Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Tue, 31 Dec 2002 08:19:33 -0500 Message-ID: X-Original-Return-Path: Received: from [64.4.38.120] (HELO hotmail.com) by logan.com (CommuniGate Pro SMTP 4.0.3) with ESMTP id 1942198 for flyrotary@lancaironline.net; Tue, 31 Dec 2002 00:30:28 -0500 Received: from mail pickup service by hotmail.com with Microsoft SMTPSVC; Mon, 30 Dec 2002 21:30:27 -0800 X-Originating-IP: [65.137.50.98] Reply-To: "Tracy Crook" From: "Tracy Crook" X-Original-To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Cruise info X-Original-Date: Tue, 31 Dec 2002 00:36:17 -0500 Organization: Real World Solutions Inc. MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1106 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-Original-Message-ID: X-OriginalArrivalTime: 31 Dec 2002 05:30:27.0665 (UTC) FILETIME=[B9F71410:01C2B08D] ----- Original Message ----- From: "john" To: "Rotary motors in aircraft" Sent: Monday, December 30, 2002 10:58 PM Subject: [FlyRotary] Cruise info > I'm still working out the info to get the prop carved, and am wondering what > is the optimum engine rpm at cruise and the fuel consumption you fellows are > getting? All input would be greatly appreciated. Thanks JohnD If you are using a fixed pitch prop, about the only thing you can do is aim for target max engine RPM at top speed. A lot also depends on max tip speed and keeping it in the efficient range below mach .85. If your prop length is around 68 - 70 inches (typical RV prop) then the highest you want to go is about 6350 rpm with a reduction ratio of 2.176: 1. You really don't have much choice but to let cruise rpm fall where it may. I my case, cruise is between 5000 to 5600 rpm. This is not a bad place to be as the rotary has its best BSFC in this range. I burn around 6.5 GPH at econo cruise (175 mph) and 8.25 GPH at 202 (both measured at 14,000 ft). A little efficiency could be gained by increasing pitch & slowing the engine down at cruise but you would loose takeoff & climb performance so it's a bad deal. Tracy Crook tcrook@rotaryaviation.com www.rotaryaviation.com