Received-SPF: none
 receiver=logan.com; client-ip=201.225.225.169; envelope-from=rijakits@cwpanama.net
Message-ID: <00bc01c4dff3$1c357950$6e5de0c9@usuarioq3efog0>
From: "rijakits" <rijakits@cwpanama.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-563830@logan.com>
Subject: Re: [FlyRotary] Re: Serious single rotor questions (serious??)
Date: Sat, 11 Dec 2004 21:34:31 -0500
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit


----- Original Message -----
From: <echristley@nc.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, December 11, 2004 9:25 PM
Subject: [FlyRotary] Re: Serious single rotor questions (serious??)


>
>
> ----- Original Message -----
> From: rijakits <rijakits@cwpanama.net>
> Date: Saturday, December 11, 2004 9:07 pm
> Subject: [FlyRotary] Re: Serious single rotor
> questions (serious??)
>
> > The neat thing is you hardly hear it, in
> comparrison to a regular
> > Tailrotor it
> > is silent. EC does this with irregular spacing of
> the fanblades.
> >
>
>
> I remember reading a NACA report on silencing
> helicoptor rotors using this technique.  It's been a
> while, but you might want to check the LARC server
> if you have any desire to pursue this.
>
Well actually the main rotor noise is a lot harde to come by. Actual Tests
use "Smart Rotors", which have piezo electric actuated flaps at the outboard
end of the rotor blades.
The different spacing works well on the fan, as the flow velocities over the
individual blades are pretty much the same for all blades at all times. On
the main rotor you have huge speed differences depending where the blade is
( advancing or retreading or some where in between...)
I think EC did this with the Tailfan the first time on the EC120, but plans
to incorporate this into all Tailfan equipped EC-Helicopters...

Thomas J.