic couplings, and this has nothing to do with the shaft tilt. Lu knows almost nothing about what he posts.
The only thing I can offer to readers of this forum is to somehow remember that if the post is signed by Lu, it is probably wrong, and definately wrong-headed. Should you be foolish enough to start discussing it with Lu, you will quickly get clouded under by a stream of bull*** that will leave you in the dust.
Forum readers, do what you will, but I will start taking everything Lu has said as pure Bull, and life will be simpler. I will no longer respond to Lu, but will gladly discuss issues with any other forum member.
The only thing I can offer to readers of this forum is to somehow remember that if the post is signed by Lu, it is probably wrong, and definately wrong-headed. Should you be foolish enough to start discussing it with Lu, you will quickly get clouded under by a stream of bull*** that will leave you in the dust.
Forum readers, do what you will, but I will start taking everything Lu has said as pure Bull, and life will be simpler. I will no longer respond to Lu, but will gladly discuss issues with any other forum member.
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To:Nick Lappos
You and RW-1 must have gone to the same charm school as you both get very personal in your postings. First of all, if you would check the history of the various Sikorsky helicopters you will find that the mixing units on several helicopter, the S-58 being one of them, had the mixing unit designed so that when the pilot pulled collective and the cyclic stick was in the neutral position the swashplate would tip 7-degrees forward and to the left. This swashplate tilt was to compensate for the right translation caused by the propeller effect of the tail rotor. Now maybe in today’s design there is no forward tilt to the transmission in relation to the vertical but in my day there was. This in effect gave the pilot more forward control. The 3-degree forward tilt is why the helicopter hangs tail low as the rotor will try to align itself in the radial position and because of the lock the helicopter will align itself with the rotor. The reason the older Sikorsky helicopters hung down to the left is because of the left bias in the rotor system. I added in the part about the ASE and the SONAR because they had to be compensated for the tail down fuselage to the left so that the helicopter could hover in this position and the ASE would not send out a corrective signal. The same is true for the SONAR cable pick offs'.
Since you indicated in you post that all helicopters hang down to the left and tail low I asked if the newer Sikorsky helicopters had the same built in bias as the older models or, if the pilot had to compensate by moving the cyclic to the left. I expected an answer to that question and not the scathing remarks about my lack of understanding of how a helicopter works.
Now you indicate that the mixing unit is designed to compensate for coupling so I’ll ask another question based on my antiquated knowledge of Sikorsky helicopters. On all Sikorsky helicopters that I am familiar with up to the S-61 when the pilot moved his cyclic to the forward position the fore and aft servo would move the swashplate down and to the right. This tilting action would react about the left and right lateral servos, which did not move. Conversely, if the stick were to be moved to the left the swash plate would tilt down to the left and the tilting would react about the fore and aft servo and the rotating scissors. This indicates to me that there is no compensation for coupling in the mixing unit at least on those helicopters. The question is, is this different on the UH-60 and the S-76?
I read you post on the 18-degree thread and once again you make everything personal. Based on what you said about the positioning of the servos on the S-76 I now know that they are different from its’ Sikorsky predecessors. However it seems that your knowledge base stems from your association with the latest designs that take advantage in the advances in helicopter aerodynamics and if anything is said that contravenes that knowledge you say it is not true. Again, I would suggest you go back in history to see where I am coming from by looking at the flight controls in the S-55, S-56, S-58 and the S-61.
Regarding my comments about the Lynx these are not my words I was repeating what a Royal Army Aviation Captain Pilot stated in a past thread when we were discussing the 18-degree offset on the Robinson. If you have objections to these words, challenge him on an open forum and tell him he is wrong but don’t mention gyroscopic precession as that will set off a firestorm.
[ 28 July 2001: Message edited by: Lu Zuckerman ]
You and RW-1 must have gone to the same charm school as you both get very personal in your postings. First of all, if you would check the history of the various Sikorsky helicopters you will find that the mixing units on several helicopter, the S-58 being one of them, had the mixing unit designed so that when the pilot pulled collective and the cyclic stick was in the neutral position the swashplate would tip 7-degrees forward and to the left. This swashplate tilt was to compensate for the right translation caused by the propeller effect of the tail rotor. Now maybe in today’s design there is no forward tilt to the transmission in relation to the vertical but in my day there was. This in effect gave the pilot more forward control. The 3-degree forward tilt is why the helicopter hangs tail low as the rotor will try to align itself in the radial position and because of the lock the helicopter will align itself with the rotor. The reason the older Sikorsky helicopters hung down to the left is because of the left bias in the rotor system. I added in the part about the ASE and the SONAR because they had to be compensated for the tail down fuselage to the left so that the helicopter could hover in this position and the ASE would not send out a corrective signal. The same is true for the SONAR cable pick offs'.
