Transverse Flow Effect in Helicopters

Helicopter Lessons In 10 Minutes or Less

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Welcome back to Helicopters Lessons in 10 Minutes or Less!
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This episode explains Transverse Flow Effect. By definition, this is the difference in lift, drag, and induced flow that exists between the forward half and aft half of the rotor system between 10 to 20 knots of airspeed. This is due to the fact that airflow is more horizontal over the front half and more vertical over the rear half of the rotor disk. The more horizontal air flow over the front half will produce a larger angle of attack and therefore more lift. The reverse is true for the aft portion of the rotor system which has a decreased angle of attack due to more downward airflow (induced flow).
Due to Gyroscopic Precession (explained in my video here: • Gyroscopic Precession ... ) the difference in angle of attack is manifested 90° later as a right rolling motion. Pilots also experience slight vibration's due to unequal drag between the front and rear side of the river system. Less experienced pilots who are unfamiliar with the concept of transverse flow may notice themselves constantly drifting to the right on takeoffs and landings. By understanding this aerodynamic phenomenon, pilots can adjust for it. During the 10 to 20 knots of transverse flow airspeed the corrective action for the pilot is to apply left cyclic to compensate for the right roll.
Thanks again for watching! Please like the video if you enjoyed it as well as leave a comment to let me know what you think.
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

Опубликовано:

9 июн 2017

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Комментарии : 131

@33protoman 3 года назад

I know you made these videos three years ago but I just started my pilot school last week. I'm going through all your video goes one by one and I just wanted to let you know they're very helpful and I appreciate the effort you put into them. Hopefully someday you'll look back and see this comment on old videos.

@OculusQuestFun 2 года назад

I'm willing to bet he sees the comments. Even if you don't get a reply. Especially now that's he's back to making videos again.

@jakeshumway9487 5 дней назад

In school right now and these videos are a life saver

@michaelr.moodysr.7525 4 года назад

At the 2:00 minute mark you misspoke concerning the horizontal flow on the forward half of the disc and the vertical flow on the aft half of the disc. You said the flow was horizontal on both halves of the disc. I know this is a little picky but might throw a newbie for a loop. I knew what you meant. Great series on helio basics. I really appreciate you taking the time an effort in producing these videos. I'm 77 years old and starting basic helicopter training on 10/27/2019. Currently Commercial MEI

@shibainuhodler7255 4 года назад

Time traveler!

@johntyrone307 7 лет назад

Another good video....suggestion....use colored markers for air flow, etc.

@robertcawley3044 3 года назад

Yeah my thoughts exactly

@marcelodorio1 5 лет назад

many explanations online, yours is one of the best ones. Thanks!!

@PankajKumar-km1ui 3 года назад

These videos are really helping..Helps a pilot understand the basic fundamentals of flying better.

@reissessions 17 дней назад

Thank you so much. Currently in common core and this helps so much.

@karzem1 4 года назад

After watching 2 or 3 of your videos, I push the like button now before the end of introduction

@Hockeysktr17 6 лет назад

Thanks for these videos! Super helpful to explain concepts more clearly as I read the "helicopter flying handbook".

@paranoiahax 5 лет назад

I read about this in the TC but the way you explained it helps me understand it better. Thanks 🤙🏼

@hamer4261 6 лет назад

Thx for video, that I was looking for! GJ!

@LJayasuriya 5 лет назад

Thanks for those valuable videos. Those are very helpful!!!

@207pilot 6 лет назад

great teaching, very articulated and clear with your explanations, congratulations

@elelyon555 6 лет назад

Thanks so much explaining, so much better than the books! 👍🏼👏

@cques123 7 лет назад

Very good explanation Jacob. Your videos are great!

@ryu1940 2 месяца назад

I love your videos. I fly the Hip in DCS but I always send your videos to those in my discord trying to learn helicopters in DCS for the first time because there’s so much too it and you break it down in great digestible sizes. Thank you!

