I enjoyed hearing about the historical context of the design of the components. it's important to understanding why things were designed the way they were. I wouldn't have known that the blackhawk main rotor hub uses bearings instead of flex plates due to lack of experience with flex plates, for example. it's also practically impossible to find these little specific bits of information quickly, so it's nice for it to just be in the video so one doesn't have to go searching for the answer afterward.
it was a youtube viewer who recommended Leoni's book to me. I need to dig that comment up and thank that person. I also like mixing the history of technology with the study of technology... I think a lot of less-than-good designs make it to market because people don't take time to study history.
@ Just finished, and was going to post another comment on exactly this question in the last 20 seconds of the video, and in fact was going to do that before I even saw that part. The new format is wonderful, because I learned a bunch of new details I had never known before. Also, for my style of learning, I really need to know the history, alternatives, and why, which you did wonderfully. Moffett is just down the highway from me, and I’m pissed at what history they have sold or destroyed or let rot. _cough_ Hangar 1’s original roof. _cough_ I still miss when they had open houses. Airshow-sized crowds.
Found your channel while trying to find articles and videos that have relatively simple, understandable and correct explanations of how helicopters work. Your videos are the best that I have found. Much of this is familiar to me from five years as a flight controls specialist on H-53s but my ability to explain something like a swashplate seemed unnecessarily complex. While I do not want to deliberately plagiarize your content it will help me to explain some of the "magic" to visitors on a mostly historical tour about the helicopters we have in the National Museum of the United States Air Force (I am a volunteer, not an employee) . If you are concerned about that please let me know. I will not use your videos at any time though I may pass the links to other docents who may need to beef up their own knowledge in order to answer a guest's questions.
You are welcome to share these videos with anyone who's interested. I'd be honored if you showed these at a museum. Thanks for asking and thanks for the nice words.
Yes to historical context, it adds to the understanding. The subject is one of the hardest to understand so anything that helps to get that across makes for a better video. It took a few impressions for me to click on this video because tail rotors aren't as interesting as main rotors but I'm so glad I did. Do you work in the industry or is it a personal interest?
thanks for that feedback! I worked military and industry, but I'd have to say it's also a personal interest. It's amazing how much I realize I didn't know when I do the research to make these videos.
@ Exactly right, I've been on a similar journey and finding out information is not straight forward, not easy to find on the internet. I went to an air show and asked Leonardo helicopters what the phase lag angle of the rotor was on the model they had on display. None of them knew the answer and they are the ones building the machine.
that's good to hear. I saw an image (I think on reddit) of the one at Novosel, and it was less than pristine. That must have been a pre-restoration photo.
@ there’s a private collection behind the aviation museum, part of the Training Support Facility. They had an open house 2 weeks ago and showed off the SB-1 Defiant, that’s where its final home will be. Look up “U.S. Army Aviation Museum and Training Support Facility” and if you look on the far right corner you will see the S-69
@bzig4929 look up "U.S. Army Aviation Museum and Training Support Facility" you can see the pictures of the closed collection and the S-69 is in the back right corner. There's other super cool aircraft that you can't see anywhere else.
17:44 I was wondering if the air transportability comes further into it. The blades fold back for transport. Any length of the helicopter in front of the MR shaft is a penalty, adding to the overall folded length. If the TR is producing 400 pounds of lift, at the end of a very long moment arm then that's several times that weight (on a much shorter moment arm) that doesn't need to be in front of the MR shaft for the helicopter to be in balanced flight. Hence the MR shaft can be fitted closer to the nose of the helicopter, reducing the overall length of the helicopter, when folded for transport. (Less nose length in front of the MR shaft). The static balance will be tail heavy but with the 400 pounds of lift when the TR is operating, it will be perfectly balanced. They have obviously done this to some extent (otherwise it wouldn't be balanced in flight) but my concern is that it's going to be tail heavy if its in autorotation with loss of TR drive. Plenty of flare authority but it would need a lot of forward cyclic to make up for the loss of lift from the TR. That amount of forward cyclic might make the auto relatively inefficient. Another way of looking at it is that conventionally, the centre of lift is on the MR shaft, so that's where the C of G needs to be. (More or less). On the UH-60 the lift is shared between the MR and the TR, so the centre of lift is slightly behind the MR, so the C of G needs to also be slightly behind the MR shaft. Hence the nose (in front of the MR shaft) will be shorter, giving a shorter overall folded length for transport. In the autorotation scenario, you can think of it as the centre of lift moving back to the MR shaft (where it would always be on a conventional heli) so, as this heli was designed with the C of G behind the MR shaft, it will be tail heavy during an autorotation. (In autorotation, the TR isn't producing sideways thrust to counter MR drive torque, therefore neither is it producing the 400 pounds of vertical lift component that it normally would).
good observation and you're correct. Leoni says, "the canter tail rotor resulted in a more compact aircraft in two ways, first by reducing the lift required by the main rotor... and second by permitting a shortened fuselage" He also says the lift produced by the tail rotor is at less power per pound of lift than the main rotor.
