X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 21 Aug 2013 07:40:20 -0400 Message-ID: X-Original-Return-Path: Received: from mail-pb0-f41.google.com ([209.85.160.41] verified) by logan.com (CommuniGate Pro SMTP 6.0.6) with ESMTPS id 6434716 for lml@lancaironline.net; Tue, 20 Aug 2013 16:00:03 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.160.41; envelope-from=pjdmiller@gmail.com Received: by mail-pb0-f41.google.com with SMTP id rp2so803524pbb.28 for ; Tue, 20 Aug 2013 12:59:28 -0700 (PDT) X-Received: by 10.66.170.168 with SMTP id an8mr5786797pac.58.1377028768386; Tue, 20 Aug 2013 12:59:28 -0700 (PDT) X-Original-Return-Path: Received: from [192.168.1.143] (S010620aa4b008706.cg.shawcable.net. [174.0.112.194]) by mx.google.com with ESMTPSA id vz4sm5521641pab.11.1969.12.31.16.00.00 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 20 Aug 2013 12:59:27 -0700 (PDT) From: Paul Miller Content-Type: multipart/alternative; boundary="Apple-Mail=_8231D862-28A4-4A3B-949E-9B6B81B96236" X-Original-Message-Id: <68CEFB08-0F8F-4873-8C66-B73DE4C7CA71@gmail.com> Mime-Version: 1.0 (Mac OS X Mail 6.5 \(1508\)) Subject: Re: [LML] Prop governor's X-Original-Date: Tue, 20 Aug 2013 13:59:25 -0600 References: X-Original-To: "Lancair Mailing List" In-Reply-To: X-Mailer: Apple Mail (2.1508) --Apple-Mail=_8231D862-28A4-4A3B-949E-9B6B81B96236 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Maybe we should refer to the manuals on how props go to low pitch. It = ain't relative wind or any other kind of wind. It is a "really big = spring" in the hub. =46rom Hartzell: > (2) Centrifugal twisting moment acting on the blades moves the blades = to a low blade angle (low pitch) to increase RPM. Since the centrifugal = twisting moment is only present when the propeller is rotating, a = mechanical spring is installed within the propeller to assist movement = of the blades to a lower pitch position as RPM decays, and to reduce the = propeller pitch to the low pitch stop when the propeller is static. With = the blades at low pitch, the load on the starter when starting the = engine is reduced significantly.=20 > (3) Oil pressure opposes the spring and centrifugal twisting moment to = move the blades to a high blade angle (high pitch), reducing engine RPM.=20= > (4) If oil pressure is lost at any time, the propeller will move to = low pitch. This occurs because the spring and blade centrifugal twisting = moment are no longer opposed by hydraulic oil pressure. The propeller = will then reduce blade pitch to the low pitch stop. On 2013-08-20, at 1:45 PM, Jack Morgan wrote: > If oil pressure fails, standard CS props are driven flat by the = relative wind ... --Apple-Mail=_8231D862-28A4-4A3B-949E-9B6B81B96236 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Maybe = we should refer to the manuals on how props go to low pitch. It = ain't relative wind or any other kind of wind. It is a "really big = spring" in the hub. =46rom Hartzell:

(2) Centrifugal twisting moment acting on the = blades moves the blades to a low blade angle (low pitch) to increase = RPM. Since the centrifugal twisting moment is only present when the = propeller is rotating, a mechanical spring is installed within the = propeller to assist movement of the blades to a lower pitch position as = RPM decays, and to reduce the propeller pitch to the low pitch stop when = the propeller is static. With the blades at low pitch, the load on the = starter when starting the engine is reduced = significantly.
(3) Oil pressure = opposes the spring and centrifugal twisting moment to move the blades to = a high blade angle (high pitch), reducing engine RPM.
(4) If oil pressure is lost at any time, the = propeller will move to low pitch. This occurs because the spring and = blade centrifugal twisting moment are no longer opposed by hydraulic oil = pressure. The propeller will then reduce blade pitch to the low pitch = stop.

On 2013-08-20, at 1:45 PM, = Jack Morgan <jmorgan1023@comcast.net> = wrote:

If oil pressure = fails, standard CS props are driven flat by the relative wind = ...

= --Apple-Mail=_8231D862-28A4-4A3B-949E-9B6B81B96236--