If it helps... I learned this stuff in the 80s/90s and I've been using it ever since, but trying to re-learn to the point of making a coherent (I hope) presentation has me going back over and over again to text books.
I fly gyros and while I understand this stuff already this is an awesome video. Our system of simple two bladed teetering is less complicated but same principles in play. Well done.
Just Brilliant ! I'm a long time fixed wing pilot. The more ya know I guess. If we'd had this QUALITY of training material in the early 1980's when I learned to fly, I'd have probably gone on to my rotor wing license. I'm now Subscribed, Liked, and that BELL has Been RUNG !
Interesting, when I learned to fly helicopters in 1965, what he called “lead-lag” was called “hunting.” Neither rigid nor semi-rigid main rotor systems have a flap hinge. Semi-rigid or see-saw system blades flap but at the fulcrum, the rotor hub or rotor head, which is hinged to the mast. The best known helicopter with a semi-rigid system is this Bell UH-1 “HUEY.” The example in the video is an articulated system, with the rotor head “fixed” to the mast, requiring flapping and hunting hinges for the rotor blades. A rigid system also has a fixed rotor head but no flapping or hunting hinges. On this system, flapping and hunting are accomplished by flexibility designed into the rotor blades. The response to a stall in an airplane is to add power (among other things); the response to retreating blade stall in a helicopter is to reduce power (among a few other things).
hunt-drag are still used as terms for lead-lag. I've heard both used... I probably should have called out both as acceptable terminology in the video. Thanks for commenting and for sharing the observation about teeters.
Your video animations are awesome. I sense countless hours spent on this! I am a retired helicopter flight instructor and I also used to teach heli aerodynamics. So here are a few comments on the aerody: Although blade flapping can be the same mechanical movement as blade coning, it's important to separate the two. Coning angle depends on disc loading (weight and G-forces) and flapping angle depends on disc tilting. So where your animation is showing all blades 'flapping up', this can a bit confusing as you are actually showing coning. Flapping = Disc tilting And maybe most important, unless you fly an autogyro or a CH 47 Chinook, the so-called Dissymmetry of Lift in forward flight is actually not controlled with blade flapping. As you correctly showed at the end of the video, a forward cyclic input is always required to check the undesired resulting flapback. You will need progressively more forward cyclic input to check flapback at faster speeds or the heli will slow down. So in the conventional heli, Dissymmetry of lift is controlled mostly through cyclic blade feathering. Maybe not what you are told in flight school, most books and most videos etc but such is life. Another detail worth mentioning in your video is about blade 'flapping to equality' (which is what happens 'temporarily all the time' during both flapback, any variations in induced flow across the rotor disc and most importantly with any cyclic control input) I am guilty of teaching this theory in the past but it is NOT a variation in induced flow velocity that changes the angle of attack. Induced flow remains perpendicular to the disc as it tilts so induced flow velocity is not changed much. Instead it is a purely mechanical action that alters AoA. As the blade pitch remains fairly set, the blades flapping up and down with the same pitch angle will alter the AoA. So Flapping to Equality always results in disc tilting. Difficult to explain in theory but I reckon your animations would nail it! cheers.
Awesome comment and thanks for the feedback! I hear you on flapping vs coning. It's the same mechanical degree of freedom and I did intend to convey the difference between the two motions. Also on flapping induced velocity vs induced flow... This is where simple drawings are more clear than the 3d animation. When I showed the blade sections, I should have showed both the induced flow (unchanging as you say) and the flapping induced component before showing the resultant normal vector. I thought about that, but didn't do it because the drawings would have been cluttered. Thanks for the feedback... it will help me make future videos better.
Another aspect you could look at is the flapping removing the negative impacts of gyroscopic precession. Cierva who developed the flapping hinge for his autogiros commented that the flapping hinge was developed to solve the difference in lift between advancing and retreating. The blades had no cyclic control were fixed and used elevators and ailerons to control the aircraft the blades were a lift device and essentially anti-stall protection. Latter the full head was developed in the early 1930's for autogiros. At the time though he commented that the early experiments suffered from dis-symetry of lift issues and gyroscopic precession. This one hinge solved both. But agree the video needed to stop where you did. You have excellent explanations and having played with some CGI animation your animation skills are amazing too. I know how hard it is even on our simpler heads to explain things your model is amazing. Well done. If your interested in the history Sir Reginald Bree (Ceriva's test pilot) wrote a book on gyros in the 1930's that went into the head development (which was latter adopted by helicopters). The early gyros had fully articulated heads even jump heads with collective pitch control. th-cam.com/video/SMBe1nBAmN0/w-d-xo.html
There was a time in the 30's and 40's, when the early helicopters were in development, the autogyro was much more advanced and most would have predicted an autogyro future. If you're interested, look up the "Franklin Institute Meeting of 1938" and the Dorsey Logan act. The autogyro community campaigned for more military funding of this technology but at the last minute, the meeting changed to include all "rotating wing aircraft." No doubt many helicopter innovations cam about from autogyros. Thanks for the video link.
@@bzig4929 Yep the flapping hinge once you understand it is a wonderful thing. I used to fly in ultralights before I got into gyros. I remember having flown gyros for years getting offered a ride in the same ultralight I'd been trained in. We took off and the owner said want to fly it. You Bet! We hit a thermal under one wing and the ultralight kicked that wing up "You going to correct that?" he said "oh yeah" and I corrected then the other wing came up in another bump "You going to correct that?" he said again. I couldn't figure out why I was flying so badly and I actively flew for the rest of the flight but after landing and getting into my gyro I worked out I don't touch the controls in thermals (even though I don't even feel the small ones). Anyway I worked out it was the teeter hinge my blades can't tell if they have more lift from extra airspeed on the advancing side or from a thermal hitting on one side before the other. It just compensates and you don't have to do anything to you learn to fly passively. Gyros are more fixed free stable than helicopters but I realized why all rotary winged craft can handle the rough weather better than fixed wings and all with one hinge (on a twin bladed rotorcraft). Such an elegant solution. He (Cierva) apparently got the idea from stress relieving hinges on bridges which compensate for expansion and heat on metal bridges. I will look up that meeting - I was aware of some of this and issues around patents around ww2 when Pitcan held many of the patents and the war engine allowed them to be walked over. He really got screwed over unfortunately. But I'm glad they contributed to the helicopter I like all aircraft - especially anything with rotary wings.
Your choice to not model the links between the collective/cyclic and the rotor system at this point is excellent. It avoids us getting distracted by trying to understand that complexity and focus just on what the controls do to the rotor system.
Really well done! I've only flown as a pax and 2x as intro right seat so don't know much other than these are amazing machines. As a heli-ski pax, I have to say, the pilots LOVED pitching down to gain a lot speed very quickly so they didn't seem to be too concerned about over-speeding.
When I was flying, I loved doing that also... lift to a hover on a mountain peak and cyclic forward to increase speed and also stay close to the terrain. Good times!
