helicopter rotor control - phase delay

How a helicopter works

Helicopter aerodynamics and rotor control - phase delay

The concept of helicopter control phase delay is that the maximum aerodynamic force applied to a helicopter rotor blade takes some time before it manifests as a control input. This is referred to as phase delay by some texts, and gyroscopic precession by others. For typical helicopters this delay is about 90 degrees of blade rotation.

This animation shows how the swashplate moves, in response to pilot control inputs, and where the motion has to occur in order to account for phase delay.

[adrianlindsay]

One of the best descriptions and videos I've ever seen regarding controls, rotor system and aerodynamic phenomenon like gyroscopic procession (phase lag).

[ziggy]

My grandpa was an electrical and mechanical engineer, earned his degree at Pratt institute in 1920. When I was like 8 or 9 he started to teach me so so many things relating to the mechanical world. To witness this video and all the beautiful detail and moving parts in real time animation brings a tear to my eye… and his too, wherever he may be watching. Bless you for creating this fantastic visual treat. Ziggy

[coreybennett]

Great job! It’s fantastic that you’re taking more time to describe everything you considered in building the model! Would love to see you animate a tilt rotor! No one is doing anything remotely this detailed! Keep up the great work!

[spankyharland]

it is called moving the big saucer plate above your head. great video representation that took me a while to figure out. add a video on what the anti-torque pedals do and everyone will know how to "get on the choppa" and fly it.

[andrewtsang]

Thank you for this excellent explanation. I have been trying to convert my flybar RC helicopter to flybarless and this describes perfectly the phase delay I was seeing that confused me at first!

[jessysaintauret]

it's rare when I put a comment, but this was a very instructive and amazing explanation video thank you.

[Ben-Dixey]

Great video, ! it was my understanding that the blade pitch horn sets the phase lag and the swash plate tilts in the direction of travel. You can see how the horn pitches the blade out of phase.

[chrishard]

Thanks for this explanation. I was playing around with an RC helicopter and couldn’t understand why the blade pitch appeared to be out by 90 degrees. Now I know why!

[charlieguenther]

It would help to describe procession in its entirety. It's a simple concept that has the greatest influence on phase delay. Thankyou for the presentation.

[Workerbee-zynx]

Great grafix, fixed wing pilots will be confused. 😉😳👍

[petehalasz]

Absolutely perfect explanation on your first and second vids.. love the animation.. as a heli pilot, this explanation drove me nuts, and I thought would have to prematurely input. At the end, didn't have to worry.. as you mentioned this goes out the window for 2, ,4,,,,5,,6 blade machines.. and let's not forget fixed hubs, or lead/lag flex hubs..
Excellent work.. when I use fly i also had several RC helis, , and holy poop it was tougher to those RC then the real ones..

[jeeberlewis]

Really well done. I have heard different POV's, but is it universally an 85 degree lead? I have also heard of a 90 degree lead. Does that change with respect to the type of rotor system (rigid, semi-rigid, fully articulate) or how many blades we have on the helicopter? Thanks again. Keep these coming! I am an aspiring Army Aviator and I am studying for the Army SIFT - your videos help immensely.

[ahmedkamiss]

Unfortunately, I am unable to give two thumbs up. Great explanation and something the world was missing ❤

[benhill]

I always had that question! Excellent video. I knew about gyroscopic procession, but was unsure where the max pitch of the blade would be in relation to the actual desired direction of flight. Thank you for this!

[nachosanchez]

This is a very good explanation of phase lag but, keep in mind that lift vector is always parallel to rotation axis “the mast”, creating a torque that will tilt the whole aircraft and hence tilting the thrust vector. Otherwise, the helicopter would neither pitch nor roll.

[markusanderson]

Very cool. Great animation work and explanation.

[whlre]

Well done.
Helicopters are the best way to fly when you don't have anywhere to go.

[maffysdad]

You've just reinvented the Swash Plate! 😀

[peterscherzer]

Thank you very much for this impressive presentation

[llwellyn]

I subscribed after seeing this well composed technical presentation. I look forward to reviewing more from you. Keep up the good work!