Dissymmetry of Lift in Helicopters
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- Опубліковано 2 чер 2017
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This is the first video in a series I'll be continuously working to develop. My goal is to take topics associated with flying helicopters , one by one, and teach them in a format that's easy to grasp. That said, I want to make videos that are clear enough to explain a subject, but also brief enough to not get too bogged down in all the little details.
The subject in this video is dissymmetry of lift. As defined in the FAA's Rotorcraft Handbook, dissymmetry of lift is, "When the helicopter moves through the air, the relative airflow through the main rotor disc is different on the advancing side than on the retreating side. The relative wind encountered by the advancing blade is increased by the forward speed of the helicopter, while the relative wind speed acting on the retreating blade is reduced by the helicopter’s forward airspeed. Therefore, as a result of the relative wind speed, the advancing blade side of the rotor disc produces more lift than the retreating blade side." In the video I use a simple diagram with a blade tip speed of 300 knots and a forward airspeed of 100 knots to illustrate this principle. As the advancing blade moves forward in its plane of rotation, it's relative wind is 400 knots (300+100). The retreating blade is moving away from from the relative wind which results in a relative speed of 200 knots (300-100). This difference in speed results in a difference in lift. As the name implies, there is "dis" "symmetry" in the lift of the rotor system. This occurs in any direction of flight (foreword, sideward, and rearward) and can even occur in hover flight if sufficient wind creates an advancing and retreating blade.
I hope you enjoyed the video! Thanks for watching!
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If you're just getting started and want more information, pictures, and more explanations, I'd recommend reading the Rotorcraft Flying Handbook - amzn.to/2ifPlnZ
If you've already got a basic understanding, and want to further your professional helicopter education with advanced helicopter concepts, I'd recommend reading Cyclic and Collective, by Shawn Coyle - amzn.to/2ifQGLx
2,000 hour fixed wing guy getting commercial rotor this week, thanks for all your videos. Been training with multiple guys from the 160th and we all love your content.
The "thumbs down" people must be drone "pilots". Great job and I hope you keep the videos coming. They're helping lots of people such as myself get through training.
Please do a video on the SIFT! Maybe talk about your experience. Any help would be great.
Thanks for taking the time to create these videos. They are a huge help!
Just watched your first video. Excellent job! You simplified the subject and made it easy to understand. I look forward to going through the rest of your series. I hope you make some others for more topics in the helicopter world.
You are awesome, THANKYOU! I have been wanting to take chopper lessons but wasn't sure if I would understand it too well. The hands on side of things I know I would have no problem with but the theory of these aircraft kinda baffles me until I found this channel... you are a god send so thankyou and keep em coming please.
Amazing explanation!, I got any idea that I did not understand in ground class from these videos. Thank you so much!
So simple and straightforward, very easy to understand, thank you!
🙂
Wonderful illustrations.
You remind me of my best instructors.
Cheers!
Thank you for making and sharing these videos. They have been a great help in earning my commercial certificate and furthering my knowledge.
Thank you, a very clear and concise lesson
I failed to mention that you are doing a great job!
This has been SSOOO helpful. I’m currently studying fo the SIFT. Thank you!
Utilizing this content for DCS and the Apache! Heli have always been a love of mine, more like the bird watching kind. Recently though I’ve found an interest in the actual flight of.
Thank you for all the work you put into these videos. I passed my pvt check ride this summer using a lot of knowledge I learned from the lessons you provide.
Zolvot. That's great!
Advancing blade ( more blade pitch +)is always in the direction of travel & the retreating blade (less blade pitch-) is in the opposite of directional travel. Didnt know ya was an US Army helo pilot! I wanted to fly helos for the US Navy but there was no way i was gonnuh pass military colledge for the OTC, so i became a jet engine mech. At least i was still in Naval aviation. Thankya sir. . . . .a "fellow warrior", for your service, sacrifice, faithfulness, & dedication to our nation!!!🇺🇲🇺🇲🇺🇲🇺🇲🇺🇲🇺🇲🇺🇲🇺🇲🇺🇲SALUTE!!!💪💪💪
Brilliant, keep them coming!