Just coming back to watch this a third time... Bought the heli in my mind, should probably learn how to fly it first... ❤ Great information, thank you for taking the time to explain this so completely. Guaranteed to be bored in class after watching your channel, you heartless bastard...
The hub moment is relieved when the fuselage (and shaft) tilt to follow the rotor which is dragging them along. Which means that the stick must return to near center in steady-state forward flight. Also, the forward movement of the rotor increases lift as it goes into cleaner air - so collective must be reduced as forward velocity increases.
As you add forward cyclic for gaining air speed, cyclic feathering also reduces on the advancing blade pitch and increases on the retreating blade - It's not just all flapping you have but it sure helps... Great animation
I’m glad someone else knows this. However I would take it one step further and argue that the advancing blade in constant speed forward flight is not flapping up at all. If you look at the path of a blade from the 6 o’clock position to the 12 o’clock position you will see that the blade is moving from a higher to lower position. With the appropriate control input from the pilot, the dissymmetry of lift is cancelled by adjusting pitch cyclically. If, as a majority of instructors teach, the flapping cancels out the dissymmetry of lift, then you wouldn’t get flap back as you accelerate.
@@tommyandmyf What's interesting is blades act like loose chains flapping up & down along the full span, Seen it in old high speed films Sikorsky Hughes and Bell tests You can look them up - Cool stuff
@ yeah I’ve seen those videos. Very interesting. I still don’t agree with the very common teachings that “flapping cancels out the effects of dissymmetry of lift”.
@@tommyandmyf Hub flexibility the key flapping for removing mast moments on the air frame. hinges for lead lag & under slung to reduce conservation of energy effects from fatiguing the hub. Flapping is nice but not as important as cyclic feathering - The MBB 105 has a big pitch roll coupling in forward flight as you use collective... Very pronounced ... rigid rotor with only feathering bearings, Lots to learn th-cam.com/video/fRp2uAYWa_A/w-d-xo.html I Built this in 1995
If I fly, it's a fixed wing, even then, I prefer to be on the ground unless I can reach the yoke or stick. I put too many R/C models of mine into the dirt to screw around, I have stick and rudder skills, and I don't crash anymore. One glider I have has 500+ flights, it really helps to know how to control an aircraft, and fixed wing has so much less to go wrong.
Again - another beautifully executed animation of helicopter aerodynamics. this series will be a pandoras box to any helictoper training school & trainee pilot. kudos
Outstanding video. Subscribed... gonna go watch the rest.. Looks like the coning angle is similar to the dihedral of an airplane wing, providing stability, flexing or "flapping" as the wing load increases or decreases.
As an ex Airframe Tech, your vid tells more of what is occurring at the moment of lift, angle of rotation than anything provided in text books in my forty five years of experience, not saying I didn’t already know what was happening, but your explanation is very detailed and of high quality and explains it expertly. Well done!
Wonderful vid again. Amazing the engineering in a rotor head. I fly large RCs 700 size with 5-foot Dia rotor disc and I have a two blade and three blade 700. My favorite thing is take offs and landings. Can hold them in a perfect hover as well. If I had 15 million sitting around, I would own a Bell 429 or AS355.
if someone gave me a 429, out-right, I probably couldn't afford the operating costs :) RC helicopters are amazing. It's hard to believe the same physics of flight apply to RC helos, doing 3d aerobatics, as applies to manned helicopters.
@@bzig4929 Absolutely true, the bigger the RC the more it behaves like a full size. The blade chop on my two blade is amazing, luv that sound, kinda like a Huey. It also autos nicely. As for the operating costs on the 429, I heard to run a Sikorsky Sky Crane around 140k per hour!
@@rcas350pilot8Yes, and their pilots get insulted if you start asking silly questions like why wheels instead of skids and calling that beast a chopper. Don’t ask me how I know! (Skids are for kids, and don’t ever equate a Skycrane with a motorcycle.)
Something that came to mind the other day, I don't think centrifugal forces are the only forces applied to the rotor hub. Considering that while flapping, a blade has angular momentum, as that blade turns, and the flapping hinge changes the plane of rotation, some of that rotation must be converted to a linear force. Take this example: The advancing blade on the right has an upward flapping velocity. This is constrained by the flapping hinge. By the time that blade has rotated 90 degrees counter-clockwise, now at the forward blade position, all angular velocity from the right position is 90 degrees out of plane, meaning it is now applying a twisting force along the span of the blade. Constrained by the flapping hinge, this applies an additional linear force on the rotor hub.
I need to do another video about lead-lag. Lead-lag exists to correct the changes in angular momentum due to flapping. As the blade flaps up, the CG moves inward... making the blade want to advance. Because it can't, due to conservation of angular momentum, it leads forward. Then it lags aft when it flaps down.
@@bzig4929This explanation video will be cool. When writing the script, please take note that at least I am confused by your use of advance here. I would interpret that the same as leading, but that can’t be so, because you’re saying they are different.
@@bzig4929 Just a side note on why helicopters are far more expensive than fixed wing, per pound of payload capability. Each blade is continually flapping, AND lead/lagging, AND long axis twisting, for each single cycle of hub rotation. For a rotor speed of 324 rpm (+ 9% / -4%) for one model of light helicopter, so too are all the bearings hub and blade grip interface, constantly reversing at the same frequency. Obviously wear is far accelerated, and materials used must be top purity of hardness and/ or compliance. One axiom I've heard is: " A helicopter is a large collection of spare parts, all flying in formation, and wanting to fling themselves to pieces" 😱 The best damn helo pilot I've ever seen was a former Cobra pilot in Nam. In his middle age he flew AS315 Lama. I once saw him regularly hold a 100 foot long line with ballast ball and hook in high hover for 3-5 minutes at a pick, while pipeline handlers below were manipulating their choke cables. The ball was about 5 feet above their heads, and all that time never swayed more than 6" in radius. When he was signaled by the pipe handlers he gently lowered the hover by 7 feet, to ground the static braid and they hooked it up, and away he went. A true skyhook master. He had told me that he had "bent a bird", several years earlier. I did not ask him to elaborate, as his answer was terse. He had several 1000 hrs in Helos. Several years later, I asked his fueler guy what happened too him. FG said "He had another accident, some bearing had failed, but he wasn't hurt. However immediately retired, saying he wasn't going to risk a third time as that would be the end of him, and his mother needed him for home care." So that was that
How does rotor size and stiffness affect flapping? I have a radio controlled helicopter (T-Rex 600 with a 4 blade rotor head) and there is no flapping hinge at all, but the blades must flap to allow forward flight so I'm guessing most of the flapping occurs by the blades themselves flexing close to the blade roots (the blades are carbon fibre). There is also a rubber bushing in the blade grip but it is extremely hard and you can't see or feel any obvious movement if you try to pull on the blade grip in the axis the blades should flap. (Lead/lag is taken care of by the mounting bolt in the blade grip going through a bronze bushing in the blade root acting as a hinge, allowing the blades to lead/lag quite easily).