@m.c.musgrove2298 4 года назад

You are AUSOME!! Thank you for your Informative videos!

@danielkliewer1323 5 лет назад

Thanks for doing all this, new rotor pilot and this really helps..

@cadetcadet1814 6 лет назад

You are seriously a life saver!! Thank you for making it easier to understand, the drawings are the key for me. ** I agree with John, different color markers would help

@sudapolt1624 6 лет назад

You're a godsend. Thank you.

@m.n.9496 5 лет назад

This is so much better than the book!

@ryanbeech6917 Год назад

I go to SUU doing the rotor program and I swear these videos are absolute gold brother

@Tsmace33 8 месяцев назад

Thank you for your videos

@skateparkpvorg Год назад

yes the Apache flights at the start are cool - tanks for all the great lessons.

@LockheedHav 6 лет назад

Nice video, Jacob!

@gs550t81 2 года назад

I know I'm late to the show but these videos are amazing!!!! I know there are newer videos but didnt want to leave a comment on every video lol. Keep it up!!!! Currently working towards my private and ifr at the same time..... this video is funny to me bc I struggled with this at first and I had no idea what it was..... this is an excellent video and I'm glad you made this. Please keep doing what you are doing. Once I get my cfi cert i want to make videos like yours. I feel there is a huge lack of free knowledge out there for people looking to get there helicopter cert. And I love that you do what you do and I can not wait to contribute. Ground knowledge is so important yet so much more difficult than the actual flying itself. Again, Thank you. Keep it up and hopefully one day soon I'll be able to contribute and help other aspiring pilots to become knowledgeable, safe, and competent pilots!!!!

@crawford323 4 года назад

You know so much and you are a great teacher with all the respect and honor which that word brings. I am a fixed wing pilot however my greatest joy is Gyroplanes. It is a growing aspect of aviation which has been in the shadows and misunderstood perhaps even maligned by certainly the fixed wing world but perhaps by those pilots who would not be flying without the efforts of Juan de la Cierva and Harold Pitcairn. I and others would be delighted for you to explore and teach us the airflow of autorotation and other aspects gyroplane operation.

@joemattress6177 3 года назад

Excellent!! Thank you.

@La_Pucelle_dOrleans 2 года назад

These are helpful, i’m sure these will help me on the SIFT

@Kakoa102 4 года назад

Great video, thank you

@mariojorgepiresdasilva9956 3 года назад

Good vídeo ! Thanks ! 👏🏾👏🏾👏🏾🚁

@charifnouaoura1170 8 месяцев назад

Hello! I'd like to express my appreciation for your helicopter video. It's a topic closely related to my PhD research. Your content is quite informative, and I find it valuable. To make it even better, I suggest including more details about wind forces "direction" and the helicopter's movement in your video or accompanying materials. This would provide viewers with a more comprehensive understanding of the subject. Keep up the good work, and I look forward to more insightful content from you!

@youngmairnes 3 года назад

Your video are awesome, fellow soldier here learning to fly helicopter.

@waynejones3428 6 лет назад

Good job. 🚁

@ryanmobley863 6 лет назад

Great explanations! I am studying for the Army SIFT. This is really helpful.

@paranoiahax 5 лет назад

Ryan Mobley how did you do?

@freeeagle2295 5 лет назад

We want more videos. Thanks 👍🏼

@skipwood2059 3 года назад

Jacob, if you could slow your verbal present just a bit, you would be right on. colored markers would be a plus. Keep up the great work.

@kristiandunn6612 6 лет назад

Cool video! I'm an R22 pilot and I never seem to notice the TFE, but definitely notice ETL. Good stuff, look forward to checking out more of these videos.

@helicopterlessonsin10minut10 6 лет назад

Kristian Dunn. Not everyone notices. But it's more noticeable in helicopters with wheels during a rolling takeoff. Thanks for the feedback!