I'm gonna watch every single video you have posted so far, I've seen some of them and I really like them, I hope I can become a Helicopter pilot someday. 🚁🚁❤️
Thx for your service 👍
Excellent job 👍👏👌🙏
Jacob thank you for posting these. Currently working on my CFI down in Florida 😃 Using these to reinforce some concepts. Thanks again brother! #SkyBaum
Just wanted to say thank you for these videos! They literally got me through flight school. Any chance you could do some videos on Aeromed such as visual illusions?
good video. Thanks!
currently at Fort Rucker learning the mike. Great review thx
I'm glad you enjoyed it! Good luck in your course.
Thank you for your videos! useful !
Thanks Crystal Clear
Mate, you are a hell of a great instructor/teacher, amazing!!!
Good vídeo 👍🏾🚁
well explained thank you.
This is good stuff! I’m at Rucker now and these videos are great.
Adelson Militao I report I. August for WOCS, what phase of school are you in?
@@spaceman152E what all did you study for your sift? I’ve been watching these videos along with books, any help?
@@timmymullray5470 the SIFT prep guide at clothing and sales helped a good bit. I knew my math and science sucked, so I studied that more than anything. Don’t over stress about SIFT tho, I would recommend studying for three weeks tops in the subjects you aren’t good at, then send it. Set goals and keep to them or you’ll end up like me and get accepted five years after I originally wanted to fly. Still flying and got the aircraft I wanted (Apache), but I could have been doing this long ago
@@spaceman152E thank you so much! I appreciate it! I’m currently an 11b at bragg and my packet is due in July, so I’m hoping all goes well with the sift at the end of this month. Definitely ready to expand my career and get out of infantry lol
@@timmymullray5470 any updates with your progress?
So helpful! Thank you :)
Welcome
Nice Channel! :)
Great work, just one comment; you mentioned that the lift on the advancing side would be double due to the velocity of the advancing blade being double that of the retreating blade.
It would, in theory, be 4 times the lift. L = CL.1\2.p.V2.S
also any other channels or videos you or anyone would recommend. subbed to you too by the way
This is amazing! I’m reading the faa handbook and going through a sift study guide to prep for my sift hopefully in a couple of months. I’m so glad I found this channel!!! Thank you! One question though. What kind of issues does dissymmetry of lift cause that a pilot needs to be aware of while moving. I.e. does finesse of balance become a factor? Or are there instruments built in to counteract dissymmetry I’d lift?
I believe the angle of attack of the airfoils increases where the lift is lacking automatically.
The Fuselage starts to roll to the left, even though in articulated rotors blade flapping does compensate somewhat, but what is happening is the blade at the 9 o'clock position is reaching the same speed as the airspeed of the aircraft, so there is no lift at all... As speed increases, so does the stall area as illustrated. Once, coming n going speeds match-up, all forces cancel out, n you have no lift on the left side, hence, the helicopter rolls to the left. Just slowing down will get you back in trim...
So this was made a long time ago and I really hope you're still monitoring this channel. I'm really confused. You said the advancing blade is moving into a 100 knot wind moving at 300 knots. I understand that. The next part is where I'm stuck. If the advancing blade is moving INTO the wind, wouldn't that slow it down, and the retreating blade is essentially being pushed by the wind, so shouldn't that speed it up?
I can grasp the overall concept of what you're explaining as far as how the differential forces causes the rotor disc, and therefore the helicopter itself, to move through the air. The numbers are what I'm getting hung up on though
The blade would slow down if you didn’t have an engine pushing it into the air maintaining a specific RPM. If the same RPM is always maintained, pushing the helicopter forward would therefore cause more airspeed on the advancing blade (rotational speed plus forward movement).
THANKS SOOOOOOOO MUCH!!!!!!
Thank you
I love your videos and I am learning a lot through them, but I believe that if you double the speed the lift should be 4 times greater. See Lift = 0.5*density*speed(squared)*lift-coeff.*surface. You could maybe make a note on the video about this. I don't know much about helicopters as I study airplanes. I could be wrong. Keep posting vids!
