Helicopter Rotor Lead-Lag

[@ofdlttwo]

Just want to say, thank you so much for sharing your knowledge for free. You content is/are the "shoulders" for people to continue to build on.

[@bzig4929]

I appreciate that!

[@ColinDH12345]

Exceptional quality. Well done and thank you for taking the time.

[@royshashibrock3990]

Other commenters have said essentially the same thing as I will say: this is an exceptionally clear and concise video that is well made. There is no BS, just straight ahead information that is easy to understand. Where an explanation of the underlying principles is needed, it is given. Bravo.

[@bzig4929]

Thanks!

[@quantum3472]

I have a helicopter dynamics final in a few days, you explained all these topics in a much more understandable and concise way than the senile professor did over the course of a semester! Well done :)

[@tomthetank8036]

Got my rotorcraft exam tomorrow and wish i found this channel sooner, the to the point explanations plus animations explain it 10 times better than a monotone lecturer in a quarter of the time. Cheers mate

[@bzig4929]

that's awesome to hear. I hope the exam went well!

[@mxcollin95]

Awesome modeling and explanation! 👍

[@rollamichael]

OMG, best thing ever, "if you're not committed to a full length vid, here's the answer". Every KZbinr and TikToker should do this, imo.

[@bzig4929]

Yup. Twitter was the start of the downfall for all of us... If I don't understand in the first 30 seconds I'm swiping 🙂

[@rollamichael]

@@bzig4929 Some people spend 10x more time on a topic than needed and some spend that time and never get to the point at all. So your "here's the answer" upfront was perfect and I still watched until the end.

[@fanBladeOne]

If only you published this video whilst I was in college, I would have known what I was talking about. Great animations!

[@KostasMakris_aircraft_engineer]

Excellent work. Thank you

[@19Borneo67]

Stripping away all the covering gives a stark view of how small the driving parts of the engine are compared to the driven rotors. Wind driving wind. The importance of the right size and shape rotors for the flow regimes is also shown. Also shows the size of the different metal components relative to the structural demand on them. Ignoring temperature requirements and specialized materials for that, it's still an incredible sizing problem to get all those blades the right size and shape to extract/impart the momentum on them that you want while meeting the structural demands on them. Incredible.

[@mr.stratholm4999]

YES! Please cover the tail rotor and auto rotation! I want to know these things!

[@bzig4929]

will do!

[@lafarms]

Very understandable. Thank you.

[@nicksharp7972]

As a fixed wing pilot trying to understand all the sky blender witch magic, I've loved your videos. It would be amazing if you could make additional videos on teetering rotor systems vs fully articulated, and the aerodynamics of autorotation. Your videos explain things in a way I understand easily and my apologies if these subjects were covered in a video I missed.

[@bzig4929]

yes! I plan to do a teetering rotor in the future. Thanks for the comment.

[@Darrylx444]

A mast bump failure animation / discussion would be interesting. PS: thanks for the 4K!

[@bzig4929]

The 4k wasn't as bad is I thought it would be. My render time went from 10 sec/frame to about 30-45 sec/frame. (At 30 frames/sec). Of course, I start the render and let it cook... So even though it triples the time it doesn't really impact my time. That was a good suggestion. Thanks!

[@fanBladeOne]

fact

[@pilot3016]

Amazing! Good work on your part!

[@ariaYThandle]

Yes! A new one!

[@DumbledoreMcCracken]

I laughed; I cried; it was the best story ever!

[@JAIPALCHAUHAN1]

Nicely explained

[@nothinghere1996]

Isn't physics amazing. Great tutorial. thx. ❤

[@PetesGuide]

5:15 Awesome as usual! Why does autorotation cause lead to behave differently? Is it simply the lack of engine input to the rotor shaft? Does this lead change happen identically when in forward autorotation flight and at the final hover?

[@bzig4929]

During normal flight, the blade is at a high angle of attack so there is a lot of drag. With autorotation, the whole idea is that you reduce the angle of attack so much that the drag is no longer pulling the blade opposite the rotation; drag pulls the blade forward. It's this forward tilt of the blade lift vector (reversal of the drag) that creates the condition to allow autorotation. So instead of pulling the blade, back, into a lag position, it pulls the blade, forward, into a lead position. (by back and forward, I mean relative to the direction of rotation and not relative to the nose of the aircraft). I think it was you that had a comment about differentiating between lead-lag and rotation... I hope I addressed that in this video. Thanks!

[@PetesGuide]

@@bzig4929 This clarifies a few things, and confuses me on another. My aha moment is the reduction of drag-it sounds like this is equivalent to feathering the prop on a dead engine (in terms of necessary for safe outcome, not that the rotor is feathered WRT the direction of travel). The bit that confuses me above is how does negative drag happen? Why wouldn’t the blade simply be in the neutral lag position? And I’ve never heard anyone else describe this in so much detail; I recommend expanding on that and the fact that this is what allows autorotation. This feels fundamental and complex. Some on-screen vectors might help the explanation. Glad you’re finding my comments helpful!