I'm skeptical about a 20-degree cant angle reducing the MR radius by 2 feet. I’d guess it might adjust hover or level flight trim pitch attitude by around 1-2 degrees instead. Given that TR thrust times sin(20 degrees) would likely be negligible compared to MR thrust, the effect may still be meaningful in terms of overall pitch moment about the CG. Great video nonetheless :^)
I was wondering if the air transportability comes into it. The blades fold back for transport. Any length of the helicopter in front of the MR shaft is a penalty, adding to the overall folded length. If the TR is producing 400 pounds of lift, at the end of a very long moment arm then that's several times that weight (on a much shorter moment arm) that doesn't need to be in front of the MR shaft for the helicopter to be in balanced flight. Hence the MR shaft can be fitted closer to the nose of the helicopter, reducing the overall length of the helicopter, when folded for transport. (Less nose length in front of the MR shaft). The static balance will be tail heavy but with the 400 pounds of lift when the TR is operating, it will be perfectly balanced. They have obviously done this to some extent (otherwise it wouldn't be balanced in flight) but my concern is that it's going to be tail heavy if its in autorotation with loss of TR drive. Plenty of flare authority but it would need a lot of forward cyclic to make up for the loss of lift from the TR. That amount of forward cyclic might make the auto relatively inefficient. Another way of looking at it is that conventionally, the centre of lift is on the MR shaft, so that's where the C of G needs to be. (More or less). On the UH-60 the lift is shared between the MR and the TR, so the centre of lift is slightly behind the MR, so the C of G needs to also be slightly behind the MR shaft. Hence the nose (in front of the MR shaft) will be shorter, giving a shorter overall folded length for transport. In the autorotation scenario, you can think of it as the centre of lift moving back to the MR shaft (where it would always be on a conventional heli) so, as this heli was designed with the C of G behind the MR shaft, it will be tail heavy during an autorotation. (In autorotation, the TR isn't producing sideways thrust to counter MR drive torque, therefore neither is it producing the 400 pounds of vertical lift that it normally would).
That's healthy skepticism. Leoni says the tail rotor produces 400 lbs of lift, so I started doing a simple blade element analysis to see if 400lbs could be accounted for with a 1-2 ft reduction in diameter. I realized it's not that simple... at first, I held all variables constant except for diameter, but then realized the smaller rotor isn't constrained to the same blade pitch. So with both the full size rotor and the smaller rotor, I could set total lift = the weight of the aircraft. It must be something about the high-hot-heavy perf numbers they had to come up with. I agree, for a 20K helicopter, 400 lbs and a 20 cant don't seem to point to that much of a reduction in blade size. But that's what he said in his book.
Because of the great losses of UH 1 during landing and take off in the battlefields in Vietnam, the designer had to think about how to make the black hawk move forward quickly after take off. That's why the 400 pounds lifting ability of the TR comes from.
@@stanleylee8084 that's certainly interesting. I was thinking that it has to be pretty much balanced fore/aft at all times, so it isn't going to make much difference whether it's balanced using weight or balanced by lift. (From tail rotor). However, after a bit more thought, I'm thinking you've hit the nail on the head! If they're doing an urgent _get us out of here_ type of takeoff, then they will be pulling maximum collective. That's going to need extra pitch on the tail rotor to counter the increased main rotor shaft torque. The extra pitch on the (slanted) tail rotor is going generate more lift at the tail, tilting the tail up (& nose down) aiding the quick getaway. It's a design that's very much _go minded_ in the situation you outlined, while being balanced in cruise. (Which wouldn't be the case if it was just nose heavy by weight distribution). Quite a clever solution to the design aim they were given.
I am also very curious about the bearings of the delta hinge. The tail rotor blades must flap very frequently, I wonder what kind of bearings are used and how often they need to be replaced.
it's called a "bearingless" tailrotor because they use composite beams that bend. Here is some reading... US Patent; Optimized Composite Flexbeam for Helicopter Rotors, Schmalling, D. N, US 1998/5738494 if you throw that into a search engine, it should bring up the text of the patent. Here are some words from that doc... "As such, these configurations are termed "Bearingless Rotors" inasmuch as they replace antiquated bearing element rotors which accommodate motion by hinge or journal type bearings at the rotor blade root end." Stay curious!
a picture is worth... check out Fig 18 of this ref: rotorcraft.arc.nasa.gov/Publications/files/Acree_AHSF02.pdf the elastomeric allows D3, but the kinematics is forced by offsetting the pitch link away from the no-delta-3 axis.