@diegoplata5570 Год назад

great instructor

@ChopperKool 3 года назад

Very good video! You really help me out to improve in my way to teach! And also with my English, cause it's my second lenguage.

@fridayfrankr1099 3 года назад

Thanks for taking time to make these videos. I am currently taking flight classes myself. This does help a lot. I do have a question about the introductory music you have at the beginning of this video. Did you make it yourself or did you download it from somewhere? I'd like to use it in a video of my own if okay.

@shibainuhodler7255 4 года назад

Subscribed. Thanks for the videos. I guess you are a 64 guy with all the intro videos. I used to be a 64 Mechanic before flight school. Thanks for the videos! Keeping my RL3 Brain from having to read aerodynamics all day to refresh. Now if only you could make using an E6B as simple as the rest of these topics, I might actually look like a halfway decent aviator :P.

@kalamantea 2 года назад

thank you for that, it is my exam later and this helped greatly.

@AH-64E 4 года назад

I just ended my ground school you were so helpful thank you very much

@bcrane2010 2 года назад

SUPER helpful. I'm taking the SIFT next week and have reread this portion so many in the helicopter handbook and this helped me in 1 view

@jaceboix1461 5 месяцев назад

I'm about to take the sift. If you see this comment, how did it go?

@bcrane2010 5 месяцев назад

@jaceboix1461 not as hard as I expected. Don't panic if you don't get through all the questions.. I studied for a month and got a 65 (I already have a fixed wing pilot license so I had a bit of advantage)

@jaceboix1461 5 месяцев назад

Oh nice, thanks.@@bcrane2010

@christopherpeters5916 2 месяца назад

Thank you Jacob

@noahpfeifer6931 6 месяцев назад

Good video, helped me to understand this effect! Although it is reversed for me, as I fly the Cabri G2 which has a cklockwise turning rotor.

@RamadiTaxiDriver60M 3 года назад

10 times better than the Fort Rucker classes...

@sriccharon4398 5 лет назад

Your explanation is really good... I have a doubt of what happens after that 20 knots

@jaraelhicks 3 года назад

I have been studying for the SIFT for about the last month. I have been in the Marine Corps Reserves for about 13 years now and am attempting to join the National Gaurd and Fly. Your videos have been extremely helpful and have helped build my confidence.

@helicopterlessonsin10minut10 3 года назад

Great to hear! Be sure to recommend any video topics you’re interested in and I’ll try to work those into the production mix.

@jaraelhicks 3 года назад

@@helicopterlessonsin10minut10 i Def will. Thank you

@ArjitRaj 4 года назад

Beautiful video. May you please tell the reason why the flow is horizontal at front and more vertical at aft?

@jjinyourlife 6 лет назад

Hi Jacob, thanks for the video, but I'm a bit confused by why the induced flow is more perpendicular to the rotor at the rear part? Thank you

@mariotadeu1190 Год назад

muito bom

@theredkitechannel3194 9 месяцев назад

I fly gyroplanes in addition to helicopters. Would you mind doing a video on how transverse flow effect, and translating tendency for that matter, work on a rotor system in an autorotative state?

@ChristopherKellum 4 года назад

Thanks for the videos! I am taking my SIFT tomorrow Morning and these have been a great help in learning about helicopters

@ChristopherKellum 4 года назад

Update: Passed the SIFT definitely crushed the aviation section due to these videos!

@edwarddjorgensen4848 4 года назад

Christopher Kellum got any tips? Taking it in a few days.

@Gofornification 3 года назад

@@edwarddjorgensen4848 any surprise ?'s i should study for?

@edwarddjorgensen4848 3 года назад

Valak just take as many practice tests as possible, study math to calc 1. Got a 64 was frustrating but its doable.

@edwarddjorgensen4848 3 года назад

Aaron Rubinstein all of them

@SkyBaum 2 года назад

Thank you Jacob #HLI10OL 😎

@blake8ism 2 года назад

Why couldn't this Helicopter I bought just say this????Sheesh....great video!

