Does tractor airstream improves lift?

[jucie]

I don't know if this issue fits here or at the Aerodynamics branch.

I was wondering if the airstream coming from the helix in a tractor design can improve lift as the air goes thru rotor disk.

Is that true? Is only a theoretical advantage or it really happens?

Thanks in advance.

[quadrirotor]

At least you can have a bigger prop!
I have seen a video of one of these, landing almost vertically like an helicopter, but nose up...

[RHerron]

Quadrirotor,


The biggest advantage (performance-wise) is the ability to use a really long propeller. The prop is also much quieter than in a pusher due to "clean" inflow.

Ron

[Udi]

I was wondering if the airstream coming from the helix in a tractor design can improve lift as the air goes thru rotor disk.

Is that true? Is only a theoretical advantage or it really happens?

Thanks in advance.

Jucie - I would think that during normal flight the prop wash (which is what I assume you meant by Helix) is passing underneath the rotor disc, thus not making any difference in terms of rotor performance. Prop wash may, however, help with pre-rotation, when the disk is tilted all the way back. Ron please correct me if I'm wrong, but I believe some early Autogiros were able to tilt the engine nose down and direct more of the prop wash into the rotor disc for pre-rotation.

Udi-

[jucie]

Udi, I think you are correct, the prop wash is passing underneath the rotor disc.

Thank you, guys.

[quadrirotor]

In a steep descent, the rotor of a tractor is most of the time in the prop wash of the prop!...

[RHerron]

Udi,

I don't know of any of the old Autogiros that used a tilted
engine to spin the blades.
Cierva and
Pitcairn both experimented with tailplanes that would deflect the prop blast into the rotor for spinup. The PCA-1 was like this as was Cierva's C-19.