Tiziano Buzzigoli. Great point and you're absolutely right. I plan on going more in depth on this in a future video covering the lift equation. Thanks for the feedback!
Thank you! We're teaching one another ;)
Hello! I am so glad I found your channel! I am hoping to study and get ready to take the SIFT test soon! Was wondering if you do any classes on live or something?
He has some helpful videos on what was on the SIFT. What helped me best were buying the practice books.
Excellent explanation, thanks so much, could you explain the retracting blade stall and compressibility?? That’s two topic are broking my brain
Guasave camacho montoya. Sure thing. I'll add it to the list.
Love your apache videos, what I hope to fly when I get to flight school! Are you still an IP at Rucker? I report there in August
Jacob, excellent videos. You are wonderful teacher!!!
I wondering if you can recommend aerodynamic books, or manuals.
Thanks!!
David Escobar. Thanks! I just recently my own aerodynamics study book. Here are the links (iBooks: itunes.apple.com/us/book/id1446961574)(Kobo: www.kobo.com/us/en/ebook/helicopter-fundamentals-booklet). I also recommend checking out the Rotorcraft Flying Handbook - (amzn.to/2ifPlnZ) and Cyclic and Collective, by Shawn Coyle - (amzn.to/2ifQGLx). These should get you in the right direction.
In relation to dissymmetry of lift, certain helicopters have the ability to lead and lag (aka hunt) to better equalize lift along with blade flapping and cyclic feathering, would I be right to assume that the leading and lagging of blades works to equalize lift. The advancing side lags while the retreating side leads in order to equalize lift.
Thanks, and I appreciate your videos good material to watch to refresh knowledge of aerodynamics
DGXJ94. Leading and lagging are ways rotor systems can better absorb Coriolis forces but do not equalize lift. As the blades flap up and down, Conservation of Angular Momentum causes them to speed up and slow down. In fully articulated rotor systems these forces can be absorbed by lead-lag dampeners. In other rotor systems the blades must absorb the stress of these forces. My video Types of Rotor Systems (ua-cam.com/video/7gM3rMDpJt4/v-deo.html) explains this in a bit more detail. I'm also in the process of making a video to explain Coriolis forces as well. I hope this helps!
Hi Jacob, any plans for creating videos on the technical side of Helicopters, I am doing my CPL subjects and struggling with the technical side, thing such as Hydraulics, electrical systems and engines
Good morning, I liked your video, but I would like to know if this can help in the DCS simulator?
thanks
I have a quick question about the video. Why do we add the speed to the advancing blade since it’s heading into the wind. I would think it would be opposite because of the drag caused by the relative wind. You used the “hand out the window” example that has me confused. Seems that your hand would go slower against the wind than with it. Am I completely wrong? Or is the number giving just dealing with lift?
TuckTuckonTwitch. The advancing blade speeds up because it flaps upwards. This causes the center of mass to shift inward and the blade to accelerate. I explain how this occurs in greater detail in my video Conservation of Angular Momentum (ua-cam.com/video/KObbd5mvn54/v-deo.html).
When you factor in gyroscopic precession, wont that make the helicopter move to the right based on having the advancing blades at the rear, which would equal more lift on the right side of the blades and less lift on the left side since the retreating blades are at the front.
Shamar Younge. The advancing blade would be on the right side of the rotor disk in a counter-clockwise rotating rotor system traveling forward. The retreating on the left. That said, the blades flap and feather to compensate for this Dissymmetry of Lift. When factoring in gyroscopic precession, the input to make the helicopter go forward in flight would be an increase in pitch at the 9 o'clock position. This would manifest 90 degrees later as an increase in pitch at the 6 o'clock position. By having more lift at the aft portion of the disk, a forward motion is created. I explain it more in my Gyroscopic Precession (ua-cam.com/video/MH1emIx5Ubs/v-deo.html) and Compensation for Dissymmetry of Lift videos (ua-cam.com/video/culBbvszRpk/v-deo.html). I hope this helps answer your question. Thanks for the feedback!