@leyhuezeyhur1440 5 лет назад

Keep up these kinds of drawings and you'll be recruited for the next Steve on Blue's Clues

@helicopterlessonsin10minut10 5 лет назад

Haha! That’s ultimately my goal here. Let’s be honest.

@leyhuezeyhur1440 5 лет назад

@@helicopterlessonsin10minut10 It's good to have aspirations. Go from Apache driver to detective with an animated partner. Natural progression.

@javierg2290 Год назад

Can you please do limits and EPs for the Lakota?

@davidwallace5738 6 лет назад

Hi Jacob! What about the effects of blow back on the right roll tendency. Thanks for your time and effort. Great job !

@helicopterlessonsin10minut10 6 лет назад

David Wallace. Although the initial onset of Blowback takes place at roughly the same time as Transverse Flow Effect, Blowback is actually caused by the flapping up of the advancing blade as the helicopter compensates for Dissymmetry of Lift. As the advancing blade flaps up, Gyroscopic Precession causes this to manifest 90 degrees later as a pitching up of the nose. I explain how how all these forces affect the takeoff in more detail in my video Aerodynamics of a Takeoff (ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-23iUG7Wttz0.html). Thanks for watching!

@davidwallace5738 6 лет назад

Helicopter Lessons In 10 Minutes or Less Ok sir, and thank you for your prompt reply. Fly safe !

@jacklathey5223 4 года назад

Hey, can someone please explain why this becomes less effective past 20kts? Is it due to the induced flow now being lower across the whole disc due to our higher airspeed?

@realvanman 3 года назад

Then there is also the greater lift on the right side than the left side due to relative wind, causing the nose to pitch up? So is the combined effect a pitch up and roll to the right?

@ashutoshbhakuni303 4 года назад

In the compensation for dissymetry of lift video you said at about 1.00 that the dissymetry will cause a left roll, and there you didnt consider the 90deg advancement effect due to precession which would cause a pitching up motion instead of left roll as you said). There I was wondering why you did that. In this video you have done it. I am confused.

@shubhamsingh-km2cv 5 лет назад

A video, explanation on vibration control system tha active & passive

@jeffreylebowski4927 Год назад

If a larger angle of attack and lift in the front of the blade manifests 90 degrees later, then why isnt the same thing true for the collectiv inputs??? - Collective is doing the same thing of changing the angle of attack so the cyclic should be 90 degree off set, so in order to pitch forward I would have to increase lift on the left side so it will manifest in the back 90 after... (in a ccw rotating system)... ???????????

@swanoflove6833 2 года назад

I do have a question, does the way the helicopter rolls depend on the direction of the rotor? some helicopters rotors spin counter clockwise, some spin clockwise, depending on which direction it spins, could that make you roll left instead? and also, if so, then which way do either direction roll? does clockwise roll right, or left? im just wondering :o Im not even sure if this has anything to do with the rolling at all - ,w, -

@sebastianfhughes6534 4 года назад

Wish I had these videos when I learnt to fly

@Aviator168 2 года назад

Will the rotor rotation direction have a directional effect on the transverse flow effect?

@kylefort7761 6 лет назад

Would it be possible to see a video of helicopter component like the parts of an engine or maybe like the parts of a rotor system or maybe even like the sections of the aircraft?

@helicopterlessonsin10minut10 6 лет назад

Kyle Fort. I could see about adding basic engine and other system theory of operation videos. However I'm not at liberty to address specifics of the Apache. I'll see what I can do.

@kylefort7761 6 лет назад

Okay that would be great! Thank You!!

@sunilraiKVT 3 года назад

Why have you stopped making more videos on Helicopter Concepts ?.. Plz Continue the good Work

@helicopterlessonsin10minut10 3 года назад

Is there a specific topic you’d like to see?

