Return-Path: Received: from fed1rmmtao02.cox.net ([68.230.241.37] verified) by logan.com (CommuniGate Pro SMTP 4.2b1) with ESMTP id 3146727 for flyrotary@lancaironline.net; Mon, 05 Apr 2004 10:40:25 -0400 Received: from BigAl ([68.107.116.221]) by fed1rmmtao02.cox.net (InterMail vM.6.01.03.01 201-2131-111-101-20040311) with ESMTP id <20040405144025.UERV25770.fed1rmmtao02.cox.net@BigAl> for ; Mon, 5 Apr 2004 10:40:25 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: Re: idle speeds (prop stopped flight) Date: Mon, 5 Apr 2004 07:40:33 -0700 Message-ID: <001001c41b1b$f3a1ca30$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0011_01C41AE1.4742F230" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 In-Reply-To: Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_0011_01C41AE1.4742F230 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Subject: [FlyRotary] Re: idle speeds (prop stopped flight) =20 Hi Charlie, =20 I had a cruise prop (80 inch pitch) sensenich metal prop on the 6A. When = I was doing engine off glide testing, some thought I would do better with engine stopped rather than turning. Really had to slow way down to get = prop to stop. Could not measure the difference in glide engine stopped or windmilling. Really had to go fast, over a hundred to get it going = again! =20 Bernie Kerr, painting the 9A waiting to get rotary back from Bruce T at = SnF =20 A stopped prop is in a complete stall condition, and would be expected = to provide less drag than one that is turning at an RPM of incipient stall. There will be some RPM for a given pitch and touchdown speed that will provide the most drag. We just have to figure out what that is. =20 =20 Landing speed in Kts times 100 gives you ft/min. Pitch divided by 12 = gives you ft/min per revolution of the prop for neutral thrust (approx.). So = my 85 pitch prop at 70 kt landing speed is neutral at 1000 RPM. So maybe = the max drag point is somewhere around 650 RPM (mas o menos 100). Just a = guess. Someone less propeller-design challenged than I may have a better = answer. =20 Al ------=_NextPart_000_0011_01C41AE1.4742F230 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Subject: [FlyRotary] Re: idle speeds (prop stopped flight)

 

Hi Charlie,

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I had a cruise prop (80 inch pitch) sensenich metal prop on the 6A. When I = was doing engine off glide testing, some thought I would do better with = engine stopped rather than turning. Really had to slow way down to get prop to = stop. Could not measure the difference in glide engine stopped or windmilling. = Really had to go fast, over a hundred to get it going again!

 <= /font>

Bernie Kerr, painting the 9A waiting to get rotary back from Bruce T at = SnF

=

 

A stopped prop is in a complete = stall condition, and would be expected to provide less drag than one that is = turning at an RPM of incipient stall.  There will be some RPM for a given = pitch and touchdown speed that will provide the most drag.  We just have = to figure out what that is. 

 

Landing speed in Kts times 100 = gives you ft/min.  Pitch divided by 12 gives you ft/min per revolution of the = prop for neutral thrust (approx.).  So my 85 pitch prop at 70 kt landing = speed is neutral at 1000 RPM.   So maybe the max drag point is = somewhere around 650 RPM (mas o menos 100).  Just a guess.  Someone less = propeller-design challenged than I may have a better answer.

 

Al

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