Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2881742 for flyrotary@lancaironline.net; Mon, 08 Dec 2003 10:35:09 -0500 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id hB8FZ4xt017174 for ; Mon, 8 Dec 2003 10:35:06 -0500 (EST) Message-ID: <000701c3bda0$671bd480$1702a8c0@WorkGroup> From: "Ed Anderson" To: "Rotary motors in aircraft" Subject: Air Density at altitude Date: Mon, 8 Dec 2003 10:31:51 -0500 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-Virus-Scanned: Symantec AntiVirus Scan Engine Found a table of air density vs Altitude Sea level Density = .00237 Slug/Ft^3 Density at 20,000 = 0.001267 Slug/Ft^3 or a 47% decrease So taking formula for air mass W = p*V*A with p 47% less than at sea level means you would get 47% less air mass flow (with the same cubic feet/minute of air volume flow) at 20,000 ft compared to what you would get at sea level for the same volume flow. While cooler temps would help, it would not compensate for a 45% less air mass flow. Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com