Since you indicated in you post that all helicopters hang down to the left and tail low I asked if the newer Sikorsky helicopters had the same built in bias as the older models or, if the pilot had to compensate by moving the cyclic to the left. I expected an answer to that question and not the scathing remarks about my lack of understanding of how a helicopter works.
Now you indicate that the mixing unit is designed to compensate for coupling so I’ll ask another question based on my antiquated knowledge of Sikorsky helicopters. On all Sikorsky helicopters that I am familiar with up to the S-61 when the pilot moved his cyclic to the forward position the fore and aft servo would move the swashplate down and to the right. This tilting action would react about the left and right lateral servos, which did not move. Conversely, if the stick were to be moved to the left the swash plate would tilt down to the left and the tilting would react about the fore and aft servo and the rotating scissors. This indicates to me that there is no compensation for coupling in the mixing unit at least on those helicopters. The question is, is this different on the UH-60 and the S-76?
I read you post on the 18-degree thread and once again you make everything personal. Based on what you said about the positioning of the servos on the S-76 I now know that they are different from its’ Sikorsky predecessors. However it seems that your knowledge base stems from your association with the latest designs that take advantage in the advances in helicopter aerodynamics and if anything is said that contravenes that knowledge you say it is not true. Again, I would suggest you go back in history to see where I am coming from by looking at the flight controls in the S-55, S-56, S-58 and the S-61.
Regarding my comments about the Lynx these are not my words I was repeating what a Royal Army Aviation Captain Pilot stated in a past thread when we were discussing the 18-degree offset on the Robinson. If you have objections to these words, challenge him on an open forum and tell him he is wrong but don’t mention gyroscopic precession as that will set off a firestorm.
[ 28 July 2001: Message edited by: Lu Zuckerman ]
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Forum readers be careful, most of what Lu says above is simply incorrect. I suggest that we not use Lu to translate what someone else told him, as he gets it quite wrong most of the time, especially such stuff as the shaft tilt causing the nose to ride high in a hover!!
I will not respond to Lu's drivel, as I noted above.
I will not respond to Lu's drivel, as I noted above.
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Nick, you get a great deal of enjoyment in telling everybody that I am an Idiot. I think the fact that you know so much has put you on an ego trip and that you want to be the guru on these threads. It was stated on a previous post that you say everything I say is wrong and in some cases you can prove it by tapping into you knowledge base. If I am wrong about the hover attitude of “some” Sikorsky helicopters then please provide an answer to these questions to the other members of the forum.
Did you check to see if the helicopters I referenced had a three degree forward tilt to the transmission and did you check to see if the helicopter hovered nose high / tail low because of this three degree forward tilt. Now, go out to your S76 and UH-60 to see if the transmission has a 3-degree forward tilt and if it does, ask yourself what causes the helicopter to hover in that position. Or better still answer this why does the helicopter hover in the condition you described.
Regarding the helicopters I referenced I stated that they hovered left side low because of the bias built into the mixing unit. Please respond to that and don’t just tell everybody I am an idiot. The more you do this you become less in the eyes of the participants on these threads.
[ 28 July 2001: Message edited by: Lu Zuckerman ]
Did you check to see if the helicopters I referenced had a three degree forward tilt to the transmission and did you check to see if the helicopter hovered nose high / tail low because of this three degree forward tilt. Now, go out to your S76 and UH-60 to see if the transmission has a 3-degree forward tilt and if it does, ask yourself what causes the helicopter to hover in that position. Or better still answer this why does the helicopter hover in the condition you described.
Regarding the helicopters I referenced I stated that they hovered left side low because of the bias built into the mixing unit. Please respond to that and don’t just tell everybody I am an idiot. The more you do this you become less in the eyes of the participants on these threads.
[ 28 July 2001: Message edited by: Lu Zuckerman ]
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Sling Load asked:
The S-64 and Ch-54 have noticeable differences in the height of each individual engine intake, was there a reason for this that you are aware of?
