X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 27 Apr 2006 01:30:01 -0400 Message-ID: X-Original-Return-Path: Received: from imo-m21.mx.aol.com ([64.12.137.2] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTP id 1082372 for lml@lancaironline.net; Wed, 26 Apr 2006 19:23:17 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.2; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-m21.mx.aol.com (mail_out_v38_r7.5.) id q.28d.9bd1cfe (4402) for ; Wed, 26 Apr 2006 19:22:26 -0400 (EDT) From: Sky2high@aol.com X-Original-Message-ID: <28d.9bd1cfe.31815ab2@aol.com> X-Original-Date: Wed, 26 Apr 2006 19:22:26 EDT Subject: Re: [LML] FW: Drag Data X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1146093746" X-Mailer: 9.0 Security Edition for Windows sub 5300 X-Spam-Flag: NO -------------------------------1146093746 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 4/26/2006 9:58:28 A.M. Central Standard Time, fredmoreno@optusnet.com.au writes: Comment on measuring OAT which is only an issue beginning above maybe 200-250 knots. If the OAT measurement is made outside of the air stream (like the skin temperature, for example), it is still subject to aerodynamic frictional heating. One can calculate this via something called the Recovery Temperature which varies a bit from stagnation temperature rise. But for our purposes, the recovery temperature rise (which is effectively the skin temperature on unheated parts of the airframe) is about 80% of the stagnation temperature rise. In short, there is no way to avoid the aerodynamic heating error. It goes as the square of the TAS. You have to allow for it. It is always there, and it will always create an error when you calculate corrections with your E6B. Fred, Ahhh, error is in the calculation of the beholder....... Fortunately, those utilizing the Rocky Mountain Instrument's micro encoder note that it displays KTAS (corrected for compression temperature rise) and TAT. In other words, my TAS calibration based on quality GPS data over a 3 or 4 legged course really is within a Knot. Airspeed and TAS from my temperature/altitude corrected analog airspeed steam gauge varies a bit from the RMI device. I would have to assume that all of the modern EFISes, widescreen video cockpit displays, fancy-dancy synthetic vision devices, MFDs, etc. more properly calculate a compensated TAS, whether in Knots, MPH, KPH, or Furlongs per Fortnight (FPF) - depending of your choice of scale. I could be wrong - nothing new for me.... Scott Krueger AKA Grayhawk Lancair N92EX IO320 CS Prop Slow Build 1989, Flown 1996 Aurora, IL (KARR) Eschew Obfuscation! -------------------------------1146093746 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 4/26/2006 9:58:28 A.M. Central Standard Time,=20 fredmoreno@optusnet.com.au writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D3>

Comment on mea= suring=20 OAT which is only an issue beginning above maybe 200-250 knots. If t= he=20 OAT measurement is made outside of the air stream (like the skin temperatu= re,=20 for example), it is still subject to aerodynamic frictional=20 heating. One can calculate this via something called the Recovery=20 Temperature which varies a bit from stagnation temperature rise. But= for=20 our purposes, the recovery temperature rise (which is effectively the skin= =20 temperature on unheated parts of the airframe) is about 80% of the stagnat= ion=20 temperature rise. In short, there is no way to avoid the aerodynamic= =20 heating error. It goes as the square of the TAS. You have to a= llow=20 for it. It is always there, and it will always create an error when=20= you=20 calculate corrections with your E6B. =20

Fred,

Ahhh, error is in the calculation of the beholder.......

Fortunately, those utilizing the Rocky Mountain Instrument's micro enco= der=20 note that it displays KTAS (corrected for compression temperature=20 rise) and TAT. In other words, my TAS calibration based on qualit= y=20 GPS data over a 3 or 4 legged course really is within a Knot. Airspeed= and=20 TAS from my temperature/altitude corrected analog airspeed steam gauge=20 varies a bit from the RMI device.

I would have to assume that all of the modern EFISes, widescreen video=20 cockpit displays, fancy-dancy synthetic vision devices, MFDs, etc. more prop= erly=20 calculate a compensated TAS, whether in Knots, MPH, KPH, or Furlongs pe= r=20 Fortnight (FPF) - depending of your choice of scale.

I could be wrong - nothing new for me....=20

Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 CS Prop
Slow Build 1989, Flown 1996=20
Aurora, IL (KARR)

Eschew=20 Obfuscation!

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