The flapping hinge can exist without the presence of a mechanical hinge. These are called "virtual" hinges that rely on bending to achieve the same result as a mechanical device. I'm guessing the vertical pin rubber bushing is the lead-lag degree of freedom. This only needs 1 or 2 degrees of motion. I think you are correct that flapping is taken up entirely by bending of the blades. This would give a very high hinge offset which results in a very responsive (some say "twitchy" helicopter). Full-size helos with this arrangement (lynx and BO-105) usually have stability augmentation that lag-filters pilot input to take some of this responsiveness away from the pilot. It doesn't surprise me that RC helos would have this control system... they are insanely responsive to control inputs!
@@bzig4929 I don't understand the absolute need for the flapping motion for the helicopter to work. Why would a totally stiff blade without a flapping hinge not be able to make the whole helicopter tilt into the direction the pilot wants to go? When there is a cyclic input even with 100% rigid blades (in terms of flapping), I don't see how it would not cause the whole helicopter to tilt (with precession of course)
@@bzig4929 Such 100% rigid helicopter might not be pleasant to fly if it was a full size one. But at least it should be able to respond to inputs. RC helicopters used to be equipped with the additional "paddles" (the flybar) with complicated mechanical mixing into the main blades in order to make the helicopter more stable and counter unwanted movements. Also to amplify the forces of the servos. But today they just have very minimalistic rotorheads where the swashplate is directly linked to the blade grip. The blade grips sit on the same feathering shaft, so their only axis of freedom relative to each other is their blade pitch. It is all very rigid. Gyro controllers (flybarless systems) take care of the unwanted effects and dissymetries. But some people have also flown these without the gyro systems. So I think that a helicopter without any flapping is still able to be flown, but just much more difficult to keep under control.
I wish you would make one video about the tail rotor of UH 60 as the axis is not at 90 degrees to the ground and there are elevators underneath, many people confused about that.
Your videos are very well-done, and I really appreciate the proper visuals to better understand helicopter aerodynamics. What helicopter's rotor system is that from the video?
Excellent and instructive video, you have earned a subscriber!! I wanted to ask you, what do the blue, green, yellow and red rings on the pitch shift links mean? Thank you so much!!
Those are for the maintainers to identify the blades (and for me to identify which blade I'm looking at as I make changes to the animation). Here's a scenario... The pilots collect rotor track and balance data and then maintenance writes a work order to add tip weight to a particular rotor blade; they could identify this by blade srno, but it's much easier if the blades are colored to make it easier for the mechanic doing the work. Thanks for the question!
It can be on either side, regardless of the main rotor rotation direction. The tail rotor is either a "pusher" or a "puller". Industry seems to favor mounting on the left side by a slight margin.
It does! In tandem helicopters yaw is accomplished with alternating lateral cyclic input. To yaw left, for example, a left lateral cyclic input is sent to the front rotor, and a right lateral cyclic input is sent to the aft rotor. This is all done in a flight control mixing unit, so the pilot is doing this with the pedals.
Another solid video! You mentioned at 8:49 that absent of flapping, the dissymmetry of lift would cause higher lift in the advancing side and cause the helicopter to ROLL. You later mention that retreating blade stall causes a loss of lift on the retreating blade causing the helicopter to PITCH up caused by phase delay. Wouldn’t dissymmetry of lift also be subject to phase delay causing the helicopter to PITCH up? I also believe this action is the cause of Blow Back and what requires more forward stick input from the pilot. The amount of additional forward cyclic is proportional to the forward speed of the helicopter. This forward cyclic input in turn mechanically changes the pitch (less on advancing and more on retreating) of the blades and reduces (or eliminates) flapping due to dissymmetry of lift. (Pilot induced delta 3 hinge) One more crazy phenomenon. More induced flow at the rear of the disk in forward flight causing a reduction in AOA and lift resulting in a ROLL to the advancing side. Curious to hear your thoughts. I could very well have some (or all) of this wrong.
my thoughts... if there were no flapping hinge, the aircraft would roll due to FFDOL, but the flapping prevents this increased lift from ever happening. And you are correct... this is what leads to blowback of the rotor disk. Instead of a left roll, there is blowback due to FFDOL. But this doesn't cause the aircraft to pitch up... the rotor disk pitches up (blowback) but not the aircraft. The autogyro pioneers were the first to figure this out. I believe de la Cierva attempted a rigid rotor and only after seeing the controlability issues did he add the flapping hinge. I can see why you say "a pilot induced delta 3." Delta 3 creates a natural coupling between flapping an feathering. So if the pilot changes feathering based on the blow back... I get the analogy. It's interesting now that many are attempting to develop eVTOL aircraft without flapping hinges (like Joby, Archer, Beta) I understand, with side-by-side rotors, they won't see the issues de la Cievra saw on a single rotor autogyro, but all of those rolling moments have to go somewhere. If it isn't a control moment, it will be loads absorbed by the rotor masts and the airframe. I wonder if their flight test campaigns will point them to the same epiphany of Cievra. I think your last point is talking about transverse flow and this is one of the many subjects I didn't cover in the video. I have a book written by Sikorsky (the company, not Igor) "Sikorsky Helicopter Flight Theory for Pilots and Mechanics" This book deals with these subjects much more completely that I can do in 10-15 minute videos. It would probably take 10 hours to cover the materiel in the same depth as a book. Hopefully these videos stimulate questions and thoughts that point viewers to other sources and more study. Stay curious!
@@bzig4929 I truly appreciate the amount of effort you’ve put into this and the amount of knowledge you have on this subject. In my opinion, helicopters are one of the most fascinating mechanical things in the world! I have a copy of Helicopter Theory by Wayne Johnson. I’ll have to pick up a copy of Sikorsky Helicopter Flight Theory for Pilots and Mechanics. I still struggle to understand why the helicopter would roll due to FFDOL. I need to do some more research. If you want to pitch the rotor in any direction, you increase (or decrease) the lift 90 degrees (or whatever phase delay angle the system has) behind that intended direction. What scenario will a rotor tilt in the exact direction where the lift changes? That is where I am getting lost. As far as blow back pitching the rotor and not the heli, I can see that being true for a semi rigid head but not a fully articulated head. Any pitching of the rotor on a fully articulated head will induce a moment on the helicopter due to the offset hinge. Full transparency here, I most definitely could be misunderstanding something here! I too have thought a lot about these eVTOL aircraft. They make zero sense by the way. I can’t come up with a single scenario where they are successful. The blades must be subjected to significantly more stress than a helicopter blade due to their rigid design. It’s probably within the design envelope as traditional airplanes experience the same dissymmetry at high alpha with the descending blade having a higher angle of attack. The rolling moment gets thrown into the airframe and is balanced by the counter rotating blade on the other side of the fuselage. (At least that’s my theory) I don’t mean to challenge you in any way. I respect your opinions greatly. Many beers could be drank discussing helicopter theory but I think most people would lose interest fairly quickly. I look forward to your next video.
