Return-Path: Received: from [24.25.9.101] (HELO ms-smtp-02-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2882510 for flyrotary@lancaironline.net; Mon, 08 Dec 2003 21:18:30 -0500 Received: from o7y6b5 (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-02-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id hB92IQd3012872 for ; Mon, 8 Dec 2003 21:18:28 -0500 (EST) Message-ID: <003201c3bdfa$44c2da00$1702a8c0@WorkGroup> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Air Density at altitude Date: Mon, 8 Dec 2003 21:15:08 -0500 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_002F_01C3BDD0.5B98E5A0" 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 This is a multi-part message in MIME format. ------=_NextPart_000_002F_01C3BDD0.5B98E5A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable =20 ----- Original Message -----=20 From: Bill Schertz=20 To: Rotary motors in aircraft=20 Sent: Monday, December 08, 2003 4:33 PM Subject: [FlyRotary] Re: Air Density at altitude Ed, I think you left out a 1/2 factor, see my analysis attached Bill Schertz KIS Cruiser # 4045 Your absolutely correct, Bill. I had the 1/2 in the formula but = failed to include it in the math {:<( So the dynamic pressure at sea level would be around 0.25 psi rather = 0.51 psi. That in turn would require less true airspeed at 20,000 feet to = generate only 0.25 psi dynmaic pressure for the same IAS reading as at = sea level which in turn would generate less mass flow since the true = airspeed require (163 mph) is quite a bit less than my erroneous figure = of 232 mph. So, of course, that means the mass flow is about 27% less for the same = indicated airspeed as it was at sea level or only 73% of the sea level = mass flow whichever way you want to look at it. =20 So using indicated airspeed would put you almost 30% off at 20,000 = rather than the 3% I initially calculated. So IAS it turns out does not = provide that good an estimate of mass air flow and therefore cooling at = different altitudes. Air density still rules {:>) Appreciate you catching the error, Bill Ed Anderson =20 ------=_NextPart_000_002F_01C3BDD0.5B98E5A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
----- Original Message -----
From:=20 Bill=20 Schertz
Sent: Monday, December 08, 2003 = 4:33=20 PM
Subject: [FlyRotary] Re: Air = Density at=20 altitude

Ed, I think you left out a 1/2 factor, see my analysis = attached

Bill Schertz
KIS Cruiser # 4045

 Your absolutely correct, = Bill.  I had=20 the 1/2 in the formula but failed to include it in the math=20 {:<(
 
  So the dynamic pressure at sea = level would=20 be around 0.25 psi rather 0.51 psi.
That in turn would require less true = airspeed at=20 20,000 feet to generate only 0.25 psi dynmaic pressure for the same = IAS=20 reading as at sea level which in turn would generate less mass flow = since the=20 true airspeed require (163 mph) is quite a bit less than my erroneous = figure=20 of 232 mph.
 
So, of course, that means the mass = flow is about=20 27% less for the same indicated airspeed as it was at sea level or = only 73% of=20 the sea level mass flow whichever way you want to look at it. =20
 
So using indicated airspeed would put = you almost=20 30% off at 20,000 rather than the 3% I initially calculated. So IAS it = turns=20 out does not provide that good an estimate of mass air flow and = therefore=20 cooling at different altitudes.  Air density still rules=20 {:>)
 
Appreciate you catching the error,=20 Bill
 
Ed Anderson

 
 
 
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