Nick sez:
I don't think there is a difference in the engines at all, except for the designation, military T73, civil JFTD12. The Army version (CH-54) has no fire walls between the engines, and no support framework for them, the FAA version (S-64) has them. There are other details that differ, but I don't know that the engines are at all. There are two versions of the crane, the A and B, which differ in gross weight (42 vs 50 thousand pounds) and other areas. I can't summon up any specs that explain any of this on the web.
Maybe a Crane driver out there will help out!
The S-64 and Ch-54 have noticeable differences in the height of each individual engine intake, was there a reason for this that you are aware of?
Nick sez:
I don't think there is a difference in the engines at all, except for the designation, military T73, civil JFTD12. The Army version (CH-54) has no fire walls between the engines, and no support framework for them, the FAA version (S-64) has them. There are other details that differ, but I don't know that the engines are at all. There are two versions of the crane, the A and B, which differ in gross weight (42 vs 50 thousand pounds) and other areas. I can't summon up any specs that explain any of this on the web.
Maybe a Crane driver out there will help out!
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Note to the Forum:
If anyone out there thinks that a bias of the controls will make the helicopter hover with one wheel low, or that the Chief R&D test pilot for a manufacturer has to look up the shaft tilt of one of their models, I have a Big, Expensive Bridge that they can buy, cheap.
Drivel!!
If anyone out there thinks that a bias of the controls will make the helicopter hover with one wheel low, or that the Chief R&D test pilot for a manufacturer has to look up the shaft tilt of one of their models, I have a Big, Expensive Bridge that they can buy, cheap.
Drivel!!
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Nick
You keep evading the question saying in essence that your opinions are beyond reproach. The collective bias causes the disc to tilt to the left. This slight change in the thrust vector counters the thrust of the tail rotor. Because the disc is tilted to the left the interlock between the blades and the rotorhead will cause the helicopter to tilt to the left or as you indicated left wheel low. Because the mast is tilted three degrees forward the helicopter will align itself with the rotorhead because of that same interlock between the blades and the head resulting in a nose high attitude. Now get off your high horse and tell the forum why Sikorsky helicopters at least those that I am familiar with hover at such an odd angle. I was taught this in five different Sikorsky factory schools and I was taught about rigging the ASE in autopilot school and it was not my interpretation of what was said it is exactly what was said. I also rigged autopilots on the production line at Sikorsky. Go over to the service school and find out what is being taught. If you disagree, tell them, not me or for that matter the members of this forum.
[ 28 July 2001: Message edited by: Lu Zuckerman ]
You keep evading the question saying in essence that your opinions are beyond reproach. The collective bias causes the disc to tilt to the left. This slight change in the thrust vector counters the thrust of the tail rotor. Because the disc is tilted to the left the interlock between the blades and the rotorhead will cause the helicopter to tilt to the left or as you indicated left wheel low. Because the mast is tilted three degrees forward the helicopter will align itself with the rotorhead because of that same interlock between the blades and the head resulting in a nose high attitude. Now get off your high horse and tell the forum why Sikorsky helicopters at least those that I am familiar with hover at such an odd angle. I was taught this in five different Sikorsky factory schools and I was taught about rigging the ASE in autopilot school and it was not my interpretation of what was said it is exactly what was said. I also rigged autopilots on the production line at Sikorsky. Go over to the service school and find out what is being taught. If you disagree, tell them, not me or for that matter the members of this forum.
[ 28 July 2001: Message edited by: Lu Zuckerman ]
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Nick,
I probably should have asked the question another way, in the way the engines on the S64 and CH 54 are mounted, the height above the cabin appears different, the port engine appears lower than the starboard, that was what i meant to ask, thanks.
I probably should have asked the question another way, in the way the engines on the S64 and CH 54 are mounted, the height above the cabin appears different, the port engine appears lower than the starboard, that was what i meant to ask, thanks.
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Lu driveled, ands I answer point by point:
1) You keep evading the question saying in essence that your opinions are beyond reproach.
2) The collective bias causes the disc to tilt to the left. This slight change in the thrust vector counters the thrust of the tail rotor. Because the disc is tilted to the left the interlock between the blades and the rotorhead will cause the helicopter to tilt to the left or as you indicated left wheel low.
3) Because the mast is tilted three degrees
forward the helicopter will align itself with the rotorhead because of that same interlock between the blades and the head resulting in a nose high attitude.
4) Now get off your high horse and tell the forum why Sikorsky helicopters at least those that I am familiar with hover at such an odd angle. I was taught this in five different Sikorsky factory schools and I was taught about rigging the ASE in autopilot school and it was not my interpretation of what was said it is exactly what was said. I also rigged autopilots on the production line at Sikorsky. Go over to the service school and find out what is being taught. If you disagree, tell them, not me or for that matter the members of this forum.
