Plane of Rotation vs Tip Path Plane

[hammerhat]

Newbie question. What is Plane of Rotation? How is it different from the Tip Path Plane? Many sources imply they are the same. I'm reading Principles of Helicopt Flight by Wagtendonk and it seems to differentiate between the two. But it never clearly defines it.

[Astro]

The plane of rotation is the path the blades take as they spin around. It is the reference point for blade pitch angle, (as opposed to relative wind which is the reference point for blade angle of attack). The tip path plane is simply the blades plane of rotation as seen through the cockpit (used as a reference for things like straight and level flight).

[WolftalonID]

I believe to explain it better. Plane of rotation is the angle of the disk in comparison to the mast. This is changed with the cyclic movement.

 

The tip path plane is the plane developed by the tip of the blades in the plane of rotation. This changes with coning angles created with load or with collective input.

[superstallion6113]

The plan of rotation would be at a 90 degree angle in relation to the rotor mast. The tip path plane would be the path the blades tips are moving in, after taking into account blade flapping and coning. Basically the same thing the last guy said.

Edited October 4, 2013 by superstallion6113

[Mikemv]

The plan of rotation would be at a 90 degree angle in relation to the rotor mast. The tip path plane would be the path the blades tips are moving in, after taking into account blade flapping and coning. Basically the same thing the last guy said.

SS,

 

So if the POR is 90 degrees to the mast, how do we ever tilt the rotor system? WolfID had it correct.

[iChris]

Newbie question. What is Plane of Rotation? How is it different from the Tip Path Plane? Many sources imply they are the same. I'm reading Principles of Helicopt Flight by Wagtendonk and it seems to differentiate between the two. But it never clearly defines it.

It’s as you’ve already studied in Principles of Helicopter Flight by Wagtendonk. It was clearly defined, take a closer look…

 

 

If it weren’t for blade coning and unequal flapping angles between blades, the tip path plane and the plane-of-rotation lines would coincide. The tip-path-plane defines the circle scribed by the average flight path of the blade tips in a rotor system. The tip-path-plane is most often referred to as the rotor disk.

 

What can be said about the plane-of-rotation and tip-path-plane is they are both parallel to each other and both are perpendicular to the axis of rotation.

 

If there were no coning (angle β₀) and the up flap equaled the down flap, in the figure below, the tip-path-plane would coincide with the plane-of-rotation line as both would pass through the rotor hub.

 

Edited October 4, 2013 by iChris

[crashed_05]

iChris is spot on. Another question though...in an underslung rotor system with no coning, would the tip-path-plane be slightly below the Plane-of-rotation?