X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 872382 for flyrotary@lancaironline.net; Mon, 12 Dec 2005 10:52:23 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.25.9.101; envelope-from=eanderson@carolina.rr.com Received: from edward2 (cpe-024-074-025-165.carolina.res.rr.com [24.74.25.165]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id jBCFpV4p007193 for ; Mon, 12 Dec 2005 10:51:31 -0500 (EST) Message-ID: <001501c5ff33$ec9a0920$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: "P" factor? Re: Static Engine RPM Date: Mon, 12 Dec 2005 10:51:31 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0012_01C5FF0A.0321F4C0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0012_01C5FF0A.0321F4C0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable No familiar with the SA-16, Bob, but are both props turning same = direction or opposite - would make a significant difference in whether = there is a swirl (my spell checker says OK {:>)) effect or not. If in = opposite directions then I would agree, if both props rotating in same = direction then harder to say. For a long time I thought that Torque was the major cause, however, I = remain convinced (at this point) that the low rolling and large yaw = force is primarily caused by swirl. Having encountered prop swirl on = take off roll too close behind Finn's RV3 there is no question in my = mind that prop swirl is a powerful force. But, regardless whether = torque or swirl (or combination), the 2.85 gear box and larger prop = makes a considerable change. =20 I don't recall whether Tracy adjusted his motor mount for his 2.85 and = larger prop or not. Ed A ----- Original Message -----=20 From: Bob Darrah=20 To: Rotary motors in aircraft=20 Sent: Monday, December 12, 2005 10:01 AM Subject: [FlyRotary] Re: "P" factor? Re: Static Engine RPM As I understand it, the P factor only comes in when the prop is = advancing in a direction different than it's axis. Like a tail wheeld = airplane with it's tail still on the ground or any airplane at a high = angle of attack. That is not a factor on a tri geared aircraft on = innitial role. An engine properly trimed for a counter-clockwise prop (1 or 2 = degrees left thrust) would have a large effect when changing to a = standard (American direction) prop. A lot of left turning reaction = tendencies plus left thrust would require lots of right rudder. A major = force is torque. More HP, more torgue. The swerl effect is mild in = comparison. As an example, the SA-16 (large twin amphibion) drivers start their = max take-off run from the left side of the runway, pointed about 45 = toward the center line. Said that there was no way, when quickly = adding full power that they could keep it from turning-so they just = planned for the turn. No swerl effect here. FWIW Bob Darrah (I know, but my spell checker said it was ok) ------=_NextPart_000_0012_01C5FF0A.0321F4C0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
No familiar with the SA-16, Bob, but are both props turning same = direction=20 or opposite - would make a significant difference in whether there is a = swirl=20 (my spell checker says OK {:>)) effect or not.  If in opposite=20 directions then I would agree, if both props rotating in same direction = then=20 harder to say.
 
For a long time I thought that Torque was the major cause, however, = I=20 remain convinced (at this point) that the low rolling and large yaw = force is=20 primarily caused by swirl. Having encountered prop swirl on take off = roll too=20 close behind Finn's RV3 there is no question in my mind that prop swirl = is a=20 powerful force.   But, regardless whether torque or swirl (or=20 combination), the 2.85 gear box and larger prop makes a considerable=20 change. 
 
I don't recall whether Tracy adjusted his motor mount for his 2.85 = and=20 larger prop or not.
 
Ed A
----- Original Message -----
From:=20 Bob=20 Darrah
Sent: Monday, December 12, 2005 = 10:01=20 AM
Subject: [FlyRotary] Re: "P" = factor? Re:=20 Static Engine RPM

 
As I understand it, the P factor only comes in = when the=20 prop is advancing in a direction different than it's axis.  = Like a tail=20 wheeld airplane with it's tail still on the ground or any airplane = at a high=20 angle of attack.  That is not a factor on a tri geared aircraft = on=20 innitial role.
 
An engine properly trimed for a = counter-clockwise prop (1=20 or 2 degrees left thrust) would have a large effect when changing to = a=20 standard (American direction) prop.  A lot of left turning = reaction=20 tendencies plus left thrust would require lots of right = rudder.  A=20 major force is torque.  More HP, more torgue. The swerl effect = is mild=20 in comparison.
 
As an example, the SA-16 (large twin amphibion) = drivers=20 start their max take-off run from the left side of the runway, = pointed about=20 45 toward the center line.   Said that there was no = way, when=20 quickly adding full power that they could keep it from turning-so = they just=20 planned for the turn.  No swerl effect here.
 
FWIW
 
Bob Darrah
 
(I know, but my spell checker said it was = ok) =20
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