Nick sez, to each dull point:
1) I try not to give opinions except when clearly stated as such. I give facts, unlike you, who drivel opinions, many inane and misapplied, and call them facts. I predict that when I take apart your latest crap, you will post about 500 words of garbage explaining how your misunderstanding is not your fault, and then you will spout another inane untrue "physical fact" and start this all over again. It is like wrestling a pig in the mud, after a while, you realize the pig doesn't want to win, it wants to wrestle!
2) Biasing the controls, such as the 1 degree of left lateral stick per 20 degrees of up collective on a Sikorsky, does not and can notmake the machine tilt in a hover. Your small understanding of a helicopter's force balance is exposed in your belief that this could happen. I explained above about the tail rotor's influence on the hover attitude, but you ignored that, didn't you? Biased controls only move the stick in the cockpit to recenter the stick and relieve the pilot of the task, otherwise we could make the helicopter fly upside down if we simply biased the controls enough, huh?
3) Mast tilt is not the same as biased controls, and mast tilt does influence the hover attitude. The 3 degree forward mast tilt causes some rotor moment to lift the nose a bit, so the hover attitude is raised about 2 degrees as a result. The tilt is there to relieve the mast moment (bending) in cruise, and to prevent big, draggy nose down attitudes in cruise flight. I don't have to look it up, Lu. I helped select the shaft tilt of the S-76 and Comanche (both 5 degrees, by the way).
4) I have no high horse, I have small tolerance for ignorant windbags, Lu. You are just that, and all your quotes about how many schools you (obviously) slept through do not make any justification for spouting misleading drivel to the forum members. I should do a DEJA search of your past postings and publish a book showing how you have helped a generation of new helo pilots mistrust manufacturers, misunderstand the aerodynamics of their aircraft, and perhaps even mistrust their machines.
I have broken my rule and directly responded only because you are so very very ignorant, and so very verbose it is hard not to respond.
1) You keep evading the question saying in essence that your opinions are beyond reproach.
2) The collective bias causes the disc to tilt to the left. This slight change in the thrust vector counters the thrust of the tail rotor. Because the disc is tilted to the left the interlock between the blades and the rotorhead will cause the helicopter to tilt to the left or as you indicated left wheel low.
3) Because the mast is tilted three degrees
forward the helicopter will align itself with the rotorhead because of that same interlock between the blades and the head resulting in a nose high attitude.
4) Now get off your high horse and tell the forum why Sikorsky helicopters at least those that I am familiar with hover at such an odd angle. I was taught this in five different Sikorsky factory schools and I was taught about rigging the ASE in autopilot school and it was not my interpretation of what was said it is exactly what was said. I also rigged autopilots on the production line at Sikorsky. Go over to the service school and find out what is being taught. If you disagree, tell them, not me or for that matter the members of this forum.
Nick sez, to each dull point:
1) I try not to give opinions except when clearly stated as such. I give facts, unlike you, who drivel opinions, many inane and misapplied, and call them facts. I predict that when I take apart your latest crap, you will post about 500 words of garbage explaining how your misunderstanding is not your fault, and then you will spout another inane untrue "physical fact" and start this all over again. It is like wrestling a pig in the mud, after a while, you realize the pig doesn't want to win, it wants to wrestle!
2) Biasing the controls, such as the 1 degree of left lateral stick per 20 degrees of up collective on a Sikorsky, does not and can notmake the machine tilt in a hover. Your small understanding of a helicopter's force balance is exposed in your belief that this could happen. I explained above about the tail rotor's influence on the hover attitude, but you ignored that, didn't you? Biased controls only move the stick in the cockpit to recenter the stick and relieve the pilot of the task, otherwise we could make the helicopter fly upside down if we simply biased the controls enough, huh?
3) Mast tilt is not the same as biased controls, and mast tilt does influence the hover attitude. The 3 degree forward mast tilt causes some rotor moment to lift the nose a bit, so the hover attitude is raised about 2 degrees as a result. The tilt is there to relieve the mast moment (bending) in cruise, and to prevent big, draggy nose down attitudes in cruise flight. I don't have to look it up, Lu. I helped select the shaft tilt of the S-76 and Comanche (both 5 degrees, by the way).