@QonCalculations 3 года назад

Could you explain how the angle of attack is less on the back of the disc and more on the front of the disc in the case of transverse flow effect?

@helicopterlessonsin10minut10 3 года назад

It’s all based on more induced flow on the rear half compared to the front. Check out my Airflow at a Hover video to show how induced flow affects lift. It should answer your question fairly well.

@null2470 2 года назад

So this would be encountered right before ETL flight, correct?

@gehadqaki 4 года назад

I don't understand why the angle of the downwash would change if the rotor disk is all tilted at one single angle. Wouldn't the air more from horizontal to vertical at the same angle on the entire rotor disk, with the only difference being that the change in angle will occur later at the aft portion of the helicopter? (AKA the air hits the front before it hits the back, but the change in the angle of flow would still be the same.) What exactly is causing the air to dive more vertically at the aft portion of the helicopter compared to the front?

@helicopterlessonsin10minut10 4 года назад

Great question. The air over the aft portion of the disk has had more time to be influenced by downwash. At the front of the disk it’s clean, undisturbed air. But the further back you go, the air has had more time to be influenced and changed by downward flowing air.

@andrewmoran9161 6 лет назад

Would this effect be the same if the rotor disk was rotating in the opposite direction? For ex. Counterclockwise vs. clockwise rotation of the rotor blades... thanks, great videos!!

@helicopterlessonsin10minut10 6 лет назад

Andrew Moran. It would be reversed because Gyroscopic Precession always translates 90 degrees later in the plane of rotation. The increase in lift from the front half would rotate around to the right of the disk and cause a left roll for a counterclockwise rotor system. Thanks for the question!

@Hillcapper1 6 лет назад

Andrew Moran Good question!

@andrewmoran9161 6 лет назад

Helicopter Lessons In 10 Minutes or Less ahhh i see. Makes sense. Thanks again

@yunsongli6384 6 лет назад

I think the lift is equal on the rotor disc, the reason helicopter roll to the right is rotor disc tilts to the right due to flapping.If I am wrong,please tell me.

@helicopterlessonsin10minut10 6 лет назад

Yunsong Li. I'd have to disagree. During 10-20 knots there is a substantial difference in airflow on the front half and rear half of the rotor disk. This is the case even despite flapping. Because of gyroscopic Precession, this manifests as a right roll / drift when transitioning through these air speeds.

@tmanf22 5 лет назад

Is the front half getting a more horizantal airflow and the back half less due to cyclic feathering? I think of a disk and it being a flat plane, tilted it still exposes the surface of the disk at the same angle to the airflow. So the only thing I can think of is the due to coning and feathering the aft half is not in the same flat plane across the disk. Yay or Nay?

@helicopterlessonsin10minut10 5 лет назад

T Phillips. The rear half is more vertical because there is more time/distance for induced flow to be pronounced. The airflow starts fairly horizontal and is pulled downwards through the disk as the helicopter moves forward. By the time the air gets to the back half of the disk the velocity of air is no longer horizontal. It's not a product of cyclic feathering but a product of change in Resultant Relative Wind on the airfoil as a result of increased induced flow. I hope this helps answer your question.

@timothyparker9889 7 лет назад

Perhaps I'm misunderstanding some concepts but my understanding is that a smaller AOA increases the lift. So, there is more lift from the aft rotors due to a smaller AOA than in the front. Induced flow and lift drops towards zero in the front of the rotor system and increases in the rear and causes AOA in the front to increase and decrease in the back. Wouldn't the increase in vertical, downward airflow explained around 2:00 cause more lift in the rear rotors? Could anyone explain where I'm becoming confused?

