Dynamic Rollover in Helicopters - Part 1

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This video is Part 1 of 2 covering Dynamic Rollover in helicopters. Dynamic Rollover is defined as the point at which a helicopter will roll over despite pilot inputs. Before jumping into dynamic Rollover, however, its best to understand static rollover first. Static Rollover is the point where any object rolls over from a stationary or static position. This can be anything from a table to a chair to a car or even a helicopter. Any object with a center of gravity (CG) above the ground can statically rollover. All this requires is a pivot point and to exceed the critical angle. The pivot point is just a point where an object has made contact with the ground and can then pivot from that point. The critical angle determines which direction an object will fall or rotate. In the first example I demonstrate how a table will fall either left or right depending on which side of the pivot point the CG is over. This same concept applies to a helicopter in a static condition.
If you were to tip a helicopter over just like a table, there would be a point where the helicopter would fall over on its side despite not having any more force being applied on it. That's the point where the critical angle is exceeded. Now if the helicopter were to be moving it would no longer be in a static position. It would be dynamic. Thus it would be subject to dynamic rollover due to its momentum creating a rolling motion once a pivot point was encountered. This rolling motion reduces its critical angle and makes it easier for a helicopter to roll over. This is due to Newton's law of motion stating that an object in motion will continue to stay in motion. The momentum of the helicopter translates into a rolling motion when a pivot point is introduced. This reduces the critical angle and instead of rolling over at say 15 degrees, now it may only take 5-10 degrees of roll angle to make the helicopter tip over on its side.
This wraps up the first video. Make sure to check out Part 2 ( • Dynamic Rollover in He... ) to see causes, physical and human factors, as well as avoidance of Dynamic Rollover
As always, safe flying!
If you enjoyed the video or have any questions or comments, hit the like button and comment below.
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

[@imachavel]

Wow your videos are better than I could ever comprehend trying to make. But at 4:50 you say Newton's 3rd law is "an object in motion tends to stay in motion." Well by that principle I'm going to say that Newton's first law is "for every action there is an equal and opposite reaction." See what I did there? 😊

[@suresh1957]

Brilliant ! The fact that you explained static rollover first greatly improved my ability to understand dynamic rollover. Thanks for a very lucid explanation. Cheers Suresh France

[@imachavel]

Don't forget something. A dynamic roll over means the blades are spinning. The helicopter is in a dynamic state. A static rollover means that the helicopter is completely still. A lot of people like to describe a dynamic rollover is you are trying to hover and one of the skids get stuck on something and instead of lowering the collective and immediately bringing the helicopter back into the ground you trying to pull up on the collective with the correlator putting more power into the rotors which if you're already starting to tip the helicopter over will just put more power into the energy of that state. Hence Dynamic rollover. And yet a lot of people would say if the engine quits on you and you're in a hover and you roll the throttle into the over travel spring and you put a little bit of right pedal to stop the yacht to the left because of the sudden loss of anti torque can you pull up on the collective prior to contacting the ground to cushion The Landing but somehow you inadvertently land on a slope and tip the helicopter over that because the engine is off it is a static rollover. Well the blades are still spinning so it's not a static rollover. The only way it's a static roll over is if the helicopters on the ground and you're inside it and you haven't started the engine you haven't waited for the starter motor on light to go out you haven't engaged the clutch the blades are not spinning in a hurricane comes along and just blows the helicopter over and it rolls over on the ground that would be called static roll over. Although a lot of people like to try to apply that a dynamic rollover would be if the engine is on in the bladed are spinning but the throttle is rolled off into the over travel spring the engine is decoupled the transmission is no longer powering energy and therefore RPMs to the blades and the helicopter rolls over. But if the blades are still spinning and they're still energy and RPMs in the blades than it's still dynamic. I guess no one really tries to prepare for a terrible static rollover event when you get in a helicopter you're more worried about the dynamic problems with all the kinetic energy. But you know whatever just to be technical about it

[@suresh1957]

Thanks for the explanations !@@imachavel

[@susannewilliams]

Brilliant series of videos - please keep them coming! Thank you for digesting Shawn Coyle's "Cyclic and Collective" for us, and sharing your experiences and diagrams. I now better understand the effects I am seeing simulated in XP11 when transitioning from hover into ETL, and back again from hover taxi into IGE hover. (Mostly in the 407). I would love videos on Loss of Tail Rotor Effectiveness, retreating blade stall and how to recover...

[@helicopterlessonsin10minut10]

Susanne Williams. I'm glad they're helping out! I've actually got LTE and RBS both on my list of videos to make (a list that's growing faster than I can create videos at this point haha). Stay tuned to the channel and you should see them in the near future. Thanks again for watching.

[@charliekeyes6206]

Great explanation Jacob

[@obsoleteprofessor2034]

Dynamic disassembly follows.

[@rvdaero1]

superb explanation.. tnks.. giving phpl checkride this week..

[@simonjones6419]

Great explanation​, love it, thank you.

[@davidwallace5738]

Thank you, sir!

[@bushtrash2286]

Just go around, if not happy, why this is so hard for other pilots to understand is beyond me. GOOD VIDIO !!!!!!!

[@dipankarboruah3528]

I like your videos....

[@kamron8558]

I think you mean newton's "first" law.... ;) 4:53

[@helicopterlessonsin10minut10]

Appreciate it :)

[@walterriely4032]

Well describd👍

[@Hammett175]

So basically it tips over sometimes.

[@ahmedabdallah24]

How can I build a dynamic model of small-scale unmanned helicopter in Matlab Simulink?

[@helicopterlessonsin10minut10]

Ahmed Farouk. Sorry but I'm not the one to ask about building that.

[@niveawithq1072]

Just noticed the Griffith after thinking that the background looked familiar. Looks pretty 1-3 to me.

[@helicopterlessonsin10minut10]

You’d be right ;)

[@niveawithq1072]

@@helicopterlessonsin10minut10 I saw you posted this 3 years ago. If you also recorded the video about 3 years ago then there was a chance I was there with you working on the birds Armament style. Small world

[@helicopterlessonsin10minut10]

Been closer to 4 years since I left. But there’s a chance we overlapped. Our Armament guys kicked ass in that unit so you came from good stock lol.

[@venkyvenkatesh999]

Very rudimentary explanation. More treatment of the toppling forces and restoring forces would help pilots understand recovery actions. In all cases reducing rotor thrust to minimum is the only hope of recovery Secondly, the recovery through cyclic correction depends on the rate of roll set up Visa vis control power available

[@smartyrdumb4681]

My brain just experienced rotor stall..

[@user-fx4pi9vp9g]

It's Newton's First Law. ;)

[@robhaylock7742]

Jacob, I was disappointed to see basic errors in every one of your videos. From an Apache instructor, that is not very good, perpetuating myths and stating some outright untruths, while omitting to include the important vector diagrams that explain how things happen. So sad that so many people have watched these videos, and will go on to teach the same errors. Go back to Shawn Coyle's books and see how the lessons should be taught. Look up Nick Lappos's (was chief Sikorsky test pilot) "Helicopter urban Myths".