@@bzig4929 Compressibilty before retreating blade stall - You get a rough ride then at stall the helicopter will pitch up and roll to retreating blade side. - Seen test footage and data. Family was friends of Igor during the Los Angeles Airways days... Before I started flying...
Really love your stuff, I was wondering if you could discuss tail rotor flapping in another video? I've heard of it briefly but haven't looked too much into it. I'm wondering if it's even a thing.
Definitely! It may not be the next video, but I'll get to the trail rotor. I'm still trying to figure out if the 60 has delta-3 on the tail rotor flexbeams. It doesn't appear to, but I may be missing some detail.
no. Flapping is naturally a heavily damped motion - aerodynamics provide all of the needed damping. I cover this in the video I did on the lead-lag DOF. Here is the link to that video... th-cam.com/video/5sLZcvagEbs/w-d-xo.html
Coning is mostly influenced by the weight of the aircraft. This can be the actual weight, or the weight due to g loading. An autorotation is a 1g maneuver so coning is about the same as any other 1g flight condition.
Yes... I used public source technical data for the Sikorsky Blackhawk to create this model. I have a playlist with 6 videos showing how I modeled this and it also covers the technical reports used to define all of the design parameters.
The only thing I can’t get straight in my mind is how the advancing blade…If I understand right…will increase feather/pitch angle but will decrease angle of attack/lift….and just the opposite on the retreating blade. It seems like that would have the same affect as raising the collective and increasing lift? I need more coffee…
The blade doesn't change pitch/feather angle; that is constant unless the pilot moves the controls. The blade on the right side sees more airflow, so it makes more lift and flaps up. The upward flapping essentially reduces the normal (not tangential) component of velocity seen by the blades. The angle of the relative air changes, but not the angle of the blade. It's easier to explain standing in front of you and flapping my arms up and down. But it's a good question and I need to improve the graphics and the words to make it more clear. Thanks!
I'm not really sure what "Sikorsky shake" is. All helicopters have vibration modes. But I think most pilots don't experience tip stall because they stay withing the limits on the aircraft. Sikorsky seems to take pride in high Vne aircraft so I think this would be especially true for that product line. Tip stall, in aircraft with hydraulics, is often not felt by the pilot until it gets pretty bad. I flew CH46s and that aircraft had an indicator... They put strain gauges on the control links at the rotor and fed that into a gauge for the pilots to show tip stall approaching.
@@bzig4929 I’ve only heard Sikorsky Shake a few times over the years, but my recollection is that several pilots described it as a common trait with all Sikorsky helicopters, and that the company even had to add a vibration damping system into their rotor systems. But a quick Google doesn’t find more than a couple of references. But Google can’t find a lot of things it used to. Maybe the dynamics of the Vertol twin rotors is different enough the dynamics are different?
I may try that for a short. I'm processing the videos in davinci resolve... I think that can do 4k. The resuloution coming out of the animation software may also be limiting, but it will be fun to try.
here's an unlisted clip that I did in 4k. let me know of you think it looks any different. To me, it's about the same as my other videos, so the limitation is the rendered clips coming from the animation s/w. I suppose it makes sense that processing low-res clips in 4k is still low res. th-cam.com/video/pPkUydVIXiI/w-d-xo.htmlsi=AYRGYJGx9SVa-4MT
@@bzig4929 That 4K one definitely looks better, by a quite a noticeable margin on my 48" 4K OLED. Small details on the blades and tail rotor drive shaft are very much enhanced compared to a similar scene in the original at 1:50, for example. And on the later hub close-up too. It would be best to render at 4K high quality first, of course, but whatever you did worked for me at least. Your animation is so nice it's a shame to hide it!
All I know is that if you lose the spinning thing on the top of the helicopter, your helicopter will land immediately with lots of gravitational force😢
Yes! But we can be comfortable knowing that humanity has gotten good at designing highly-reliable, safety-critical and complex systems. If you peel back the skin of cars, helicopters, airplanes and escalators you'll see things that scare you and make you realize how many times, during an average day, we trust out lives to people we don't know and never see. Thanks for watching!
As a helicopter pilot, your videos are exceptional. Well done and thank you for taking the time. It's appreciated by many I'm sure. Brilliant!
Thanks!
Asseriously, Amazing and digestible. Your best video yet and they are all good.
Thanks so much!
Agreed I am a former 60 crew chief love how you laid it out and explained
A helicopter pilot here too, and I agree. These videos are amazing.
My brain hurts now. Information dense video that I need to watch again and again in order to apsorb all the knowledge. Keep good work please.
If it helps... I learned this stuff in the 80s/90s and I've been using it ever since, but trying to re-learn to the point of making a coherent (I hope) presentation has me going back over and over again to text books.
not sure who is more brilliant, the guy who invented this concept or the ones like you teaching the aftermath. your videos are such a delight!
Thank you so much! I'm personally more amazed by those other people, but your comment made me smile.
I hadn't considered induced flow's effect in my simulation. Very helpful demonstrations to show why it's important in counteracting asymmetric lift.
Plane is built to fly. Helicopter is forced to fly.
Both are always falling
I fly gyros and while I understand this stuff already this is an awesome video. Our system of simple two bladed teetering is less complicated but same principles in play. Well done.
Just Brilliant ! I'm a long time fixed wing pilot. The more ya know I guess. If we'd had this QUALITY of training material in the early 1980's when I learned to fly, I'd have probably gone on to my rotor wing license.
I'm now Subscribed, Liked, and that BELL has Been RUNG !
Awesome! Thanks for the nice comment.
Interesting, when I learned to fly helicopters in 1965, what he called “lead-lag” was called “hunting.” Neither rigid nor semi-rigid main rotor systems have a flap hinge. Semi-rigid or see-saw system blades flap but at the fulcrum, the rotor hub or rotor head, which is hinged to the mast. The best known helicopter with a semi-rigid system is this Bell UH-1 “HUEY.” The example in the video is an articulated system, with the rotor head “fixed” to the mast, requiring flapping and hunting hinges for the rotor blades. A rigid system also has a fixed rotor head but no flapping or hunting hinges. On this system, flapping and hunting are accomplished by flexibility designed into the rotor blades.
The response to a stall in an airplane is to add power (among other things); the response to retreating blade stall in a helicopter is to reduce power (among a few other things).
hunt-drag are still used as terms for lead-lag. I've heard both used... I probably should have called out both as acceptable terminology in the video. Thanks for commenting and for sharing the observation about teeters.
Your video animations are awesome. I sense countless hours spent on this!
