X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 09 Jun 2011 14:13:20 -0400 Message-ID: X-Original-Return-Path: Received: from imr-da04.mx.aol.com ([205.188.105.146] verified) by logan.com (CommuniGate Pro SMTP 5.4.0) with ESMTP id 5014363 for lml@lancaironline.net; Wed, 08 Jun 2011 16:02:33 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.105.146; envelope-from=VTAILJEFF@aol.com Received: from imo-ma02.mx.aol.com (imo-ma02.mx.aol.com [64.12.78.137]) by imr-da04.mx.aol.com (8.14.1/8.14.1) with ESMTP id p58K1oHr015559 for ; Wed, 8 Jun 2011 16:01:50 -0400 Received: from VTAILJEFF@aol.com by imo-ma02.mx.aol.com (mail_out_v42.9.) id q.10e6.161be9d (44048) for ; Wed, 8 Jun 2011 16:01:46 -0400 (EDT) Received: from smtprly-dc03.mx.aol.com (smtprly-dc03.mx.aol.com [205.188.170.3]) by cia-dd07.mx.aol.com (v129.10) with ESMTP id MAILCIADD074-d3a24defd524205; Wed, 08 Jun 2011 16:01:45 -0400 Received: from webmail-m147 (webmail-m147.sim.aol.com [149.174.9.30]) by smtprly-dc03.mx.aol.com (v129.10) with ESMTP id MAILSMTPRLYDC032-d3a24defd524205; Wed, 08 Jun 2011 16:01:40 -0400 References: X-Original-To: lml@lancaironline.net Subject: Re: [LML] Re: L-IV Choice of Engine X-Original-Date: Wed, 08 Jun 2011 16:01:40 -0400 X-AOL-IP: 76.215.111.99 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: vtailjeff@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8CDF42E043654F8_272C_EAEE2_webmail-m147.sysops.aol.com" X-Mailer: AOL Webmail 33790-STANDARD Received: from 76.215.111.99 by webmail-m147.sysops.aol.com (149.174.9.30) with HTTP (WebMailUI); Wed, 08 Jun 2011 16:01:40 -0400 X-Original-Message-Id: <8CDF42E03E30492-272C-72DA6@webmail-m147.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: VTAILJEFF@aol.com ----------MB_8CDF42E043654F8_272C_EAEE2_webmail-m147.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" Finally, I don't know of any prop failures related to the engine to which= they were attached. It is usually what we don't know that bites us in the ass. Jeff -----Original Message----- From: Gary Casey To: lml@lancaironline.net Sent: Wed, Jun 8, 2011 7:25 am Subject: [LML] Re: L-IV Choice of Engine Certainly there is some testing that goes into propeller selection, but I'= m not sure I would categorize it as "a lot." That would imply that most= combinations are bad, there is no science that allows a correct selection= , and therefore it is just luck. Sure, there is testing that confirms per= formance optimization, but that's not what we are talking about here. If= my memory serves correctly, to certify a propeller installation in a give= n airframe the FAA requires a torsional study be performed, which involves= internal sensor be installed to measure the torsional vibration of the cr= ankshaft. This costs money, so STC's for new propellers come slowly. Fra= nkly, I don't understand at all the requirement for the prop/engine/airfra= me combination to be verified. The engine is stiffly connected to the pro= p (big bolts, metal/metal joints, etc) and softly connected to the airfram= e (rubber), so how could the torsional vibrations involve the airframe? = In any event, I recall that the number of operational hours required is= small, something like 50. And then to confuse and obscure the issue furt= her, the only FAA requirement for experimental aircraft is that if the eng= ine/prop combination (not airframe) has been certified the fly-off require= s only 25 hours - otherwise 40. So they sort of admit that the airframe= has nothing to do with it. Finally, I don't know of any prop failures re= lated to the engine to which they were attached. So with great trepidatio= n I might slightly disagree with Brent in that I doubt that attaching an= otherwise-successful prop to a V8 engine will almost certainly result in= a prop failure. In the end, we have to decide on the odds with which we= are willing to play. Is being "pretty sure" something will work good eno= ugh? For some it seems so, but for others not. Gary Casey Ted, =20 A lot of testing goes into propeller selection for engines. =20 Jeff Edwards ----------MB_8CDF42E043654F8_272C_EAEE2_webmail-m147.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii"
Final= ly, I don't know of any prop failures related to the engine to which they= were attached.
It is usually what we don't know that bites us in the ass.
 
Jeff



-----Original Message-----
From: Gary Casey <casey.gary@yahoo.com>
To: lml@lancaironline.net
Sent: Wed, Jun 8, 2011 7:25 am
Subject: [LML] Re: L-IV Choice of Engine

= Certainly there is some testing that goes into propeller selection, but I'= m not sure I would categorize it as "a lot."  That would imply that= most combinations are bad, there is no science that allows a correct sele= ction, and therefore it is just luck.  Sure, there is testing that co= nfirms performance optimization, but that's not what we are talking about= here.  If my memory serves correctly, to certify a propeller install= ation in a given airframe the FAA requires a torsional study be performed,= which involves internal sensor be installed to measure the torsional vibr= ation of the crankshaft.  This costs money, so STC's for new propelle= rs come slowly.  Frankly, I don't understand at all the requirement= for the prop/engine/airframe combination to be verified.  The engine= is stiffly connected to the prop (big bolts, metal/metal joints, etc) and= softly connected to the airframe (rubber), so how could the torsional vib= rations involve the airframe?  In any event, I recall that the number= of operational hours required is small, something like 50.  And then= to confuse and obscure the issue further, the only FAA requirement for ex= perimental aircraft is that if the engine/prop combination (not airframe)= has been certified the fly-off requires only 25 hours - otherwise 40. &nb= sp;So they sort of admit that the airframe has nothing to do with it. &nbs= p;Finally, I don't know of any prop failures related to the engine to whic= h they were attached.  So with great trepidation I might slightly dis= agree with Brent in that I doubt that attaching an otherwise-successful pr= op to a V8 engine will almost certainly result in a prop failure.  In= the end, we have to decide on the odds with which we are willing to play.=  Is being "pretty sure" something will work good enough?  For= some it seems so, but for others not.
= Gary Casey
=

Ted,
 
A lot of testing goes into propeller selection for engines.
 
Jeff Edwards
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