Return-Path: Received: from snipe.mail.pas.earthlink.net ([207.217.120.62] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 3050388 for flyrotary@lancaironline.net; Sat, 28 Feb 2004 23:24:38 -0500 Received: from user-118bon9.cable.mindspring.com ([66.133.226.233] helo=earthlink.net) by snipe.mail.pas.earthlink.net with esmtp (Exim 3.33 #1) id 1AxIVJ-0005Wn-00 for flyrotary@lancaironline.net; Sat, 28 Feb 2004 20:24:37 -0800 Message-ID: <40416983.60706@earthlink.net> Date: Sat, 28 Feb 2004 20:24:35 -0800 From: Dale Smith User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: FW: [VAF Mailing List] Engine Choice (windmilling drag) References: In-Reply-To: Content-Type: multipart/alternative; boundary="------------060800020501060606020703" This is a multi-part message in MIME format. --------------060800020501060606020703 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit WALTER KERR wrote: > Hi Dale, > > Did the 123's windmilling engine have the blades at flat pitch? Yes, about as flat as you can get. When the jug blew, it came off with such force that it went through the cowling, and severed all the oil pressure feathering lines to the prop. Large fire blazing away with all that oil everywhere Large quantity of 115 / 145 octane in nacelle tanks behind the engine. Lots of pucker factor. When the engine seized, the blades were still very flat to the wind and still a lot of drag ... but a lot less than having to wind crank 18 dead cylinders. We were almost able to maintain altitude with the other engine running at max continuous power. > I did engine off testing in my RV6A 160 lyc with 80 inch pitch metal > sensenich prop. The glide slope was not measured to be any difference > whether I windmilled the prop at best L/D speed or whether I pulled up > slowed enough to stop the prop turning and then returned to same speed. There is a massive difference in drag between a shut off engine with an uncontrollable prop that cannot be feathered forcing you to continue turning the cylinders over by the "windmilling effect" alone ... and just powering back a perfectly good motor. Imagine the drag you would have if you threw a rod, shut off the fuel, but still had to continue turning the engine over at the same speed. FORCED windmilling of a dead engine ... no fun at all. In all fairness, the sprague clutch mentioned would be closer to the situation you relate ... it would disengage, and thus NOT be required to turn the engine over. Dale Smith --------------060800020501060606020703 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit

WALTER KERR wrote:

Hi Dale,

Did the 123's windmilling engine have the blades at flat pitch?

Yes, about as flat as you can get. When the jug blew, it came off with such force that it went through the cowling, and severed all the oil pressure feathering lines to the prop. Large fire blazing away with all that oil everywhere Large quantity of 115 / 145 octane in nacelle tanks behind the engine. Lots of pucker factor. When the engine seized, the blades were still very flat to the wind and still a lot of drag ... but a lot less than having to wind crank 18 dead cylinders. We were almost able to maintain altitude with the other engine running at max continuous power.

I did engine off testing in my RV6A 160 lyc with 80 inch pitch metal sensenich prop. The glide slope was not measured to be any difference whether I windmilled the prop at best L/D speed or whether I pulled up slowed enough to stop the prop turning and then returned to same speed.

There is a massive difference in drag between a shut off engine with an uncontrollable prop that cannot be feathered forcing you to continue turning the cylinders over by the "windmilling effect" alone ... and just powering back a perfectly good motor. Imagine the drag you would have if you threw a rod, shut off the fuel, but still had to continue turning the engine over at the same speed. FORCED windmilling of a dead engine ... no fun at all.

In all fairness, the sprague clutch mentioned would be closer to the situation you relate ... it would disengage, and thus NOT be required to turn the engine over.

Dale Smith

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