X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [24.93.47.41] (HELO ms-smtp-02-eri0.texas.rr.com) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 872329 for flyrotary@lancaironline.net; Mon, 12 Dec 2005 10:01:50 -0500 Received-SPF: pass receiver=logan.com; client-ip=24.93.47.41; envelope-from=RDarrah@austin.rr.com Received: from dell (cpe-66-69-251-170.austin.res.rr.com [66.69.251.170]) by ms-smtp-02-eri0.texas.rr.com (8.12.10/8.12.7) with SMTP id jBCF0Qe3020794 for ; Mon, 12 Dec 2005 09:00:47 -0600 (CST) Message-ID: <003901c5ff2c$de79df20$6401a8c0@austin.rr.com> From: "Bob Darrah" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: "P" factor? Re: Static Engine RPM Date: Mon, 12 Dec 2005 09:01:01 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0036_01C5FEFA.93518700" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0036_01C5FEFA.93518700 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable 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) =20 ------=_NextPart_000_0036_01C5FEFA.93518700 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
As I understand it, the P factor only comes in = when the prop=20 is advancing in a direction different than it's axis.  Like a = tail wheeld=20 airplane with it's tail still on the ground or any airplane at a high = angle of=20 attack.  That is not a factor on a tri geared aircraft on = innitial=20 role.
 
An engine properly trimed for a counter-clockwise = prop (1 or=20 2 degrees left thrust) would have a large effect when changing to a = standard=20 (American direction) prop.  A lot of left turning reaction = tendencies=20 plus left thrust would require lots of right rudder.  A major = force is=20 torque.  More HP, more torgue. The swerl effect is mild in=20 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
------=_NextPart_000_0036_01C5FEFA.93518700--