I am a retired helicopter flight instructor and I also used to teach heli aerodynamics. So here are a few comments on the aerody:
Although blade flapping can be the same mechanical movement as blade coning, it's important to separate the two. Coning angle depends on disc loading (weight and G-forces) and flapping angle depends on disc tilting. So where your animation is showing all blades 'flapping up', this can a bit confusing as you are actually showing coning. Flapping = Disc tilting
And maybe most important, unless you fly an autogyro or a CH 47 Chinook, the so-called Dissymmetry of Lift in forward flight is actually not controlled with blade flapping. As you correctly showed at the end of the video, a forward cyclic input is always required to check the undesired resulting flapback. You will need progressively more forward cyclic input to check flapback at faster speeds or the heli will slow down. So in the conventional heli, Dissymmetry of lift is controlled mostly through cyclic blade feathering. Maybe not what you are told in flight school, most books and most videos etc but such is life.
Another detail worth mentioning in your video is about blade 'flapping to equality' (which is what happens 'temporarily all the time' during both flapback, any variations in induced flow across the rotor disc and most importantly with any cyclic control input) I am guilty of teaching this theory in the past but it is NOT a variation in induced flow velocity that changes the angle of attack. Induced flow remains perpendicular to the disc as it tilts so induced flow velocity is not changed much. Instead it is a purely mechanical action that alters AoA. As the blade pitch remains fairly set, the blades flapping up and down with the same pitch angle will alter the AoA. So Flapping to Equality always results in disc tilting. Difficult to explain in theory but I reckon your animations would nail it!
cheers.
Awesome comment and thanks for the feedback! I hear you on flapping vs coning. It's the same mechanical degree of freedom and I did intend to convey the difference between the two motions. Also on flapping induced velocity vs induced flow... This is where simple drawings are more clear than the 3d animation. When I showed the blade sections, I should have showed both the induced flow (unchanging as you say) and the flapping induced component before showing the resultant normal vector. I thought about that, but didn't do it because the drawings would have been cluttered.
Thanks for the feedback... it will help me make future videos better.
Another aspect you could look at is the flapping removing the negative impacts of gyroscopic precession. Cierva who developed the flapping hinge for his autogiros commented that the flapping hinge was developed to solve the difference in lift between advancing and retreating. The blades had no cyclic control were fixed and used elevators and ailerons to control the aircraft the blades were a lift device and essentially anti-stall protection. Latter the full head was developed in the early 1930's for autogiros. At the time though he commented that the early experiments suffered from dis-symetry of lift issues and gyroscopic precession. This one hinge solved both. But agree the video needed to stop where you did. You have excellent explanations and having played with some CGI animation your animation skills are amazing too. I know how hard it is even on our simpler heads to explain things your model is amazing. Well done. If your interested in the history Sir Reginald Bree (Ceriva's test pilot) wrote a book on gyros in the 1930's that went into the head development (which was latter adopted by helicopters). The early gyros had fully articulated heads even jump heads with collective pitch control. th-cam.com/video/SMBe1nBAmN0/w-d-xo.html
There was a time in the 30's and 40's, when the early helicopters were in development, the autogyro was much more advanced and most would have predicted an autogyro future. If you're interested, look up the "Franklin Institute Meeting of 1938" and the Dorsey Logan act. The autogyro community campaigned for more military funding of this technology but at the last minute, the meeting changed to include all "rotating wing aircraft." No doubt many helicopter innovations cam about from autogyros. Thanks for the video link.
@@bzig4929 Yep the flapping hinge once you understand it is a wonderful thing. I used to fly in ultralights before I got into gyros. I remember having flown gyros for years getting offered a ride in the same ultralight I'd been trained in. We took off and the owner said want to fly it. You Bet! We hit a thermal under one wing and the ultralight kicked that wing up "You going to correct that?" he said "oh yeah" and I corrected then the other wing came up in another bump "You going to correct that?" he said again. I couldn't figure out why I was flying so badly and I actively flew for the rest of the flight but after landing and getting into my gyro I worked out I don't touch the controls in thermals (even though I don't even feel the small ones). Anyway I worked out it was the teeter hinge my blades can't tell if they have more lift from extra airspeed on the advancing side or from a thermal hitting on one side before the other. It just compensates and you don't have to do anything to you learn to fly passively. Gyros are more fixed free stable than helicopters but I realized why all rotary winged craft can handle the rough weather better than fixed wings and all with one hinge (on a twin bladed rotorcraft). Such an elegant solution. He (Cierva) apparently got the idea from stress relieving hinges on bridges which compensate for expansion and heat on metal bridges.
I will look up that meeting - I was aware of some of this and issues around patents around ww2 when Pitcan held many of the patents and the war engine allowed them to be walked over. He really got screwed over unfortunately. But I'm glad they contributed to the helicopter I like all aircraft - especially anything with rotary wings.
Your choice to not model the links between the collective/cyclic and the rotor system at this point is excellent. It avoids us getting distracted by trying to understand that complexity and focus just on what the controls do to the rotor system.
Really well done! I've only flown as a pax and 2x as intro right seat so don't know much other than these are amazing machines. As a heli-ski pax, I have to say, the pilots LOVED pitching down to gain a lot speed very quickly so they didn't seem to be too concerned about over-speeding.
When I was flying, I loved doing that also... lift to a hover on a mountain peak and cyclic forward to increase speed and also stay close to the terrain. Good times!
Пожалуй, наилучшее объяснение полета вертолета, что я видел! Спасибо!
Thanks for the nice comment!
As an ex Technical Instructor on Blackhawk I wish I had access to this animation when I was teaching. Great work.
I am helicopter mechanic and i have to say your vídeos are AWSOME and STUNNING!!👏🏼👏🏼👏🏼👏🏼
Just coming back to watch this a third time... Bought the heli in my mind, should probably learn how to fly it first... ❤ Great information, thank you for taking the time to explain this so completely. Guaranteed to be bored in class after watching your channel, you heartless bastard...
awesome comment! thanks
The hub moment is relieved when the fuselage (and shaft) tilt to follow the rotor which is dragging them along. Which means that the stick must return to near center in steady-state forward flight. Also, the forward movement of the rotor increases lift as it goes into cleaner air - so collective must be reduced as forward velocity increases.
Really well done. Helicopters are such an amazing invention with a lot of physics to be considered.
Brilliant video, thanks very much.
You did it again. A masterpiece video. Greetings from Brazil.
Thank you very much!
I saw various vids about these over the years but first time hearing coning angle, and it immediately makes sense why it's named as, nice vid!
thanks!
Brilliant explanation and illustration!
Thank you for a great video. Great animation, clear audio and very well explanations.
Awesome explanation !! ❤❤
As you add forward cyclic for gaining air speed, cyclic feathering also reduces on the advancing blade pitch and increases on the retreating blade - It's not just all flapping you have but it sure helps... Great animation
I’m glad someone else knows this. However I would take it one step further and argue that the advancing blade in constant speed forward flight is not flapping up at all. If you look at the path of a blade from the 6 o’clock position to the 12 o’clock position you will see that the blade is moving from a higher to lower position.
With the appropriate control input from the pilot, the dissymmetry of lift is cancelled by adjusting pitch cyclically.
If, as a majority of instructors teach, the flapping cancels out the dissymmetry of lift, then you wouldn’t get flap back as you accelerate.