One of the innovations on the Blackhawk was titanium spar rotor blades. Before this, they used extruded aluminum d-spars and before this they actually used wood spar blades. Nowdays, most rotor blades are all composite... usually carbon fiber spars with some other material (fiberglass and nomex honeycomb) after bodies. As for the rest... steel, titanium, aluminum... all sorts of materials.
as someone who flew tandems (mostly)... and if only talking about perf and flying qualities, I agree. The single main rotor with a tail rotor configuration isn't the best. But it's good enough and it's the lowest production cost and this explains it's ubiquity in the market.
@@bzig4929 Would you ever do a video on it? Of all the US military helicopters of recent years I feel as if the phrog got the least limelight so its somewhat hard to find info on it.
Good idea. My next was going to be a tiltrotor. I started the drive system on that. But I like the idea of the history and "how it works" on the tandems.
I doubt if anyone can ever create a more accurate and optimally informing video on helicopters than you brother !!
Sick video!!! As a current HH60M pilot I found your video to be very helpful and certainly answered some questions I also had pondered. Subscribed!
This is by far your best video to date! I'm always blown away by your videos and your depth of knowledge.
thanks so much for the comment!
Awesome video!! The historical aspect is also a great addition
Amazing video. Thank you for taking your time to model all of this and compile it into a playlist.
Another excellent video! Thank you for incorporating the historical references.
I enjoyed hearing about the historical context of the design of the components. it's important to understanding why things were designed the way they were. I wouldn't have known that the blackhawk main rotor hub uses bearings instead of flex plates due to lack of experience with flex plates, for example. it's also practically impossible to find these little specific bits of information quickly, so it's nice for it to just be in the video so one doesn't have to go searching for the answer afterward.
it was a youtube viewer who recommended Leoni's book to me. I need to dig that comment up and thank that person. I also like mixing the history of technology with the study of technology... I think a lot of less-than-good designs make it to market because people don't take time to study history.
I quite like the format of this video.
Adding historical context makes a better video i reckon, good choice.
9:20 ka-27 has 36 degrees of delta 3 on the main rotors.
thanks for sharing that!
How did you find out that information ? interesting
@@Ben-Dixey My first reply didn't show somehow. I read it in 'Вертолет Ка-27. Военное издательство, Книга 1, 1983.'
Excellent video!!! I don’t know how you could make them any better. 🍻
Only 60 seconds in but I know it’s going to be awesome already!
Cool! What did you think of adding the history to the technical discussion?
@ Just finished, and was going to post another comment on exactly this question in the last 20 seconds of the video, and in fact was going to do that before I even saw that part.
The new format is wonderful, because I learned a bunch of new details I had never known before. Also, for my style of learning, I really need to know the history, alternatives, and why, which you did wonderfully.
Moffett is just down the highway from me, and I’m pissed at what history they have sold or destroyed or let rot. _cough_ Hangar 1’s original roof. _cough_
I still miss when they had open houses. Airshow-sized crowds.
Found your channel while trying to find articles and videos that have relatively simple, understandable and correct explanations of how helicopters work. Your videos are the best that I have found. Much of this is familiar to me from five years as a flight controls specialist on H-53s but my ability to explain something like a swashplate seemed unnecessarily complex. While I do not want to deliberately plagiarize your content it will help me to explain some of the "magic" to visitors on a mostly historical tour about the helicopters we have in the National Museum of the United States Air Force (I am a volunteer, not an employee) . If you are concerned about that please let me know. I will not use your videos at any time though I may pass the links to other docents who may need to beef up their own knowledge in order to answer a guest's questions.
You are welcome to share these videos with anyone who's interested. I'd be honored if you showed these at a museum. Thanks for asking and thanks for the nice words.
Fascinating. Like your presentation too. I'm subscribing.
Excellent video presentation as usual 👏 👌 👍 This is why, as a aviation, and helicopter buff, I subscribed!
thanks for the sub!
Yes to historical context, it adds to the understanding. The subject is one of the hardest to understand so anything that helps to get that across makes for a better video. It took a few impressions for me to click on this video because tail rotors aren't as interesting as main rotors but I'm so glad I did. Do you work in the industry or is it a personal interest?
thanks for that feedback! I worked military and industry, but I'd have to say it's also a personal interest. It's amazing how much I realize I didn't know when I do the research to make these videos.
