X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost04.isp.att.net ([204.127.217.104] verified) by logan.com (CommuniGate Pro SMTP 5.2.10) with ESMTP id 3288471 for flyrotary@lancaironline.net; Wed, 12 Nov 2008 23:56:45 -0500 Received-SPF: pass receiver=logan.com; client-ip=204.127.217.104; envelope-from=ceengland@bellsouth.net Received: from [192.168.10.6] (unknown[70.152.109.100]) by isp.att.net (frfwmhc04) with ESMTP id <20081113045608H04006vmo5e>; Thu, 13 Nov 2008 04:56:09 +0000 X-Originating-IP: [70.152.109.100] Message-ID: <491BB369.2090300@bellsouth.net> Date: Wed, 12 Nov 2008 22:56:09 -0600 From: Charlie England User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.17) Gecko/20080829 SeaMonkey/1.1.12 MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: IVO Props, etc. References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit George Lendich wrote: > >> I prowled around the test page a bit, & the numbers are really not good >> at all (pitiful, really) if you compare numbers to Lyc powered RVs. >> The 'best' numbers from the latest chart he supplied (copied below) >> show 151 kts (173mph) tas at 9.3 gph (56 lbs per hr). That speed is >> roughly what Van claims for a 160hp -6A at 55% power (7.3 gph) at >> 8000 ft. That's a 26% penalty even if you ignore the 3,000 ft >> altitude (lower drag) efficiency advantage. At 11,000 ft & that fuel >> burn, he would be going around 200 mph with a Lyc. >> >> Since there are 2 big variables (plus airframe/cooling drag) in this >> equation, you can't tell how much blame to assign to the engine or >> the prop. >> >> Don't be seduced by the *potential* advantage of a controllable prop. >> It's already obvious that the cruise/top speed numbers are much >> worse. I'm a bit too lazy to dig this deep, but you should also >> compare his climb rate/fuel flow numbers to Van's fixed pitch >> numbers. Do you really need a climb rate in excess of what the a/c >> can supply with a fixed pitch prop? If not, the only remaining reason >> is a drag brake for landing. That's the one area where fixed pitch >> RV's suffer. High sink rate low speed descents into emergency landing >> zones are a lot more difficult to achieve, but the -9's already lower >> landing speed than a -6 should help you there. >> >> Charlie > > Charlie, > I looked at the RV6 and the landing speed is lower because of the > different airfoil, much longer wing, and much bigger flaps. > Interesting airfoil though. > George ( down under) I know. :-) Charlie