Isn’t the flapping blade supposed to counteract the dissymetry of lift? Does it factor in airspeed, the direction of travel vis-à-vis where the nose of aircraft is pointed and wind direction or does it always assume no wind and forward travel at an average airspeed, leaving the pilot to sort out all the details?
muito bom
Thanks for the great video! I've just began with watching your channel in order to have several questions answered I have with rotorcraft aerodynamics. You are doing a great job with your explanations!
However, to this one specifically I have some remarks: The speed of a rotor is not measured in knots nor any linear unit of measurement such as mph, km/h or m/sec as that would provide misleading information. The speed of a rotor is measured, as any rotation, in angular velocity of ° per second which can be translated into a linear speed, dependent at which distance from the rotation center the measurement is taken. E.g. the rotor of an Agusta AW109 has a diameter of 10.83m, which translates to a circumference of 34.02m. At 100% rotor speed with for that aircraft standard 380rpm, this translates to a velocity in air of roughly 775 km/h or 419 knots, but only at the rotor tips. At e.g. 1m from the rotor center, the linear velocity would translate to Pi x distance from center (=1, so Pi) x 380(RPM) x 60 (minutes) to 71.63 km/h or 38.68 knots (divided by 1.852).
This actually has some implications, because whereas lift increases in a linear manor from the center to the outside (ideally, with a perfectly twisted rotor blade), the forward velocity in your example remains constant through the whole length of the blade. This however should influence the grade of compensation through flapping and feathering as you described it in your compensation video. Additionally, my figures as presented above, indicate that at the example speed of 100 knots, the rotor will actually have no lift at all on the inside quarter of the retracting side, as the rotation speed vector there is overcompensated by the velocity vector so the inner quarter of the rotor disc in that area has no laminar air current at all, resulting in no lift. This effect should also result in increasing dissymmetry with increasing aircraft speed. So, as far as I understand it, at maximum cruise speed of the AW109 of 158 knots, this effect will be even larger, leading to roughly half the rotor blade producing no lift on the retracting side of the disc perpendicular to the movement of the aircraft.
Is that so or am I missing something? And how does the aforementioned compensation by flapping and feathering work with increasing speeds and thus increasing dissymmetry?
😂😂😂 - Now I feel stupid! I wish I had watched your video 'Dissymmetry of lift - Expanded' before I wrote my comment. - All explained there!
Thank you, when the advancing blade speeds up it increases the linear flow, would that decrease or increase the AOA on that blade causing it to flap up?
Ashley Koenig. When the advancing blade flaps up, it speeds up due to Coriolis force/ Conservation of Angular Momentum. This, in essence, creates an increase in induced flow velocity which decreases angle of attack in the blade.
Great video but as a newbie wanting to take his first lesson, what does this mean to the pilot? Do you need to compensate while flying for this difference in lift?
No, Mike. The aircraft compensates on its own by the rotors also moving in the vertical plane. This motion is called flapping. Flapping will cause minor side effects that we do have to compensate for though - blowback, retreating blade stall, etc.
I understand that in Forward flight the retreiving blade produces less lift than the advancing blade.
But is this disssymetry also subject to gyroscopic precession? (So, Does the dissymetry cause the helicopter to tilt backward somewhat instead of tending to "roll" to the right) ?
Can you give us tip for the sift test
I just started seriously studying the Army Sift study guide about a week ago, have been referring to your videos off and on so far and they have been helpful. I am curious if the Army Sift Study guide is good enough in tandem with your videos for the actual sift test itself and to move further on to the actual school, or if there is any other reading material you would suggest to further help.
I would go through those guides and take practice tests as much as possible until you can breeze through the exam quickly and accurately.
is there like any specific order i should watch these or does it not matter, learning for SIFT
Hi, this is off topic to the video but why will the blade increase pitch if you let go of the collective? I would think due to aerodynamic twisting that the pitch would decrease..... thank you.
That 300kts, is that in the middle of the radius or at the rim of the rotor? (The center moves slower)
When are you going to do a video about induce flow and talk about the retreating blade stall. Also, have you made more than the six viedos that are currently posted in UA-cam?
penman62. I recently moved and plan on making more videos as soon as I set up a work space. I do have intentions to cover both of those topics. Thanks for the feedback!