@@tommyandmyf What's interesting is blades act like loose chains flapping up & down along the full span, Seen it in old high speed films Sikorsky Hughes and Bell tests
You can look them up - Cool stuff
@ yeah I’ve seen those videos. Very interesting. I still don’t agree with the very common teachings that “flapping cancels out the effects of dissymmetry of lift”.
@@tommyandmyf Hub flexibility the key flapping for removing mast moments on the air frame. hinges for lead lag & under slung to reduce conservation of energy effects from fatiguing the hub. Flapping is nice but not as important as cyclic feathering - The MBB 105 has a big pitch roll coupling in forward flight as you use collective... Very pronounced ... rigid rotor with only feathering bearings, Lots to learn
th-cam.com/video/fRp2uAYWa_A/w-d-xo.html
I Built this in 1995
If I fly, it's a fixed wing, even then, I prefer to be on the ground unless I can reach the yoke or stick.
I put too many R/C models of mine into the dirt to screw around, I have stick and rudder skills, and I don't crash anymore.
One glider I have has 500+ flights, it really helps to know how to control an aircraft, and fixed wing has so much less to go wrong.
Wow great videos. Deserves more views.
Again - another beautifully executed animation of helicopter aerodynamics.
this series will be a pandoras box to any helictoper training school & trainee pilot.
kudos
Thank you for the great videos! I look forward to the next entry in the series!
Wonderful instruction!
Amazing video and animations, highly highly appreciated
Outstanding video. Subscribed... gonna go watch the rest.. Looks like the coning angle is similar to the dihedral of an airplane wing, providing stability, flexing or "flapping" as the wing load increases or decreases.
Thank you for putting together these videos. Very informative and I learned quite a bit.
Awesome! I'm glad you got something out of them.
Thankyou for the Lovely video.. great help towards my test pilot preparation
I wished I had this series when I got my training in the Belgian Airforce in 1995 !
Awesome video Mr.
Thanks!
As an ex Airframe Tech, your vid tells more of what is occurring at the moment of lift, angle of rotation than anything provided in text books in my forty five years of experience, not saying I didn’t already know what was happening, but your explanation is very detailed and of high quality and explains it expertly. Well done!
thanks... I love hearing feedback like this!
Wonderful vid again. Amazing the engineering in a rotor head. I fly large RCs 700 size with 5-foot Dia rotor disc and I have a two blade and three blade 700. My favorite thing is take offs and landings. Can hold them in a perfect hover as well. If I had 15 million sitting around, I would own a Bell 429 or AS355.
if someone gave me a 429, out-right, I probably couldn't afford the operating costs :)
RC helicopters are amazing. It's hard to believe the same physics of flight apply to RC helos, doing 3d aerobatics, as applies to manned helicopters.
@@bzig4929 Absolutely true, the bigger the RC the more it behaves like a full size. The blade chop on my two blade is amazing, luv that sound, kinda like a Huey. It also autos nicely.
As for the operating costs on the 429, I heard to run a Sikorsky Sky Crane around 140k per hour!
@@rcas350pilot8Yes, and their pilots get insulted if you start asking silly questions like why wheels instead of skids and calling that beast a chopper.
Don’t ask me how I know!
(Skids are for kids, and don’t ever equate a Skycrane with a motorcycle.)
@@PetesGuide Got it Pete, name here is also Pete
Something that came to mind the other day, I don't think centrifugal forces are the only forces applied to the rotor hub. Considering that while flapping, a blade has angular momentum, as that blade turns, and the flapping hinge changes the plane of rotation, some of that rotation must be converted to a linear force.
Take this example: The advancing blade on the right has an upward flapping velocity. This is constrained by the flapping hinge. By the time that blade has rotated 90 degrees counter-clockwise, now at the forward blade position, all angular velocity from the right position is 90 degrees out of plane, meaning it is now applying a twisting force along the span of the blade. Constrained by the flapping hinge, this applies an additional linear force on the rotor hub.
I need to do another video about lead-lag. Lead-lag exists to correct the changes in angular momentum due to flapping. As the blade flaps up, the CG moves inward... making the blade want to advance. Because it can't, due to conservation of angular momentum, it leads forward. Then it lags aft when it flaps down.
@@bzig4929This explanation video will be cool. When writing the script, please take note that at least I am confused by your use of advance here. I would interpret that the same as leading, but that can’t be so, because you’re saying they are different.
@@bzig4929 Just a side note on why helicopters are far more expensive than fixed wing, per pound of payload capability. Each blade is continually flapping, AND lead/lagging, AND long axis twisting, for each single cycle of hub rotation. For a rotor speed of 324 rpm (+ 9% / -4%) for one model of light helicopter, so too are all the bearings hub and blade grip interface, constantly reversing at the same frequency. Obviously wear is far accelerated, and materials used must be top purity of hardness and/ or compliance. One axiom I've heard is: " A helicopter is a large collection of spare parts, all flying in formation, and wanting to fling themselves to pieces" 😱
The best damn helo pilot I've ever seen was a former Cobra pilot in Nam. In his middle age he flew AS315 Lama. I once saw him regularly hold a 100 foot long line with ballast ball and hook in high hover for 3-5 minutes at a pick, while pipeline handlers below were manipulating their choke cables. The ball was about 5 feet above their heads, and all that time never swayed more than 6" in radius. When he was signaled by the pipe handlers he gently lowered the hover by 7 feet, to ground the static braid and they hooked it up, and away he went. A true skyhook master. He had told me that he had "bent a bird", several years earlier. I did not ask him to elaborate, as his answer was terse. He had several 1000 hrs in Helos. Several years later, I asked his fueler guy what happened too him. FG said "He had another accident, some bearing had failed, but he wasn't hurt. However immediately retired, saying he wasn't going to risk a third time as that would be the end of him, and his mother needed him for home care." So that was that
Top knotch work !
Wonderful explanation
Thanks!
Great vid !!
I bet Leonardo Da Vinci would have been your prime subscriber back then 😉
That would be cool!
Very clear presentation.....
Great job
Will you be able to help a University to design a helicopter
great explanations! thx
Brilliant. Thank you!
How does rotor size and stiffness affect flapping? I have a radio controlled helicopter (T-Rex 600 with a 4 blade rotor head) and there is no flapping hinge at all, but the blades must flap to allow forward flight so I'm guessing most of the flapping occurs by the blades themselves flexing close to the blade roots (the blades are carbon fibre). There is also a rubber bushing in the blade grip but it is extremely hard and you can't see or feel any obvious movement if you try to pull on the blade grip in the axis the blades should flap. (Lead/lag is taken care of by the mounting bolt in the blade grip going through a bronze bushing in the blade root acting as a hinge, allowing the blades to lead/lag quite easily).
The flapping hinge can exist without the presence of a mechanical hinge. These are called "virtual" hinges that rely on bending to achieve the same result as a mechanical device. I'm guessing the vertical pin rubber bushing is the lead-lag degree of freedom. This only needs 1 or 2 degrees of motion.
