X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mx2.netapp.com ([216.240.18.37] verified) by logan.com (CommuniGate Pro SMTP 5.3.3) with ESMTPS id 4152531 for flyrotary@lancaironline.net; Thu, 04 Mar 2010 16:04:04 -0500 Received-SPF: softfail receiver=logan.com; client-ip=216.240.18.37; envelope-from=echristley@nc.rr.com X-IronPort-AV: E=Sophos;i="4.49,582,1262592000"; d="scan'208";a="326342321" Received: from smtp1.corp.netapp.com ([10.57.156.124]) by mx2-out.netapp.com with ESMTP; 04 Mar 2010 13:03:28 -0800 Received: from [10.62.16.80] (ernestc-laptop.hq.netapp.com [10.62.16.80]) by smtp1.corp.netapp.com (8.13.1/8.13.1/NTAP-1.6) with ESMTP id o24L3SYJ001678 for ; Thu, 4 Mar 2010 13:03:28 -0800 (PST) Message-ID: <4B90201F.9000202@nc.rr.com> Date: Thu, 04 Mar 2010 16:03:27 -0500 From: Ernest Christley Reply-To: echristley@nc.rr.com User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Vance Jaqua and Propellers References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Ernest Christley wrote: > Bryan Winberry wrote: >> Thanks Ernest, >> Can you splain me one thin. How does the AoA change on a fixed pitch >> prop? >> > The blade move side to side. > The airplane move forward (for non-aerobatic modes of flight). > The AoA is affected by the relationship of the side-to-side and > forward motions. > > Twirl a flat blade with the brakes locked. The AoA is zero degrees. > With an engine out, and prop stopped and flat. The AoA is 90 degrees. > Under normal operation. The AoA is a vector sum of the forward > movement and the side-to-side movement. Oh, another thing that makes it even more interesting. The vector sum of the "forward movement" to the "side-to-side movement" is different for each section of the blade. Each section as you step away from the center of the hub moves from side to side at a different rate. The outside pieces have to make a bigger circle than the inside pieces, so they have to move faster. But the forward motion is all the same. At 200kts, for instance, you can potentially have a problematically twisted propeller where the tips are stalled yet the blade near the hub has a negative AoA!!