Still being recommended at Cairns
Jacob, I am a CFI-IA and very interested in adding on helicopter ratings. I also instructed various subjects while in the Army, and I appreciate your style and the conciseness of your presentations.
I understand the way you have shown how the relative wind effects the advancing and retreating blades. My question is, and you may already cover it in subsequent videos. Assume the helicopter is in forward flight at 100 kts IAS, resulting in a relative wind of 100 kts. As a blade is directly over the tail boom, the effect of dissymmetry of lift would be nil. As the blade continues to rotate into the advancing blade region wouldn't the effective advancing blade lift be negligible and increase the farther the blade travels into the region, reaching its peak effect at 90 degrees to the mast. After that point, doesn't the additional lift generated by the advancing blade begin to decrease, until reaching the point where the blade is exactly parallel to the relative wind? At the point where the blade becomes the retreating blade then the opposite effects would be in play?
Fred C Rogge Sr. I’m not quite sure I understand what you are asking. At the nose and tail, there isn’t much of a dissymmetry to lift. But on the advancing and retreating sides there is due to the relative wind combined with the rotational velocity in the blades. The reason the advancing blade produces more lift (if left uncompensated) is because the airflow over that side has been increased. And with everything else constant in the lift equation, this increase in speed results in increased lift. This occurs anywhere the blade has increased airflow relative to the disk which encompasses the entire advancing side. As the blade gets close to the nose, the relative wind is decreases because the velocity of perpendicular to the airfoil. Then, as the blade retreats away, the relative wind of the airfoil would be the rotational velocity minus the forward velocity. With all things constant in the lift equation, this reduction in speed results in less lift produced. If this dissymmetry in lift was left uncompensated for, the helicopter couldn’t maintain directional flight. I hope this helps answer your question. Also try checking out my videos “Dissymmetry if Lift - Expanded” and “Compensation for Dissymmetry it Lift.”
@@helicopterlessonsin10minut10 Thanks for the quick reply Jacob. Yes, you did answer my question. As I thought, when the blades are at the 12 & 6 o'clock positions there is very little, if any dissymmetry to lift. As the rear blade rotates to the 5 o'clock position it begins to develop additional lift. As the blade continues to move towards the 3 o'clock position the dissymmetry to lift increases to its maximum amount. Then as the blade moves forward, passing through the 2 & 1 o'clock positions that lift diminishes to the point when the blade reaches the 12 o'clock position the dissymmetry to lift is again almost non-existent. (The opposite effects would occure to the retreating blade.) I did watch the two videos you mentioned, and they both helped to clear this up for me. Great videos - I look forward to watching all of them.
I have a question regarding the helicopter situation you are describing as the helicopter in a field who wants to slide to the right. As you say, the advancing side of the rotation gain more lift and in this situation it was the lower half of the plane of rotation. If that side gains more lift, due to the gyroscopic precession it should be the right side of the plane of rotation which moves the helicopter to the right. Am i correct?
To slide right you need more lift on the left side of the rotor disk. This input has to be made 90 degrees prior. So the pitch increase happens over the nose to manifest over the left side in a counter clockwise rotating rotor system.
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I didn't understand why I need to understand this concept.
Is this changed at all with coaxial rotors?
Can you explaim dissymetry of during hover?
You will not sliding left or right because the gyroscopic precession. You will tilt foward or backward.
Just a quick question. I'm just confused about the one thing - if you're travelling forward at 300 kts and you're going against the wind which is 100 kts why is the wind speeding you up on the advancing side? I would have thought it would be the opposite and slow you down to 200 on the right and speed you up to 400 on the left in this example.
Helo standing still. Rotor spins at 300 rpm. Rotor speed at center = 0 whereas rotor speed at rotor tip is 300 knots all the way around, even at standstill. Now imagine the helo flying forward at 100 knots. Relative wind speed at tip: advancing tip moving forward at max 400 knots into relative wind ; retreating tip moving "forward" relative to the wind which is following it, so retreating tip speed is reduced by 100 knots , ergo 200 knots relative to the "wind" produced by forward speed. Dissymetry is to the square of the airspeed, so an order of magnitude different lift between forward and treating blades when at 90 degrees to the longitudinal axis of the helo AKA relative wind. It is hard to grasp at first, till you have a "lightbulb" moment.