I think you are correct that flapping is taken up entirely by bending of the blades. This would give a very high hinge offset which results in a very responsive (some say "twitchy" helicopter). Full-size helos with this arrangement (lynx and BO-105) usually have stability augmentation that lag-filters pilot input to take some of this responsiveness away from the pilot.
It doesn't surprise me that RC helos would have this control system... they are insanely responsive to control inputs!
@@bzig4929 No stability system in the MBB 105 only a mast moment gauge on bending forces
@@bzig4929 I don't understand the absolute need for the flapping motion for the helicopter to work. Why would a totally stiff blade without a flapping hinge not be able to make the whole helicopter tilt into the direction the pilot wants to go?
When there is a cyclic input even with 100% rigid blades (in terms of flapping), I don't see how it would not cause the whole helicopter to tilt (with precession of course)
@@bzig4929 Such 100% rigid helicopter might not be pleasant to fly if it was a full size one. But at least it should be able to respond to inputs.
RC helicopters used to be equipped with the additional "paddles" (the flybar) with complicated mechanical mixing into the main blades in order to make the helicopter more stable and counter unwanted movements. Also to amplify the forces of the servos. But today they just have very minimalistic rotorheads where the swashplate is directly linked to the blade grip. The blade grips sit on the same feathering shaft, so their only axis of freedom relative to each other is their blade pitch. It is all very rigid. Gyro controllers (flybarless systems) take care of the unwanted effects and dissymetries. But some people have also flown these without the gyro systems.
So I think that a helicopter without any flapping is still able to be flown, but just much more difficult to keep under control.
I wish you would make one video about the tail rotor of UH 60 as the axis is not at 90 degrees to the ground and there are elevators underneath, many people confused about that.
It's on the list!
@@bzig4929 Many thanks !
Your videos are very well-done, and I really appreciate the proper visuals to better understand helicopter aerodynamics.
What helicopter's rotor system is that from the video?
thanks!
🤘🏻🤘🏻🤘🏻🤘🏻🤘🏻🤘🏻🤘🏻🔥🔥🔥🔥🔥🔥🤘🏻🤘🏻🤘🏻🤘🏻🤘🏻🤘🏻🤘🏻 Excellent presentation! Subbed!
Thank you! I appreciate the sub.
Great video.
Brilliant!
Excellent and instructive video, you have earned a subscriber!!
I wanted to ask you, what do the blue, green, yellow and red rings on the pitch shift links mean? Thank you so much!!
Those are for the maintainers to identify the blades (and for me to identify which blade I'm looking at as I make changes to the animation). Here's a scenario... The pilots collect rotor track and balance data and then maintenance writes a work order to add tip weight to a particular rotor blade; they could identify this by blade srno, but it's much easier if the blades are colored to make it easier for the mechanic doing the work. Thanks for the question!
@@bzig4929 Thank you very much for your time and willingness to teach us.
Are you gonna do one on the tail rotor too?
I will. My next video will be on lead-lag of the main rotor, and i'd also like to do one on autorotation. But tail rotor control is a good topic.
@@bzig4929 thank you as former 60 crew chief I love the videos keep it up
Sehr gut gemachtes video. Liebe Grüße vom Aeroclub BEXBACH EDRX
Vielen Dank! Ich war schon viele mal in Stuttgart, aber noch nie in Bexbach. Fliegen Sie Sicher!
should tail rotor on right side or left side when main rotor is rotating counter clock-wise ?
It can be on either side, regardless of the main rotor rotation direction. The tail rotor is either a "pusher" or a "puller". Industry seems to favor mounting on the left side by a slight margin.
Muito instrutivo.
Great video! So, the tip path plane does play a significant role in the yaw movement of a tandem rotor helicopter, doesn't it?
It does! In tandem helicopters yaw is accomplished with alternating lateral cyclic input. To yaw left, for example, a left lateral cyclic input is sent to the front rotor, and a right lateral cyclic input is sent to the aft rotor. This is all done in a flight control mixing unit, so the pilot is doing this with the pedals.
I’ve always wondered about tgat
Another solid video! You mentioned at 8:49 that absent of flapping, the dissymmetry of lift would cause higher lift in the advancing side and cause the helicopter to ROLL. You later mention that retreating blade stall causes a loss of lift on the retreating blade causing the helicopter to PITCH up caused by phase delay.
Wouldn’t dissymmetry of lift also be subject to phase delay causing the helicopter to PITCH up? I also believe this action is the cause of Blow Back and what requires more forward stick input from the pilot. The amount of additional forward cyclic is proportional to the forward speed of the helicopter. This forward cyclic input in turn mechanically changes the pitch (less on advancing and more on retreating) of the blades and reduces (or eliminates) flapping due to dissymmetry of lift. (Pilot induced delta 3 hinge)
One more crazy phenomenon. More induced flow at the rear of the disk in forward flight causing a reduction in AOA and lift resulting in a ROLL to the advancing side.
Curious to hear your thoughts. I could very well have some (or all) of this wrong.
my thoughts... if there were no flapping hinge, the aircraft would roll due to FFDOL, but the flapping prevents this increased lift from ever happening. And you are correct... this is what leads to blowback of the rotor disk. Instead of a left roll, there is blowback due to FFDOL. But this doesn't cause the aircraft to pitch up... the rotor disk pitches up (blowback) but not the aircraft. The autogyro pioneers were the first to figure this out. I believe de la Cierva attempted a rigid rotor and only after seeing the controlability issues did he add the flapping hinge.
I can see why you say "a pilot induced delta 3." Delta 3 creates a natural coupling between flapping an feathering. So if the pilot changes feathering based on the blow back... I get the analogy.
It's interesting now that many are attempting to develop eVTOL aircraft without flapping hinges (like Joby, Archer, Beta) I understand, with side-by-side rotors, they won't see the issues de la Cievra saw on a single rotor autogyro, but all of those rolling moments have to go somewhere. If it isn't a control moment, it will be loads absorbed by the rotor masts and the airframe. I wonder if their flight test campaigns will point them to the same epiphany of Cievra.
I think your last point is talking about transverse flow and this is one of the many subjects I didn't cover in the video. I have a book written by Sikorsky (the company, not Igor) "Sikorsky Helicopter Flight Theory for Pilots and Mechanics" This book deals with these subjects much more completely that I can do in 10-15 minute videos. It would probably take 10 hours to cover the materiel in the same depth as a book. Hopefully these videos stimulate questions and thoughts that point viewers to other sources and more study.
Stay curious!
@@bzig4929 I truly appreciate the amount of effort you’ve put into this and the amount of knowledge you have on this subject. In my opinion, helicopters are one of the most fascinating mechanical things in the world!
I have a copy of Helicopter Theory by Wayne Johnson. I’ll have to pick up a copy of Sikorsky Helicopter Flight Theory for Pilots and Mechanics.