@ Exactly right, I've been on a similar journey and finding out information is not straight forward, not easy to find on the internet.
I went to an air show and asked Leonardo helicopters what the phase lag angle of the rotor was on the model they had on display. None of them knew the answer and they are the ones building the machine.
Wow your videos are fantastic!
Thanks for the comment!
Wou nice kreatip helikopter rotor and swasplhate keren sir canggih!,,.
thanks for the video
Theres a pristine S69 in Fort Novosel, in the Training Support Facility.
that's good to hear. I saw an image (I think on reddit) of the one at Novosel, and it was less than pristine. That must have been a pre-restoration photo.
@ there’s a private collection behind the aviation museum, part of the Training Support Facility. They had an open house 2 weeks ago and showed off the SB-1 Defiant, that’s where its final home will be.
Look up “U.S. Army Aviation Museum and Training Support Facility” and if you look on the far right corner you will see the S-69
@bzig4929 look up "U.S. Army Aviation Museum and Training Support Facility" you can see the pictures of the closed collection and the S-69 is in the back right corner.
There's other super cool aircraft that you can't see anywhere else.
17:44 I was wondering if the air transportability comes further into it. The blades fold back for transport. Any length of the helicopter in front of the MR shaft is a penalty, adding to the overall folded length. If the TR is producing 400 pounds of lift, at the end of a very long moment arm then that's several times that weight (on a much shorter moment arm) that doesn't need to be in front of the MR shaft for the helicopter to be in balanced flight. Hence the MR shaft can be fitted closer to the nose of the helicopter, reducing the overall length of the helicopter, when folded for transport. (Less nose length in front of the MR shaft).
The static balance will be tail heavy but with the 400 pounds of lift when the TR is operating, it will be perfectly balanced.
They have obviously done this to some extent (otherwise it wouldn't be balanced in flight) but my concern is that it's going to be tail heavy if its in autorotation with loss of TR drive. Plenty of flare authority but it would need a lot of forward cyclic to make up for the loss of lift from the TR. That amount of forward cyclic might make the auto relatively inefficient.
Another way of looking at it is that conventionally, the centre of lift is on the MR shaft, so that's where the C of G needs to be. (More or less).
On the UH-60 the lift is shared between the MR and the TR, so the centre of lift is slightly behind the MR, so the C of G needs to also be slightly behind the MR shaft. Hence the nose (in front of the MR shaft) will be shorter, giving a shorter overall folded length for transport.
In the autorotation scenario, you can think of it as the centre of lift moving back to the MR shaft (where it would always be on a conventional heli) so, as this heli was designed with the C of G behind the MR shaft, it will be tail heavy during an autorotation. (In autorotation, the TR isn't producing sideways thrust to counter MR drive torque, therefore neither is it producing the 400 pounds of vertical lift component that it normally would).
good observation and you're correct. Leoni says, "the canter tail rotor resulted in a more compact aircraft in two ways, first by reducing the lift required by the main rotor... and second by permitting a shortened fuselage" He also says the lift produced by the tail rotor is at less power per pound of lift than the main rotor.
nice work
I'm skeptical about a 20-degree cant angle reducing the MR radius by 2 feet. I’d guess it might adjust hover or level flight trim pitch attitude by around 1-2 degrees instead. Given that TR thrust times sin(20 degrees) would likely be negligible compared to MR thrust, the effect may still be meaningful in terms of overall pitch moment about the CG. Great video nonetheless :^)
I was wondering if the air transportability comes into it. The blades fold back for transport. Any length of the helicopter in front of the MR shaft is a penalty, adding to the overall folded length. If the TR is producing 400 pounds of lift, at the end of a very long moment arm then that's several times that weight (on a much shorter moment arm) that doesn't need to be in front of the MR shaft for the helicopter to be in balanced flight. Hence the MR shaft can be fitted closer to the nose of the helicopter, reducing the overall length of the helicopter, when folded for transport. (Less nose length in front of the MR shaft).
The static balance will be tail heavy but with the 400 pounds of lift when the TR is operating, it will be perfectly balanced.
They have obviously done this to some extent (otherwise it wouldn't be balanced in flight) but my concern is that it's going to be tail heavy if its in autorotation with loss of TR drive. Plenty of flare authority but it would need a lot of forward cyclic to make up for the loss of lift from the TR. That amount of forward cyclic might make the auto relatively inefficient.
Another way of looking at it is that conventionally, the centre of lift is on the MR shaft, so that's where the C of G needs to be. (More or less).
