Coaxial rotorsystem.

[MrEdd]

God morning, afternoon or evning ladies and gent's.

I have 2 things i wonder a bit about.

Im doing some briefings for my CFI education.
And you all now how easy you can sidetracked on internet.
So i went from dissymmetry of lift, and got curious if coaxial rotorsystems can fly faster than "normal" rotorsystems, who are limited by retreating blade stall?

Any one?

What i could figure and find was that, yes they can in theory.
Having a Vne limit due to rotorblades can´t exeed supersonic speed (about mach 0.8).
But in practic they fly slower due to more drag.

So leading us over to Sikorsky's X-2, who has a coaxial M/R system designed for less drag.
Now they have set the A/S to 288mph on the X-2.
I assume that is close to the subsonic tip speed(which defines Vne for coaxial system), so if they put on "BURP" blades, woulden't they in theory be able to push that baby even faster?


Thankfull or any idea if im on right track or just way out there?

Best regards
Henrik B

[Dave_Jackson]

Henrik,

This page may answer some of your questions; Coaxial - Sikorsky ~ S-69 (XH-59) ABC (http://www.synchrolite.com/0891.html)

Dave J

[IFMU]

Now they have set the A/S to 288mph on the X-2.
I assume that is close to the subsonic tip speed(which defines Vne for coaxial system), so if they put on "BURP" blades, woulden't they in theory be able to push that baby even faster?
Henrik,
With a rip-snorting airspeed goal of 288mph, They must be doing their homework on blades. If the burp blades were the best, I bet they would be on there. Since they are not, I would think the blades they are making for the X2 are the best for speed, assuming they succeed.
-- IFMU

[MrEdd]

IFMU

Well i guess your right, perhaps i diden´t think that one thru enough.:rolleyes:
Im not so experienced with blade design(hell pretty FNG to the heli in all :cool: )
Just that i couldn´t find any info on the blades, so i got wondering about it.

Thanks for the link Dave.