[@19Borneo67]

@@PetesGuide Autorotation happens like this: In the middle of the disk, the upflow drives the rotor because the collective is down enough that the lift vector is inclined enough that the horizontal component will drive the rotation. However in the outer part of the disk, the blade is moving faster, and the relative wind is more horizontal, providing more vertical lift. The inner part of the disk is driving the outer part - the inner part is the "motor," the outer part is the "rotor."

[@ExecuteBrandon]

Skater did expend energy to tuck hands in. The rotational energy increased, but the angular momentum remained the same.

[@mouldy9466]

Can you go more in depth how 2 bladed helicopters get away with not including lead-lag degree of freedom in their rotor hub and are you ever going to go over more unusual helicopter systems like servo-flap rotors and tip jet rotor configurations?

[@bzig4929]

I can, but I have to build a two-blade teeter in CAD first. I plan to do that, but it may be awhile.

[@andrerousseau5730]

Great video, excellent graphics. Could you do one delving into gyrocopter 2-blade vs multi-bladed rotor design. The little Focke-Achgelis 330-A 3-blader would make for a good design study.

[@bzig4929]

That's a cool machine! I'm working on a video on helicopter tail rotors and this includes an explanation of the pitch-flap coupling motion that's normally found on tail rotor blades. Looking at the images on the 330-A it appears to incorporate pitch-flap coupling (also called delta-3) motion in the main rotor. I'm going to see if I can find more tech info on that design. Thanks for the suggestion.

[@buditarigangersang3692]

Wou ide kreativ !!

[@ducembarr7057]

Man this awesome, I hope God's of algorithms bless you with millions of views, but I would buy a beer if you create a patrion or subscription of some kind. This is a ton of work you put in

[@bzig4929]

It's a lot of work, but... it's fun and I enjoy it. I keep doing it for these kinds of comments! Thank you.

[@fr3ddyfr3sh]

Does the lead-lag damper contain two opposing springs/elastomers to center (between lead and lag) the blade? Or is centering done by the centrifugal force? PS: Thanks for this excellent educational video.

[@bzig4929]

there is no centering mechanism. The dampers are just dampers... not spring-dampers. It's just the CF loads. Great questions.

[@sadeghsafarzadeh4728]

❤❤❤❤❤👏👏👏🙏

[@kusanagi533d]

Can you cover blade stall causes and effects.

[@bzig4929]

check out this video... kzbin.info/www/bejne/Z4GbZaWCnKdkbas I go over the region of reversed flow and retreating blade stall

[@PetesGuide]

Have you seen the news about the medivac 206 that crashed in Kentucky? ATP pilot with 17,000 hours flew into a 1.5-inch diameter guy wire holding up a bright red and white radio tower, at about 5pm while landing in a large sports field to pick up a cardiac patient. (Source: NTSB on-scene briefing and one other video showing location on Google earth) This crash isn’t strictly your bailiwick, but I’m wondering if you’ve thought about explaining the dynamics involved in related things, like wire cutters on the front of helicopters, or sensing systems for wires? Like what are the speed ranges and wire sizes in which those devices work? Surely they work on telephone lines, but surely they are iffy for high tension lines? What happens to the rotor system and airframe when they are used successfully? Inspected and returned to flight or scrapped?

[@bzig4929]

I only heard about it after reading your message here. I looked on pprune and read the posts and news article there.

[@bzig4929]

I know that helicopter air ambulance are required to have HTAWS and those systems are very effective for terrain and towers. I believe they also warn against power lines... But I'm not entirely sure. Even if they do I can imagine they database for power lines isn't as robust as towers

[@PetesGuide]

@@bzig4929 Awesome. I didn’t know about HTAWS or the mandate that started in 2017. I was familiar with the existence (prototype?) of a system that detected the EMF from power lines, and that it was useful for lines that didn’t have markers on them, but I’m not sure if that was ever commercially available. As usual, I’m learning a bunch from you.

[@PetesGuide]

KZbin somehow unsubscribed me from your channel. You should query others to see if anyone else had the problem. Also, searching for bzig shows only videos, not your channel. I’m not sure if there are any channel settings that might fix this.

[@bzig4929]

That's good to know. I've also been unsubscribed from channels. I'll look at my setting to see if there's something I can do. Thanks!

[@a_li12fathar87]

Yes auto rotation. I will see it so dangerous.

[@wedgie502]

i don't know much about two-bladed rotor systems in full-scale application, but in R/C, I tend to leave my main rotors just a tad loose at the blade grip so they can lead/lag a little bit. this helps to negate low frequency vibration and smooth out my flight. I don't know if my rotor system is behaving like your excellent animation, but it's definitely not hurting my aircraft performance. of course, my rotor system also turns at least 10x faster than full-scale and my model responds a lot quicker to subtle changes than a full-scale would. great videos and explanations of the systems. a suggested topic for future videos, bell/hiller mixing.

[@bzig4929]

That's really cool insight. The amount of lead lag is small... Even smaller with low offset, so it makes sense that "just a bit loose at the hub" is effective.