I still struggle to understand why the helicopter would roll due to FFDOL. I need to do some more research. If you want to pitch the rotor in any direction, you increase (or decrease) the lift 90 degrees (or whatever phase delay angle the system has) behind that intended direction. What scenario will a rotor tilt in the exact direction where the lift changes? That is where I am getting lost.
As far as blow back pitching the rotor and not the heli, I can see that being true for a semi rigid head but not a fully articulated head. Any pitching of the rotor on a fully articulated head will induce a moment on the helicopter due to the offset hinge. Full transparency here, I most definitely could be misunderstanding something here!
I too have thought a lot about these eVTOL aircraft. They make zero sense by the way. I can’t come up with a single scenario where they are successful. The blades must be subjected to significantly more stress than a helicopter blade due to their rigid design. It’s probably within the design envelope as traditional airplanes experience the same dissymmetry at high alpha with the descending blade having a higher angle of attack. The rolling moment gets thrown into the airframe and is balanced by the counter rotating blade on the other side of the fuselage. (At least that’s my theory)
I don’t mean to challenge you in any way. I respect your opinions greatly. Many beers could be drank discussing helicopter theory but I think most people would lose interest fairly quickly.
I look forward to your next video.
@@bzig4929 Compressibilty before retreating blade stall - You get a rough ride then at stall the helicopter will pitch up and roll to retreating blade side. - Seen test footage and data. Family was friends of Igor during the Los Angeles Airways days... Before I started flying...
Ia yes goods kreatip buat gearbox keren sir!!,.
Really love your stuff, I was wondering if you could discuss tail rotor flapping in another video? I've heard of it briefly but haven't looked too much into it. I'm wondering if it's even a thing.
Definitely! It may not be the next video, but I'll get to the trail rotor. I'm still trying to figure out if the 60 has delta-3 on the tail rotor flexbeams. It doesn't appear to, but I may be missing some detail.
is there flap damper
no. Flapping is naturally a heavily damped motion - aerodynamics provide all of the needed damping. I cover this in the video I did on the lead-lag DOF. Here is the link to that video... th-cam.com/video/5sLZcvagEbs/w-d-xo.html
@@bzig4929 thanks
its a uh60 blackhawk system
Yes! I spent a lot of time researching blackhawk data to come up to with the design. Thanks for noticing.
Is the coning angle different in any ways during autorotation? (Both practice and emergency if different)
Coning is mostly influenced by the weight of the aircraft. This can be the actual weight, or the weight due to g loading. An autorotation is a 1g maneuver so coning is about the same as any other 1g flight condition.
This is the first time I see this video, I just have only one question about this diagram, is the system from UH -60 helicopter?
Yes... I used public source technical data for the Sikorsky Blackhawk to create this model. I have a playlist with 6 videos showing how I modeled this and it also covers the technical reports used to define all of the design parameters.
The only thing I can’t get straight in my mind is how the advancing blade…If I understand right…will increase feather/pitch angle but will decrease angle of attack/lift….and just the opposite on the retreating blade. It seems like that would have the same affect as raising the collective and increasing lift? I need more coffee…
The blade doesn't change pitch/feather angle; that is constant unless the pilot moves the controls. The blade on the right side sees more airflow, so it makes more lift and flaps up. The upward flapping essentially reduces the normal (not tangential) component of velocity seen by the blades. The angle of the relative air changes, but not the angle of the blade. It's easier to explain standing in front of you and flapping my arms up and down. But it's a good question and I need to improve the graphics and the words to make it more clear. Thanks!
Is the Sikorsky Shake caused by tip stall?
I'm not really sure what "Sikorsky shake" is. All helicopters have vibration modes. But I think most pilots don't experience tip stall because they stay withing the limits on the aircraft. Sikorsky seems to take pride in high Vne aircraft so I think this would be especially true for that product line.
Tip stall, in aircraft with hydraulics, is often not felt by the pilot until it gets pretty bad. I flew CH46s and that aircraft had an indicator... They put strain gauges on the control links at the rotor and fed that into a gauge for the pilots to show tip stall approaching.
@@bzig4929 I’ve only heard Sikorsky Shake a few times over the years, but my recollection is that several pilots described it as a common trait with all Sikorsky helicopters, and that the company even had to add a vibration damping system into their rotor systems. But a quick Google doesn’t find more than a couple of references. But Google can’t find a lot of things it used to.
Maybe the dynamics of the Vertol twin rotors is different enough the dynamics are different?
@@bzig4929 Also, maybe I misremembered, and it’s the Sikorsky Shimmy not the Sikorsky Shake.
Sikorsky Shuffle. It’s a feature, not a bug.
So, the 3 motions are feathering, dragging and flapping.
Yes. I called it "lead-lag," but "hunt-drag" is also accepted terminology.
@@bzig4929 Thanks a lot ！
I'm confused. What's a Helicopter? :) Great video great animation.
4K would be very cool, if you can.
I may try that for a short. I'm processing the videos in davinci resolve... I think that can do 4k.
The resuloution coming out of the animation software may also be limiting, but it will be fun to try.
here's an unlisted clip that I did in 4k. let me know of you think it looks any different. To me, it's about the same as my other videos, so the limitation is the rendered clips coming from the animation s/w. I suppose it makes sense that processing low-res clips in 4k is still low res. th-cam.com/video/pPkUydVIXiI/w-d-xo.htmlsi=AYRGYJGx9SVa-4MT
@@bzig4929 That 4K one definitely looks better, by a quite a noticeable margin on my 48" 4K OLED. Small details on the blades and tail rotor drive shaft are very much enhanced compared to a similar scene in the original at 1:50, for example. And on the later hub close-up too. It would be best to render at 4K high quality first, of course, but whatever you did worked for me at least. Your animation is so nice it's a shame to hide it!
I now understand that I should have gone into rotor engineering
If the blades were hard mounted, during control changes, they would snap off.
Im so high right now i dont know how i got here😂
Why is no one really can see what the Wright Brothers notice and let them know why it was possible to fly!!!
Okay…..got it.
Ain't getting in a helicopter 😅
All I know is that if you lose the spinning thing on the top of the helicopter, your helicopter will land immediately with lots of gravitational force😢
this is true. Thank goodness that doesn't happen that often.
all of that is very complex mechanically - lots of parts to fail
Yes! But we can be comfortable knowing that humanity has gotten good at designing highly-reliable, safety-critical and complex systems.
If you peel back the skin of cars, helicopters, airplanes and escalators you'll see things that scare you and make you realize how many times, during an average day, we trust out lives to people we don't know and never see.
Thanks for watching!
I was lost at flap..................
Ohhh Very simple
Helicopters don't fly, they beat the air into submission!
Hah , never knew that about helicopters , stalling at high speed.
What's your major man ? Big brain stuff hurts my brain
As a conclusion: helicopters are not able to fly.
Check out Harry Reasoner's quote on helicopter pilots
Pretty much the worst machines in the world.
Air ambulances are saving lives everyday.
do for Gyros
Excellent! Thank you!