@@PatPrice123 Thank you! Ya, my boyfriend is a private pilot single engine so he's been trying to explain some of this stuff to me because I'm in a weird scenario - I'm studying to be an AME and I was signed up to start getting flight hours for both helicopter and fixed wing but I had to postpone all of it because Covid mask + glasses = flying blind (for me at least) so I'm having this huge disadvantage of not having any context.
Anyone got tips for the sift ? I’m studying and just want some additional tips and tricks and things I should focus on
The sift study guides are a great resource. You can take the practice tests inside the study guides.
Is there no dissymmetry in a no wind hover?
I just learned about Gyroscopic Precession and question about it comes to my mind. Isn't it suppose to make helicopter pitch up if it generates more lift at 3 o'clock position of rotor ?According to gyroscopic precession, effect of increased lift shows up after rotor travels 90 degree. but the truth is, as you mentioned, helicopter goes left roll. What am i misunderstanding?
For dissymmetry of lift, the advancing blade creates more lift which manifests as a pitching up of the nose. You must apply forward cyclic to continue accelerating forward.
why is the advancing blade and retreating blade are on the sides of the helicopter? wouldn't it be forward of the helicopter? and retreating would be on the rearward side?
Skye Fuego. This is because "advancing" and "retreating" terms are referring to the blade's position as it moves into and away from the relative winds. The advancing blade on the right side is moving towards or advancing into the Relative Wind when in forward flight. The reverse is true for the retreating blade.
Helicopter Lessons In 10 Minutes or Less makes much more sense. thank you!
Please give a brief on helicopter coriols effect
Check out my video on Conservation of Angular Momentum. It has a thorough breakdown of the Coriolis effect.
It's way more than double the lift. speed is a square term in th lift equation
What is rate dampening? Always confuses me.
Could you recommend a good study guide for the SIFT test?
Fred Costello. I'm currently working on a SIFT prep videos series that should have its first video out soon. But in the meantime check out amzn.to/2STLnPw.
3:47 wouldn't it be quadruple the lift since it's double the speed?
Asgbdhj. You're right. I didn't catch that when making that first video.
Hey there, I’m trying to join through the WOFT program and I’m hoping these videos will help with the SIFT test. Do you have any advice for me?
Austin Taylor. I'm getting a lot of people asking this question so I'm considering starting an entire SIFT prep series. But for now I'd recommend going through all of the study guides you can no continue to learn as much about helicopters as you can.
Helicopter Lessons In 10 Minutes or Less that would be awesome! I’m currently going over the FAA rotorcraft flying handbook. Thank you as well for your swift response! I’m going to go watch all your vids once I finish the book.
Getting ready for the SIFT, do you have any advice?
Tony La. Read the Rotorcraft Flying Handbook (amzn.to/2ifPlnZ) to understand the Helicopter questions (watch these videos also). From there make sure you study a SIFT prep book for the rest.
Does the effect of dissymmetry of lift get affected by gyroscopic precession ?
It does. Check out my Aerodynamics of a Takeoff video where it merges all the fundamentals.
You've covered the math nicely but you must take it to the application.
What does the helicopter do? Having more lift in one area and less in another causes the helicopter to do what?
How does the pilot anticipate and compensate for the effect?
When you teach THAT you'll be an instructor pilot. Until then, you're good at math and regurgitating.
(p.s. I'm not an instructor pilot. Just a retired army aviator who barely squeaked by the oral exam.)
How do you schedule a flight physical
Recruiter should have locations for the nearst surgeon's office.
Do you provide any tutoring services outside of these videos?
Not at this time but I am considering it.
I failed the sift. Want to take it again. I stink at teaching myself. Do you tutor? Aside from videos. Like a one on one thing or like a group thing. Just curious!
