X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao101.cox.net ([68.230.241.45] verified) by logan.com (CommuniGate Pro SMTP 5.1.9) with ESMTP id 2083420 for flyrotary@lancaironline.net; Mon, 04 Jun 2007 12:23:14 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.45; envelope-from=alventures@cox.net Received: from fed1rmimpo02.cox.net ([70.169.32.72]) by fed1rmmtao101.cox.net (InterMail vM.7.05.02.00 201-2174-114-20060621) with ESMTP id <20070604162237.QZPU7825.fed1rmmtao101.cox.net@fed1rmimpo02.cox.net> for ; Mon, 4 Jun 2007 12:22:37 -0400 Received: from BigAl ([72.192.132.90]) by fed1rmimpo02.cox.net with bizsmtp id 7UNc1X00X1xAn3c0000000; Mon, 04 Jun 2007 12:22:36 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: EC-2/EM-2 manifold pressure Date: Mon, 4 Jun 2007 09:23:37 -0800 Message-ID: <000001c7a6cd$169aaad0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C7A68A.08776AD0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3028 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C7A68A.08776AD0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Well Bill, if the Kolsman window is where you set your altimeter setting (mb or = inches mercury) you will never see field elevation (pressure) unless you are at sealevel. =20 E.g. if you have 29.92" at sealevel (and in the window) you still have = 29.92 in the window (you set it there!) when you get to 6500'. Your actual ambient pressure is around 23.42".... (which you should be reading on = your manifold pressure gauge - engine stopped...=20 =20 Unless, I got it wrong the last 15 years and 9500 hours - ohhh my...!! TJ I think you've got it right. It seems to me that if you want to find = what your MAP out to be when parked, engine off; you set 29.92 in the = altimeter window to get pressure altitude, then either use a formula or chart to = get the expected air pressure at that altitude. For example, if you set = 29.92 and it shows your pressure altitude to be 2000 ft, then your chart will = tell you that the air pressure where you are is 27.8 in. HG for a standard = day, then correct for temp. =20 So unless I'm mistaken, that is the same as calling the tower (or = weather observation station, or get out your handy-dandy flight computer) and = get the density altitude, then vary the altimeter setting until the altitude reads density altitude, and get the pressure from the Kolsman window. =20 Al =20 ------=_NextPart_000_0001_01C7A68A.08776AD0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Well Bill,

if the Kolsman window is where you set your = altimeter setting (mb or inches mercury) you will never see field elevation = (pressure) unless you are at sealevel.

 

E.g. if you have 29.92" at sealevel (and = in the window) you still have 29.92 in the window (you set it there!) = when  you get to 6500'. Your actual ambient pressure is around 23.42".... = (which you should be reading on your manifold pressure gauge - engine stopped... =

 

Unless, I got it wrong the last 15 years and = 9500 hours - ohhh my...!!

 TJ

I think you’ve got it = right.  It seems to me that if you want to find what your MAP out to be when = parked, engine off; you set 29.92 in the altimeter window to get pressure = altitude, then either use a formula or chart to get the expected air pressure at = that altitude.  For example, if you set 29.92 and it shows your pressure altitude to be 2000 ft, then your chart will tell you that the air = pressure where you are is 27.8 in. HG for a standard day, then correct for = temp.

 

So unless I’m mistaken, = that is the same as calling the tower (or weather observation station, or = get out your handy-dandy flight computer) and get the density altitude, then = vary the altimeter setting until the altitude reads density altitude, and get the pressure from the Kolsman window.

 

Al

 

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