@helicopterlessonsin10minut10 7 лет назад

Thanks for the comment timothy. I believe the confusion comes from your understanding of Angle of Attack. This angle is an arrow dynamic angle that forms between the Chord Line and the Resultant Relative Wind. This gets into the basics of how airfoils create lift using Bernoulli's principle, the Venturi effect, and Newtons 3 laws (which I plan on discussing in a later video). Simply put, is airflow is accelerated faster over the top of the airfoil than the bottom, a low-pressure area forms above the airfoil. This pressure differential combined with the action-reaction of the downwards deflection of air "lifts" the airfoil up. Therefore, the greater the Angle of Attack (a.k.a. the more pronounced effect these forces have), the greater the Lift. When you have a more vertical, downward airflow with no change to Angle of Incidence, your Angle of Attack will be reduced because of the greater Induced Flow. The reason the Angle of Attack is reduced is because the downward flow of air adjusts the Resultant Relative Wind (the wind that results from the Rotational Relative Wind and all upflow/downflow velocities). Simply put, less Angle of Attack means less lift on that specific portion of the airfoil.

@MrEngineer_ 3 года назад

It would be awesome to understand if you had a rc helicopter along with your paper ...anyway nice!!

@aolson8283 3 года назад

Looks like FARP West!

@Wolfhound_81 3 года назад

I think I found another error (next to the Horizontal/Horizontal one at 2:00 that Michael pointed out) at 5:10 - As you say correctly, he loses that right roll when he's decelerating on the approach. But this time, it would lead to him banking left and he has to correct with right roll. Or am I mixing up something? :)

@Wolfhound_81 3 года назад

Btw missed to point out the obvious: Your videos are the best resource around to simply link to ppl not understanding heli aerodynamics.

@generalx5220 3 года назад

I don't get it, one blade is going into the wind, the other blade is swinging back and away from the incoming wind. So.... Ones losing lift the other is too much lift.?

@jamesberlo4298 6 лет назад

The left Cylcic to compensate is for counter clockwise Rotor , right?

@helicopterlessonsin10minut10 6 лет назад

James Berlo. That's correct.

@ffmedic12 5 лет назад

How does the right roll associated with TFE differ from Dysymmetry of lift?

@helicopterlessonsin10minut10 5 лет назад

Transverse flow effect causes a right roll whereas Dissymmetry of Lift causing the nose to pitch up.

@majidkamiyab6731 4 года назад

what is the difference between this effect and dissymmetry of lift

@helicopterlessonsin10minut10 4 года назад

It’s all put together in my video titled Aerodynamics of a Takeoff. It shows how transverse flow, dissymmetry of lift, and effective translational lift all interact.

@juliosilvestre9416 3 года назад

Could you explain de Vmin at H60? Tks

@helicopterlessonsin10minut10 3 года назад

I’ll add Vmin to the list. Short answer is that a helicopter could be operating at max gross weight or environmentally limited to the point where it can’t hover. But if it can roll down a runway for a takeoff it can still fly as long as it stays above VMin which is the minimum airspeed to maintain flight.

@juliosilvestre9416 2 года назад

can you indicate a query source for these terms?? I flew the French line and I don't know some of them. thank you so much as532svr@me.com

@pamir87 6 лет назад

would be great if you would use different colors to draw

@helicopterlessonsin10minut10 6 лет назад

Alijon Boynazarov. I appreciate the feedback. I'll take note of that for future videos.

@stevejh69 2 года назад

It is NOT Rotational Wind. Wind is the Horizontal Motion of air. Helicopters still fly with NO wind. It is Rotational Airflow!

@nizarmohammedhabibhissain5698 3 года назад

You know I watch your videos since 2018 and didn't be a tension that I didn't do subscribe to your channel hhhhhh sorry dod

@supercobrapro7470 3 года назад

Jesus Loving Christ! Heloz are more complicated than i thought 😟😟

@robhaylock7742 4 года назад

Yet another wrong diagram. The disc isn't flat. The rotors are coning up, and when this is tilted forward to fly, the front blade receives air that is more horizontal, and the rear blade receives more vertical (induced flow) air. Simple diagrams might help some people, but they perpetuate disinformation.