Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Fri, 06 Aug 2004 21:14:37 -0400 Message-ID: X-Original-Return-Path: Received: from [65.32.5.131] (HELO ms-smtp-01.tampabay.rr.com) by logan.com (CommuniGate Pro SMTP 4.2) with ESMTP id 355436 for lml@lancaironline.net; Fri, 06 Aug 2004 20:48:06 -0400 Received-SPF: none receiver=logan.com; client-ip=65.32.5.131; envelope-from=tednoel@cfl.rr.com Received: from tednoel (227.199.27.24.cfl.rr.com [24.27.199.227]) by ms-smtp-01.tampabay.rr.com (8.12.10/8.12.7) with SMTP id i770lXjK027437 for ; Fri, 6 Aug 2004 20:47:34 -0400 (EDT) X-Original-Message-ID: <008801c47c18$4a153660$0100000a@tednoel> From: "Ted Noel" X-Original-To: "Lancair Mail List" Subject: Prop pitch with engine failure X-Original-Date: Fri, 6 Aug 2004 20:48:43 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0085_01C47BF6.C2BC2D20" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0085_01C47BF6.C2BC2D20 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable I spent some time with Harry Griswold of AeroComposites at Lakeland this = year discussing prop pitch with engine failure. It turns out that the = answer may not have to do with philosophy of handling emergencies but = with mechanical complexity (cost) and weight. If you spin a prop without a governor, the mechanical forces will drive = it to flat pitch. That means that there must be a force applied to drive = the prop back to coarse pitch. This is typically done by using oil = pressure to drive pistons that move the prop. Of course, when the engine = stops, the oil pressure goes away, and the prop spins to flat pitch if = it is windmilling. The only way to reverse this behavior is to have a massive spring in the = hub to force the prop to coarse pitch at engine out. Then the pistons = use engine oil to drive the prop to fine pitch. This spring increases = complexity (cost) and weight. Ted Noel L-IV-P Eagle at airport, starting ground checks N540TF ------=_NextPart_000_0085_01C47BF6.C2BC2D20 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

I spent some time with Harry Griswold = of=20 AeroComposites at Lakeland this year discussing prop pitch with engine = failure.=20 It turns out that the answer may not have to do with philosophy of = handling=20 emergencies but with mechanical complexity (cost) and = weight.

If you spin a prop without a governor, = the=20 mechanical forces will drive it to flat pitch. That means that there = must be a=20 force applied to drive the prop back to coarse pitch. This is typically = done by=20 using oil pressure to drive pistons that move the prop. Of course, when = the=20 engine stops, the oil pressure goes away, and the prop spins to flat = pitch if it=20 is windmilling.

The only way to reverse this behavior = is to have a=20 massive spring in the hub to force the prop to coarse pitch at engine = out. Then=20 the pistons use engine oil to drive the prop to fine pitch. This spring=20 increases complexity (cost) and weight.

Ted Noel

L-IV-P Eagle

at airport, starting ground = checks

N540TF

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