On the UH-60 the lift is shared between the MR and the TR, so the centre of lift is slightly behind the MR, so the C of G needs to also be slightly behind the MR shaft. Hence the nose (in front of the MR shaft) will be shorter, giving a shorter overall folded length for transport.
In the autorotation scenario, you can think of it as the centre of lift moving back to the MR shaft (where it would always be on a conventional heli) so, as this heli was designed with the C of G behind the MR shaft, it will be tail heavy during an autorotation. (In autorotation, the TR isn't producing sideways thrust to counter MR drive torque, therefore neither is it producing the 400 pounds of vertical lift that it normally would).
That's healthy skepticism. Leoni says the tail rotor produces 400 lbs of lift, so I started doing a simple blade element analysis to see if 400lbs could be accounted for with a 1-2 ft reduction in diameter. I realized it's not that simple... at first, I held all variables constant except for diameter, but then realized the smaller rotor isn't constrained to the same blade pitch. So with both the full size rotor and the smaller rotor, I could set total lift = the weight of the aircraft.
It must be something about the high-hot-heavy perf numbers they had to come up with.
I agree, for a 20K helicopter, 400 lbs and a 20 cant don't seem to point to that much of a reduction in blade size. But that's what he said in his book.
Because of the great losses of UH 1 during landing and take off in the battlefields in Vietnam, the designer had to think about how to make the black hawk move forward quickly after take off. That's why the 400 pounds lifting ability of the TR comes from.
@@stanleylee8084 that's certainly interesting.
I was thinking that it has to be pretty much balanced fore/aft at all times, so it isn't going to make much difference whether it's balanced using weight or balanced by lift. (From tail rotor).
However, after a bit more thought, I'm thinking you've hit the nail on the head!
If they're doing an urgent _get us out of here_ type of takeoff, then they will be pulling maximum collective. That's going to need extra pitch on the tail rotor to counter the increased main rotor shaft torque. The extra pitch on the (slanted) tail rotor is going generate more lift at the tail, tilting the tail up (& nose down) aiding the quick getaway.
It's a design that's very much _go minded_ in the situation you outlined, while being balanced in cruise. (Which wouldn't be the case if it was just nose heavy by weight distribution). Quite a clever solution to the design aim they were given.
@alanm8932 Yes, exactly！The lifting ability can be changed by adjusting the angle of the horizontal rudder underneath.
Thank you boss
amazing
Como voa para frente e ré ?
I am also very curious about the bearings of the delta hinge. The tail rotor blades must flap very frequently, I wonder what kind of bearings are used and how often they need to be replaced.
it's called a "bearingless" tailrotor because they use composite beams that bend. Here is some reading... US Patent; Optimized Composite Flexbeam for Helicopter Rotors, Schmalling, D. N, US 1998/5738494 if you throw that into a search engine, it should bring up the text of the patent. Here are some words from that doc... "As such, these configurations are termed "Bearingless Rotors" inasmuch as they replace antiquated bearing element rotors which accommodate motion by hinge or journal type bearings at the rotor blade root end." Stay curious!
Qual o material das pás ?
How does the elastomeric hinge equate to the delta-3 hinge? I'm having a hard time seeing how that allows or guides movement in the desired DOF.
a picture is worth... check out Fig 18 of this ref: rotorcraft.arc.nasa.gov/Publications/files/Acree_AHSF02.pdf the elastomeric allows D3, but the kinematics is forced by offsetting the pitch link away from the no-delta-3 axis.
What are the materials used to create these components steal? titanum?
One of the innovations on the Blackhawk was titanium spar rotor blades. Before this, they used extruded aluminum d-spars and before this they actually used wood spar blades. Nowdays, most rotor blades are all composite... usually carbon fiber spars with some other material (fiberglass and nomex honeycomb) after bodies. As for the rest... steel, titanium, aluminum... all sorts of materials.
Lemme see you pitch your tail rotor!
Time stamp (4:16) Cannot hjelp but cringe at :And-eye instead of An-tee.
Stupid design
as someone who flew tandems (mostly)... and if only talking about perf and flying qualities, I agree. The single main rotor with a tail rotor configuration isn't the best. But it's good enough and it's the lowest production cost and this explains it's ubiquity in the market.
@@bzig4929 Did you fly phrogs?
I did. HMM-261.
@@bzig4929 Would you ever do a video on it? Of all the US military helicopters of recent years I feel as if the phrog got the least limelight so its somewhat hard to find info on it.
Good idea. My next was going to be a tiltrotor. I started the drive system on that. But I like the idea of the history and "how it works" on the tandems.