X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao105.cox.net ([68.230.241.41] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3700941 for flyrotary@lancaironline.net; Tue, 23 Jun 2009 13:12:07 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.41; envelope-from=alventures@cox.net Received: from fed1rmimpo01.cox.net ([70.169.32.71]) by fed1rmmtao105.cox.net (InterMail vM.7.08.02.01 201-2186-121-102-20070209) with ESMTP id <20090623171125.EBJM20430.fed1rmmtao105.cox.net@fed1rmimpo01.cox.net> for ; Tue, 23 Jun 2009 13:11:25 -0400 Received: from BigAl ([72.192.135.181]) by fed1rmimpo01.cox.net with bizsmtp id 7VBQ1c00D3uzsQg03VBQC9; Tue, 23 Jun 2009 13:11:24 -0400 X-VR-Score: 0.00 X-Authority-Analysis: v=1.0 c=1 a=paBUCOFK8LgA:10 a=6ttVS2iXLWBuEOxFG8oA:9 a=quh6RRJP0uj2whuIYIbPsIQOJOgA:4 a=Y2az4Sjb9EmeZ_zg:21 a=pbJPHf7mqnjw2neK:21 a=uNCv8LhM2HBlMLbOgYoA:9 a=oH6KVx1yrkeHUfFQQkMA:7 a=3IiL8MfOeILnd2Wj6ll-2Z5rmnYA:4 a=4_ZUgYM002NtjOIw:21 a=s0qnRhOyjUVAZr39:21 X-CM-Score: 0.00 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: progress report #347c Date: Tue, 23 Jun 2009 10:11:37 -0800 Message-ID: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0016_01C9F3EA.FEE299D0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6838 Importance: Normal Thread-Index: Acn0GhEZecBwFKxBQ9uLQLN4z8KKAwAEiUew In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_0016_01C9F3EA.FEE299D0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Al, Hmmmm, Further explanation would be helpful here. I thought that the altimeter was actually reading the air column weight or pressure at its location. If you set the altimeter to the field elevation, it seems it should read the barometric pressure in the window =20 Gees; I was hoping you wouldn't ask - then I wouldn't have to think = about it:-). =20 Well; it goes something like this; your altimeter setting is the = barometric pressure of the station as if the station were at sea level. So the altimeter setting is barometric pressure with an altitude correction applied. Your MAP is absolute ambient pressure. Absolute pressure is measurement relative to a perfect vacuum, as in = outer space. A zero reading occurs when the pressure is reduced to near = perfect vacuum conditions. The ambient atmospheric pressure at sea level is approximately 29.92 inches of mercury, or 14.7 pounds per square inch, = or 760 mm of mercury. As you go up the ambient atmospheric pressure = decreases and your Absolute pressure gauge (MAP) reading also decreases. =20 I have a chart of the barometric vs ambient pressure, but I don't know = where I got it. Anybody know? I'll check the internet and see if I can find something; or I could scan it and send it. =20 Al G ------=_NextPart_000_0016_01C9F3EA.FEE299D0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Al,

Hmmmm, Further explanation would be helpful here.  I thought that = the

altimeter was actually reading the air column weight or pressure at = its

location.  If you set the altimeter to the field elevation, it seems = it

should read the barometric pressure in the window

 

Gees; I was = hoping you wouldn’t ask – then I wouldn’t have to think about = itJ.

 

Well; it goes = something like this; your altimeter setting is the barometric pressure of the = station as if the station were at sea level. So the altimeter setting is barometric = pressure with an altitude correction applied.  Your MAP is absolute ambient pressure.

Absolute pressure is measurement relative to a perfect vacuum, as in = outer space. A zero reading occurs when the pressure is reduced to near = perfect vacuum conditions. The ambient atmospheric pressure at sea level is approximately 29.92 inches of mercury, or 14.7 pounds per square inch, = or 760 mm of mercury. As you go up the ambient atmospheric pressure decreases = and your Absolute pressure gauge (MAP) reading = also decreases.

 <= /font>

I have a chart = of the barometric vs ambient pressure, but I don’t know where I got it. = Anybody know?  I’ll check the internet and see if I can find = something; or I could scan it and send it.

 <= /font>

Al = G

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