Unfortunately no. I still work full time in the Army training pilots everyday and make videos on the side. That combined with a family leaves me with little time leftover. Which modules of the SIFT gave you the most trouble if you don’t mind me asking? I recently made SIFT prep videos to try to open up communication between people who have recently taken the test to give feedback to help others.
@@helicopterlessonsin10minut10 well unfortunately the test results do not show what section you struggled in (I'm sure you are aware) but I'm very certain it was on the actually avionics portion. I didn't study hard enough and went into it with a cocky attitude, that's my fault. Just hard to really focus on this stuff with no prior knowledge. A side question for you as well, I've flown in a helicopter and I got motion sickness. And I get it somewhat easy...I've talked to pilots that say I'll get use to it and that being in control changes things drastically...is that actually true tho? I hate to say it, but I almost don't want to give becoming a pilot a try just because if I got to school and get sick all the time, that'd be a waste of the army's time and money.
You’ll have to wait 6 months before taking it again. I’d recommend try to get in a plane or helicopter again to see how you do and study aviation topics. See if it’s for you or not based that flight and the retest.
@@helicopterlessonsin10minut10 I appreciate you taking time to make these videos and responding to comments!
Please, more volume
I’m a new student 40 hours
For real estate use
What do I need ?
Can you clarify the question?
Hey Jacob, I have a personal question where can I message you ?
Thee Best. You can reach me at 10minhelicopter@gmail.com
ring seems a bit tight
Sir what does disymmetry of lift do?
Archana Singhal. Dissymmetry of lift does not necessarily “do” anything. It is an aerodynamic principle that exists in rotary wing flight. It is unique to helicopters/gyrocopters and doesn’t exist in planes. It is the reason for unequal amounts of lift created between the advancing and retreating blades of a helicopter. It has to be compensated for in order to maintain continued, controlled flight. Does this help answer your question?
Helicopter Lessons In 10 Minutes or Less
Hi Jacob,
Congrats on the great work.
As you have explained, the dissymetry of lift causes the relative rotational velocity of the air to increase at advancing side and decrease at retreating side, which in turn increases the AOA on advancing side and decreases at the retreating side. If that is true then this change in angle of attack will have a difference in lift after 90 degrees due to phase lag (gyroscopic precision) and that is the reason for flap back. Please let me know if my understanding is correct.
4 times the lift* 1/2 ρ v^2
Not sure what European helicopters turn clockwise, I’ve only ever seen them turn anti clockwise.
Thanks for the video! But it's "asymmetry", not dissymmetry which doesn't exist.
Hello i am working on a final year project related to aerospace. I need some guidance from you would you please contact me ?
What can I help you with?
@@helicopterlessonsin10minut10 i am congused in some terms. I am working on the design of hybrid vstol drone which would be atonomous and i am confused in the the selection of wing arrangement.
I’m not sure if I’d be much help due to never working with/on drones.
Am I the only one that wonders why the Blades PICK UP speed while travelling into a wind and LOOSE speed when the wind is at the Blades back?
Charles, the blade does not “pick up speed”. The blade is moving at a constant speed. He is talking about the speed of the air flowing across the blade. The blade is rotating at 300 knots constantly for this example. If you fly 100 knots forward you would have the additional amount of air flowing over the advancing blade.
I figured that out watching the video a few more times. But thanks for giving me that info. It all helps!!
Not bad ! Fairly well.
But…. If you are going to teach a lesson. Teach it all. No mention of RB reaching its critical angle of attack or Vne. What caused it? How to recognize it ? Recovery?
All needs to be in the same lesson.
Causes. - could be one or combo of:
H igh FwdAirspeed.
H igh DA
H igh gross weight.
L ow rotor rpm.
S teep or abrupt turns.
T urbulence.
Indications:
Unusual vibrations.
Nose pitches up
Roll to retreating side.
Recovery.
Lower collective.
Aft cyclic.
RPM in green
Minimize maneuvers.
I appreciate the feedback. Most of that content is covered in subsequent videos. Each concept is taken piece by piece without overloading new and aspiring pilots with too much information.
Do you have Instagram?