4) I have no high horse, I have small tolerance for ignorant windbags, Lu. You are just that, and all your quotes about how many schools you (obviously) slept through do not make any justification for spouting misleading drivel to the forum members. I should do a DEJA search of your past postings and publish a book showing how you have helped a generation of new helo pilots mistrust manufacturers, misunderstand the aerodynamics of their aircraft, and perhaps even mistrust their machines.
I have broken my rule and directly responded only because you are so very very ignorant, and so very verbose it is hard not to respond.
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Sling Load asked:
I probably should have asked the question another way, in the way the engines on the S64 and CH-54 are mounted, the height above the cabin appears different, the port engine appears lower than the starboard, that was what i meant to ask, thanks.
Nick sez:
Sling Load, you have sharp eyes. What you see is not a difference between the CH-54 and the S-64, but that they both have the transmissions tilted 3 degrees to the left, which makes the port engine a bit lower (closer to the deck) than the starboard when the aircraft is level on the ground. If the engines are 60 inches apart (a guess on my part) then the left engine would be 3 inches lower. The shaft is also straight up , with no forward tilt, unlike virtually every other helicopter.
For these Flying Cranes, Mr. Sikorsky aligned the mast so that the mast sees no lateral or longitudinal bending in a hover, and the crew is nice and level when placing loads precisely where they are wanted. This means that in cruise, the cabin is tilted to the right and very nose down. The pilots literally hang in their straps!
I probably should have asked the question another way, in the way the engines on the S64 and CH-54 are mounted, the height above the cabin appears different, the port engine appears lower than the starboard, that was what i meant to ask, thanks.
Nick sez:
Sling Load, you have sharp eyes. What you see is not a difference between the CH-54 and the S-64, but that they both have the transmissions tilted 3 degrees to the left, which makes the port engine a bit lower (closer to the deck) than the starboard when the aircraft is level on the ground. If the engines are 60 inches apart (a guess on my part) then the left engine would be 3 inches lower. The shaft is also straight up , with no forward tilt, unlike virtually every other helicopter.
For these Flying Cranes, Mr. Sikorsky aligned the mast so that the mast sees no lateral or longitudinal bending in a hover, and the crew is nice and level when placing loads precisely where they are wanted. This means that in cruise, the cabin is tilted to the right and very nose down. The pilots literally hang in their straps!
The CH-54 and S64 engines are at different heights for the reason stated above (3 degree mast tilt to the left). The mast is tilted forward on the Crane however, it has an inbuilt 3 degree forward tilt.
The CH-54 did have firewalls between the engines, but the S64 has the firewall extended over the top of the engine (but nothing on the outside).
There were two models of Crane built, the CH-54A (essentially equivalent to the S64E) and the CH-54B, which only had a Restricted Category TC and was never placed into commercial production (but became the S64F). To the casual observer, the most significant outward difference, is the S64E has single large mainwheels and the S64F has smaller twin mainwheels.
As is typical with Sikorsky products, each derived considerably from previous, or contemporary models. The CH-54A (S64E) utilized a rotor system derived from the CH-37A. The CH-54B (S64F) utilized a rotor system derived from the CH-53A series.
As a result there is very little commonality between the MGB, MRH and blades on the two models, which presents a challenge to anyone operating these machines. Although there are other differences, the other most significant difference is the engines; the S64E utilizing the P&W JFTD12-4A (4500 s.hp) and the S64E the P&W JFTD12-5A (4800 s.hp). Although there is only a dash number change in these engines, they are significantly different.
For the S64E total power for two-engine operation is limited to 6,600 s.hp.for takeoff, and 5,400 s.hp. maximum continuous.
For the S64F total power for two-engine operation is limited to 7,900 s.hp. for takeoff, and 6,600 s.hp. maximum continuous.
With derated limits like this, the machine has tons of reserve.
Sikorsky sold the the S64 Type Certificate to Erickson Aircrane in the early 90's and Erickson has been converting CH-54A's to S64E's, and CH-54B's to S64F's ever since. They have a very impressive operation and capability there, as they have to manufacture a considerable number of parts to keep this programme operational.
The CH-54 did have firewalls between the engines, but the S64 has the firewall extended over the top of the engine (but nothing on the outside).
There were two models of Crane built, the CH-54A (essentially equivalent to the S64E) and the CH-54B, which only had a Restricted Category TC and was never placed into commercial production (but became the S64F). To the casual observer, the most significant outward difference, is the S64E has single large mainwheels and the S64F has smaller twin mainwheels.
