Return-Path: Sender: (Marvin Kaye) To: lml@lancaironline.net Date: Sun, 08 Aug 2004 08:21:28 -0400 Message-ID: X-Original-Return-Path: Received: from rhombus.bright.net ([209.143.0.75] verified) by logan.com (CommuniGate Pro SMTP 4.2) with ESMTP id 356491 for lml@lancaironline.net; Sun, 08 Aug 2004 00:38:57 -0400 Received-SPF: none receiver=logan.com; client-ip=209.143.0.75; envelope-from=airmale@bright.net Received: from bright.net (paul-bryn-breeze-122.wireless.bright.net [216.201.20.123] (may be forged)) by rhombus.bright.net (8.12.10/8.12.10) with ESMTP id i784cGEE003771; Sun, 8 Aug 2004 00:38:26 -0400 (EDT) X-Original-Message-ID: <4115AE29.5050000@bright.net> X-Original-Date: Sun, 08 Aug 2004 00:38:01 -0400 From: J H Webb 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 X-Original-To: Ed McCauley , Lancair Mailing List Subject: Prop stopped. Content-Type: multipart/alternative; boundary="------------060105020000010104000006" This is a multi-part message in MIME format. --------------060105020000010104000006 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Ed, while I was working for an aircraft manufacturer we did a fair amount of flying with the prop stopped. Two things pop out one is the the most efficient position is without the prop being horizontal. I.e. don't align it with the wing it causes separation drag. More interestingly, in my Lancair 360 I have tried several configurations, Prop stopped, prop windmilling and prop windmilling full course (low rpm) and the results were suprising. The airplane had a better glide distance with the prop windmilling and prop full coarse. This is initially suprising but when you think about it , it makes sense. The Lancair is very low drag and the flat plate area of the stopped prop is very large compared to the total drag of the airplane. No other airplane that I have tested has this unusual performance change. The turbine Lancair with it's big prop is also suprising with the prop in feather, it will glide with an apparent L/d of about 20. Scott is quite right that the gliding distance is remarkable with the prop in full decrease. I have done a fair amount of gliding with the engine stopped (close to a long airport) and the change is gliding distance (L/D) is huge. One must keep in mind that the engine may not restart so care is required. Jack Webb L 360, L IV ATP, CFI Airplanes & Instruments, Multi, & Sea Many Type Ratings Experienced Experimental Test Pilot both multi and single engine Former Chief Engineering Test Pilot for a Major Manufacturer AeroSpace Engineer BSAE Ohio >One other thought which I hope will spawn further input, I've been told by many that, given the altitude, one should consider pulling up and stopping the prop. Again, I've >been told that the flat plate drag drops dramatically. Anyone have any hard info on this? --------------060105020000010104000006 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Ed, while I was working for an aircraft manufacturer we did a fair amount of flying with the prop stopped. Two things pop out one is the the most efficient position is without the prop being horizontal. I.e. don't align it with the wing it causes separation drag. More interestingly, in my Lancair 360 I have tried several configurations, Prop stopped, prop windmilling and prop windmilling full course (low rpm) and the results were suprising. The airplane had a better glide distance with the prop windmilling and prop full coarse. This is initially suprising but when you think about it , it makes sense. The Lancair is very low drag and the flat plate area of the stopped prop is very large compared to the total drag of the airplane. No other airplane that I have tested has this unusual performance change. The turbine Lancair with it's big prop is also suprising with the prop in feather, it will glide with an apparent L/d of about 20.
Scott is quite right that the gliding distance is remarkable with the prop in full decrease. I have done a fair amount of gliding with the engine stopped (close to a long airport) and the change is gliding distance (L/D) is huge. One must keep in mind that the engine may not restart so care is required.

Jack Webb
L 360, L IV
ATP, CFI Airplanes & Instruments, Multi, & Sea
Many Type Ratings
Experienced Experimental Test Pilot both multi and single engine
Former Chief Engineering Test Pilot for a Major Manufacturer
AeroSpace Engineer BSAE
Ohio

>One other thought which I hope will spawn further input, I've been told by many that, given the altitude, one should consider pulling up and stopping the prop. Again, I've >been told that the flat plate drag drops dramatically. Anyone have any hard info on this?
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