X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 26 Apr 2006 10:57:47 -0400 Message-ID: X-Original-Return-Path: Received: from mail08.syd.optusnet.com.au ([211.29.132.189] verified) by logan.com (CommuniGate Pro SMTP 5.0.9) with ESMTPS id 1081429 for lml@lancaironline.net; Wed, 26 Apr 2006 02:03:50 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.189; envelope-from=fredmoreno@optusnet.com.au Received: from fred ([59.154.24.146]) (authenticated sender fredmoreno) by mail08.syd.optusnet.com.au (8.12.11/8.12.11) with ESMTP id k3Q62ep5022451 for ; Wed, 26 Apr 2006 16:02:57 +1000 From: "Frederick Moreno" X-Original-To: "Lancair Mail" Subject: FW: Drag Data X-Original-Date: Wed, 26 Apr 2006 14:03:28 +0800 X-Original-Message-ID: <000701c668f7$292eedb0$c211140a@fred> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0008_01C6693A.37522DB0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.2627 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2869 Importance: Normal This is a multi-part message in MIME format. ------=_NextPart_000_0008_01C6693A.37522DB0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Paul: Real DATA! Many thanks. Let's see: if I interpret correctly the 110 HP 0-235 with higher compression pistons puts out 125 HP (plus 8=-9%) at the same RPM? Is that right, a guess, or a reasonable certainty? 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. That is why a lot of Lancair IV pilots think they cruise at 300 knots plus. They don't. The combined compressibility error (about 1/3) and aerodynamic heating error (about 2/3's) total something around 20 knots making true cruise speeds about 285 knots.. Just like the book. Sorry. Fred -----Original Message----- From: Paul Lipps [mailto:elippse@sbcglobal.net] Sent: Tuesday, 25 April 2006 12:43 PM Subject: Drag Data Frank! I have never flown around with someone with another 235, so I have nothing for comparison. I have flown alongside Klaus several times and he and I had the same IAS/TAS on our systems, with him, of course, throttled back to stay with me. I have a well calibrated pitot and static. I've done many two-way runs using my autopilot and altitude hold to calibrate them vs GPS groundspeed; TAS always comes out within 1 MPH of GPS GS avg. My two OATs are also mounted out of the airstream, so they show no stagnation rise and I get correct dalt and TAS. My O-235 has 9.7:1 pistons, and I get about 125 hp. I get 214 mph TAS at 1000' dalt, 2950 rpm, 206 mph TAS at 8000' dalt, and 198 mph TAS at 2750 rpm, 14,500 dalt, 5.7 gph, all when leaned for best power. I designed the prop to give 200 mph TAS at 2800 rpm, 10,000' dalt; I actually get about 201 mph TAS. ROC at 1000' dalt, 2430 rpm, 110 mph IAS, 1350 lb is 1500-1550 ft/min. My induction system gives me the correct pressure recovery, which is total pressure minus carb drop. Lycoming charts for the MA-3A shows the carb drop to be 1.1" at 12,500 pressure altitude. I have 43 gallons total, so I can get 1250-1300 miles with reserves, no wind, at altitude. I adjust my flap reflex angle to give me the best speed. Varying it can change speed 3 mph or more from max (8 deg) reflex when at higher altitude and higher weight. My wing-tip additions increase my span to 25.2', area to 77.5 sq ft, and AR to 8.17:1. ------=_NextPart_000_0008_01C6693A.37522DB0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Paul:

 

Real DATA!  Many = thanks. 

 

Let’s see: if I interpret = correctly the 110 HP 0-235 with higher compression pistons puts out 125 HP (plus = 8=3D-9%) at the same RPM?  Is that right, a guess, or a reasonable = certainty? 

 

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. 

 

That is why a lot of Lancair IV = pilots think they cruise at 300 knots plus.  They don’t.  The = combined compressibility error (about 1/3) and aerodynamic heating error (about = 2/3’s) total something around 20 knots making true cruise speeds about 285 = knots….

 

Just like the = book.

 

Sorry.

 

Fred

 

-----Original Message-----
From: Paul Lipps [mailto:elippse@sbcglobal.net]
Sent: Tuesday, 25 April 2006 12:43 PM
Subject: Drag = Data

 

Frank! I have never flown around with someone = with another 235, so I have nothing for comparison. I have flown alongside = Klaus several times and he and I had the same IAS/TAS on our systems, with = him, of course, throttled back to stay with me. I have a well calibrated = pitot and static. I've done many two-way runs using my autopilot and altitude = hold to calibrate them vs GPS groundspeed; TAS always comes out within 1 MPH = of GPS GS avg. My two OATs are also mounted out of the airstream, so they show = no stagnation rise and I get correct dalt and TAS. My O-235 has 9.7:1 = pistons, and I get about 125 hp. I get 214 mph TAS at 1000' dalt, 2950 rpm, 206 = mph TAS at 8000' dalt, and 198 mph TAS at 2750 rpm, 14,500 dalt, 5.7 gph, all when leaned for best power. I designed the prop to give 200 mph TAS at 2800 rpm, 10,000' dalt; I actually get about 201 mph TAS. = ROC at 1000' dalt, 2430 rpm, 110 mph IAS, 1350 lb is 1500-1550 ft/min. My induction system gives me the correct pressure recovery, which is total = pressure minus carb drop. Lycoming charts for the MA-3A shows the carb drop = to be 1.1" at 12,500 pressure altitude. I have 43 gallons = total, so I can get 1250-1300 miles with reserves, no wind, at altitude. I adjust my = flap reflex angle to give me the best speed. Varying it can change speed 3 = mph or more from max (8 deg) reflex when at higher altitude and = higher weight. My wing-tip additions increase my span to 25.2', area to = 77.5 sq ft, and AR to 8.17:1.

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