As is typical with Sikorsky products, each derived considerably from previous, or contemporary models. The CH-54A (S64E) utilized a rotor system derived from the CH-37A. The CH-54B (S64F) utilized a rotor system derived from the CH-53A series.
As a result there is very little commonality between the MGB, MRH and blades on the two models, which presents a challenge to anyone operating these machines. Although there are other differences, the other most significant difference is the engines; the S64E utilizing the P&W JFTD12-4A (4500 s.hp) and the S64E the P&W JFTD12-5A (4800 s.hp). Although there is only a dash number change in these engines, they are significantly different.
For the S64E total power for two-engine operation is limited to 6,600 s.hp.for takeoff, and 5,400 s.hp. maximum continuous.
For the S64F total power for two-engine operation is limited to 7,900 s.hp. for takeoff, and 6,600 s.hp. maximum continuous.
With derated limits like this, the machine has tons of reserve.
Sikorsky sold the the S64 Type Certificate to Erickson Aircrane in the early 90's and Erickson has been converting CH-54A's to S64E's, and CH-54B's to S64F's ever since. They have a very impressive operation and capability there, as they have to manufacture a considerable number of parts to keep this programme operational.
Iconoclast
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To: Cyclic Hotline
You obviously have access to a great deal of technical information so I will ask you without getting involved with Nick Lappos. You indicated that the mast is tilted to the left by three degrees and forward by three degrees which prompts two questions:
1) What is the effect on fuselage attitude when in a hover? I would think it would be left side down by three degrees and tail down by three degrees, What do you think?
2) Why was the transmission tilted to the left? I would think that it is to counter the propeller effect of the tail rotor. What do you think? Like most Sikorsky helicopters the mast is tilted three degree forward and from what I was told in service school it in effect gave the pilot additional forward control. I was also told in service school that the effect in hovering was that the tail would hang down making the nose high. What do you think?
You obviously have access to a great deal of technical information so I will ask you without getting involved with Nick Lappos. You indicated that the mast is tilted to the left by three degrees and forward by three degrees which prompts two questions:
1) What is the effect on fuselage attitude when in a hover? I would think it would be left side down by three degrees and tail down by three degrees, What do you think?
2) Why was the transmission tilted to the left? I would think that it is to counter the propeller effect of the tail rotor. What do you think? Like most Sikorsky helicopters the mast is tilted three degree forward and from what I was told in service school it in effect gave the pilot additional forward control. I was also told in service school that the effect in hovering was that the tail would hang down making the nose high. What do you think?
Join Date: Dec 1999
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Lu,
Going back to basic helicopter aerodynamics the tail rotor pushs the helicopter to the right in addition to keeping the nose pointed where the pilot wants it to be. The rotor must be tilted to the left to counteract the right drift.
The pilot can move the cyclic to the left when hovering, or the designer can tilt the trasmission to the left or make the mixing unit apply left cyclic when the collective is raised. What ever way is used left cyclic has to get in there. The rotor will be left side low and most likly the fuselage will too.
Give it a rest Lu the tilt gets into the system one way or the other.
Forward tilt, if used, is to allow the fuselage to be level in forward flight. Some have it some don't. It has the effect though of raising the nose when hovering.
Fly the H-500 or B0-105 or BK-117 for a taste of no forward tilt.
I hope this helps.
Going back to basic helicopter aerodynamics the tail rotor pushs the helicopter to the right in addition to keeping the nose pointed where the pilot wants it to be. The rotor must be tilted to the left to counteract the right drift.
The pilot can move the cyclic to the left when hovering, or the designer can tilt the trasmission to the left or make the mixing unit apply left cyclic when the collective is raised. What ever way is used left cyclic has to get in there. The rotor will be left side low and most likly the fuselage will too.
Give it a rest Lu the tilt gets into the system one way or the other.
Forward tilt, if used, is to allow the fuselage to be level in forward flight. Some have it some don't. It has the effect though of raising the nose when hovering.
Fly the H-500 or B0-105 or BK-117 for a taste of no forward tilt.
I hope this helps.
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Well, in response to the reason why the H60's T/R is canted up, it is to help with the CG situtation by supplying 2.5 % of lift of the helicopter at the aft end. And the reason why helos hover left side low (Bell, Sikorsky etc) as opposed to right side low (Russian, French) in a no-wind condition is do the correction applied to counteract translating tendency(to oppose the drift from the tailrotor and torque pushing the helo sideways. 